blown film workbook draft
TRANSCRIPT
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Higher Institute for Plastics Fabrication
WORKBOOK
for
Blown Film Extrusion
Practical Course
Prepared by
Blown Film Extrusion Department
1st Edition 2009
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Workbook for Blown F i lm Pract ica l Course
ACKNOWLEDGEMENT
In its program to continuously improve the quality of instructions at the
Higher Institute for Plastics Fabrication, the Curriculum Steering Committee
initiated the creation of the workbooks for all practical courses being offered
in the Institute. The Committee is headed by Dr. Khaled Al-Ghefaili, and the
members are Dr. Ahmad Al-Ghamdi, Mr. Hiroshi Takeshita, Engr. Issa Al-
Khormi, Mr. Sumio Iwase, Mr. Kazuhiko Sawada, Mr. Sanjay Rawat, Mr.
Zakaria Musa, and Mr. Virgilio Calpe.
This is the HIPF Workbook for Injection Molding for Practical Course. The
contents of this workbook were compiled through the efforts of the members
of the Blown Film Department, namely, Raul R. Clave (Head of the
Department), Isagani Aldover, Philip Floyd Yumul, Jovanny Quilala, Jovef
Pangue, Alfred Bacosa, Kirankumar Daraji (Senior Instructors) and Mr.
Sumio Iwase and Mr. Takuma Nakashima (Blown Film Expert Advisers).
Editing, formatting and design by Virgilio Calpe.
February 2009
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Workbook for Blown F i lm Pract ica l Course
TABLE OF CONTENTS
Introduction … … … … … … … … … … … … … … … … … … . 4
Course Objectives … … … … … … … … … … … … … … … … . 5
General Safety Guidelines … … … … … … … … … … … … … ... 6
Grades Summary Sheet … … … … … … … … … … … … … … ... 7
Workshop Activities
Activity 1—Basic Theory of Blown Film Extrusion … … … … … .. 8
Activity 2—Polyethylene Films… … … … … … … … … … … … 14
Activity 3—Emergency Stop and Safety Devices … … … … … … . 19
Activity 4—Blown Film Die … … … … … … … … … … … … … 26
Activity 5—Blown Film Air Cooling Ring … … … … … … … … .. 31
Activity 6—Blown Film Width and Thickness… … … … … … … .. 37
Activity 7—Corona Treatment … … … … … … … … … … … … . 42
Activity 8—Flexographic Printing … … … … … … … … … … … 48
Activity 9—Bag Making … … … … … … … … … … … … … … . 55
Activity 10—Polyethylene Film Recycling … … … … … … … … . 64
Glossary … … … … … … … … … … … … … … … … … … … . 92
References … … … … … … … … … … … … … … … … … … ... 110
Activity 11—Practice Plant Operations (LDPE) … …. … … … … .. 73
Activity 12—Practice Plant Operations (LLDPE) … …. … … … … . 81
Formulas … … … … … … … … … … … … … … … … … … … 89
Activity 13—Practice Plant Operations (HDPE) … …. … … … … .. 85
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Workbook for Blown F i lm Pract ica l Course
INTRODUCTION
Blown film extrusion is one of the most commonly used thin-gauge
fabrication processes in the world. The majority of the commodity films
such as grocery bags, agricultural films and other flexible packaging films
used by consumers are produced by this method. The process of producing
film by extruding molten resin into a continuous tube is simple. Yet, in fact
the system is one of the most complex and sensitive of all the plastics
fabricating technologies and it presents many inherent difficulties.
A simple blown film line consists of an extruder, die, air ring, iris or bubble
cage, collapsing frame, and a winder.
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Workbook for Blown F i lm Pract ica l Course
COURSE OBJECTIVES
The purpose of this workbook is to enable the trainees to understand and
carry out important activities being done in a blown film extrusion process.
Focus will be on the most important functions of the machine and the
terminologies used in the enterprise.
Upon successful completion of this course, the trainee will be able to:
• Know the main components of film extruders and their purposes.
• Describe blown film extrusion process.
• Identify common polyethylene films.
• Perform emergency stop using emergency switches.
• Know the operation of an air ring, die, nip rolls and gusseting equipment.
• Know the operation of a simple flexographic in-line printer.
• Know the basic operation of a recycling machine.
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Workbook for Blown F i lm Pract ica l Course
GENERAL SAFETY PRECAUTIONS
Instead of starting operations carelessly, all trainees should discuss the
following before starting any activity:
(1.) What types of activities are we going to do?
(2.) What kind of risks are hidden behind those types of activities?
(3.) What should we do to avoid those risks?
Here are some safety reminders to always keep in mind:
• Keep the work area clean at all times.
• Use proper hand gloves. Avoid using loose hand gloves.
• Use the appropriate tool and wear protective dry gloves when you throw
away purged resin.
• Do not lean against the cage guard of the ladder when you work.
• Pay attention to where your hands are to ensure that your hands are not
pinched between rollers and other rotating equipment.
• Do not run the machine without the protective covers on rotating parts.
• Avoid clothing or accessories that could easily be pinched or caught in
machines.
• Specifically, do not wear items that hang far from your neck such as long
necklaces and IDs’. Do not wear rings or loose bracelets. Do not wear
clothing that is pleated, sags or has strings. Make sure that you button or
fasten your shirt and jacket cuffs, pant cuffs and jacket hem.
• Do not stand in front of the die.
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Workbook for Blown F i lm Pract ica l Course
GRADES SUMMARY SHEET
Trainee Name: _________________________ Group: ________
Semester ___ School Year ___________
ACTIVITIES GRADE
Activity 1—Basic Theory of Blown Film Extrusion
Activity 2—Polyethylene Films
Activity 3—Emergency Stop and Safety Devices
Activity 4—Blown Film Die
Activity 5—Blown Film Air Cooling Ring
Activity 6—Blown Film Width and Thickness
Activity 7—Corona Treatment
Activity 8—Flexographic Printing
Activity 9—Bag Making
Activity 10—Polyethylene Film Recycling
Activity 11—Practice Plant Operations (LDPE)
Activity 12—Practice Plant Operations (LLDPE)
Activity 13—Practice Plant Operations (HDPE)
AVERAGE GRADE
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THEORETICAL BACKGROUND
Blown films are created by feeding plastics pellets into an extruder where
they are melted and homogenised before they are pumped through a circular
blown film die. The melted plastics form a continuous tube which is drawn
from the die. It is inflated and simultaneously cooled by rapidly moving air.
The tube, also called a “bubble,” is then flattened as it passes the collapsing
frames and drawn through nip rolls and over idler rolls to a winder which
pulls and winds the finished rolls of film.
A typical film blown film machine consists of the following five major units:
• Extruder unit—converts the solid pellets into hot melt.
• Die unit—forms the hot melt into tube.
• Cooling unit—cools down and solidifies the hot melt.
• Take-off unit—pulls and flattens the tube at constant speed.
• Winding unit—winds-up the flattened tube into finish rolls.
WORKSHOP ACTIVITY #1
Basic Theory of Blown Film Extrusion
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OBJECTIVES OF THE ACTIVITY
1. To learn the basics of operating a blown film machine
2. To identify the parts of the five major units of a blown film and their
elements
PROCEDURE
PART I—The Basic Operations of Blown Film Machine
1. Go to the Workshop floor and observe any of the blown film machine
that is being run by your Instructor.
2. Using data sheet on the following pages, list down accordingly the steps
of the blown film process you have observed.
Example:
Step 1. Put material in the hopper.
Step 2. etc…
PART II—The Five Major Units of a Blown Film Machine
1. Using the drawing of Blown Film Machine in your data sheet, label the
following:
a. name of the part/s of each major units.
b. name the other elements needed in the process.
WORKSHOP ACTIVITY #1—Basic Theory of Blown Film Extrusion
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DATA SHEET
PART I—The Basic Operations of Blown Film Machine
Steps in Blown Film Operations
ACTIVITY #1—Basic Theory of Blown Film Extrusion
TRAINEE NAME GROUP NO.
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Report Form Report Form Report Form Report Form ---- Page 1 of 4 Page 1 of 4 Page 1 of 4 Page 1 of 4
Description of the Step Step No.
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DATA SHEET
PART II—The Five Major Units of a Blown Film Machine
ACTIVITY #1—Basic Theory of Blown Film Extrusion
TRAINEE NAME GROUP NO.
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Report Form Report Form Report Form Report Form ---- Page 2 of 4 Page 2 of 4 Page 2 of 4 Page 2 of 4
Properly label the Blown Film
Proce
ss Diagram
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Workbook for Blown F i lm Pract ica l Course
QUESTIONS & EXERCISES
A. Choose the correct answer.
1. What is the most common material used for blown films?
(a.) PVC (c.) Nylon
(b.) PET (d.) PE
2. What is the common type of blown film used all over the world?
(a.) Downward BF (c.) Upward BF
(b.) Horizontal BF (d.) None of the above
3. What part of the blown film machine makes the screw rotates?
(a.) blower (c.) haul-off
(b.) main motor (d.) winder
4. What is the process of feeding a single die with two or more different
polymer melt streams?
(a.) blower (c.) haul-off
(b.) main motor (d.) none of the above
B. How does blown film differs from other plastics fabrications?
Check (�) if applicable, and cross out (�) if not applicable.
WORKSHOP ACTIVITY #1—Basic Theory of Blown Film Extrusion
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Report Form Report Form Report Form Report Form ---- Page 3 of 4 Page 3 of 4 Page 3 of 4 Page 3 of 4
PROCESS Die Mould Screw and
Barrel
Haul-off /
Take-off Winder
Blown Film
Extrusion
Blow
Molding
Pipe
Extrusion
Injection
Molding
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CONCLUSION & RECOMMENDATIONS
INSTRUCTOR’S COMMENTS
WORKSHOP ACTIVITY #1—Basic Theory of Blown Film Extrusion
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TRAINEE’S GRADE
FOR THIS ACTIVITY
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INSTRUCTOR’S SIGNATURE
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Report Form Report Form Report Form Report Form ---- Page 4 of 4 Page 4 of 4 Page 4 of 4 Page 4 of 4
DATE: __________________
DATE: __________________
________________________
TRAINEE’S SIGNATURE
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THEORETICAL BACKGROUND
• The ethylene polymer is available in three main grades, low, medium and
high density film.
• Polyethylene, PE, film is slightly opaque, the opacity increasing with
density.
• PE film is waxy to the touch, and is a good moisture barrier.
• Low and medium density PE films are flexible even when cold.
• PE is readily heat sealed.
• High density PE film is suitable for boil-in-the-bag packs, whereas low
and medium density films are not.
• PE film that has a lower MFR means a higher molecular weight and
better mechanical strength.
WORKSHOP ACTIVITY #2
Polyethylene Films
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OBJECTIVES OF THE ACTIVITY
1. To learn the physical properties of Polyethylene (PE) films
2. To compare the differences among the three common types of PE films
used in blown film packaging
PROCEDURE
PART I—Physical Characteristics of PE Films
1. Collect three samples for each type of the PE films from the plant
• LDPE @ 400mm & 30microns
• LLDPE @ 400mm & 30microns
• HDPE @ 400mm & 30microns
2. Correctly label the different films.
3. Each film sample should have the same thickness, length and width.
4. Try to stretch each film and write your observation in your data sheet.
PART II—Process Parameters for PE Films
1. Try to find the Melt Temperature and Pressure for processing each type
of PE films.
2. Write your data in the table provided in your data sheet.
3. Compare MFR, Density, Melt Temperature, and Pressure for each type of
PE films.
4. Which materials do you think is the easiest to process?
WORKSHOP ACTIVITY #2—Polyethylene Films
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DATA SHEET
PART I—Physical Characteristics of PE Films
Stretch the plastics samples:
PART II—Process Parameters for PE Films
ACTIVITY #2—Polyethylene Films
TRAINEE NAME GROUP NO.
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Report Form Report Form Report Form Report Form ---- Page 1 of 3 Page 1 of 3 Page 1 of 3 Page 1 of 3
PE Sample
MFR Density Extruder Melt Temperature
Extruder Melt Pressure
LDPE 0.2 to 5 0.912 to 0.925
LLDPE 0.5 to 2 0.912 to 0.925
HDPE 0.03 to 0.1 0.945 to 0.955
PE Sample Observations
LDPE
(400mm, 30microns)
LLDPE
(400mm, 30microns)
HDPE
(400mm, 30microns)
Based on the above data, which materials is easy to process?
Why?
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QUESTIONS & EXERCISES
Choose the correct answer and mark ( � ) the correct ones.
