design and fabrication of compression molding machine …iaiest.com/dl/journals/8- iaj of innovative...

International

Academic

Journal

of

Innovative Research International Academic Journal of Innovative Research Vol. 3, No. 11, 2016, pp. 1-20. ISSN 2454-390X

1

www.iaiest.com

International Academic Institute for Science and Technology

Design and Fabrication of Compression Molding Machine for

Plastic Waste Recycling in Nigeria

Ejiroghene Kelly Orhorhoroa*, Eruero Victor Atuma

b, Ayodele Samuel Adeniyi

c

aCemek Machinery Company, Technology Incubation Centre, Federal Ministry of Science and Technogy, 188, Sapele Roadd,

Benin City, Edo State, Nigeria b

Department of Mechanical Engineering Engineering, ,Faculty of Engineering, Delta State Polytechnic, Ote-Oghara, Delta State. cDepartment of Mechanical Engineering, Faculty of Engineering, University of Benin, Benin City, Edo State, Nigeria

Abstract

The current study was aimed at the design and fabrication of compression molding machine for plastic

waste recycling in Nigeria. The machine was designed, fabricated and assembled from locally available raw materials in Nigeria. The machine consists mainly of threaded screw, hopper, heater, heating

chamber, forming chamber, steel frame, and control switch. The raw materials (waste plastics) were

loaded through the hopper and heated within a temperature range of 1800C-220

0C and under a pressure of

3.77 MN/m2. The control switch was used to control the system. Newtonian fluid flow and Non-

Newtonian fluid flow were applied. The working temperature was determined as 2200C. Thus at that

temperature, the polythene solid plastic waste material undergo change of state from solid to completely

liquid. Others parameters calculated for are molding temperature (420C), material plasticizing rate

(1kg/hr), heat transfer per unit mass (2520W), total force (142.58KN), pressure distributed in the barrel

(3.77MN/m2), volume flow rate (1.178 x 10

-5m

3/sec), and factor of safety (1.33). From the results

obtained based on the quality of mold produced by the compression molding machine, the fabricated

machine performance was satisfactory and can be used locally and industrially in small scale.

Keywords: Waste, plastic, compression molding machine, recycling, Nigeria

Introduction:

The rapid growth of plastic products industry in Nigeria accounts in part for its attractiveness to

entrepreneurs. Almost every storage containers, eating plates, sockets, household appliances are made

with plastic products. The continuous increase in quantity of plastic waste generated in Nigeria is due to

International Academic Journal of Science and Engineering,

Vol. 3, No. 11, pp. 1-20.

2

larger volume purchases of finished product made of plastics (Orhorhoro et al., 2016). Plastic product

after used and dumped, contribute about 8.69% of total municipal solid waste generated in Nigeria

(Igbinomwanhia, 2011; Gideon et al., 2014) as shown in Table 1.

Table 1: Average component of solid waste generated per person per day in Oredo LGA, Benin

City, Edo State, Nigeria (Igbinomwanhia, 2011)

Type of solid wastes Weight (kg) % Component

Food waste 0.334 78.59

Plastic/Rubber 0.037 8.65

Paper 0.016 3.67

Metal waste 0.017 4.11

Glass 0.012 2.83

Other waste (Textile, foam, ceramics, ash, etc.) 0.009 2.10

Total solid waste (ppd.) 0.425 100

Nigeria has poor policy of waste management and this is of concern and threat to the entire populace.

Plastic waste poses a serious threat to average Nigeria household and if something urgent is not done, it

will become uncontrollable (Figure 1). Continuous dumping of plastic waste in water way, road side,

institution, market places, churches, mosque, event centres, etc. is of health concern. This indiscriminate

dumping of waste is the major causes of blockage of drainage systems, causing erosion and flooding.

They are a breeding ground for mosquitoes, thus, posing a serious health risk to the entire populace. Due

to the inadequacy of local recycling facilities in Nigeria, the generation of plastic waste has multiplied

steadily over the years as a result of rising population, urbanization and industrialization (Nkwoh, 2006;

Oziegbe, et al., 2016). The problem of solid waste started in Nigeria with the rapid increase in urban

growth resulting partly from the increase in population status (Eguniobi, 1996). No town in Nigeria can

boast of finding a lasting solution to the problem of filth and huge piles of solid waste, rather the problem

continues to assume monstrous dimensions (Okpala, 2002). To urban and city dwellers, public hygiene

starts and ends in their immediate surrounding and indeed the city would take care of itself. The situation

has so deteriorated that today the problem of solid waste has become one of the nations most serious

environmental problem (Titus and Anim, 2014). In Nigeria, the commonly practiced waste management

option is basically the collection of mixed waste materials and subsequent dumping at designated

dumpsites. It is not a practice to separate waste materials at source or any point during its management

(Akintokun et al., 2011).

