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Designand Fabricationof Mini Injection Moulding Machinefor Small to Medium Scale Plastic Processing

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fliud mechanics (2222222)

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Design and Fabrication of Mini-Injection Moulding Machine for Small-to-

Medium Scale Plastic Processing

Article · December 2019

CITATIONS

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1 author:

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Nwadinobi Chibundo Princewill

Abia State University, Uturu, Abia State

40 PUBLICATIONS 35 CITATIONS

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Design and Fabrication of Mini-Injection Moulding Machine for Small-to-Medium Scale

Plastic Processing

Nwadinobi, C. *1, Ezeaku, I. 1 and Ugwu, V. 2

1 Department of Mechanical Engineering, Abia State University, Uturu, Abia State, Nigeria.

2 Department of Mechanical Engineering, Abia State Polytechnic, Aba, Abia State, Nigeria.

*Corresponding author’s email: chibundop@gmail

Abstract

This paper presents the design process and manufacturing of plastic injection moulding machine

that is inexpensive and for use in the production industry for producing small size plastic

products. The components of the machine are the hopper, screw, the barrel assembly, and the

injection nozzle. The machine is a batch processing machine and fabricated using locally sourced

materials. The machine was tested with polypropylene (pp) and Acrylonitrile Butadiene Styrene

(ABS) materials. Temperatures of 200oC and 300oC were used to test the rate of melting of the

plastic grains and their fluidity. The performance test of the machine indicated average

throughput and injection efficiency, of 261/hr and 92% respectively at a displacement time

of 0. Therefore, this innovation is recommended for small scale plastic industries. The

production cost implication of this machine considering bought out components, material cost,

job cost (machining and non-machining) is approximately fifty-four thousand, eight hundred and

twenty naira only (₦54,820).

Keywords: Injection moulding, Design, Plastics, Throughput, Injection efficiency

Received: 15th November, 2019 Accepted: 23rd December, 2019

1. Introduction

Plastic moulding operates with the concept of

placing a polymer in a molten state into a mould

cavity so that the polymer can take the required

shape. This is achieved with the help of alternating

temperature and pressure. Moulding of plastics can

be done through blow moulding, injection

moulding, rotational moulding and compression

moulding (John, 2009). This work will concentrate

on injection moulding. Injection moulding has

enjoyed sustained growth since its beginnings in

the late 1800s till date (Melick, 1995; Singha and

Vermaa, 2016). The implementation of the

injection moulding technique as a means of plastic

production has evolved from the production of

simple products like combs and buttons to major

consumer, industrial, medical, and aerospace

products (Yi-qi et al., 2013; Siregar et al., 2017).

Plastic injection moulding is one of the most

popular methods for the manufacturing of plastic

components. By using the injection moulding

machine wide variety of products can be

manufactured such as children’s toys, chair caps,

mobile panels, plastic cups, bottle caps, water

bottles and water pipes, chemical drums, TV

cabinets, refrigerator stands, dustbins, and others.

The advantages of plastic injection moulding

machine process include good surface finish of the

product can be produced, less scrap and flashes are

produced, and the process has relatively low labour

costs.

According to Samson (2011), injection

moulding is a method of forming a plastic product

from pellets or powdered thermoplastics. This is

achieved by feeding the material through the

machine component known as the hopper through

to a heated chamber. This is aimed at making it

soft and thereafter force the material into the

mould by the use of the screw. In this whole

process, pressure should be retained until the

material is hardened and ready to be removed from

the mould. This technique appears to be the most

common and preferred form of producing plastic

products with any complexity and size.

Uniport Journal of

Engineering and Scientific

Research (UJESR)

Vol. 4, Issue 1, 2019, Page 25- 33

ISSN: 2616-

© Faculty of Engineering, University of Port Harcourt, Nigeria.

(ujesr)

Processing

Fig. 1: Diagram of the plastic injection machine

Fig. 2: Sectional view of the plastic injection machine

The hopper is fabricated with 3mm flat metal

sheet, this part helps direct the plastic grains into

the barrel for melting and injecting. A circular pipe

of 55mm internal diameter was used for the

construction of the plastic injection moulding

barrel, where the screw is given 0 tolerance

so it can rotate and move linearly in the barrel.

Also, 55mm thick shaft was used to construct the

plastic injection moulding screw by threading

operation in a lathe machine. The torpedo consists

of an assembly of valve and a locking ring for

preventing backward movement during the

injection process. These parts were constructed by

machining using a lathe machine. In addition, the

injection nozzle was fabricated. This part is

connected to the end of the barrel in which the

Processing

molten materials come out from and then go into

the mould cavity. The platen is constructed from a

flat metal sheet. Next is the heater band which is

an electric device that generates the amount of heat

required to melt the plastic grains, it is of different

sizes and capacities. The type used is called the

Mica heater band. The selection of the heater band

depends on the amount of heat needed in a system.

