PNEUMATIC BENCH VICE MODEL

MINOR PROJECT REPORT

Submitted to

GURU GOBIND SINGH INDRAPRATHA UNIVERITY

&

G.B.PANT GOVERNMENT ENGINEERING COLLEGE

By

JATIN GULATI (06520903609)

DHANANJAY KUMAR (00120907410)

SAGAR GUPTA (00720903609)

In partial fulfillment for the award of the degree

BACHELOR OF TECHNOLOGY

IN

MECHANICAL AND AUTOMATION ENGINEERING

DEPARTMENT OF MECHANICAL AND AUTOMATION ENGINEERING

G.B.PANT GOVERNMENT ENGINEERING COLLEGE

OKHLA INDUSTRIAL ESTATE, PHASE-III, NEW DELHI-110020

NOVEMBER 2012

CERTIFICATE

This is to certify that MR. JATIN GULATI, MR. SAGAR GUPTA & MR. DHANANJAY

KUMAR has carried out a live consulting project in G.B.PANT GOVERNMENT

ENGINEERING COLLEGE & the report has been prepared under my supervision.

_____________________

DATE: Mrs. Chanchal Singh

Assistant Professor, MAE

G.B.P.G.E.C, Delhi

ACKNOWLEDGEMENT

We would like to express our gratitude towards MRS.CHANCHAL SINGH for allowing us to

conduct a project titled PNEUMATIC BENCH VICE MODEL. I would also like to thank

MR. AMIT MADAAN for his valuable guidance during my project work.

We sincerely thank the officials and other staff members who rendered their help during the

period of my project work. It would never be possible for me to take the project to this level

without their innovative ideas, relentless support and encouragement.

JATIN GULATI SAGAR GUPTA DHANANJAY KUMAR

06520903609 00720903609 00120907410

ABSTRACT

The goal of this project is to create a model of bench vice which is pneumatically operated.

Using air pressure to create mechanical motion in the spindle of the vice provides a safe &

efficient way to reduce human effort.

The mechanical motion in the spindle is created with the help of a double actuating cylinder

which is operated by a 5/2 pilot valve & two 3/2 push buttons with the help of the air hoses.

TABLE OF CONTENTS

S.NO

TOPIC

PAGE NUMBER

1.

LIST OF FIGURES

1

2.

LIST OF ABBREVIATIONS USED

3

3.

CHAPTER-1(BENCH VICE)

4-6

1.1.

INTRODUCTION

4

1.2.

TYPES

5

1.3.

MATERIALS

6

4.

CHAPTER-2(PNEUMATICS)

7-13

2.1.

INTRODUCTION

7

2.2.

ELEMENTS OF A BASIC

COMPRESSED AIR PNEUMATIC SYSTEM

8

2.3.

SCHEMATIC DIAGRAM OF

PNEUMATIC CONTROL SYSTEM

13

5.

CHAPTER-3(DOUBLE ACTING ACTUATORS)

14-17

6.

CHAPTER-4(EXPERIMENTAL

SETUP)

18-19

4.1.

INTRODUCTION

18

4.2.

THE MODEL

18

4.3.

EXPERIMENTAL TARGET

18

4.4.

EXPERIMENTAL STRATEGY

18

4.5.

SCHEMATIC DIAGRAM

18

4.6.

PROCEDURE

19

7.

CHAPTER-5(EXPERIMENTAL RESULTS & DISCUSSIONS)

20

5.1.

INTRODUCTION

20

5.2.

PNEUMATIC BENCH VICE

ANALYSIS

20

8.

CONCLUSION

21

9.

REFERENCES

22

10.

SUMMARY

23

11.

APPENDIX-I

(i)

12.

APPENDIX-II

(ii)

CHAPTER-1

BENCH VICE

1.1. INTRODUCTION Its a device used to hold the work pieces for different machining operations such as fitting,

finishing etc. & is fixed to the work table with the bolts & nuts through slots provided on the vice

base.

FIG.1

It consists of four main parts:

FIXED JAW: It is usually cast integral with vice body or base.

MOVABLE JAW: It slides on the ways of the casting & is operated with a screw or

spindle.

SCREW: It gives movable jaw the forward or backward movement.

CASTING: It constitutes the base of the vice & has ways for the movable bar.