The problem of plastic waste is not only limited to Nigeria. It is a global phenomenon. The worlds

annual consumption of plastic materials have increased from around 5 million tons in the 50s to more

than 100 million tons; thus, twenty (20) times more plastic is produced today than 50 years ago (UNEP,

2009). This implies that more resources are being used to meet the increased demand for plastic, on the

other hand, more plastic waste is being generated (UNEP, 2009, Orhorhoro et al., 2016). Looking at the

volume of plastic waste generated in Nigeria, there is urgent need for proper plastic waste management,

thus, this research work. This research work is centre on plastic waste management via compressor

molding technology. Solid plastic waste can be recycled by the process of compression molding and this


Vol. 3, No. 11, pp. 1-20.

3

will not only reduce environmental pollution as a result of plastic waste but it will also lead to production

of useful plastic materials for both home and industrial use.

Figure 1: Blockage of drainage by used PET bottles

Compression molding is a major technology in the plastic industry, and is one of the original processing

methods for manufacturing plastic and it components (Figure 2). The technology has evolved from the

production of the simple things like combs and buttons to major consumer, industrial, medical, and

aerospace products. In fact, it was widely used in the bakery industry for cookie or cake molding before

plastic materials exist. Although is also applicable to thermoplastics, compression molding is commonly

used in manufacturing thermoset parts. The raw materials for compression molding are usually in the

form of granules, putty like masses. The main concept of plastic molding is placing a polymer in a molten

state into the mold cavity so that the polymer can take the required shape with the help of varying

temperature and pressure. The mold is then closed and pressure is applied to force the materials to fill the

cavity. A hydraulic ram is often utilized to produce sufficient force during the molding process. The heat

and pressure are maintained until the plastic is used.

Figure 2: Pictorial view of Compression molding machine (Kamal, 2009)


Vol. 3, No. 11, pp. 1-20.

4

Operation of Compression molding

The operations required to produce plastics products by compression molding include:

1. Preparation of molding material

2. Melting the material

3. Forcing the material through a nozzle and into a mold

4. Ejecting the molded part

5. Machining and finishing the product

Figure 3 shows the various operation of compression molding. As showed in Figure 3a, the molding

compound is placed in an open heated mold cavity, where the mold is closed and pressure is applied to

force the material to fill up the entire mold cavity (Figure 3b). Excess materials are usually channeled by

the overflow grooves. The heat and pressure are maintained until the plastic materials are cured. The

produced final product is removed as shown in Figure 3c.

Figure 3: Various operation of compression molding

Primary factors of compression molding

There are four major primary factors in a successful compression molding processes

1. Quantity of materials

2. Heating time and techniques

3. Force applied to the mold, and

4. Cooling time and techniques

Critical process parameters of compression molding method

The critical process parameters of compression molding method are as follow (Figure 4) 1. Time

2. Temperature, and

3. Pressure


Vol. 3, No. 11, pp. 1-20.

5

Figure 4: Critical process parameters of compression molding method

Research Methodology

The amount of requires heat and pressure is applied for a define period of time. The material is placed in

between the molding plates flows, and this is to ensure that there is application of pressure and heat for

the sole purpose of acquiring the required shape of the mold cavity with high dimensional accuracy.

Temperature and pressure facilitate the process of flow raw material into the cavity, which has been

generated between the two mold halves. This was allowed for the curing process to takes place. The

temperature accelerates the curing process. Curing is done at an elevated temperature. The two mold

halves are open and the final product taken out. Figure 5 shows the process flow chart.

Figure 5: Process flow chart

Conceptual Design

The main aim of the research work is to design and fabricate a perfectly working compression molding

machine for the sole purpose of waste management in Nigeria. To achieve the said aim, a conceptual

design was generated (Figure 6).


Vol. 3, No. 11, pp. 1-20.

6

Figure 6: Conceptual Design

Functional requirement and Design parameter

To achieve the said aim, a set of functional requirements and design parameters were drawn. Any design

that satisfies all of the functional requirements will fulfill the aim, and the design parameters specify how

each functional requirement must be satisfied. The summary of functional requirement and design

parameter used for the research work is showed in Table 2.


Vol. 3, No. 11, pp. 1-20.