Mica heater bands provide excellent thermal

conductivity. These bands are basically of mica

insulator a nickel-chrome resistant ribbon wire.

Mica bands are capable of attaining a temperature

up to 90oF and a normal watt density of 20-45W on

a barrel. This rotating handle was constructed with

a circular pipe. Its function is to help in rotating the

screw manual by hand. The frame was also

constructed with angle iron bars, which act as

support and carrier for the other machine

components. Fig. 3 presents a detailed drawing of

the components of the injection moulding machine.

Fig. 3: Detailed drawing of injection moulding machine component

2 Design analysis of the plastic injection

machine

The machine was designed for safe use, ease of

operation at low maintenance cost. The

components of the plastic injection machine are as

follows: feed hopper, screw, barrel and feed throat,

heating elements, frame/stand, bearing assembly

and temperature controller.

2.4 Design of injection screw conveyor

One important component of the machine is

the injection screw also known as the reciprocating

screw used in compressing, melting and conveying

the plastic material. The screw is a cylindrical rod

with constant outside diameter. The screw rotates

within the barrel. As the screw rotates, it forces the

plastic materials in the channel forward which is

heated, melted and the molten material will be

ready for injection. Injection mould screw of

55mm was employed with the following

parameters models as recommended by

Rauwendaal (2013):

Total length of screw (L) = 10D (1)

Length of feeding zone section (Lf) = 2D (2)

Length of transition zone section (Lt) =3D (3)

Length of melting zone section (Lm) = L – (Lf + Lt) (4)

Helix angle (𝜑) = 18o (5)

Flight pitch = D/2 (6)

Flight width = 0 (7)

From the equations given, the total length of screw

(L) was obtained as 550mm, length of feeding

zone section (Lf) as 110mm, length of transition

zone section (Lt) as 165mm, length of melting zone

section (Lm) as 275mm, helix angle (𝜑) as 18o,

flight pitch as 27 and flight width as 5.

Diagram of Barrel Diagram of a screw Diagram of a Topedo
Diagram of a nozzle Diagram of a fixed platen Diagram of heater band
Diagram of Hopper Diagram of rotating handle Diagram of table

Processing

to enhance injection pressure and to avoid cold

short before getting into mould cavity. The

machine temperature controller was set at 200oC

and then 300 oC for the experimental runs

undertaken. For the temperature measurements, a

thermocouple was used.

Fig. 4 presents the effect of initial barrel

temperature on the material output temperature

using pp which has a melting point of 160oC. The

duration of time taken for plastic material grain to

travel from the hopper to the nozzle was tested

with respect to machine temperature at times

ranging from 10secs to 30secs. The rate of

displacement of plastic grains was dependent on

the rotating speed of the screw, thus when the

screw handle is rotated faster the plastic grains

then moved at a faster rate through the barrel.

Besides, the longer the material stays in the barrel,

the more heat it gains and there is increased

temperature.

Fig. 4: Melting temperature test using polypropylene (PP) material

Fig. 5: Melting temperature test using Acrylonitrile Butadiene Styrene (ABS) material

In addition, ABS was also used which has a

melting point of 105oC. From the result obtained as

shown in Fig. 5, it was observed that when the

machine heating system is set to a higher

temperature the rate of melting of the plastic grains

became faster and discharges at high temperature

thus retaining its fluidity.

0
50
100
150
200
250
300
350
0 5 10 15 20 25 30 35
Final Melting Temperature (
oC
)
Material displacement time (seconds)

Effect of Initial barrel temperature on material output temperature

using polypropylene (PP) material

Final temperature of moulding material at 200oC
Final temperature of moulding material at 300oC
0
50
100
150
200
250
300
350
0 5 10 15 20 25 30 35
Final Melting Temperature (
oC
)
Material displacement time (seconds)

Effect of Initial barrel temperature on material output temperature

using Acrylonitrile Butadiene Styrene (ABS)

Final temperature of moulding material at 200oC
Final temperature of moulding material at 300oC

Processing

The injection machine performance was

further tested by the evaluation of the Machine

injection efficiency (IE) and Throughput (TP). The

performance test was carried out after the

fabrication and assembly of the machine. The

machine was fed with samples of equal-weighted

mass of the plastic materials used through the

hopper per time. A stopwatch was used to record

the time taken for the processing of each

experimental batch.