1. Which of these films has a better clarity?
a. LDPE
b. LLDPE
c. HDPE
2. Which is the toughest among these polyethylene films?
a. HDPE
b. LDPE
c. LLDPE
3. Which blown film bag is suitable for carrying more weight?
a. LLDPE
b. LDPE
c. HDPE
4. Choose the correct application of LDPE film.
a. food packaging
b. shopping bag
c. garments packaging
d. floor covering
5. Which of these films can be stretch more?
a. HDPE
b. LDPE
c. LLDPE
WORKSHOP ACTIVITY #2—Polyethylene Films
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Report Form Report Form Report Form Report Form ---- Page 2 of 3 Page 2 of 3 Page 2 of 3 Page 2 of 3
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WORKSHOP ACTIVITY #2—Polyethylene Films
CONCLUSION & RECOMMENDATIONS
INSTRUCTOR’S COMMENTS
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TRAINEE’S GRADE
FOR THIS ACTIVITY
________________________
INSTRUCTOR’S SIGNATURE
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Report Form Report Form Report Form Report Form ---- Page 3 of 3 Page 3 of 3 Page 3 of 3 Page 3 of 3
DATE: __________________
DATE: __________________
________________________
TRAINEE’S SIGNATURE
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Workbook for Blown F i lm Pract ica l Course
THEORETICAL BACKGROUND
MACHINE SAFETY GUARDS & DEVICES
Safety devices in facilities, machinery and equipment are an essential means
of ensuring worker safety. Foolproof devices, failsafe devices and others are
used to ensure intrinsic (essential) safety. These devices are usually built
into facilities, machinery and equipment so that workers cannot easily
remove them.
The foolproof function is a safety mechanism designed with a focus on
human factors. On the other hand, the failsafe function is a safety
mechanism designed with a focus on the protection of facilities, machinery
and equipment.
Types of safety devices typically used in blown film machine:
• Mechanical Interlock
• Electrical Interlock
All Dangerous spots of the blown film line must be secured by suitable
protective devices. If proper guards cannot be mounted due to the conditions
at hand, these areas are secured by Emergency devices.
Guarding and Barriers
The purpose of machine guarding and barrier is to protect the machine
operator and other employees in the work area from hazards created by
moving parts, rotating parts, flying chips & sparks. Some examples of this
are barrier guards, safety gates, etc.
WORKSHOP ACTIVITY #3
Emergency Stop and Safety Devices
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THEORETICAL BACKGROUND … continued
WORKSHOP ACTIVITY #3—Emergency Stop and Safety Devices
Pull-Down
Electrical Interlock
Safety Interlock Switch
Push
WARNING SIGN WARNING SIGN
SAFETY COVER GUARD RAILS
EMERGENCY STOP EMERGENCY STOP
SAFETY SWITCH SAFETY GATE
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OBJECTIVES OF THE ACTIVITY
1. To know the purposes of each of the safety devices installed in a blown
film machine
2. To learn how to pause or stop the blown film machine in emergency
cases
3. To develop awareness of the dangers of blown film machine if safety
devices are tampered or by-passed
PROCEDURE
Types of Safety Devices Typically Used in Blown Film Machines
Walk around the blown film machine assigned to you by your Instructor and
try to locate all the safety devices and the emergency stop buttons.
PART I—Safety Devices and their Functions
1. In your data sheet, write down the names of the safety devices and their
functions and answer the questions.
PART II—Emergency Stops
1. In your data sheet, indicate all the emergency stop buttons of the blown
film machine available in WS02 and answer all the questions.
WORKSHOP ACTIVITY #3—Emergency Stop and Safety Devices
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DATA SHEET
PART I—Safety Devices and their Functions
Safety Devices of Blown Film Machine, where are they?
ACTIVITY #3—Emergency Stop and Safety Devices
TRAINEE NAME GROUP NO.
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Report Form Report Form Report Form Report Form ---- Page 1 of 4 Page 1 of 4 Page 1 of 4 Page 1 of 4
SAFETY DEVICES of BLOWN FILM MACHINE
1.
2.
3.
4.
5.
1. Do these safety devices really help by reminding you of the danger if
they are not activated?
2. How?
YESYESYESYES NONONONO
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DATA SHEET
PART II—Emergency Stops
Emergency stop buttons of Blown Film Machine, where are they?
ACTIVITY #3—Emergency Stop and Safety Devices
TRAINEE NAME GROUP NO.
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Report Form Report Form Report Form Report Form ---- Page 2 of 4 Page 2 of 4 Page 2 of 4 Page 2 of 4
1. When are we going to use the emergency stop buttons, is it during
scheduled shutdown?
2. Why?
3. If something happens to the machine or to the operator and we need to
stop immediately, are we going to use the emergency stop?
4. Why?
YESYESYESYES NONONONO
YESYESYESYES NONONONO
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QUESTIONS & EXERCISES
Choose the correct answer.
1. What type of emergency device is installed above and across the
width of the winding station?
(a.) emergency stop button (c.) emergency stop cord
(b.) warning alarm (d.) none of the above
2. What warning sign is available in the machine indicating danger of
being burn?
3. What will you do to stop the machine in case of emergency?
(a.) switch off the main switch
(b.) leave the machine
(c.) press the “Emergency Stop” push button
(d.) follow the shutdown procedure
4. Which mandatory safety sign that informs operator to wear hand
protection?
5. Which of the following is an example of safeguarding devices?
(a.) printing gear cover (b.) railings
(b.) winder gates (c.) all of the above
WORKSHOP ACTIVITY #3—Emergency Stop and Safety Devices
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(a.) (b.)
(c.) (d.)
(a.) (b.)
(c.) (d.)
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WORKSHOP ACTIVITY #3—Emergency Stop and Safety Devices
CONCLUSION & RECOMMENDATIONS
INSTRUCTOR’S COMMENTS
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TRAINEE’S GRADE
FOR THIS ACTIVITY
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INSTRUCTOR’S SIGNATURE
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Report Form Report Form Report Form Report Form ---- Page 4 of 4 Page 4 of 4 Page 4 of 4 Page 4 of 4
DATE: __________________
DATE: __________________
________________________
TRAINEE’S SIGNATURE
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THEORETICAL BACKGROUND
In various kinds of plastics fabrication processes, molten resin that leaves the
extruder is forced through an orifice (opening, slit) called a die. By this die
the molten resin is given its final shape appropriate for the end product.
A die used for blown film extrusion has an annular (ring-shaped) outlet
(called a lip) through which the molten resin passes. Such a die is called a
circular die. The size of a die is expressed by the lip diameter. The lip
diameter ranges from a small diameter of about 30 mm to a large diameter of
about 1,500 mm.
The Two Types of Die Lip Gap Adjustments: Figure 4.1
WORKSHOP ACTIVITY #4
Blown Film Die
Upper Die Goes that way
Tightening the bolt
Upper Die
Tightening the bolt
Upper Die Goes that way
Upper Die
A
B
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OBJECTIVES OF THE ACTIVITY
1. To learn the basic principles of die mechanisms
2. To understand the die mechanisms and how to adjust the lip gap
PROCEDURE
PART I—Die Lip Adjustment
1. Prepare the half die head available in the Workshop.
2. Examine carefully what type of die lip gap adjustment the die has.
3. Confirm the movement of the die lip. Confirm whether it is A- or B-type
lip gap adjustment.
4. When making adjustment, loosen the bolt on the other side first. Refer to
Figure 4.1:
• For A type, tightening the bolt will widen the gap.
For this type, when the die ring is screwed in, the ring is moved in a
way that pulls the ring with the bolt to widen the lip gap (see Figure
4.1).
• For B type, tightening the bolt will narrow the gap.
For this other type, when the die ring is screwed in, the ring is moved
in a way that pushes the ring with the bolt to narrow the lip gap (see
Figure 4.1).
5. Try turning the bolts of your die and observe the outer lip movement of
the die. Answer all the questions in your data sheet.
PART II—Parts of the Die
1. Properly label the parts of the die using the drawing found in your data
sheet.
WORKSHOP ACTIVITY #4—Blown Film Die
Important!
Before you adjust the gap, you should know which type of adjust-you should know which type of adjust-you should know which type of adjust-you should know which type of adjust-able die ring is used for the die able die ring is used for the die able die ring is used for the die able die ring is used for the die available. You should also under-stand that the adjustable die ring just moves horizontally as a as a as a as a
whole whole whole whole by rotating the adjusting bolt.
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DATA SHEET
PART I—Die Lip Adjustment
ACTIVITY #4—Blown Film Die
TRAINEE NAME GROUP NO.
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Report Form Report Form Report Form Report Form ---- Page 1 of 3 Page 1 of 3 Page 1 of 3 Page 1 of 3
1. Referring to the Figure 4.1, what type of die do we have in Workshop 02
Blown Film?
2. What happens when you tighten the bolt of this type?
3. In your own opinion, if you widen the die lip gap, does this makes the
corresponding blown film wall thicker?
4. Why?
PART II—Parts of the Die
AAAA----TypeTypeTypeType BBBB----TypeTypeTypeType
YESYESYESYES NONONONO
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Workbook for Blown F i lm Pract ica l Course
QUESTIONS & EXERCISES
1. It is the part of the Blown Film machine where the molten resin is forced
through its round opening slit and forms a tube.
a. screw and barrel
b. adapter
c. die
d. none of these
2. Describe briefly how the material flows as it enters the spiral and outside the
spiral.
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4. When the die is not properly centered, why is a thinner film produced from the
wider die gap and a thicker film from the narrower gap?
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WORKSHOP ACTIVITY #4—Blown Film Die
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WORKSHOP ACTIVITY #4—Blown Film Die
CONCLUSION & RECOMMENDATIONS
INSTRUCTOR’S COMMENTS
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TRAINEE’S GRADE
FOR THIS ACTIVITY
________________________
INSTRUCTOR’S SIGNATURE
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Report Form Report Form Report Form Report Form ---- Page 3 of 3 Page 3 of 3 Page 3 of 3 Page 3 of 3
DATE: __________________
DATE: __________________
________________________
TRAINEE’S SIGNATURE
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THEORETICAL BACKGROUND
Blown film air rings are used primarily to stabilize the bubble and
secondarily to cool the melt. In plastics forming, a circular manifold
distributes an even flow of cool air into a hollow tubular form passing
through the manifold.
An air ring is installed just above the die in an upward air cooling blown film
machine. The air outlet called a lip (or slit) has an annular shape that
surrounds the molten resin extruded from the die. Air is introduced into the
ring by the blower, and the air is turned into a uniform flow inside the air
ring. Then the air is blown through the lip against the molten resin for
cooling. If the flow of air blown out of the lip is not uniform, it leads to non-
uniform cooling. As a result, film thickness will be uneven. To prevent this,
the air ring is designed to ensure uniform air flow over the entire lip.
As the molten resin is cooled, it becomes “frosty,” or less clear (transparent),
and a solidification border appears. This borderline is called a frost line.
WORKSHOP ACTIVITY #5
Blown Film Air Cooling Ring
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WORKSHOP ACTIVITY #5—Blown Film Air Cooling Ring
PA
RT
S O
F A
SIN
GL
E L
IP B
LO
WN
FIL
M A
IR R
ING
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OBJECTIVES OF THE ACTIVITY
1. To know the importance of air ring to blown film extrusion
2. To understand the construction of an air ring and how to adjust it
PROCEDURE
1. Run the blown film line assigned to you by your Instructor.
2. With the supervision of your Instructor, set the parameters to produce a
30microns by 300mm lay flat width film.
3. Once the process has stabilized (as checked by your Instructor), adjust
the threaded adjusting ring of the air ring by the doing the following
trials:
• Trial 1—Turn the adjusting ring one-fourth ( ¼ ) down
• Trial 2—Turn the adjusting ring another one-fourth ( ¼ ) down
• Trial 3—Turn the adjusting ring still another one-fourth ( ¼ )
down
• Trial 4—Turn the adjusting ring one-fourth ( ¼ ) upward
• Trial 5—Turn the adjusting ring another one-fourth ( ¼ ) upward
4. Allow 5minutes intervals for each trial and ensure that the bubble is
stable each time.
5. For each trial, observe what will happen to the bubble and take note of
what happens to the height of the frost line.
6. Write all your observations on the table provided in your data sheet, and
answer all the questions.
WORKSHOP ACTIVITY #5—Blown Film Air Cooling Ring
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DATA SHEET
OBSERVATIONS
ACTIVITY #5—Blown Film Air Cooling Ring
TRAINEE NAME GROUP NO.
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Report Form Report Form Report Form Report Form ---- Page 1 of 3 Page 1 of 3 Page 1 of 3 Page 1 of 3
Trial
No.
Number of Turns
and Direction
Pressure
Reading Bubble Observations
1 ¼ turn down
2 another ¼ turn down
3 another ¼ turn down
4 ¼ turn upward
5 another ¼ turn upward
1. When the threaded adjustable ring is adjusted downwards, what happens
to the frost line height? goes up or down?
2. What type of air ring does workshop 02 blown film has,
Is it single lip or dual lip?
3. How did you know that it is a _____________lip?
4. If the inside of the air ring is dirty and causing obstruction, will you have
an even flow of air in the bubble, yes or no?
5. Does this obstruction cause uneven thickness of the film, yes or no?
goes upgoes upgoes upgoes up goes downgoes downgoes downgoes down
single lipsingle lipsingle lipsingle lip dual lipdual lipdual lipdual lip
yesyesyesyes nononono
yesyesyesyes nononono
Page 35
Workbook for Blown F i lm Pract ica l Course
QUESTIONS & EXERCISES
1. _______________________is the part of the Blown Film machine that
uniformly cools and then evenly solidifies (make solid) the molten resin
extruded from the die.
2. The blowing angle should be appropriately set depending on the type of
resin is used, the type of product being made, and other factors.
True or False?
3. In the given drawing below, the air ring is called a dual lip because it has
_______________, _________________, and ____________________.
4. In the given drawing below, which of these two air rings is used for
LLDPE and which is for HDPE?
