Experimental Analysis and Optimization of Process Parameters of Plastic Injection Moulding for the M

IJSRD - International Journal for Scientific Research & Development| Vol. 4, Issue 05, 2016 | ISSN (online): 2321-0613

Experimental Analysis and Optimization of Process Parameters of Plastic Injection Moulding for the Material Polypropylene S.S.Bajaj1 J.J.Salunke2 1,2 Assistant Professor 1,2 Department of Mechanical Engineering 1,2 DIEMS, Maharashtra, India Abstract— In present work, experimental analysis and optimization of process parameters of plastic injection moulding has been reported. Response surface methodology (RSM) has been utilized to investigate the influence of three important input parameters – plasticizing temperature, injection pressure and cooling time on two performance characteristics- Tensile Strength of material Polypropylene (PP). Centered central composite design was employed to conduct the experiments and to develop a correlation between the process parameters and performance characteristics. The analysis of experimental work is performed using MINITAB 16 statistical software.

Response surface methodology (RSM) was applied for developing the mathematical models in the form of regression equation and to find optimized values of process parameters. The optimum set of process parameters obtained are cross validated by using ANOVA method. The influence of all factors has been identified which can play a key role in increasing Tensile Strength of PP. Surface plots and Contour plots have been plotted for studying combined effect of two factors while keeping other factor at their midvalues. From ANOVA it is clear that for Polypropylene to achieve maximum Tensile Strength injection pressure is the most significant factor followed by cooling time and plasticizing temperature followed by injection pressure and cooling time.

Key words: ANOVA, Polypropylene, Response Surface Methodology (RSM)

plasticizing unit, and the drive unit; they are shown in Figure 1. The clamping unit holds the mould. It is capable of closing, clamping, and opening the mould. Its main components are the fixed and moving plates, the tie bars and the mechanism for opening, closing and clamping. The injection unit or plasticizing unit melts the plastic and injects it into the mould. The drive unit provides power to the plasticizing unit and clamping unit. The clamping force of typical injection moulding machines range from 200 to 100,000 kN.

Fig. 1: Injection Moulding Process

I. INTRODUCTION Injection Moulding is an extensive global manufacturing process for making simple to intricate plastic, ceramic and metal parts. Injection Moulding converts wax, thermoplastics, thermo sets as well as powdered metals and magnesium into thousands of products. Injection Moulding is the most commonly used manufacturing process for the fabrication of plastic parts. A wide variety of products are manufactured using injection moulding, which vary greatly in their size, complexity, and application. The injection moulding process requires the use of an injection Moulding machine, raw plastic material, and a mould. Injection Moulding is a manufacturing process which is producing parts from both thermoplastic and thermosetting plastic materials. transformation of plastic pellets into a moulded part.

Fig. 2: Line diagram of mould There are three main stages in the injection moulding cycle: stage 1-injection, followed by stage 2holding pressure and plasticizing and finally stage 3ejection of the moulded part. When stage 3 is completed, the mould closes again and the cycle starts over again.

II. SYSTEM MODEL

III. PREVIOUS WORK

An injection moulding machine produces components by injection moulding process. Most commonly used machines are hydraulically powered in-line screw machines, although electric machines are appearing and will be more dominant in the market in near future. The main units of a typical injection moulding machine are the clamping unit, the

B.KC, et.al Sisal-glass fiber hybrid biocomposite: Optimization of injection molding parameters using Taguchi method for reducing shrinkage, Science Direct, 2016, had applied the Taguchi method to optimize the injection moulding (IM) process parameters for sisal and glass fiber hybrid biocomposite. Injection pressure, melt temperature,

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Experimental Analysis and Optimization of Process Parameters of Plastic Injection Moulding for the Material Polypropylene (IJSRD/Vol. 4/Issue 05/2016/265)

mold temperature, holding pressure, cooling time and holding time are the six parameters selected that influence flow and cross-flow shrinkage. Two hybrid biocomposites were used with different content of sisal(SF) and glass fiber(GF); SF20GF10 and SF10GF20.L18 orthogonal array with a mixed-level design and signal-to-noise ratio (S/N) of smaller-the-better was used for experimental design. For both hybrid biocomposites, optimal injection molding settings for minimizing the shrinkage are injection pressure 90 bar, melting temperature 210 0C, mold temperature 40 0 C, cooling time 40s, hold time 6s and optimal holding pressure for SF20GF10 was 70 bar and for SF10GF20 was 50 bar. Based on ANOVA analysis, injection pressure had significant influence on both flow shrinkage and x-flow shrinkage of SF20GF10. For SF10GF20, no factors show significant impact on flow shrinkage; however injection pressure and mold temperature had significant impact on xflow shrinkage.