1.2. TYPES

MACHINIST VICE: Also called as engineering vice, its a heavy duty vice made of

ductile iron.

There are two main differences b/wmachinist vices & other vices:

1. Thick metal construction

2. Mount.

A machinist vice is mounted with bolts to the top of a worktable. Its heavy metal

construction gives it the ability to tolerate repeated, heavy strain. Depending on the base,

a machinist vice might have multiple functions.

MECHANIC VICE: The mechanic vice is designed to function more than a mere

vice having a swivel base. They usually have an integrated anvil area & are made of low

grade iron.

POST VICE: Its a blacksmith tool & features a post going to ground so it may be

hammered upon. These vices are made of forged wrought iron allowing them to have

ductility. It is therefore possible to spring the jaws without breaking them.

WOOD WORKER VICE: Its a under mount vice with retractable dog for

clamping the work upon the workbench.

FIG.2 MACHINIST VICE FIG.3 MECHANIC VICE

FIG.4 POST VICE FIG.5 WOODWORK VICE

1.3. MATERIALS The bench vices are usually made of cast iron or ductile iron.

The phrase cast iron usually implies grey or white cast irons which are brittle due to significant

graphite component existing in the iron in flakes.

Ductile iron graphite is in a nodular shape which inhibits cracking. Its an important distinction

in vices because high quality vices are made from nodular or spheroidal iron & cheaply made

economy vices are made of grey cast iron.

CHAPTER-2

PNEUMATICS

2.1. INTRODUCTION

Pneumatics is the discipline that deals with the mechanical properties of gases such as pressure

& density & applies the principle to use compressed gas as a source of power to solve

engineering problem. The most widely used compressed gas is air & thus its use has become

synonymous with the term pneumatics.

Today the most important property of the medium air is the simple conversion of pressure into

force & translational displacement using a piston in a circular bore.

ADVANTAGES OF AIR

Does not generate sparks.

Poses no health hazard.

Can be easily stored.

Atmospheric air is free & this had led to statement that compressed air is a cheap form of

energy.

Due to low viscosity, air cannot be used to lubricate the machinery it actuates.

However, advances in electronics helped to develop control systems for electric drives that made

them superior to formerly used fluid power actuators. This technology can also enhance the

performance of the pneumatic drives.

Examples are pressure controlled chambers in lorry braking circuits or position controlled

actuators for process valves.

Typical ranges of pneumatic systems are shown in figure below:

FIG.6

AREA OF APPLICATION OF

PNEUMATICS

Damp Hopper

Stamping

Mining(Door opening & closing)

Material flow

Automobile (Braking System, engine

etc.)

Tools (Jackhammer, drills etc.)

Punching

Motion Restriction in CNC machines

Dental Care

Pneumatic gun for bolt tightening FIG.7

2.2. ELEMENTS OF A BASIC COMPRESSED AIR PNEUMATIC

SYSTEM

FIG.8

A. AIR COMPRESSOR:

Driven with the help of an electric motor, it compresses the air raising air pressure to

above ambient pressure for use in pneumatic system.

Commonly used air compressors are the ones in which successive volumes of air are

isolated & then compressed. These are:

1. SINGLE ACTING, SINGLE STAGE, VERTICAL RECIPROCATING

COMPRESSOR:

FIG.10

As shown in the figure, on the air intake stroke the descending piston causes air to be sucked into

the chamber through the spring loaded inlet valve & when the piston starts to rise again, the

trapped air forces the inlet valve to close & so becomes compressed. When the air pressure has

risen sufficiently, the spring loaded outlet valve opens & the trapped air flows into the

compressed air system. After the piston has reached the top dead centre it then begins to descend

& the cycle repeats itself.

2. ROTARY VANE COMPRESSOR:

FIG.11

This has a rotor mounted eccentrically in a cylindrical chamber. The rotor has blades, the vanes ,

which are free to slide in radial slots with rotation causing the vanes to be driven outward s

against the walls of the cylinder. As the rotor rotates, air is trapped in the pockets formed by

vanes & as the rotor rotates so the pockets become smaller & the air gets compressed.