_________ is for LDPE _________ is for HDPE
WORKSHOP ACTIVITY #5—Blown Film Air Cooling Ring
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Page 36
Workbook for Blown F i lm Pract ica l Course
WORKSHOP ACTIVITY #5—Blown Film Air Cooling Ring
CONCLUSION & RECOMMENDATIONS
INSTRUCTOR’S COMMENTS
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
TRAINEE’S GRADE
FOR THIS ACTIVITY
________________________
INSTRUCTOR’S SIGNATURE
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Report Form Report Form Report Form Report Form ---- Page 3 of 3 Page 3 of 3 Page 3 of 3 Page 3 of 3
DATE: __________________
DATE: __________________
________________________
TRAINEE’S SIGNATURE
Page 37
Workbook for Blown F i lm Pract ica l Course
THEORETICAL BACKGROUND
The width (lay-flat width) and thickness of the film to be made are always
specified in blown film extrusion. The operators need to set the width and
thickness to the specified values correctly and maintain them within the
target level during the processing. Once the process is started, first adjust the
lay-flat width to the specified value. The screw rotation speed shall be set to
the predetermined speed and the amount of air to be introduced into the
bubble shall be adjusted. Then the film thickness shall be next step.
In blown film extrusion, there are various kinds of operation requirements
that directly influence on the shape of the bubble. Examples of these
requirements are extruder take-off speed and the amount of air that enters
the bubble. In particular, they affect the bubble size and vary the film
thickness and lay-flat width.
WORKSHOP ACTIVITY #6
Blown Film Width and Thickness
D
Rolled Film
W t
tttt = thickness of film
W= width of film
Page 38
Workbook for Blown F i lm Pract ica l Course
OBJECTIVES OF THE ACTIVITY
1. To learn how to adjust the width and thickness of a blown film bubble
PROCEDURE
1. Run the blown film line assigned to you by your Instructor.
2. With the supervision of your Instructor, set the parameters to produce a
30microns by 300mm lay flat width film.
3. Once the process has stabilized (as checked by your Instructor), record
the take-off speed and winder tension on the table in your data sheet
under Trial 0.
4. Then do the following trials, each time observing what will happen to the
film thickness and film width. Record the new thickness and width on
the table in your data sheet.
5. Answer all questions relating to each trial.
WORKSHOP ACTIVITY #6—Blown Film Width and Thickness
TRIAL No. ACTION
Trial No.1 Increase the take-off speed by 2m/min. Slightly add
tension on winder to adjust the film tension.
Trial No.2 Open the air valve and let air enter the bubble for at
least 2 minutes. Wait for another 3minutes. Let your
instructor stabilize the bubble. Observe what will hap-
pen to the bubble.
Trial No.3 Increase the take-off speed by 2m/min. Slightly add
tension to winder to adjust the film tension. Observe
again what will happen to the thickness of the film.
Trial No.4 Open the air valve and let air enter the bubble for at
least 2minutes. Wait for another 3minutes. Try to sta-
bilize the bubble by yourself while the instructor
guides you. Observe what will happen to the bubble.
Page 39
DATA SHEET
DATA & OBSERVATIONS
ACTIVITY #6—Blown Film Width and Thickness
TRAINEE NAME GROUP NO.
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Report Form Report Form Report Form Report Form ---- Page 1 of 3 Page 1 of 3 Page 1 of 3 Page 1 of 3
Trial
#
Take-off Speed,
m/min
Film Thickness,
µm
Winder
Tension, N Width, mm
0 30 microns 300mm
1
2
3
4
1. When the haul-off speed is increased in Trial No.1, did the thickness also
increased, yes or no?
2. When you add some more compressed air in Trial No.2, did the width of
the film increased, yes or no?
3. What happened to the bubble when you increased again the haul-off
speed in Trial No.3?
4. What happened to the width when you add more compressed air in Trial
No.4?
yesyesyesyes nononono
yesyesyesyes nononono
Page 40
Workbook for Blown F i lm Pract ica l Course
QUESTIONS & EXERCISES
A. Choose the correct answer.
1. What happens to the lay-flat width if more air is introduced into the
bubble?
(a.) no change (c.) increase
(b.) decrease (d.) none of the above
2. If the extruder screw speed is increased, what happens to the film
average thickness?
(a.) no change (c.) increase
(b.) decrease (d.) none of the above
3. What happens to the film average thickness if the take-off speed
increased?
(a.) no change (c.) increase
(b.) decrease (d.) none of the above
4. If the extruder screw speed is decreased, what happens to the film
average thickness?
(a.) no change (c.) increase
(b.) decrease (d.) none of the above
5. What happens to the film average thickness if the take-off speed
decreased?
(a.) no change (c.) increase
(b.) decrease (d.) none of the above
WORKSHOP ACTIVITY #6—Blown Film Width and Thickness
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Report Form Report Form Report Form Report Form ---- Page 2 of 3 Page 2 of 3 Page 2 of 3 Page 2 of 3
B. How do you decrease the width of lay flat tube?
C. How do you increase the thickness of the film?
Page 41
Workbook for Blown F i lm Pract ica l Course
WORKSHOP ACTIVITY #6—Blown Film Width and Thickness
CONCLUSION & RECOMMENDATIONS
INSTRUCTOR’S COMMENTS
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
TRAINEE’S GRADE
FOR THIS ACTIVITY
________________________
INSTRUCTOR’S SIGNATURE
� Cut R
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Report Form Report Form Report Form Report Form ---- Page 3 of 3 Page 3 of 3 Page 3 of 3 Page 3 of 3
DATE: __________________
DATE: __________________
________________________
TRAINEE’S SIGNATURE
Page 42
Workbook for Blown F i lm Pract ica l Course
THEORETICAL BACKGROUND
• If a corona discharge is generated in air, ozone (O3) is created from the
oxygen (O2) in the air. Ozone is a powerful oxidizing gas. This ozone
oxidizes the surface of plastics film to make it easier for the ink to stick
to the film. This method of treating a plastics film surface is called
corona discharge treatment.
• The corona discharge treatment equipment is made up of a high
frequency generator, an electrode, and a treater roll.
• The wetting tension of PE film and PP film that have not been surface
treated is around 30 to 35 mN/m. The tension appropriate for printing on
these kinds of film is said to be normally around 40 to 45 mN/m. So,
what is wetting tension?
• Treated film surface can be checked by measuring the wetting tension of
the film surface. The wetting tension is an indication of the wettability of
a solid surface.
• Normally, wetting tension of a film that is not surface treated is around
30 to 35 mN/m compared to a treated film which has 40 to 45mN/m.
WORKSHOP ACTIVITY #7
Corona Treatment
Page 43
Workbook for Blown F i lm Pract ica l Course
Theoretical background … continued
• This activity will explain how wettability works with the polyethylene
film. Below is the schematic drawing of a corona discharge machine
(corona treater).
WETTING TENSION MEASUREMENT
• The approximate wetting tension of a film can measured by using wetting
ink supplied by Polyrema. The ink is used to write on the surface of the
film and the ink value where there is no “run-off” corresponds to the wet-
ting tension of the film.
WORKSHOP ACTIVITY #7—Corona Treatment
Page 44
Workbook for Blown F i lm Pract ica l Course
OBJECTIVES OF THE ACTIVITY
1. To know the importance of corona treater in blown film printing
2. To know how corona treater affects the film quality during secondary
processes
PROCEDURE
1. Run a blown film line.
2. Produce a 30microns by 300mm lay flat width LLDPE film. Make sure
film passes the corona discharge machine.
3. Once the blown film is stabilized and checked by your instructor, get
film samples without the corona treatment, and then with corona
treatments at different corona treatment settings.
4. Properly label each sample.
5. Check the wettability of each sample using the wetting ink supplied by
POLYREMA.
6. Follow the following settings for the trials:
7. Your Instructor will demonstrate how the wetting ink is used. Start from
the lowest wetting ink value to the highest, and record the trial results in
your data sheet for each of the sample.
8. Record whether “run-off” occurs or not when the sample is tested with
each wetting ink values.
9. Answer all questions regarding your observations.
WORKSHOP ACTIVITY #7—Corona Treatment
TRIAL NO. CORONA TREATER SETTING
1 0% treater setting (no corona treatment)
2 40% treater setting
3 70% treater setting
4 90% treater setting
Page 45
DATA SHEET
RUN-OFF OBSERVATIONS
ACTIVITY #7—Corona Treatment
TRAINEE NAME GROUP NO.
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Report Form Report Form Report Form Report Form ---- Page 1 of 3 Page 1 of 3 Page 1 of 3 Page 1 of 3
Trial
No.
Did the line “run-off”?
Wetting Ink 42 Wetting Ink 44 Wetting Ink 46
1 0%
2 40%
3 70%
4 90%
Treater
Setting
yesyesyesyes nononono
yesyesyesyes nononono
yesyesyesyes nononono
yesyesyesyes nononono
yesyesyesyes nononono
yesyesyesyes nononono
yesyesyesyes nononono
yesyesyesyes nononono
yesyesyesyes nononono
yesyesyesyes nononono
yesyesyesyes nononono
yesyesyesyes nononono
1. What happened to the wetting ink applied on the first film sample? Did
the liquid line run-off? What does this broken line shows?
2. For the 2nd sample (Trial #2) how did the wetting ink behave in the
film? Did it run-off too? What does this mean?
4. For the 3rd sample (Trial #3), do you think the value of the corona dis-
charge is very good for printing? Why?
4. For the 4th sample (Trial #4), do you think the value of the corona dis-
charge is very good for printing? Why?
5. What about sealing this film from Trial #4, do you think that the seal
will be very good?
Page 46
Workbook for Blown F i lm Pract ica l Course
QUESTIONS & EXERCISES
1. The method of treating film surface is called
a. gusseting
b. sealing
c. corona discharge treatment.
2. What is the normal surface tension for untreated PE films?
a. 20-30 mN/mtr
b. 30-35 mN/mtr
c. 40-45mN/mtr
3. Using the wetting liquid application and marking a line on the film, if
the line breaks-off or runs-off this means the film is
a. untreated
b. treated
4. Write down the three major parts of a corona discharge machine.
a. ______________________________
b. ______________________________
c. ______________________________
WORKSHOP ACTIVITY #7—Corona Treatment
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Report Form Report Form Report Form Report Form ---- Page 2 of 3 Page 2 of 3 Page 2 of 3 Page 2 of 3
Page 47
Workbook for Blown F i lm Pract ica l Course
WORKSHOP ACTIVITY #7—Corona Treatment
CONCLUSION & RECOMMENDATIONS
INSTRUCTOR’S COMMENTS
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
TRAINEE’S GRADE
FOR THIS ACTIVITY
________________________
INSTRUCTOR’S SIGNATURE
� Cut R
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Instru
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Report Form Report Form Report Form Report Form ---- Page 3 of 3 Page 3 of 3 Page 3 of 3 Page 3 of 3
DATE: __________________
DATE: __________________
________________________
TRAINEE’S SIGNATURE
Page 48
Workbook for Blown F i lm Pract ica l Course
THEORETICAL BACKGROUND
Rotary Printing—is a printing technique in which the impressions are
carved on a rubber plate and stuck on a cylinder, or carved on the cylinder
itself, so that the printing can be done on long continuous rolls of paper,
cardboard, plastic, or a large number of other substrate.
Often Used Printing Processes for Blown Film:
• Flexographic Printing
• Rotogravure Printing
FLEXOGRAPHIC PRINTING
Flexographic printing has an advantage over rotogravure in that it can use a
wider range of inks, water-based rather than oil-based inks, and is good at
printing on a variety of different materials like plastics, foils, acetate films,
brown paper, and other materials used in packaging. Typical products
printed using flexography includes flexible packaging, including retail and
shopping bags, food and hygiene bag, etc.
A flexographic print is made by creating a positive mirrored master of the
required image as a 3D relief in a rubber or polymer material. Flexographic
plates can be created with analog and digital plate-making processes. The
image areas are raised above the non-image areas on the rubber or polymer
plate. The ink is transferred from the ink roll which is partially immerged in
the ink tank. Then it transfers to the anilox roll (or meter roll) whose texture
holds a specific amount of ink since it is covered with thousands of small
wells or cups that enable it to meter ink to the printing plate in a uniform
thickness evenly and quickly.
WORKSHOP ACTIVITY #8
Flexographic Printing
Page 49
Workbook for Blown F i lm Pract ica l Course
Theoretical Background … continued
PARTS OF A FLEXOGRAPHIC PRINTER
WORKSHOP ACTIVITY #8—Flexographic Printing
Impression
Cylinder
Plate
Cylinder
Anilox
Roller
Fountain
Roller
Page 50
Workbook for Blown F i lm Pract ica l Course
OBJECTIVES OF THE ACTIVITY
1. To learn the basic operation of a flexographic printing machine for blown
film
2. To know the parts and functions of a flexographic printing machine
PROCEDURE
1. Pre-heat a blown film machine that has in-line flexographic printing
machine.
2. Prepare a rubber cliché for flexographic film print run and the schematic
drawing of a flexographic printing machine.
3. Mount the rubber plate on the plate cylinder. Make sure of the alignment
by following the groove etched on the cylinder surface. See the drawing.