7

Table 2: Functional requirement and Design parameter

Functional Requirement Design Parameter

A temperature that can supply enough heat to melt

the materials

A temperature range of 1800C to 220

0C

A pressure that will be able to sustain the process A pressure of 15.8MPa

Prevent molten leakage from heating chamber to

mold former

Airtight in both heating chamber and mold forming

chamber

Efficiency and Performance A perfect working compression molding machine

Durability Lifetime of at least 10 years

Detail Design

Flow of fluid along a channel of uniform circular cross section

Figure 7 shows flow of fluid along a channel of uniform circular cross section

Figure 7: Element of fluid in a channel

Assumption: Flow is steady (Newtonian)

0 ZF

dz

z

ppdrF 21

(1)

pdrF 22 (2)

dddF zr23 (3)

ddtdzpdzpdrpdr .222

(4)

zpd

d r

2

(5)


Vol. 3, No. 11, pp. 1-20.

8

dzdprd 2 (6) But,

Maximum shear stress is at r =R, suppose there is pressure drop of P over length L

Therefore,

L

PR

2

(7)

But,

r

v

dd

(8)

Where,

=shear viscosity

= shear strain rate

V = Velocity

Combining equation (6) and equation (8);

22271

27

1

2

22 Rr

dzdp

V

rdrdz

dpdv

dzdprr

v

v

o

r

R

oVVrAt ,20

2

471 R

dz

dpVo

(9)

2

1R

rVV o (10)

Isothermal flow in channel (Non-Newtonian fluids)

The simplest model for analysis is given by the power law equation

1

n

oo Y

Y (11)

nn

oo T

1

(12)

Where,


Vol. 3, No. 11, pp. 1-20.

9

oY = shear rate at a chosen standard state

o = shear stress at a chosen standard state

o = shear viscosity at this state

From equation (416)

n

ooYY

1

no YY (13) Then,

Yo (14) Newtonian fluids are special cases of power law fluid with

n=1

Design of the compression molding machine wall (thick wall)

Figure 8: Stresses acting on element of radius r and dr

Where,

r1= internal radius

r2= External radius

Figure 9 shows stresses acting on an element of radius r and thickness dr subtending an angle d at the

centre


Vol. 3, No. 11, pp. 1-20.

10

Figure 9: Stresses acting on section of the cylinder

Radial stress r and circumferential stress c are both assumed to be tension, considered positive.

Resolving the forces on the element

2

2

d

cdrrddddrrd rrr (15)

rcrrr ddrd

c

r

rr

d

rd

(16)

Assumption,

If longitudinal strains are uniform along the length of the barrel

.constcr

acr 2

rc a 2 (17) Substituting equation (17) into equation (16)

022

2

2

ard

drr

ad

rd

r

rr

r

r

rr

Multiply through by r

022 arrd

dr

r

barrr 22

2r

bar

(18)


Vol. 3, No. 11, pp. 1-20.

11

22

r

baa rc

(19)

Considering a common case of a cylinder with internal pressure only such as the threaded screw type

plastic compression molding machine, the distribution of stresses on the wall thickness is showed in

Figure 10.

Figure 9: Distribution of stresses on the wall thickness

This implies,

2

2r

bap

(20)

Also,

2

2

2

1

2

2

2

1

0

rr

rpa

r

ba

2

2

2

1

2

2

2

1

rr

rprb

But, from equation (18),

2r

bar

(21)

Therefore,

2

2

1

2

2

2

1

2

2 1r

r

rr

prr

(22)

2r

bac


Vol. 3, No. 11, pp. 1-20.

12

2

2

1

2

2

2

1

2

2 1r

r

rr

rp

(23)

But the maximum radial and circumferential stresses occur at,

2rr

Where,

pr

2

2

2

1

2

2

2

1

rr

rrpc

(24)

Negative sign indicate high compression

For a thin wall compression molding machine

From,

2

2

2

1

2

2

2

1

rr

rrpc

tdttdtpd

c

2

22 22

(25)

Where,

dtk

rd

rrt

/

2 2

21

If rc is constant across thickness which is reasonable enough, then

t

pdc

2

(26)

kp

c

21


Vol. 3, No. 11, pp. 1-20.

13

Design for Heat Transfer

Figure 10 shows heater on barrel

Figure 10: Heater on barrel

From;

t

T

x

T

12

2

(27)

Where equation (27) is Fouriers equation for non-steady heat flow in one dimension

T = Temperature

= thermal diffusivity But;

pc

k

(28)

Where,

= Density

k=Thermal conductivity

Cp= Specific heat capacity

Where,

sec/101 27 m (Thermoplastic)

Temperature gradient

21

23

TT

TTT

(29)

Where;

T1 = initial uniform temperature of the melt

T2 = temperature of heating or cooling medium

T3 = temperature at time, t


Vol. 3, No. 11, pp. 1-20.