3. ROTARY SCREW COMPRESSOR:

FIG.12

It has two intermeshing rotary screws which rotate in opposite directions. As the screw rotates,

air is drawn into the casing through inlet port & into the space b/w the screws. Then, this trapped

air is moved along the length of the screws & compressed as the space becomes progr. smaller,

emerging from the discharge port.

Out of these three discussed above the highest pressurized air is provided by the rotary screw

compressor.

B. CHECK VALVE: Its a one-way valve that allows pressurized air to enter the

pneumatic system, but prevents the backflow of air towards the compressor when

compressor is stopped.

FIG.13

C. ACCUMULATOR: It stores the compressed air, prevents surges in the pressure & hence prevents constant compressor operation.

FIG.14

D. DIRECTIONAL CONTROL VALVE: Controls the pressurized air flow from the accumulator. These valves can be actuated manually or electrically. They are not

intended to vary the rate flow but are either completely open or completely closed.

The symbol used for these valves consists of a square for each of its switching positions.

Ex: a) 3/2 valve

FIG.15

These control valves can be actuated by different means as shown below:

FIG.16

E. PILOT OPERATED VALVE: The force required to move the piston can be often

too large for normal valve operation. To overcome this problem a pilot operated system is

used where one valve is used to control the second valve. The pilot valve is of small

capacity & can be operated manually or by a solenoid.

FIG.17

F. ACTUATORS: Converts energy stored in compressed air into mechanical motion.

TYPES OF ACTUATORS

LINEAR ACTUATORS: These actuators produce linear motion.

a) Pneumatic cylinder: It has one moving member, which is a piston &rod

assembly that converts the air-pressurized flow into linear motion.

b) Diaphragm Actuator: In this a diaphragm is utilized as the sealing element b/w the piston (moving member) & the housing (stationary element)

which is usually called the cylinder. These actuators are widely used in valves, regulators, vibration isolation systems, braking systems, precision

polishing &grinding tools, &others mechanisms. c) Actuators with bellows: Bellows in pneumatic actuating systems are a

compressible &extensible component providing an ultra-leak-tight

connection while accommodating relative movement. They also shield the operating environment from particular contamination by encapsulating

moving mechanical components. In these actuators, metal bellows are usually used. This is critical in applications dem&ing exceptionally clean

conditions, such as vacuum &semiconductor fabrication equipment. Metal bellows are also used to eliminate elastomers because of temperature limits. The temperature range in which the metal bellows operate is from

190 to +540. Unlike rubber seals, metal bellows are virtually impervious to most liquids &gases, &do not degrade in areas of high

radiation

ROTARY ACTUATORS: It can be used to produce limited rotary motion. Most

st&ard models only turn 180 or less, but some models can turn as much as 450. With some models, the user can adjust the rotation within the maximum limit.

Similarly, most st&ard pneumatic rotary actuators have only two stopping points, although some have as many as five. Pneumatic rotary actuators can be divided

into two major groups: a) Vane actuators b) Rack-&-pinion actuators

The use of any one type should be evaluated on the basis of four primary criteria: (1) working torque, (2) bearing load, (3) kinetic energy, &(4) the environment

(e.g., clean room, hazardous, corrosive, etc.). Similar to pneumatic cylinders, rotary actuators have nonlinear characteristics because of the compressibility of air &friction forces.

PNEUMATIC MOTORS: Pneumatic motors are continuously rotating rotary

actuators &can be divided into three groups: a) Vane motors b) Piston motors

c) Turbine motors The most popular type of air motor is the vane motor. Small vane motors usually

operate at speeds exceeding 20,000 rpm (revolutions per minute) &gear down to usable speeds with planetary gearing. This maintains their very small diameter &high power-to-weight ratio, making them excellent for use in h&tools.