4. Move gear 1 (for Roll 1) towards gear 2 (for Roll 2) and mesh their teeth
by about 3mm by turning knob C clockwise.
5. Pour ink in the ink pan. Ink level at least a few millimetre of the fountain
roller lower portion.
6. Switch-on the printing drive.
WORKSHOP ACTIVITY #8—Flexographic Printing
Page 51
Workbook for Blown F i lm Pract ica l Course
Procedure … continued
7. Move the fountain roller 3 towards the anilox roller 4 by turning knob A
clockwise. Observe the ink between these rollers. Putting more pressure
between roller 3 and 4 means reducing the ink on the anilox concave
surface and lesser ink will be transferred to the rubber plate.
8. Move carriage of 3 & 4 towards 1 by turning the knob B until ink from
the anilox is transferred to the rubber plate.
9. Activate the pneumatic cylinder for the carriage D and observe the
printing on the film.
10. If print does not appear yet, turn knob C slower clockwise until print
appears.
10. When you feel you have attained the best print, take a sample printed
film and cut the printed portion.
11. Attach the printed film in your data sheet.
WORKSHOP ACTIVITY #8—Flexographic Printing
Note:
Each of the specific knobs has to be adjusted to attain
a good ink tone balance and better quality print.
Page 52
DATA SHEET ACTIVITY #8—Flexographic Printing
TRAINEE NAME GROUP NO.
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Report Form Report Form Report Form Report Form ---- Page 1 of 3 Page 1 of 3 Page 1 of 3 Page 1 of 3
ATTACH ATTACH ATTACH ATTACH
YOUR YOUR YOUR YOUR
PRINTED FILM PRINTED FILM PRINTED FILM PRINTED FILM
HERE!HERE!HERE!HERE!
FLEXOGRAPHIC PRINTED FILM
1. When you pressed the fountain roller with the anilox roller, does this
mean we are reducing the ink being transferred to the printing plate?
2. What is the function of knob A?
3. When you pressed carriage 3 & 4 to roller 1, did the image appear on the
film?
4. What is the function of knob B?
YESYESYESYES NONONONO
YESYESYESYES NONONONO
Page 53
Workbook for Blown F i lm Pract ica l Course
QUESTIONS & EXERCISES
Choose correct answer.
1. Which type of printing is done on polyethylene blown film?
a. Screen printing
b. Rotogravure printing
c. Laser printing
d. Flexographic printing
2. Which process is done before printing the polyethylene film?
a. Heat treatment
b. Chemical treatment
c. Corona treatment
d. Laser treatment
3. Why do plastics surfaces require pre-treatment for printing?
a. To make plastic thicker
b. To make plastic stronger
c. To make plastic more decorative
d. To make strong ink bonding on surface
4. What type of chemical (thinner) is used to make printing ink thin and
dryable during flexographic printing?
a. Acid
b. Kerosene
c. Petrol
d. Alcohol
5. What is that rubber-like material we use in flexographic in making a
printing plate?
a. PVC
b. Photopolymer
c. Polyethylene
d. None of these
WORKSHOP ACTIVITY #8—Flexographic Printing
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Report Form Report Form Report Form Report Form ---- Page 2 of 3 Page 2 of 3 Page 2 of 3 Page 2 of 3
Page 54
Workbook for Blown F i lm Pract ica l Course
WORKSHOP ACTIVITY #8—Flexographic Printing
CONCLUSION & RECOMMENDATIONS
INSTRUCTOR’S COMMENTS
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
TRAINEE’S GRADE
FOR THIS ACTIVITY
________________________
INSTRUCTOR’S SIGNATURE
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Report Form Report Form Report Form Report Form ---- Page 3 of 3 Page 3 of 3 Page 3 of 3 Page 3 of 3
DATE: __________________
DATE: __________________
________________________
TRAINEE’S SIGNATURE
Page 55
Workbook for Blown F i lm Pract ica l Course
THEORETICAL BACKGROUND
Every day, our lives are touched by plastics packaging
products. Polyethylene bag is one of the best applications of packaging
products.
Polyethylene bag is used for various purposes like shopping, grocery,
laundry, food packaging, garments, textiles, agriculture, industrial products
packaging, garbage, waste management, etc.
There are mainly two types of methods to make polyethylene bags.
• Bottom sealed bag
• Top and bottom sealed bag
WORKSHOP ACTIVITY #9
Bag Making
Examples of Bottom Sealed Bag Products
Examples of Top and Bottom Sealed Bag Products
Page 56
Workbook for Blown F i lm Pract ica l Course
Theoretical Background … continued
WORKSHOP ACTIVITY #9—Bag Making
BOTTOM SEALING DIAGRAM
BOTTOM SEALING PROCESS FLOW
Page 57
Workbook for Blown F i lm Pract ica l Course
Theoretical Background … continued
WORKSHOP ACTIVITY #9—Bag Making
DOUBLE SEALING DIAGRAM
DOUBLE SEALING PROCESS FLOW
Page 58
Workbook for Blown F i lm Pract ica l Course
Theoretical Background … continued
WORKSHOP ACTIVITY #9—Bag Making
TYPES OF BAGS
EXAMPLES OF BAG MAKING PRODUCTS
Page 59
Workbook for Blown F i lm Pract ica l Course
OBJECTIVES OF THE ACTIVITY
1. To learn making polyethylene poly bags for various applications
2. To learn the proper adjustment of sealing temperature to come up
with acceptable product
3. To determine the effect of product type on the production output rate
PROCEDURE
PART I—Sealing Temperature for LDPE and HDPE Bags
1. Familiarize yourself with the bag making machine assigned to you by
your Instructor.
2. Determine the effect of changing the sealing temperature to final product
by changing the temperature setting.
3. Make 5 trials with 5 different temperatures using LDPE film.
4. Each time you change the temperature, record the bag cutting speed and
inspect the product if acceptable or not.
5. Record all your data in your data sheet.
6. Do the same for HDPE film.
PART II—Production Output
1. Run five (5) different bag products (different sizes and materials) at
constant speed using the machine assigned to you by your Instructor.
2. For each run, record the bag cutting speed and the production output
(bags/min).
3. Record all your data in your data sheet.
WORKSHOP ACTIVITY #9—Bag Making
Page 60
DATA SHEET
PART I—Sealing Temperature for LDPE and HDPE Bags
SEALING TEMPERATURE FOR LDPE BAGS
ACTIVITY #9—Bag Making
TRAINEE NAME GROUP NO.
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Report Form Report Form Report Form Report Form ---- Page 1 of 4 Page 1 of 4 Page 1 of 4 Page 1 of 4
Trial No.
Sealing Temperature
Bag Cutting Speed Sealing Quality
1
2
3
4
5
acceptedacceptedacceptedaccepted rejectedrejectedrejectedrejected
acceptedacceptedacceptedaccepted rejectedrejectedrejectedrejected
acceptedacceptedacceptedaccepted rejectedrejectedrejectedrejected
acceptedacceptedacceptedaccepted rejectedrejectedrejectedrejected
acceptedacceptedacceptedaccepted rejectedrejectedrejectedrejected
Trial No.
Sealing Temperature
Bag Cutting Speed Sealing Quality
1
2
3
4
5
acceptedacceptedacceptedaccepted rejectedrejectedrejectedrejected
acceptedacceptedacceptedaccepted rejectedrejectedrejectedrejected
acceptedacceptedacceptedaccepted rejectedrejectedrejectedrejected
acceptedacceptedacceptedaccepted rejectedrejectedrejectedrejected
acceptedacceptedacceptedaccepted rejectedrejectedrejectedrejected
SEALING TEMPERATURE FOR HDPE BAGS
Page 61
DATA SHEET
PART II—Production Output
ACTIVITY #9—Bag Making
TRAINEE NAME GROUP NO.
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Report Form Report Form Report Form Report Form ---- Page 2 of 4 Page 2 of 4 Page 2 of 4 Page 2 of 4
Trial Trial Trial Trial No.No.No.No.
MaterialMaterialMaterialMaterial Bag Size Bag Size Bag Size Bag Size (length)(length)(length)(length)
Bag Cutting Bag Cutting Bag Cutting Bag Cutting SpeedSpeedSpeedSpeed
Product RateProduct RateProduct RateProduct Rate (bags/min)(bags/min)(bags/min)(bags/min)
1111
2222
3333
4444
5555
Page 62
Workbook for Blown F i lm Pract ica l Course
QUESTIONS & EXERCISES
1. Which of these three are the bottom seal and the top & bottom seal bag?
____________ is the bottom seal bag.
____________ is the top & bottom seal bag.
2. In the given drawing, why did they call this a top and bottom sealing?
Explain briefly.
___________________________
___________________________
___________________________
___________________________
___________________________
___________________________
___________________________
___________________________
3. Give at least two applications of this top & bottom sealed bags.
Clue: bags that can be found in a market.
Applications: _______________________________
_______________________________
WORKSHOP ACTIVITY #9—Bag Making
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Report Form Report Form Report Form Report Form ---- Page 3 of 4 Page 3 of 4 Page 3 of 4 Page 3 of 4
Page 63
Workbook for Blown F i lm Pract ica l Course
CONCLUSION & RECOMMENDATIONS
INSTRUCTOR’S COMMENTS
WORKSHOP ACTIVITY #9—Bag Making
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
TRAINEE’S GRADE
FOR THIS ACTIVITY
________________________
INSTRUCTOR’S SIGNATURE
� Cut R
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Report Form Report Form Report Form Report Form ---- Page 4 of 4 Page 4 of 4 Page 4 of 4 Page 4 of 4
DATE: __________________
DATE: __________________
________________________
TRAINEE’S SIGNATURE
Page 64
Workbook for Blown F i lm Pract ica l Course
THEORETICAL BACKGROUND
Recycling Procedure for Polyethylene Film
WORKSHOP ACTIVITY #10
Polyethylene Film Recycling
1. Start machine heat-up. Set the temperature according to the required set-ting for the type of material to be recycled.
2. Check the cooling water supply in/out and ensure that it is ON.
3. Set the shredder temperature at 60°C initially, then increase up to 100°C, as temperature increases after shredder start.
4. Start feeding scraps in shredder drum, ensuring that no metal or foreign matter is present. Set shredder speed to 45rpm maximum. The load must not exceed 22amps.
Scrap MaterialScrap MaterialScrap MaterialScrap Material LDPELDPELDPELDPE LLDPELLDPELLDPELLDPE HDPEHDPEHDPEHDPE
Temperature Settings Temperature Settings Temperature Settings Temperature Settings ºC 180 180 180 180 ---- 200 200 200 200 190 190 190 190 ---- 210 210 210 210 195 195 195 195 ---- 220 220 220 220
OUTOUTOUTOUT ININININ
Shredder Shredder Shredder Shredder TemperatureTemperatureTemperatureTemperature
Speed Speed Speed Speed ControlControlControlControl
Page 65
Workbook for Blown F i lm Pract ica l Course
Theoretical Background … continued
WORKSHOP ACTIVITY #10—Polyethylene Film Recycling
5. After reaching to the set barrel temperature, clean the screen or change if required and check breaker plate also.
6. Connect conveyor to the shredder and after ensuring metal detector is functioning, put conveyor in auto mode. Also connect the cooling water chamber to die-face cutter and tighten the screw properly.
7. When shedder drum temperature reaches 90°C, and barrel temperature, 185°C to 220°C, start oil pump, water pump, vibrator, blowers, and cen-trifuge.
Screen CleaningScreen CleaningScreen CleaningScreen Cleaning Screen Change ControlsScreen Change ControlsScreen Change ControlsScreen Change Controls
Up/DownUp/DownUp/DownUp/Down
Page 66
Workbook for Blown F i lm Pract ica l Course
Theoretical Background … continued
WORKSHOP ACTIVITY #10—Polyethylene Film Recycling
8. Start die face cutter and set speed to 1500 initially. Increase die face cut-ter speed in order to maintain pellet size of 2mm. Monitor the size of pellets and adjust the speed when needed.
9. Start extruder at 25 rpm initially, then increase gradually up to 45 rpm. Observe the ampere meter to control motor load (max 40 amps).
10. Observe smooth operation.
Variable Speed Variable Speed Variable Speed Variable Speed
ControlControlControlControl
Extruder Speed Extruder Speed Extruder Speed Extruder Speed
SettingSettingSettingSetting
Extruder Amps Extruder Amps Extruder Amps Extruder Amps
MeterMeterMeterMeter
Page 67
Workbook for Blown F i lm Pract ica l Course
OBJECTIVES OF THE ACTIVITY
1. To learn recycling machine operation
PROCEDURE
.Observe the recycling machine start up procedure and write start-up steps in
the given work sheet.(worksheet#9.1)
Write your observations and fill data in process parameter sheet
( work sheet #9.2)
PART I—Recycling Machine Startup Procedure
1. Observe the startup procedure for the recycling machine as performed by
your Instructor.
2. In your data sheet, write down the steps on the table provided.
PART II—Recycling Machine Process Parameters
1. Observe the actual recycling run for different plastics materials.
2. Use the Process Monitoring Sheet provided in your data sheet to record
your data on the actual machine run.
WORKSHOP ACTIVITY #10—Polyethylene Film Recycling
Page 68
DATA SHEET
PART I—Recycling Machine Startup Procedure
ACTIVITY #10—Polyethylene Film Recycling
TRAINEE NAME GROUP NO.