14

Design for Heater energy

Melting temperature of thermoplastic = 220oC (High density polyethene-measured)

Molding temperature = 42oC (measured)

Material plasticizing rate = 1kg/hour (measured)

q=Heat transfer per unit mass

W =Work transfer per unit mass

H= Enthalpy

W=0 (for plunger compression molding)

Therefore;

hmq (30)

q=56x45= 2520W

Younesi et al., 2009 reported 2000W for injection compression molding

Estimated threaded screw speed

The estimated threaded screw speed was determined as follow shown in Table 3

Table 2: Estimated threaded screw speed

Number Threaded screw speed mm/sec

1 6.5

2 5.5

3 5.7

4 7

5 6

6 6

7 5.5

8 6.5

9 6

10 6

Average = 10665.65.566755.55.6

= 6mm/sec

Working temperature = 220oC

Volume flow rate

Volume flow rate Q = Area x Velocity

Assumption,

Flow is Newtonian and Isothermal

That is;

Q = AV (31)


Vol. 3, No. 11, pp. 1-20.

15

4

1050

50

4

sec/106sec/6

23

2

3

A

mmD

DArea

mmmV

323

1064

1050

Q

sec/10178.1 35mQ

Distance between the torpedo and barrel

22 rRx

22

dDdDx

(31)

2

2550

2

2550x

(32)

mx

x

x

310473.1

0125.00375.0142.3

1000

5.12

1000

5.37142.3

Apparent strain rate

x

QY

6

(33)

sec/10259.2

10473.1

10178.16

4

3

5

mY

Y

Also,

L

px

2

(34)

And,

Y

Where,

mN /1043.15 3 , a constant value

Y


Vol. 3, No. 11, pp. 1-20.

16

MN3.6810259.2

1043.154

3

From,

L

px

2

(35)

x

Lp

2

Where,

P = pressure

2

3

33

/77.310473.1

1043.15101802mMN

mp

Force due to pressure

prF 2 (36)

Where,

F = Force due to pressure

r = internal radius

KNF 14.1421077.31012142.3 63

Surface area of torpedo DLSA (37)

Where,

SA= surface area of Torpedo

Viscous drag force DLVDF (38)

Where;

VDF = Viscous drag force

D = External diameter of barrel

=shear stress

NVDF 33.4361043.15101801050142.3 333

Total Force

VDLFTF (39) Where,

TF = Total force

F = Force due to pressure

VDL = Viscous drag force


Vol. 3, No. 11, pp. 1-20.

17

KNTF 58.14233.436140,142

Pressure distribution in barrel

Recalling,

Pressure P = 3.77MN/m2

Diameter D = 50 x 10-3

m

Thickness of barrel t=3mm = 3x10-3

m

Yield stress (max) mild steel 1050 hot rolled = 4.13x108N/m

2

Failure will occurs when the greatest principle stress exceed the elastic limit stress in a simple tension test

irrespective of the other principal stresses

Assumption,

Since machine is a threaded screw type compression molding machine, force is applied only by the

threaded screw

Thus,

oy Where,

y = stress by the application of force by the plunger

o = safe working stress of the barrel

t

pdy

2

(40)

2

3

36

/42.311

1032

10501077.3

mMNy

y

Therefore, the stress at the wall of the barrel is 311.42MN/m2 which is far below the yield stress (i.e.

4.13x108Nm

2)

Factor of Safety

Safety factor = 33.1/1042.311

/1013.426

28

mN

mN

o

y

Therefore, a barrel with a thickness of 3mm is adequate

Figure 11 shows the isometric view of the fabricated compression molding machine


Vol. 3, No. 11, pp. 1-20.

18

Figure 10: Isometric view of compression molding machine

Discussion

In this research work, design of a compression molding machine was carried out for performance

evaluation. With the manufacturing process in mind, it was essential to choose a material (polythene) that

can withstand the properties of real time mold. In making the mold it was necessary to have the best

possible product design so that it would not complicate the mold designing process. With all the required

dimensions and by the help of conceptual design which mainly based on functional requirement and

design parameters, detail design of the compression molding machine was achieved. It was crucial to find

out if there were any defects in the product design. The working temperature was determined as 2200C.

Thus at that temperature, the polythene solid plastic waste material undergo change of state from solid to

completely liquid. Others parameters calculated for are molding temperature (420C), material plasticizing

rate (1kg/hr), heat transfer per unit mass (2520W), total force (142.58KN), pressure distributed in the

barrel (3.77MN/m2), volume flow rate (1.178 x 10

-5m

3/sec), and the factor of safety (1.33). With all the

parameters calculated for, the compression molding machine was fabricated and tested. The quantity and

quality of plastic waste recycle via the technology prove that the machine can be used domestically and

for small scale industrial use.