2.3. SCHEMATIC DIAGRAM OF PNEUMATIC CONTROL SYSTEM

FIG.18

CHAPTER-3

DOUBLE ACTING ACTUATORS

FIG.19

The figure shown above is a regular double-acting pneumatic cylinder that has two ports through which the air supply is reversed to cause displacement in both directions. This construction

contains: (1) Sleeve

(2) Piston (3) Piston rod (4) Back cover

(5) Front cover The piston rod moves through the front cover that houses the rod bearing with a scraper ring &

the rod seal. The piston has piston seals. The covers are held on the sleeve by various methods including screws, rods, threaded connections &metal inserts. In this case of above figure threaded rods &fastening nuts are used. The sleeve of a cylinder can be made from cast iron,

bronze, steel, aluminum or other materials. Often, when the sleeve is of cast construction, one cover is cast integral with the sleeve. Covers for the pneumatic cylinder can be made from

different materials, but, in general, aluminum, steel, or bronze is used. Piston rods are made of polished stainless steel, nickel, or chrome-plated steel or bronze. Bronze, nylon, acetal, vesconite, pure polytetrafluoroethylene (PTFE), & PTFE containing compounds have proven

successful as slide ring materials for rod bearings. The function of a scraper ring is to prevent dirt particles from entering the components in pneumatic cylinders. In most cases, a scraper ring has one lip made of a wear-resistant elastomeric or thermoplastic material, which is sufficient,

&some have metal cases for stiffness. It is important to protect the scraping edge from damage &

to have adequate contact with the groove &piston rod diameter. The lip of the scraper ring is designed to have a preload with the piston rod, & this has an influence on the breakout friction.

In all cases where protection against corrosion & especially clean conditions are m&atory, stainless steel is used for cylinder components. Brass-based cylinder parts are ideally suited in

arduous &relatively severe, high-temperature operating environments (e.g., at 200 to 220C). The sealing function of modern elements is guaranteed by compression of an exp&er made of synthetic or natural rubber within its elastic deformation range. For static seals, this type of

material is used as a single element in most cases; for dynamic seals, it serves as an adjusting element of a slide ring, eg. , as a static sealing element in the groove depth. The functional

reliability & service life of a seal depends to a very great extent on the quality &surface finish of the mating surface for the seal. Scores, scratches, pores, concentric marks, or spiral-machining marks are not permitted. Ideally, the dynamic mating surface should be ground spiral-free. For

normal application, the piston rod seals, which seal against moving surfaces, can be damaged by fine abrasive particles that might adhere to a rough surface. Piston rods therefore should have a

low surface roughness value, &a surface similar to hard chrome or nickel. The ideal surface roughness for rods lies b/w 0.16 &0.4 m Ra. Piston seals seal against the inner surface of a cylinder. They are not affected to the same extent by abrasive particles entering from the

atmosphere & can therefore have a rougher surface. The ideal surface roughness for bores lies b/w 0.25 &0.63 m Ra. The surface finish for seal housing, where the seal is in static operation,

should be about 1.6 m Ra. The seal used for sealing a reciprocating member must meet static sealing requirements at its contact area with the stationary member, &also must seal effectively at its contact area on the reciprocating member. The ideal seal should:

Prevent leakage over the pressure ranges encountered

Have long life with minimum maintenance

Be compatible with air at operating temperatures &pressures

Have sufficient integrity to avoid air contamination

Be easy to install, remove, &replace

Exclude foreign material

Be inexpensive

Curiously, the first two properties are at odds with each other in a dynamic sealing situation. A good compression force holds the seal against a reciprocating member, thus accelerating seal wear &shortening service life. Therefore, every dynamic seal design is a compromise to produce

an acceptable balance b/w these two desirable properties. The great variety of seal shapes &materials allows the designer to select the degree of compromise for a particular application

while, at the same time, satisfying the other requirements on the list. In pneumatic actuators, O-ring &U-cup seals are widely used. The O-ring (detail A) is ideally suited for use as a static seal b/w nonmoving parts (e.g., b/w the covers &the sleeve). Use of an O-ring as the seal

element b/w linear moving parts is sometimes not recommended because it creates a high friction force, which is the main cause of the stick-slip phenomenon.