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eport F
orm
and Submit to
Instru
ctor
Report Form Report Form Report Form Report Form ---- Page 1 of 4 Page 1 of 4 Page 1 of 4 Page 1 of 4
START PROCEDURE STEP OBSERVED
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Page 69
DATA SHEET
PART II—Recycling Machine Process Parameters
ACTIVITY #10—Polyethylene Film Recycling
TRAINEE NAME GROUP NO.
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Report Form Report Form Report Form Report Form ---- Page 2 of 4 Page 2 of 4 Page 2 of 4 Page 2 of 4
SCRAP MATERIALS
LLDPE LDPE HDPE
Barre
l Temperature
Cylinder 1
Cylinder 2
Cylinder 3
Cylinder 4
Joint
Filter
Die
Shredder Tempera-ture
Shredder Speed
Shredder Motor Load (Amps)
Extruder Speed
Extruder Motor Load (Amps)
Cutting Speed
PROCESS PARAMETERS
Process Monitoring Sheet—Recycling Machine
Page 70
Workbook for Blown F i lm Pract ica l Course
QUESTIONS & EXERCISES
Choose correct answer.
1. What are the advantages of recycling plastics?
a. By recycling we can make more plastics
b. Making plastics cheaper
c. Recycling machinery business can grow up
d. Reduce the consumption of energy and less pollution
2. What is the “STANDARD MARKING CODE” for HDPE?
3. Why are “STANDARD MARKING CODES” developed?
a. To identify the strength of each plastics
b. To identify the cost of each plastics
c. To understand the number of times the plastics can be recycled
d. To help consumers identify and sort the main types of plastic
4. What is the consumption of plastics in packaging industries?
5. What is the importance of oil circulation in the gear box of the extruder?
a. To provide lubrication and reduce friction
b. To increase the speed of an extruder
c. To save power consumption of machine
d. For cooling the gear box
6. Select the barrel temperature (ºC ) range for HDPE scrap material
a. 195, 200, 205, 210, 215, 220, 225
b. 165, 170, 175, 180, 185, 190, 195
c. 175, 180, 185, 190, 195, 200, 205
d. 170, 180, 180, 187, 190, 190, 195
7. Why is a metal detector provided on the conveyor?
a. To sense metal and allow it to go into the shredder and extruder
b. To sense metal and save the extruder from damage
c. To measure the weight of plastics fed into the shredder
d. To avoid dust to go inside
8. How do you increase or decrease the size of plastics pallets?
a. By adding or reducing material to the shredder
b. By increasing or decreasing the barrel temperature
c. By increasing or decreasing the speed of die face cutter
d. By increasing or decreasing cooling temperature
WORKSHOP ACTIVITY #10—Polyethylene Film Recycling
� Cut R
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Report Form Report Form Report Form Report Form ---- Page 3 of 4 Page 3 of 4 Page 3 of 4 Page 3 of 4
a. c. d. b.
a. 35% c. 30% d. 15% b. 25%
Page 71
Workbook for Blown F i lm Pract ica l Course
CONCLUSION & RECOMMENDATIONS
INSTRUCTOR’S COMMENTS
WORKSHOP ACTIVITY #10—Polyethylene Film Recycling
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
TRAINEE’S GRADE
FOR THIS ACTIVITY
________________________
INSTRUCTOR’S SIGNATURE
� Cut R
eport F
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and Submit to
Instru
ctor
Report Form Report Form Report Form Report Form ---- Page 4 of 4 Page 4 of 4 Page 4 of 4 Page 4 of 4
DATE: __________________
DATE: __________________
________________________
TRAINEE’S SIGNATURE
Page 72
Workbook for Blown F i lm Pract ica l Course
PRACTICE YOUR OPERATIONS SKILLS!
1. Now that you have learned the basics of the Blown Film Extrusion
process, it is time to practice your skills in running the plant and
producing acceptable products.
2. Strictly follow the Standard Operating Procedures (SOP) for each
plant operations that you are going to perform.
3. Use the worksheet tables and forms in the next pages to record your
data.
4. After each practice operations, write your general comment on the
how well you have done your practice in the Conclusion &
Recommendations page.
5. Write down what you have done well, and what you should improve
for the next practice.
6. Enjoy practicing while being safe!
WORKSHOP ACTIVITY #11-13
Practice Plant Operations
Page 73
Workbook for Blown F i lm Pract ica l Course
STANDARD OPERATING PROCEDURES (SOP)
PART A—SOP for Plant Run Preparations
1. Read and understand carefully the JOB INSTRUCTIONS given by
your instructor. (See Job Instruction #1).
2. Switch on main power and pre-heat the blown film machine
according to the temperature listed in the Job Instruction.
3. Check the condition of the following:
• Chilled water for barrel and reduction gear cooling (optional).
• Air supply for downstream equipments like nip rolls, winder and
pressure roll.
4. Prepare the materials to be used according to the Job Instruction.
5. Prepare the following tools and equipments:
6. Prepare bobbins according to the width of the roll to be produced.
7. Set the bobbin to the shafts of the winder and wrap around adhesive
tape with the sticky surface exposed. Two turns are enough just to
stick the film during change roll. Have at least five bobbins for
replacements during roll change.
8. Prepare the guide twine to the web path from the die to winder.
9. Fill the hopper with the required materials.
10. Change the screen in the screen changer if necessary.
WORKSHOP ACTIVITY #11-13—Practice Plant Operations
• Dial thickness gauge
• Tape measure
• Cutting knife for film
• Silicon spray
• Cotton rags for die cleaning
• Guide twine or flat rope
• Allen wrench for die adjust-
ment
• Cotton Gloves
• Brass or copper spatula
• Scouring paste
• Scouring pad
Page 74
Workbook for Blown F i lm Pract ica l Course
Standard Operating Procedures … continued
11. Check the following blown film major parts’ conditions:
• Sizing basket — up and down movement
• Haul-off unit — roll rotation and air pressure and functions
• Collapsing device — functional adjustments
• Corona treater — if flexo printing will run
• Printing unit — functional adjustments and rolls rotations
• Winder — air pressure required for pressure roll and test for roll
change
11. Wait for 1.5 hours till the “ready” indicator light lights up and verify
again the temperature settings if the actual display temperatures
correspond to the set temperatures. If yes, machine is ready to run. If
not, check settings. If actual temperature is low, extend preheating
time.
PART B—SOP Startup
1. Open the shutter of the hopper.
2. Switch-on the main motor and adjust the screw rpm to 10.
3. Caution: Avoid facing the die during this stage. Melt material may
spurt-out.
4. Remove the initial extruded melt. This contains air trap in a material
that should be removed.
5. Increase screw speed to 30 rpm and remove the molten materials in
the die. Wait until the high melt pressure drops.
6. Do item 5 for 50, 75, and 100 rpm and back to 0.
7. Clean the die and the die lip using scouring pad and scouring paste.
8. Check die gap alignment. Align if off-centered by loosening and
tightening centering screws. Use Allen wrench for adjusting the
screws.
WORKSHOP ACTIVITY #11-13—Practice Plant Operations
Page 75
Workbook for Blown F i lm Pract ica l Course
Standard Operating Procedures … continued
9. Open the blower damper at 30 degrees. Minimal air blown at the
film for initial start.
10. Open compressed air supply for inflating the bubble at minimum
only.
11. Make a loop on the film guide twine and have it ready.
12. Switch-on again the main motor and set the screw speed to 25 rpm.
13. Switch-on the haul-off nip and set the nip roll speed to 6-8 rpm.
14. As the melt comes out let it cool to solidify and tie the film guide
twine loop on that cooled lump.
15. Pull gently the melt as it continue forming into a bubble.
16. After the solid lump passes between the nip rolls, close the nip roll
and let it do the pulling of the bubble.
17. Temporarily closed the compressed air.
18. Just pull the flat tube gently till it reaches the printing unit.
19. Using the cutting knife, cut diagonally the film to make a pointed
end.
20. Insert this pointed end between the plate and impression roller of the
printer.
21. Pass the film between the open pressure roll and winder roll.
22. Close the pressure roll pinching the film.
23. Immediately, start the winder. Set minimum winding tension.
24. Insert the film in between the rotating winder roller and bobbin with
caution and start winding the film.
25. Increase screw rpm gradually to the target rpm. (See Job Instruction.)
26. Increase bubble diameter to its required lay-flat tube width. (See Job
Instruction.)
27. Increase nip roll speed according to the required film thickness. (See
Job Instruction.)
28. Switch-on corona treater if printing unit will run.
WORKSHOP ACTIVITY #11-13—Practice Plant Operations
Page 76
Workbook for Blown F i lm Pract ica l Course
Standard Operating Procedures … continued
PART C—SOP for Shutdown
1. Close the shutter of the hopper.
2. Switch-off corona treater if printing unit is running.
3. Wait till the bubble starts to rattle. It is better to have a little material
inside the barrel and die to seal-off the barrel form air getting inside.
4. Gradually bring down the screw speed to 0 rpm.
5. Switch-off the main motor.
6. Bring down nip roll speed to 0 and switch-off.
7. Open the nip roll.
8. Bring down winder speed to 0 and switch-off.
9. Open the pressure roll.
10. Close the chilled water supply valve.
11. Start lowering the temperature for 30 minutes.
12. Switch-off the main power.
13. Bring good rolls to the bag making area. Record the total roll weight
produced in the Job Instruction.
14. Bring all scrap to the recycling area. Record the total weight of the
scrap in the Job Instruction.
15. Return all tools and equipment to their proper places.
16. Fill-up all the information needed in the Job Instruction.
17. Submit the Job Instruction to your instructor.
WORKSHOP ACTIVITY #11-13—Practice Plant Operations
Page 77
DATA SHEET
BLOWN FILM EXTRUSION PRODUCTION REPORT
ACTIVITY #11—Practice Plant Operations (LDPE)
TRAINEE NAME GROUP NO.
� Cut R
eport F
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and Submit to
Instru
ctor
Report Form Report Form Report Form Report Form ---- Page 1 of 4 Page 1 of 4 Page 1 of 4 Page 1 of 4
No. Type Resin Name / Grade Blending Ratio (%)
1
2
Material Specifications
Machine Running Condition Monitoring
1. 2. 3.
Actu
al T
emperature ( oC
)
Heater Zone 1.1
Heater Zone 1.2
Heater Zone 1.3
Heater Zone 2.1
Heater Zone 2.2
Heater Zone 3.1
Heater Zone 3.2
Heater Zone 3.3
Heater Zone 3.4
Heater Zone 4.1
MT
Extruder Screw Speed (rpm)
Extruder Melt Pressure (bar)
Air Ring Pressure (KPa)
Temperature (oC)
Haul-off Speed (mpm)
Corona Treater Power (%)
Printing Unit Motor Load (%)
Winder Tension (N)
Lay-on Pressure (bar)
Contact Pressure (bar)
Lot Number 4.
5.
Machine No.
Date:
Product Description:
Page 78
DATA SHEET
BLOWN FILM EXTRUSION PRODUCTION REPORT … continued
ACTIVITY #11—Practice Plant Operations (LDPE)
TRAINEE NAME GROUP NO.
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Report Form Report Form Report Form Report Form ---- Page 2 of 4 Page 2 of 4 Page 2 of 4 Page 2 of 4
Output Monitoring
Quality Check Monitoring
Roll Number
Thick
ness P
rofile
(µm)
Measuring Point 1
Measuring Point 2
Measuring Point 3
Measuring Point 4
Measuring Point 5
Measuring Point 6
Measuring Point 7
Measuring Point 8
Average Thickness (µm)
Lay Flat Width (mm)
Gusseted LFW (mm)
Left Gusset Width (mm)
Right Gusset Width (mm)
Treating Level (OK/NOK)
Tape Test (OK/NOK)
Print Centering (OK/NOK)
Print Repeat Length (mm)
Clarity (OK/NOK)
Color (OK/NOK)
Defects (W/WO)
Roll Disposition
(Pass / Reject / On-Hold)
Lot Number 1. 2. 3. 4. 5.
Dismount Time
Roll Number
Length (m)
Weight (kg)
Total Scrap Weight (kg)
Page 79
Workbook for Blown F i lm Pract ica l Course
QUESTIONS & EXERCISES
1. If you want to raise the frost line height, what part of the machine are
you going to adjust?
a. winder tension
b. the haul-off
c. Air adjusting ring
2. If you want to decrease the film thickness, what control are you going
to adjust?
a. haul-off speed
b. winder speed
c. main motor speed
3. How are you going to adjust the speed in question #2?
a. increase speed
b. decrease speed
4. If you want to reduce the lay-flat width, what are you going to do
with the bubble?
a. increase air inside
b. decrease air inside
5. How are you going to increase or decrease the air inside the bubble?
Describe in your own words.
______________________________________________________
______________________________________________________
6. Is it necessary to use a film guide twine during start-up? Why?
______________________________________________________
______________________________________________________
7. Give at least 3 important speed adjusting controls of the blown film
control panel.