𝑀𝑎𝑐ℎ𝑖𝑛𝑒 𝑖𝑛𝑗𝑒𝑐𝑡𝑖𝑜𝑛 𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦, 𝐼𝐸 (%) =

𝑂𝑢𝑡𝑝𝑢𝑡 𝑚𝑎𝑠𝑠 𝑓𝑟𝑜𝑚 𝑖𝑛𝑗𝑒𝑐𝑡𝑖𝑜𝑛 𝑚𝑎𝑐ℎ𝑖𝑛𝑒,𝑂𝑚 (𝑘𝑔)

𝐼𝑛𝑝𝑢𝑡 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑝𝑙𝑎𝑠𝑡𝑖𝑐 𝑝𝑒𝑙𝑙𝑒𝑡𝑠,𝐼𝑚 (𝑘𝑔) (16)

𝑇ℎ𝑟𝑜𝑢𝑔ℎ𝑝𝑢𝑡, 𝑇𝑃 (𝑘𝑔 ℎ𝑟⁄ ) =

𝑂𝑢𝑡𝑝𝑢𝑡 𝑚𝑎𝑠𝑠 𝑓𝑟𝑜𝑚 𝑖𝑛𝑗𝑒𝑐𝑡𝑖𝑜𝑛 𝑚𝑎𝑐ℎ𝑖𝑛𝑒,𝑂𝑚 (𝑘𝑔)

𝑇𝑖𝑚𝑒 𝑡𝑎𝑘𝑒𝑛,𝑇 (ℎ𝑟) (17)

Table 1: Performance test responses for the Injection machine

Experimental

runs

Input mass (Im)

(kg)

Time taken

(T) (hr)

Output mass

(Om) (kg)

Machine injection

efficiency (IE) (%)

Throughput

(TP) (kg/hr)

1 10 0 9 97 279.

2 10 0 8 86 241.

3 10 0 9 95 266.

4 10 0 9 94 268.

5 10 0 8 89 248.

Average 10 0 9 92 261.

Table 2: Injection machine production cost

Description Material Size Quantity Unit

Price (₦)

Total Price

(₦)

Barrel Circular pipe Θ50mm x 3000 1 2000 2000

Screw Shaft Θ60mm x 277mm 1 2500 2500

Nozzle Shaft Θ40mm x 70mm 1 500 500

Topedo Shaft Θ60mm x 350mm 1 3500 3500

Plating block Flat metal block 120mm x 120mm x 8mm 4 600 2400

Plating pin Mill steel pin 10mm x 150mm 8 300 2400

Plating handle Mill steel plat bare 10mm x 300mm x 5mm 4 200 800

Plating handle hinges Mill steel pipe Θ6mm x 100mm 1 200 200

Plating handle hinges Mill steel rod 5mm x 100mm 1 200 200

Rotating handle Cast iron 200mm 1 1000 1000

Table Angle iron 1 ′′ x 8ft 2 1000 2000

M5 Align bolt Mill steel 20mm 10 50 500

M12 Nut Mill steel 16 20 320

Heater Bands 3 3000 9000

Temperature controller 1 6000 6000

Thermos couple 1 1000 1000

Power breaker switch 1 500 500

Construction and Labour 15000

Miscellaneous 5000

Total 54,

Processing

Uniport Journal of Engineering & Scientific Research Vol. 4, Issue 1, 2019 Page 33

Design; McGraw-Hill Companies Inc., Eighth

Edition.

Singha, G. and Vermaa, A. (2016) A brief review

on injection moulding manufacturing process;

Proc. Int Conf. of Materials Processing and

Characterization (Materials Today:

Proceedings): 1423-1433.

Siregar, R., Khan S. and Umurani, K. (2017)

Design and development of injection moulding

machine for manufacturing maboratory; IOP

Conf. Series: Journal of Physics: Conf. Series

908: 1-6.

Yi-qi, W., Jae-gyu, K., and Jung-il, S. (2013)

Optimization of plastic injection molding

process parameters for manufacturing a brake

booster valve body J. Materials and Design,

56: 313-317.

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Designand Fabricationof Mini Injection Moulding Machinefor Small to Medium Scale Plastic Processing

Course: fliud mechanics (2222222)

16 Documents
Students shared 16 documents in this course

University: جامعة كفر الشيخ

Was this document helpful?
See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/339178794
Design and Fabrication of Mini-Injection Moulding Machine for Small-to-
Medium Scale Plastic Processing
Article · December 2019
CITATIONS
0
READS
7,470
1 author:
Some of the authors of this publication are also working on these related projects:
FOOD PRODUCTION PROCESSES View project
Systtems Analysis and Design View project
Nwadinobi Chibundo Princewill
Abia State University, Uturu, Abia State
40 PUBLICATIONS35 CITATIONS
SEE PROFILE
All content following this page was uploaded by Nwadinobi Chibundo Princewill on 11 February 2020.
The user has requested enhancement of the downloaded file.

Students also viewed

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