The U-cup seal is installed with the cup facing in the direction of the pressure side; then air pressure inflates the U-cup &the seal edge is held against the rod or sleeve surface (detail B). The U-cup is ideal for use on linear moving rods &piston heads because, unlike an O-

ring, the shape does not try to roll with the movement &does not create high friction. All elastomeric sealing compounds are a combination of many chemical ingredients. These

ingredients can be classified as:

Polymers or elastomers

Inert fillers (carbon or mineral fillers &reinforcing agents) to improve physical properties

Accelerators, activators, retardants, &curing agents to assist in curing or vulcanization

Inhibitors to inhibit undesirable chemical reactions during compounding

Plasticizers to decrease stiffness &improve low-temperature properties

For st&ard pneumatic applications, the primary compound used currently is a thermoplastic elastomer based on polyurethane (PUR). This material can be processed in rapid injection molding procedures, shows good resistance toward mineral oils, &has excellent elasticity &wear

values. In addition to having a good running behavior against steel (without stick slip), it also has a long service life in pneumatics. Its nonresistance to water, which would destroy the material by

hydrolysis, limits the general use of PUR. In addition, polyurethane delivers the pneumatic requirements b/w 35 &120C. Another compound that can be used with most of the above-mentioned parameters are

acrylonitrile butadiene rubbers (NBR or Perbunan), which have a particularly high level of quality &desirable properties. This material is used in all kinds of static &dynamic seals.

Provided that the compounds are correctly formulated &processed, the vulcanized rubbers have very good resistance to liquid fuels, mineral oils, &greases; good resistance to aging; high resistance to wear &abrasion; low permeability to gases; &good physiological properties. The

temperature range is 20 to 80C. Fluorocarbon elastomers have been compounded to meet a wide range of chemical &physical

requirements. Under the tradenames Viton Fluorel, &Kel-F, fluorocarbon seals have been employed where other materials cannot survive the severe chemical conditions. The working temperature range of fluorocarbons is b/w 30 &+200C. New compounds have greatly improved

the compression set of fluorocarbon O-ring seals. Also, PTFE is used as part of dynamic seals because this material has an

extremely low coefficient of friction &high wear resistance. By adding additives (compounds) such as carbon-graphite, bronze, glass, or molybdenum disulfide(MoS2), PTFE can be tailored to specific applications. The disadvantages of PTFE namely, low creep resistance &only limited

resilience could be avoided by developing new compounds. Blending with thermoplastic portions is

advantageous for the material when used in dynamic applications with the same good chemical &thermal resistance. Within certain limits, it is now possible to substitute elastic elements for these PTFE types.

The evolution of pneumatic cylinder construction is directed at increasing efficiency, improving the power-to-weight ratio, &rationalizing construction, as well as proposing &developing new

types of devices. The result of this effort is instrumental in:

Reducing friction &adhesion forces

Ensuring effective sealing throughout the operating pressure range

Eliminating the risk of extrusion

Guaranteeing a long service life without the use of lubricated air Using a composite material is an alternative to carbon steel, honed &chromed steel, stainless

steel, aluminum, or brass cylinder sleeve. Constructed of fiber-reinforced thermoset epoxy, the composite material cylinder has an inner surface of evenly dispersed low-friction additives, eg. molybdenum disulfide (MoS2), tungsten disulfide (WS2), or other. In this manner, a self-

lubricating cylinder wall with a low coefficient of friction can be achieved. For added cylinder strength &stability, some kinds of fibers are available as reinforcements. In the composite

industry, more than 90% of all fibers are glass. Electrical or E-glass is the most commonly used &most economical glass fiber, while structural or S-type glass has slightly higher strength

&corrosion resistance. Advanced fibers such as carbon &Kevlar exhibit higher tensile strength &stiffness than glass fibers. Due to the higher costs of these fibers, they are typically reserved for

applications dem&ing exceptional performance. Another key to reducing the friction force in pneumatic cylinders is a pneumatic actuator with

flexible chambers.

CHAPTER-4

EXPERIMENTAL SETUP

4.1. INTRODUCTION

This chapter presents the discussion on the experimental setup, experimental targets & strategies

taken while doing the project. It provides a brief overview & complete details of the bench vice

with pneumatic setup.

4.2. THE MODEL

A model of bench vice coupled with double acting cylinder which is operated by 5/2 pilot valve

& 3/2 push button (spring return) is used for the test purpose.

4.3. EXPERIMENTAL TARGET

The experiment was designed to hold the workpiece with the help of the pneumatic force

provided by the double acting cylinder rod.

4.4. EXPERIMENTAL STRATEGY

The experimental strategy was to design a bench vice with mild steel as a material & then couple

it with the rod of the double acting cylinder so as to obtain the desired pneumatic force which is

used to hold the workpiece.