_________________________________________________
_________________________________________________
_________________________________________________
WORKSHOP ACTIVITY #11—Practice Plant Operations (LDPE)
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Report Form Report Form Report Form Report Form ---- Page 3 of 4 Page 3 of 4 Page 3 of 4 Page 3 of 4
Page 80
Workbook for Blown F i lm Pract ica l Course
CONCLUSION & RECOMMENDATIONS
INSTRUCTOR’S COMMENTS
WORKSHOP ACTIVITY #11—Practice Plant Operations (LDPE)
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
TRAINEE’S GRADE
FOR THIS ACTIVITY
________________________
INSTRUCTOR’S SIGNATURE
� Cut R
eport F
orm
and Submit to
Instru
ctor
Report Form Report Form Report Form Report Form ---- Page 4 of 4 Page 4 of 4 Page 4 of 4 Page 4 of 4
DATE: __________________
DATE: __________________
________________________
TRAINEE’S SIGNATURE
Page 81
DATA SHEET
BLOWN FILM EXTRUSION PRODUCTION REPORT
ACTIVITY #12—Practice Plant Operations (LLDPE)
TRAINEE NAME GROUP NO.
� Cut R
eport F
orm
and Submit to
Instru
ctor
Report Form Report Form Report Form Report Form ---- Page 1 of 4 Page 1 of 4 Page 1 of 4 Page 1 of 4
No. Type Resin Name / Grade Blending Ratio (%)
1
2
Material Specifications
Machine Running Condition Monitoring
1. 2. 3.
Actu
al T
emperature ( oC
)
Heater Zone 1.1
Heater Zone 1.2
Heater Zone 1.3
Heater Zone 2.1
Heater Zone 2.2
Heater Zone 3.1
Heater Zone 3.2
Heater Zone 3.3
Heater Zone 3.4
Heater Zone 4.1
MT
Extruder Screw Speed (rpm)
Extruder Melt Pressure (bar)
Air Ring Pressure (KPa)
Temperature (oC)
Haul-off Speed (mpm)
Corona Treater Power (%)
Printing Unit Motor Load (%)
Winder Tension (N)
Lay-on Pressure (bar)
Contact Pressure (bar)
Lot Number 4.
5.
Machine No.
Date:
Product Description:
Page 82
DATA SHEET
BLOWN FILM EXTRUSION PRODUCTION REPORT … continued
ACTIVITY #12—Practice Plant Operations (LLDPE)
TRAINEE NAME GROUP NO.
� Cut R
eport F
orm
and Submit to
Instru
ctor
Report Form Report Form Report Form Report Form ---- Page 2 of 4 Page 2 of 4 Page 2 of 4 Page 2 of 4
Output Monitoring
Quality Check Monitoring
Roll Number
Thick
ness P
rofile
(µm)
Measuring Point 1
Measuring Point 2
Measuring Point 3
Measuring Point 4
Measuring Point 5
Measuring Point 6
Measuring Point 7
Measuring Point 8
Average Thickness (µm)
Lay Flat Width (mm)
Gusseted LFW (mm)
Left Gusset Width (mm)
Right Gusset Width (mm)
Treating Level (OK/NOK)
Tape Test (OK/NOK)
Print Centering (OK/NOK)
Print Repeat Length (mm)
Clarity (OK/NOK)
Color (OK/NOK)
Defects (W/WO)
Roll Disposition
(Pass / Reject / On-Hold)
Lot Number 1. 2. 3. 4. 5.
Dismount Time
Roll Number
Length (m)
Weight (kg)
Total Waste (kg)
Page 83
Workbook for Blown F i lm Pract ica l Course
QUESTIONS & EXERCISES
1. What does melt pressure indicate?
a. The pressure before the screen
b. The pressure after the screen
2. What does indicator means if the reading is high (500)
_______________________________________________________
_______________________________________________________
3. What happens to the output if the screen is clogged-up, increase or
decrease? Why?
_______________________________________________________
_______________________________________________________
4. If the cooling of the barrel is not working, what do you think will
happen to the bubble?
_______________________________________________________
_______________________________________________________
_______________________________________________________
5. If the rolled film in the shaft is hard to removed, what must be the
probable cause?
_______________________________________________________
_______________________________________________________
6. How are you going to prevent the problem in #5 from happening
during operations?
_______________________________________________________
_______________________________________________________
7. Give at least 2 causes why bubble is pulsating.
_______________________________________________________
_______________________________________________________
_______________________________________________________
_______________________________________________________
WORKSHOP ACTIVITY #12—Practice Plant Operations (LLDPE)
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Report Form Report Form Report Form Report Form ---- Page 3 of 4 Page 3 of 4 Page 3 of 4 Page 3 of 4
Page 84
Workbook for Blown F i lm Pract ica l Course
CONCLUSION & RECOMMENDATIONS
INSTRUCTOR’S COMMENTS
WORKSHOP ACTIVITY #12—Practice Plant Operations (LLDPE)
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
TRAINEE’S GRADE
FOR THIS ACTIVITY
________________________
INSTRUCTOR’S SIGNATURE
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eport F
orm
and Submit to
Instru
ctor
Report Form Report Form Report Form Report Form ---- Page 4 of 4 Page 4 of 4 Page 4 of 4 Page 4 of 4
DATE: __________________
DATE: __________________
________________________
TRAINEE’S SIGNATURE
Page 85
DATA SHEET
BLOWN FILM EXTRUSION PRODUCTION REPORT
ACTIVITY #13—Practice Plant Operations (HDPE)
TRAINEE NAME GROUP NO.
� Cut R
eport F
orm
and Submit to
Instru
ctor
Report Form Report Form Report Form Report Form ---- Page 1 of 4 Page 1 of 4 Page 1 of 4 Page 1 of 4
No. Type Resin Name / Grade Blending Ratio (%)
1
2
Material Specifications
Machine Running Condition Monitoring
1. 2. 3.
Actu
al T
emperature ( oC
)
Heater Zone 1.1
Heater Zone 1.2
Heater Zone 1.3
Heater Zone 2.1
Heater Zone 2.2
Heater Zone 3.1
Heater Zone 3.2
Heater Zone 3.3
Heater Zone 3.4
Heater Zone 4.1
MT
Extruder Screw Speed (rpm)
Extruder Melt Pressure (bar)
Air Ring Pressure (KPa)
Temperature (oC)
Haul-off Speed (mpm)
Corona Treater Power (%)
Printing Unit Motor Load (%)
Winder Tension (N)
Lay-on Pressure (bar)
Contact Pressure (bar)
Lot Number 4.
5.
Machine No.
Date:
Product Description:
Page 86
DATA SHEET
BLOWN FILM EXTRUSION PRODUCTION REPORT … continued
ACTIVITY #13—Practice Plant Operations (HDPE)
TRAINEE NAME GROUP NO.
� Cut R
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Instru
ctor
Report Form Report Form Report Form Report Form ---- Page 2 of 4 Page 2 of 4 Page 2 of 4 Page 2 of 4
Output Monitoring
Quality Check Monitoring
Roll Number
Thick
ness P
rofile
(µm)
Measuring Point 1
Measuring Point 2
Measuring Point 3
Measuring Point 4
Measuring Point 5
Measuring Point 6
Measuring Point 7
Measuring Point 8
Average Thickness (µm)
Lay Flat Width (mm)
Gusseted LFW (mm)
Left Gusset Width (mm)
Right Gusset Width (mm)
Treating Level (OK/NOK)
Tape Test (OK/NOK)
Print Centering (OK/NOK)
Print Repeat Length (mm)
Clarity (OK/NOK)
Color (OK/NOK)
Defects (W/WO)
Roll Disposition
(Pass / Reject / On-Hold)
Lot Number 1. 2. 3. 4. 5.
Dismount Time
Roll Number
Length (m)
Weight (kg)
Total Waste (kg)
Page 87
Workbook for Blown F i lm Pract ica l Course
QUESTIONS & EXERCISES
1. Give at least 2 causes of die lines.
_______________________________________________________
_______________________________________________________
2. Give at least 2 causes of uneven film thickness.
_______________________________________________________
_______________________________________________________
3. What are you going to do with the die if the film wall at the right side
is thicker than the left side?
_______________________________________________________
_______________________________________________________
_______________________________________________________
_______________________________________________________
4. Give at least 2 causes of film blocking.
_______________________________________________________
_______________________________________________________
5. Give at least 3 common problems of blown film process.
_______________________________________________________
_______________________________________________________
_______________________________________________________
Good Luck!!!!!
WORKSHOP ACTIVITY #13—Practice Plant Operations (HDPE)
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Report Form Report Form Report Form Report Form ---- Page 3 of 4 Page 3 of 4 Page 3 of 4 Page 3 of 4
Page 88
Workbook for Blown F i lm Pract ica l Course
CONCLUSION & RECOMMENDATIONS
INSTRUCTOR’S COMMENTS
WORKSHOP ACTIVITY #13—Practice Plant Operations (HDPE)
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
TRAINEE’S GRADE
FOR THIS ACTIVITY
________________________
INSTRUCTOR’S SIGNATURE
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eport F
orm
and Submit to
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ctor
Report Form Report Form Report Form Report Form ---- Page 4 of 4 Page 4 of 4 Page 4 of 4 Page 4 of 4
DATE: __________________
DATE: __________________
________________________
TRAINEE’S SIGNATURE
Page 89
Workbook for Blown F i lm Pract ica l Course
Formulas for Blown Film Computations
Blow Up Ratio (BUR)
Theoretical Bag Film Weight
D2
D1
Die
1
2
D Diameter, Die
D Diameter, Bubble BUR =
π
2LFW D2 ×=
LFW 0.637 D2 ×=
where:
LFW = Lay Flat Width, cm
D1 = the die diameter, cm
D2 = the bubble diameter, cm
W
Film Bag L
t =thickness, cm
where:
Wbag = theoretical bag film
weight in grams
w = width of the bag, cm
L = cut length of the bag, cm
t = thickness of the film, cm
ρ = material density, gm/cm³
ρ××××= 2Wbag tLw
Page 90
Workbook for Blown F i lm Pract ica l Course
Formulas for Blown Film Computations
Theoretical Roll Weight
Theoretical Output
• Computing for Output Rate per RPM of a Given Output:
Output Rate = ___________ kg/hr/RPM
• Getting the Needed Output of a Desired Screw RPM
Target Output = __________ kg/hr
where:
Wbag = theoretical bag film
weight in grams
w = width of the bag, cm
L = cut length of the bag, cm
t = thickness of the film, cm
ρ = material density, gm/cm³
ρ××××= 2Wbag tLw
Rolled Film
w t
RPM Speed, Screw
hourper kg Rate,Output RPMper RateOutput =
RPMper RateOutput RPM Speed, Screw Desired Output Target ×=
Page 91
Workbook for Blown F i lm Pract ica l Course
Formulas for Blown Film Computations
Theoretical Take-off Speed
DensityThickness2th LayFlatWid
RateOutput Speed off-Take lTheoretica
×××=
)(g/cm (cm)t 2(cm)LFW
(g/min) RateOutput (cm/min) Speed off-Take lTheoretica
3ρ×××
=
Page 92
Workbook for Blown F i lm Pract ica l Course
Glossary of technical terms for Blown Film
Air-ring A circular component of a blown film system that directs cool air
up the sides of a tubular blown film bubble to cool and solidify
the melt.
Alloy Plastics made by mechanically blending two or more different
polymers.
Additive Substance compounded into a resin to modify its characteristics
(i.e., antistatics, stabilizers, plasticizers, flame retardants, etc.).
Aging The process of exposing the film to a controlled environment for
an interval of time.
Ambient conditions The existing conditions of temperature and humidity in
any building or room.
Amorphous A polymer is said to be amorphous when its molecules are in long
random or coiled chains. Amorphous plastics tend to be
transparent, and are more soluble than crystalline plastics.
Having no crystalline structure.
Anilox Roll Mechanically or laser-engraved roll for transfer of ink to printing
plate. Specifications are in lines per inch and cell volume (ex.
800-line anilox will transfer a thinner film of ink than a 300-line
anilox).
Antiblock An additive used in plastic, generally at 1 or 2% that roughens the
film surface from adhering to each other. The most common anti-
blocks are based on clay by-products.
Antioxidant Additives that prevent oxygen from causing molecular breakdown
in polymers.
Anti-static agent A substance that can be applied to the surface of a plastic
article, or incorporated in the plastics from which the article is to be
made. Its function is to render the surface of the plastic article less
susceptible to accumulation of electrostatic charges which attract
and hold fine dirt or dust on the surface of the plastic article.
Auxiliary equipment The types of equipment used to enhance, support or add
to the precision and efficiency of injection, extrusion or other
primary processing machinery. (Continued on page 93)
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Arc A luminous glow by the flow of electric current through ionized
air, gas or vapor between two separated electrodes or contacts.
Band heater Electrical heating units fitted to extruder barrels, adaptors, dies,
nozzles, etc., utilized for heating the polymer to a desired
temperature.
Barrel A metal tube that houses a rotating screw, or sometimes a ram, in
which plastic is heated before extrusion or moulding.
Barrier layer A layer of material in film, sheet or a blow molded container that
prevents the passage of moisture, flavors or certain gases.
Biaxial Orientation The process of stretching a hot plastic in two directions
under conditions resulting in molecular orientation in two
directions.
Bleed (1) To give up color when in contact with water or a solvent. (2)
Undesired movement of certain materials in a plastic (e.g.,
plasticizers in vinyl) to the surface of the finished article or into
an adjacent material; also called migration. (3) An escape passage
at the parting line of a mold, like a vent but deeper, that allows
material to escape or bleed out.