Vol. 3, No. 11, pp. 1-20.

19

Conclusion

Test performance was carried out on the fabricated compression molding machine. Polythene materials in

pellet and small size particles were completely melted between 2000C to 220

0C. The time to melt and

mold forming were taken note of respectively. From the results obtained based on the quality of mold

produced by the compression molding machine, the fabricated machine performance was satisfactory and

can be used locally and industrially in small scale.

Recommendation

Considering the huge economic and environmental importance of the use of polyethenes and plastics, the

government of Nigeria and research centres should bring to the awareness of the society the importance

of recycling wastes polyethenes and plastics through compression molding technology. The government

of Nigeria should invest more on compression molding as this will not only help in re-cycling of waste

polythene and plastics but as well provide jobs among the millions unemployed Nigerian youths.

Contributions to knowledge

The following important results where attained which can be used for future fabrication of a compression

molding machine.

1. It was established that a temperature range of 1800C-220

0C and under a pressure of 3.77MN/m2 can be

used to change the polythene waste plastic materials from solid state to liquid state.

2. It was equally established that a threaded screw speed of 6mm/sec can be used for subsequent project

work.

References:

Akintokun, P.O., Adekunle, I.M., Adekunle, A.A., Akintokun, A.K., and Arowolo, T.A. (2011).

Recycling of organic wastes through composting for land applications. A Nigerian experience.

Waste management & research, 29(6), p.582-93. doi:10.1177/0734242X10387312.

Eguniobi, E. (1996). Fundamentals of urban administration in Nigeria. Enugu: HRV Publishers, p.98.

Gideon A.D, Benjamin T.A, Emmanuel E.O (2014). Characterization of municipal solid waste in the

Federal capital, Abuja, Nigeria. Global Journal of science frontier research;

Environmental and Earth Science. Volume 14 Issue 2 version 10, Year 2o14

Igbinomwanhia, D.I. (2011). Status of Waste Management, Integrated Waste Management. Volume II,

ISBN 978-953-307-447-4. p.22. [Online] Available from:

http://www.intechopen.com/books/integrated-waste-management-volume-ii/status-ofwaste-

management. [Accessed: 13th August 2016].

Kamal M. R., 2009. Compression molding Technology and Fundamentals. 1st ed. Munchen,

Germany: Hanser Publications

Nkwoh, N.B. (2006). Overview of Waste Management in Nigeria. Nigeria/ANESA. p.119

Okpala, I.C (2002). Practical Guide to Environment Auditing, Excellence Environmental System. Lagos:

Vinez Books. p.98.

Orhorhoro, E.K., Ikpe, A.E., and Tamuno, R.I. (2016) Performance Analysis of Locally Design Plastic

Crushing Machine for Domestic and Industrial Use in Nigeria. European Journal of Engineering

http://www.intechopen.com/books/integrated-waste-management-volume-ii/status-ofwaste-


Vol. 3, No. 11, pp. 1-20.

20

Research and Science, EJERS, Vol. 1, No. 2, August 2016

Oziegbe,J.I., Orhorhoro, E.K., Chughiefe L, Ogiemudia, O.G. (2016). The Design and Fabrication of a

used Polyethylene Terephthalate (PET) Bottle Washing and Sterilizing (Recycling) Machine.

International Academic Journal of Science and Engineering, Vol. 3, No. 10, 2016, pp. 17-29.

ISSN 2454-3896

Titus, E.A. and Anim, O.A. (2014). Appraisal of Solid Waste Management Practices in Enugu City,

Nigeria. Department of Geography and Environmental Science, University of Calabar, Nigeria.

A Journal of Environment and Earth Science. Vol. 4, p.98, ISSN 2225- 0948. [Online] Available

from: http://www.iiste.org/Journals/index.php/JEES/article/viewFile/10254/10460. [Accessed:

13th August 2016].

United Nations Environment Programme (UNEP) (2009). Converting Waste Plastic into a

resource. United Nations Environmental Programme Division of Technology, Industry and

Economics International Environmental Technology Centre, Osaka/Shika. p.10, 12-73. [Online]

Available from:

http://www.unep.or.jp/Ietc/Publications/spc/WastePlasticsEST_Compendium.pdf. [Accessed:

13th August 2016].
http://www.unep.or.jp/Ietc/Publications/spc/WastePlasticsEST_Compendium.pdf

design and fabrication of compression molding machine …iaiest.com/dl/journals/8- iaj of innovative...

Documents