4.5. SCHEMATIC DIAGRAM

FIG.20

4.6. PROCEDURE

1. Design a bench vice with the mild steel as its material. (Designing is done in CATIA V5

which can be seen on APPENDIX I)

2. A double acting cylinder is coupled with the 5/2 pilot valve & 3/2 push button with the

help of air hoses & its working has been checked. (pneumatic drawing is done with the

help of FESTO FLUID DRAW 5 DEMO which can be seen on APPENDIX II ).

3. The bench vice is bolted to the wooden work table.

4. The double acting cylinder is now bolted to the wooden work table from one side & on

another side it is placed in a frame which is bolted to the wooden work table at a

specified distance.

The frame is shown in the figure below:

FIG.21

The advantage of using frame is that the cylinder rod can be aligned accurately with the

bench vice spindle.

5. The cylinder rod is clamped to the bench vice spindle.

6. Working of bench vice is then checked by operating it with the help of push buttons.

CHAPTER-5

EXPERIMENTAL RESULTS & DISCUSSIONS

5.1. INTRODUCTION

The project strategy was to operate the bench vice with the help of the mechanical motion

obtained by the cylinder rod from the pneumatic force supplied by the system. The present

chapter includes the result obtained by implementing this strategy.

5.2. PNEUMATIC BENCH VICE ANALYSIS

It has been found that this bench vice can be used to hold the workpieces of different sizes &

weights with different pressures varied with the help of the pressure regulator.

Also, the stroke of the movable jaw in backward direction is not complete due to short stroke

length of the cylinder rod of the double actuating cylinder (The movable jaw displacement from

the fixed jaw can be changed or nullified by changing the stroke length of the cylinder rod of the

actuator).

PNEUMATIC DESIGN OF

BENCH VICE

LIST OF FIGURES

FIGURE NUMBER

PAGE NUMBER

DESCRIPTION

FIG.1

4

BENCH VICE

FIG.2

5

MACHINIST VICE

FIG.3

5

MECHANIC VICE

FIG.4

5

POST VICE

FIG.5

5

WOODWORK VICE

FIG.6

7

TYPICAL PRESSURE RANGE OF VARIOUS PNEUMATIC SYSTEM

FIG.7

8

DIFFERENT AREAS OF APPLICATION OF PNEUMATICS

FIG.8

8

COMPONENTS OF AIR

PNEUMATIC SYSTEM

FIG.9

9

AIR COMPRESSOR

FIG.10

9

SINGLE ACTING SINGLE STAGE

VERTICAL RECIPROCATING COMPRESSOR

FIG.11

9

ROTARY VANE COMPRESSOR

FIG.12

10

ROTARY SCREW COMPRESSOR

FIG.13

10

CHECK VALVE

FIG.14

10

ACCUMULATOR

FIG.15

11

3/2 DIRECTIONAL CONTROL

VALVE

FIG.16

11

DIFFERENT ACTUATION MECHANISM

FIG.17

11

SOLENOID VALVE

FIG.18

13

PNEUMATIC CONTROL SYSTEM SCHEMATIC DIAGRAM

FIG.19

14

DOUBLE ACTING CYLINDER

FIG.20

18

SCHEMATIC DIAGRAM OF

PNEUMATIC BENCH VICE OPERATION

FIG.21

19

FRAME

LIST OF ABBREVIATIONS USED

WORDS

ABBREVIATION USED

AND

&

BETWEEN

B/W

PROGRESSIVELY

PROGR.

m

MICROMETER

Ra

ROUGHNESS AVERAGE

MATERIAL OF THE BENCH VICE: MILD STEEL

CYLINDER: DOUBLE ACTUATING

VALVE: 1) 5/2 PILOT VALVE

2) 3/2 SPRING RETURN PUSH BUTTON VALVE

CONCLUSION

The project undertaken on operating a model of bench vice with the help of the mechanical

motion obtained due to application of pneumatic force in an actuator is found to be fully

functional.

Also, it has been seen that pneumatic vice reduces the human effort for holding the work piece in

comparison to the conventional used one.

REFERENCES

W. Bolton, Mechatronics, Pearson Education Ltd., 2003

Krivtis & krejnin, Pneumatic Actuating System for Automatic Equipment, CRC

Peter Beater, Pneumatic Drives,Springer