Blocking Substrate sticking to itself after being printed and rewound. Image
often transfers to back-side of other label.
Bloom (1) A non-continuous surface coating on plastic products that
comes from ingredients such as plasticizers, lubricants, antistatic
agents, etc., which are incorporated into the plastic resin. It is not
always visible. Bloom is the result of ingredients coming out of
solution in the plastic and migrating to its surface.
Blooming Migration of additives to the surface of the film
Blown film Film made by extruding molten plastic through a circular die, and
forming an inflated, tubular bubble that moves through a cage as
it cools, to be sliced open, collapsed and formed into rolls.
Breaker plate A metal plate installed across the flow of the stock between the
end of an extruder screw and the die, with openings through it
such as holes or slots. It usually is used to support a screen pack.
Bubble In blown film referred to as the inflated molten tube.
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Cage, blown film A structure, usually with rollers or roller beads, through
which a bubble of blown film passes at it is extruded and cooled.
Calcium carbonate (CaCO3) A filler and extender used in thermoplastics. It
occurs naturally in the form of minerals such as calcite, chalk,
limestone, marble, and whiting.
Calendering The making of sheet or film with high-quality surface
characteristics by passing molten plastic from a kneader over a
series of rollers that flatten and/or emboss it.
Caliper The thickness of the substrate usually measured in thousandths of
an inch (mils). "Microns" (metric) are specified for some
substrates.
Cartridge heater Cylindrical electrical heater used to heat nozzles, hot
runners and moulds in injection and compression molding.
Cast film A film process, used where good cosmetics are needed, in which
molten plastic flows over a chilled roll or through a quench bath.
Chiller A self-contained system comprised of a refrigeration unit and a
coolant circulation mechanism consisting of a reservoir and a
pump. Chillers maintain the optimum heat balance in
thermoplastic processing by constantly re-circulating chilled
cooling fluids to molds, machines, etc.
Coefficient of friction, COF A measure of how slippery a film is. Coefficient
of friction is a number that expresses, for a given surface, the ratio
of the force required to slide an object over a frictionless surface
to the force required to slide the same object over the actual
surface. The COF, or slip properties, of film are important in
determining how that film will perform on conversion equipment
and in final form such as in open ability or stacking. This test
determines the ability of film to slide over itself and is used to
determine the effectiveness of slip additives incorporated into
resins. Both static (starting) and kinetic (sliding) friction are
measured.
Coextrusion A process whereby two or more plastics are extruded through one
die, to produce a material combining their properties.
Collapsing frame A pair of frames that gradually collapse the film tube and
guide this flattened tube smoothly into the nip rolls.
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Compound Plastics that has colorants, additives or reinforcements added in a
compounding extruder or mixer.
Compression ratio In an extruder screw, the ratio of volume available in the
first flight at the hopper to that in the last flight at the end of the
screw.
Concentrate A measured amount of additive (e.g., dye, pigment, foaming
agent, anti-static agent, flame retardant, glass reinforcement, etc.)
that is incorporated into a predetermined small amount of plastic.
This (the concentrate) then can be mixed into larger quantities of
plastic to achieve a desired color or end-property.
Copolymer A polymer produced by reacting two different monomers together
to form long chains.
Crystallinity Polymers are said to be crystalline when their molecules are in a
regular, repeated lattice arrangement that makes them relatively
dense; non-transparent (because the crystals scatter light);
resistant to solvents or to chemical attack; and having a very sharp
melting point.
Dart impact strength A measure of a plastic's resilience, especially film's,
measured with a special dart or steel ball dropped on it.
Degradation A deleterious change in the chemical structure or physical
properties of a plastic, caused by exposure to heat, light or other
agent.
Density Weight per unit volume of a substance, expressed in grams per
cubic centimeter. Also called Specific Gravity. Polyethylene
ranges between .9100 - .9650. Water = 1.000, anything less than
that floats; greater than that will sink. LDPE is low density
polyethylene, HDPE is high density polyethylene.
Density is a basic molecular property that can affect many
essential physical properties of a polymer. Density, in part, is a
function of the crystalline structure of the polymer. It is an
excellent means of identifying a product, following physical
changes, and determining uniformity.
Die Line A line or series of lines on the film surface that run in the machine
direction. If there are numerous die lines , it is generally due to
the build-up of oxidized materials on the die. If the die line is a
single, deep line it is generally due to a foreign object on the die.
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Die-lip In blown film, the edge of the circular dies.
Discoloration Any change from the original color, often caused by overheating,
light exposure, irradiation, or chemical attack.
Dispersion Finely divided particles of a material in suspension in another
substance.
Doctor blade Thin, flexible steel, plastic or composite blade that passes over a
gravure plate cylinder or flexographic anilox roll wiping off
excess ink before ink is transferred to substrate or plate.
Downstream equipment In extrusion, winders, haul-offs, saws, vacuum
sizing tanks and other equipment that trims, cuts and finishes
extruded film or shapes.
Draw down ratio The ratio of the thickness of the die opening to the final
thickness of the product.
Drive The entire electrical and mechanical system used to supply
mechanical energy to the input shaft of a gear reducer. This
includes the motor, constant or variable speed belt system,
flexible couplings, starting equipment, etc.
Dryer A device to absorb and/or drive off moisture from resin powder or
pellets that, if heated while still containing traces of moisture,
would make defective parts.
Dynes A unit of energy, also a unit of measure for surface tension (treat).
Elastomer A plastic with some of the elastic, flexible properties of natural
rubber.
Elasticity The elasticity of material by virtue of which it tends to recover its
original size and shape after deformation. If the strain is
proportional to the applied stress, the material is said to exhibit
Hookean or ideal elasticity.
Elongation The fractional increase in length of a material stressed in tension.
Environmental Stress Cracking (ESC) The susceptibility of a thermoplastic
article to crack or craze when stressed, in the presence of surface-
active agents or in other environments.
Extruder A machine that melts plastic powder, pellets or flake, possibly
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with colorants and additives added. The basic machine consists of
a barrel, heater units around it, a drive system, and a fluted screw
inside to move and pressurize the plastic from the throat to the
extruder die.
Extrusion The process of melting plastic pellets, flake or powder by means
of heat and pressure, then forcing the melt through a die to
produce film or a three-dimensional profile shape.
Fabricate To work a material into a finished form by machining, forming or
other operation.
Feedstock Chemical source from which monomers for polymers are derived.
Feed throat The point at which resin or additives is added into an extruder or
injection unit.
Feed section First section or zone of an extruder screw, which is fed from the
hopper and conveys solids to the melting zone.
Feed zone A passage wherein a material passes through going down the
screw.
Filler Material such as calcium carbonate or wood flour used with
plastics to reduce costs and to impart additional mechanical
properties.
Fines Very small particles (usually under 200 mesh) accompanying
larger grains, usually of molding powder.
Fish-eye An unmelted lump of plastic in a melt, especially visible in clear
films.
Flexography A form of rotary web letterpress using flexible rubber or
photopolymer plates and fast-drying solvent, water-based or UV
inks. Photopolymer plates with raised surfaces that transfer ink to
the substrate are mounted to print cylinders using double faced
adhesive (stickyback).
Frost line The point in a blown film bubble at which the film tube reaches
its maximum diameter, and acquires a frosted appearance as the
plastic falls below its softening temperature.
Friction The resisting forces that arise when a surface of the film slides or
tends to slide over an adjoining surface of itself.
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Flame retardant A chemical compounded into a resin to make it fire-
resistant.
Flight The outer surface of the helical ridge of metal on an extrusion or
injection molding screw.
Gauge Film thickness express in mils or microns (µ).
Glass Transition Temperature The temperature below which a given plastic
behaves like glass, being strong but brittle.
Gear Reducer A combination of gears enclosed in a case.
Gel Count Gels are hard, unmelted particles randomly distributed throughout
the film. Gels are unattractive and, in most cases, will be
detrimental to film downgauging. The types of imperfections
vary, but four of the most common are pinpoint, arrowhead,
fisheyes, and oxidized or discoloured gels. As different
applications will tolerate varying levels of film purity, a gel count
test gives the producer or extrusion shop indications as to end-use
expectations. This test is very useful as a quality control tool.
Gloss A measure of the reflectivity (shininess) of a film's surface of
light from a given angle, in this case - 45 degrees. The higher the
number, the shinier the film. Gloss can impact desirability of
consumers to purchase the film product or something packaged
within it. Gloss in film can be optimized by adjustment of
extrusion parameters. Once processing conditions are perfect,
changing resins to a higher melt index and higher density at a
constant MW and MWD will generally results in better gloss.
Gusset A fold on the sides of an extruded film tube. May also be done at
the bottom of the formed bag.
Haze A measure of the clarity or transparency of film. It is expressed as
the amount of light that is not transmitted through a film sample.
The lower the number, the higher the clarity. In certain
applications, high clarity and minimal haze or frostiness is
desirable. This is the case in many packaging applications where
good clarity enhances the sales. Both surface roughness and
polymer structure diffuse light as it passes through film and cause
the hazy appearance. Extrusion parameters can be optimized to
improve haze along with proper resin selection.
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Half-tone A printed image of a continuous-tone original (like a photograph)
that is composed of tiny dots to create the illusion of continuous-
tone though printed with only single density. Halftones are
reproduced in screen values for flexographic printing from 80 line
(carton, fiber board and course papers) to 300 line (high gloss,
smooth finish papers). The majority of high quality flexographic
printing uses 133 to 150 lines screened halftones.
Heater band A band, normally of ceramic, mica or metal that is heated, and
transfers its heat to the barrel of an extruder.
Hopper dryer A combination feeding and drying device for extrusion and
injection molding of thermoplastics. Hot air flows upward
through the hopper containing the feed pellets.
Hydrophilic Tending to absorb water.
Hydrophobic Tending to absorb little or no water.
Hygroscopic Tending to absorb atmospheric moisture.
Impact resistance A measurement of the strength of film and its ability to
withstand the shock of a falling "dart" without breaking, in other
words, puncture resistance. Expressed as the gram weight of the
heaviest dart which doesn't break the film when dropped from a
specific height. The impact strength of film can be determined
and applied to end-use properties through a number of different
impact tests. Knowing these results aids in determining which
particular resins are best suited for high-strength applications such
as the construction and agriculture market.
Internal Bubble Cooling, IBC Injection of cold air into a tubular bubble of a
blown film, so that it cools and solidifies.
Laminate Product made by bonding two materials or two layers of one
material.
L/D ratio The length-to-diameter ratio of a screw, which affects how it
melts a given plastic.
Land (1) The bearing surface along the top of the flights of a screw in a
screw extruder. (2) The surface of an extrusion die parallel to the
direction of melt flow.
Lay flat Measurement of a film sample in the TD on a flat ruler or tape
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measure.
Lay Flat Width, LFW The width of the tubular film when it is flattened.
Light resistance The ability of a plastics material to resist fading after
exposure to sunlight or ultraviolet light.
Light transmission The amount of light that a plastic will allow to pass.
Linear Low Density Polyethylene, LLDPE A process variation of low
density polyethylene. It enables high draw down-gauging in
extruding, while maintaining high film strength.
Low Density Polyethylene, LDPE A partially crystalline, lightweight
thermoplastic, polymerized form ethylene gas at controlled
temperature and pressure.
Lubricant Additive to plastic resin to promote mixing and improve flow
properties.
Machine Direction, MD The direction of the film which corresponds to
the way it came out of the extruder. On rolled film it is the length
of the film. Some film properties vary according to film direction.
Masterbatch A plastics compound that includes a high concentration of an
additive or additives. Masterbatches are designed for use in
appropriate quantities with the basic resin or mix so that the
correct end concentration is achieved. For example, color
masterbatches for a variety of plastics are used extensively, as
they provide a clean and convenient method of obtaining accurate
color shades.
Melt Term to describe molten plastic.
Melt fracture An instability in the melt flow through a die, starting at the entry
to the die. It leads to surface irregularities on the finished article
such as a regular helix or irregularly spaced ripples.
Melt Index The amount, in grams, of a thermoplastic resin that can be forced
through a 0.0825 inch orifice when subjected to 2160 grams force
in 10 minutes at 190ºC.
Melt strength The strength of a plastic while in the molten state.
Melting Point The temperature at which a resin changes from a solid to a liquid.
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Melt zone The main section of a screw, which handles plasticising by heat
and pressure.
Metallocene catalyst A category of Ziegler-Natta catalysts for polymerizing
polyolefin. The structure of its own molecules orients the olefin
monomers into polyolefin polymers with tightly repeatable shapes
and properties.
Metering zone The relatively shallow discharge end of a screw.
Metering screw An extrusion screw that has a shallow constant depth and
a constant pitch section over, usually, the last three to four flights.
Metering section A relatively shallow portion of an extruder screw at the
discharge end with a constant depth and lead, and having a length
of at least one or more turns of the flight.
Mica Natural, plate-like silicate mineral used as a reinforcement or
mineral filler.
Mil One thousandth of an inch (0.001" or 0.001in.). Measure of the
film thickness.
Melt Index, MI Melt index is commonly used to classify polymeric
resins. Melt index uniformity is essential in maintaining control of
processing parameters, and melt index is inversely proportional to
molecular weight or polymeric chain length. Melt index heavily
influences physical properties.
Modulus of Elasticity The ratio of stress to strain in a material that is elastically
deformed.
Moisture Vapor Transmission The rate at which water vapor permeates through
a plastic film or wall at a specified temperature and relative
humidity.
Moisture resistance The ability of a material to resist absorbing ambient
moisture.
Molecular weight The sum of the atomic weights of all atoms forming a
molecule.
Molecular Weight Distribution A measure of the relative amounts of
polymers with different molecular weights within a batch of
material. This measure may be indicated by the ratio of the
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weight-average molecular weight to the number-average
molecular weight.
Monomers Single molecules, in gaseous or liquid form, that can be joined in
chains to form polymers, the building blocks of plastics.
Nip Line of contact between two rollers.
Nip rollers A pair of rolls at the top of a blown film tower that close the film
bubble, and also, by their action, regulate the rate at which molten
plastic is pulled from the extrusion die. A set of rollers used to
compress the plastic bubble into a sheet, or to feed the film to the
winder at the proper tension.
Nitriding Hardening process for steel screws and barrels, also referred to as
ion nitriding.
Nylon Term for the family of polyamide polymers, first synthesized by
DuPont scientists in 1938. These crystalline plastics are tough and
offer good heat and chemical resistance.
ODR Term used in pouching material - Odor Transmission Rate. How
fast the odor will pass through the substrate.
Olefins A group of unsaturated hydrocarbons of the general formula
CnH2n, and named after the corresponding paraffin by the
addition of “ene” to the stem. Examples are ethylene and
propylene.
Opacity The amount of light that will penetrate through a colored item.
Opacity is higher with thicker films or with greater loading of
color. It has nothing to do with the particular shade or color of the
film.
Opaque Description of a material or substance that will not transmit light;
opposite of transparent. Materials that are neither opaque nor
transparent sometimes are described as semi opaque, but are more
properly classified as translucent.
Oscillating nip rollers Collapsing system on top of a blown film tower that
rotates back and forth to randomize, or distribute, gauge
variations in the film being blown.
Orientation The direction in which polymer chains lie, or are made to flow, in
plastic film, sheet or parts.
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Overs/Unders Copies printed varying from the specified quantity. Depending on
the quantity ordered, the standard in our industry is usually 10%,
unless otherwise specified.
Oxidation A chemical process where a compound combines with oxygen to
form a different compound.
Pitch The distance from any point on the flight of a screw line to the
corresponding point on an adjacent flight, measured parallel to the
axis of the screw line or threading.
Plastic A material of organic origin, of high molecular weight, that can
be shaped by being made to flow through the application of heat
and/or pressure, and that will set solid after the forming process.
The word derives from a Greek root, plassein, which means to
mold.
Photopolymer A plastic that cures in response to ultra violet or another form of
light.
Permeability (1) The passage or diffusion of a gas, vapor, liquid or solid
through a barrier without being physically or chemically affected.
(2) The rate of such passage.
Pigment A coloring agent mixed with plastic material prior to processing
to provide a uniform color.
Pin holes Small random holes found in a film.
Plate cylinder The cylinder of a press on which the plate is mounted.
Plate Gap The space left when the plates are wrapped around the cylinder.
No copy or image can be printed in this area that is usually 1/8"
wide.
Plastics tooling Tools (e.g., dies, jigs, fixtures, etc.) for the metal forming
trades constructed of plastics, generally laminates or casting
materials.
Polymer Compound forming a chain of chemically linked monomers, or
single molecules; a chemist's description for a basic plastic.
Polyethylene In its pure form, a chemically stable plastic material. Used in film
form to make sleeves for photographic materials and other uses. A
cheaper alternative to polyester film.
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Polyester A thermoset or thermoplastic material, made by polymerizing any
of a range of ester monomers, usually with properties of
toughness, stiffness and/or a high melting point.
Polyvinylchloride, PVC Plastic usually abbreviated as PVC, or sometimes
'vinyl'. Not as chemically stable as some other plastics. It can emit
acidic components which damage cellulosic materials. Added
chemicals called plasticizers are also used to make PVC more
flexible. These also damage library materials.
Preheating The heating of a compound prior to molding in order to facilitate
the operation, reduce the cycle, and improve the product.
Primary processing equipment Machinery that actually moulds, extrudes or
initially forms plastic parts and products.
Proof A facsimile image of the final printed piece created before
presswork begins. Used for evaluation by production staff and
customer prior to printing.
Purging Cleaning one color or type of material from the cylinder of an
extruder by forcing it out with a new color or material to be used
in subsequent production. Purging materials also are available.
Recycle Material from flash, trimmings, scrap, rejects, etc., that can be
ground up or repelletized and fed back into the processing
machine.
Register The fitting of two or more images on top of each other in exact
alignment.
Reprocessing Recycling of plastics back into processible material, usually
through pulverizing or re-extrusion.
Resin Term for plastics raw materials in powder, pellet or flake form.
Rewinding The process of rewinding a roll of substrate to produce a proper
size for the customer, to splice the ends together and/or to remove
defects.
Rheology The scientific study of the deformation and flow of matter,
particularly as it moves through a processing line.
Rotogravure The printing process that involves the principal of engraving. An
engraved cylinder is immersed in a fluid ink; the ink is wiped or
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doctored from the surface of the cylinder; and the ink left in the
recessed area of the cylinder is transferred to the substrate.
Scrap Any product of a molding operation that is not part of the primary
product. Scraps in blow molding such as rejected parts and sprues
usually can be reground and remolded.
Screen A mesh plate that eliminates impurities from a melt stream.
Screen changer A device for replacing filtering screens without
interrupting the extrusion process.
Screw The rotating, flighted part of an extruder or injection unit, which,
in turning rapidly helps to melt, and convey, the plastic from the
hopper throat to the die or nozzle.
Shear An effect whereby parts of a melt separate and move against each
other. This is desired and essential in the heating stage, but
excessive shear produces breakdown of a plastic's properties.
Shrinkage A measurement of the percent of film shrinkage under a
controlled temperature and time interval. As a result of the
manufacturing process, internal stresses may be locked into the
film which can be released by heating. The temperature at which
shrinkage will occur related to the processing techniques
employed to manufacture the film and may also be related to a
phase transition in the base resin. The magnitude of the shrinkage
will vary with the temperature of the film Shrinkage of a
particular material produced by a particular process may be
characterized by this test method by making measurements at
several temperatures through the shrinkage range of the material.
This property is important to consider when handling film in
downstream equipment that requires heating.
Silicone spray Chemical derived from silica; used in molding as a release agent
and a general lubricant.
Silicone Chemical derived from silica; used in molding as a release agent
and a general lubricant.
Slip agents Substances added to make the sliding action easier. These
additives are designed to bloom to the surface and provide an
invisible coating on the film, reducing the coefficient of friction.
Fatty acid amines are an example which is widely used in film
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extrusion.
Slitting Cutting printed sheets or webs into two or more sections by
means of cutting wheels on a press or rewinder.
Smear Film surface defect, usually V-shaped, and protrude from the film
surface.
Spiral die A die used for blown film that brings the molten plastic through
spiral channels from an extruder to the die-lip, ensuring a
homogeneous melt when the melt emerges to form the bubble.
Solvent Any substance, usually a liquid that dissolves other substances.
Liquid that dissolves a solid. In ink, the evaporation of solvent
leaves the solids behind as an ink film on the substrate.
Specific gravity The density (mass per unit volume) of any material divided by
that of water.
Spider A term used to denote the membranes supporting a mandrel
within the head/die assembly.
Stabilizer An ingredient used in the formulation of some plastics to assist in
maintaining the physical and chemical properties of the
compounded materials at their initial values throughout the
processing and service life of the material.
Stabilizer, heat A chemical additive that prevents deterioration of plastic
during heating.
Stabilizer, light A chemical additive that helps screen plastic from the
deleterious effects of ultra-violet light.
Substrate Any printing surface (paper, polypropylene, polyester, PVC,
PETG, etc.).
Surface treating Any method of treating a material so as to alter the
surface and render it receptive to inks, paints, lacquers, and
adhesives, such as chemical, flame, and electronic treating.
Surging Unstable pressure build-up in an extruder leading to variable
throughput.
SWS, Single Wound Sheeting One single thickness of plastic being wound on a
core.
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Talc A natural, hydrous magnesium silicate used in plastics as
reinforcing filler.
Tear strength A measurement of the strength of a film and its ability to resist
tearing under specific conditions. Tear strength is the force
required to continue an initially started slit across a film
specimen. This widely used test has some value in quality control
of film production, but is not a very useful indicator of the
strength of film in service.
Tensile properties A measurement of the strength of a film and its ability to
withstand stretching or pulling. Tensile properties which include
tensile strength at yield, ultimate tensile (or break tensile
strength) , and elongation, are tests used to determine relative
strength of different films. Yield strength measures the point at
which the film, when, stretched, will not resume its original
shape. Ultimate tensile is the measure of a load that will cause the
film to rupture. Both yield and ultimate measurements are
measured in lb/ in2 of a cross-sectional area of useful information
on how polymers process and perform. For example, polyolefin
generally tend to process with easier and wider MWD and
improved drawdown. Within a given family of resins, many film
properties can be correlated with molecular properties.
Telescoping Lateral shifting of layers of film, causing the edge of the roll to
have a conical shape appearance.
Thermal Stress Cracking Crazing and cracking of some thermoplastic
resins that results from overexposure to elevated temperatures.
Thermocouple A temperature-sensitive device consisting of a pair of wires of
dissimilar metal welded together at one end. The electric current
created at different temperatures is measured by a calibrated
potentiometer.
Thermoplastic A polymer that can be heated and reformed any number of times.
Thermoset A polymer that, once heated and formed, cannot be re-melted
without fundamental degradation, because its polymer chains are
heavily cross-linked.
Tint A small amount of color added to a plastic film. You can see
through the film, yet there is still a noticeable color
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Tower A rigid metal frame or structure that holds the collapsing frame
and the nip rolls.
Transducer An input/output electronic device that can measure load or
pressure when placed in a sensor cell adjacent to the flow path of
a melt.
Translucent Descriptive term for a material or substance capable of
transmitting some light but not clear enough to be seen through.
Transparent Descriptive term for a material or substance capable of a high
degree of light transmission (e.g., glass).
Traverse Direction (TD) The direction at right angle to the direction of the
extrusion (MD). Film is tougher in this direction.
Treat The process of using high frequency electrical discharge to
oxidize the film surface, thereby making the surface more
acceptable of printing and other substances.
Tube Shape of molten plastics extruded from the die during blown film
process.
UV Inhibitor Used to inhibit or prevent degradation of the film from ultraviolet
radiation sources such as sunlight and fluorescent lighting.
Ultraviolet (UV) Stabilizer A chemical additive that selectively absorbs or
filters out light waves at the ultra violet end of the spectrum,
protecting plastics from their harmful effects (embrittlement,
discoloration, crazing and disintegration).
Vicat Softening Temperature Measurement of the heat distortion temperature
of a plastic material. Also called the heat deformation point.
Vinyl Common abbreviation for polyvinyl chloride, a plastic used for
some packaging and house wares but particularly for construction
items such as pipe, window frames, doors and siding for houses.
The term is also sometimes applied to other plastics in the range
of vinyl copolymers.
Virgin resin Plastic resin that has never been previously heated or formed.
Viscosity The property of an ink defined as the resistance to flow or simply
the fluidity or thickness of the ink.
Water absorption The ability of a thermoplastic material to absorb water
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from an environment.
WVTR, Water Vapor Transmission Rate Term used in pouching material -
Water Vapor Transmission Rate. How fast moisture passes
through the substrate
Weld Lines Also Weld Marks or Flow Lines. Marks on a molded plastic piece
made by the meeting of two flow fronts during the molding
operation.
Wetting Tension The ability of polyolefin films to retain inks, coatings,
adhesives, etc. is dependant upon the character of the surface and
can be improved by surface treating techniques such as corona
discharge or flame treatment. Wetting tension is utilized to
determine the degree or level of treatment applied by establishing
a correlation between surface tension (wetting tension) and
treatment level.
Winder A mechanical equipment of blown film machines that wind up the
lay flat tubular film that has been taken off.
Wrinkles Imperfections in plastic sheeting that has the appearance of a
wave or a crease
Yellowness Index A measure of the tendency of plastics to turn yellow upon
exposure to heat or light.
Yield The area of film at a given thickness produced from a given
weight of resin.
Yield Value (Yield Strength) The lowest stress at which a material undergoes
plastic deformation. Below this stress, the material is elastic;
above it, the material is viscous.
Young’s Modulus of Elasticity The modulus of elasticity in tension; the ratio of
stress in a material subjected to deformation.
Ziegler-Natta catalysts Large family of polymer catalysts discovered by Karl
Ziegler, and developed by Giulio Natta, with whom he shared the
Nobel Prize for their work in 1963.
Zippering An effect seen in blown film where a puncture or defect results in
a visible tear line appearing in the film surface.
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REFERENCES
1. CT-1-6 Introduction to Plastics Fabrication Technology, Version 3,
July 2007, SPDC Ltd.
2. PT-3-6 Blown Film Extrusion PGM, Version 3, July 2007, SPDC
Ltd.