M.I. Mat Kandara, et.al, Application of DoE for Parameters optimization of compression injection moulding for Flax reinforced bicomposites, Science Direct, 2016, widespread research on polymer composites that consist of natural fiber as reinforcement have been widely discussed.

In this work, an attempt on optimizing the hot press forming process parameters using Response Surface Methodology (RSM) have been made to improve the mechanical properties of the woven flax/PLA composites. Three independent process variables, including moulding temperature, time and pressure were studied. Through the Box Behnken approach, a set of experiment runs based on various combination of compression moulding via Minitab 16 were established. As a results the optimum value for the variables of compression moulding technique parameters were 200°C, 3 min and 30 bar in order to yield 48.902 kJ/m2ofimpact strength. The investigation of this work dealt with the application of RSM using a Box Behnken design (BBD) to optimise the mechanical properties of woven flax/PLA. The ANOVA data showed that the variables are affected the impact strength significantly. The inter-actions of variables also have significant effects on impact strength. The optimal set of processing parameters for woven flax/PLA was found to be moulding temperature (200oC), moulding time (3 min) and moulding pressure (30 bar), to achieve the maximum impact strength of 48.902 kJ/m-2.

Amit Kumar, et.al, Time-Based Optimization of Injection Moulding Process Using Response Surface Methodology, 2015 This study has been made to optimize the process parameters during forming of PVC (L-bow) fitting by injection moulding machine using response surface methodology (RSM).Four input process parameters of injection moulding machine namely filling time, refill time (RFT), tonnage time (TT) and Ejector retraction time (ERT)) is chosen as variables to determine the process performance in terms of cycle time (CT). The analysis of variance (ANOVA) is carried out to determine the effect of process parameter on process performance. The parameters filling time (23), refill time (36) tonnage time (0.68) and Ejector retraction time (1.36) are identified as the most significant optimal setting for Cycle time (CT). In this work, the application of response surface methodology (RSM) on PVC material on injection moulding machine are explained.

In addition, a quadratic model is established for Cycle Time

(CT) so as to examine the influence of process parameters on it. Following are the results to be found:  From the ANOVA it is proved that with the help of quadratic mathematical model the prediction of Cycle Time (CT) with 94.21%. Confident interval.  All the cutting parameters have significant effect but filling time(FT), tonnage time (TT), and Ejector retraction time (ERT) have the most significant effect with the contribution of 85.26%, 1.92% and 3.10% respectively in the total variability of model.

Anand K. Dwiwedi, et.al, Practical application of Taguchi method for optimization of process parameters of injection molding machine for PP material, International Research journal of engineering and technology, 2015, instead of the old concept of trial and error method to determine the process parameters for injection molding aimed to analyze the recent research to determine optimal process parameters of injection molding. The optimization of injection molding process parameters for polypropylene (PP) material has been done using Taguchi methodology.

This methodology provides the optimum value of process parameters with the help of orthogonal array by conducting very few experiments. Processing temperature, Injection pressure, Cooling time and Injection speed are the selected process parameters. The process parameters are optimized by considering Tensile strength as responding factor. The response table for S/N ratio gave the best set of combination for process parameters and highest value for each factor is selected. For Tensile strength of PP, processing temperature is found most effecting factor followed by injection speed, injection pressure and cooling time.

Michael Packianather, et.al, Micro injection moulding process parameter tuning, ScienceDirect, 2015 This paper focuses on tuning the micro injection moulding process parameters. In this study four process parameters namely, barrel temperature, mould temperature, holding pressure and injection speed were considered. In order to capture their behaviour a L16 Orthogonal Array with two levels for each parameter was employed to produce the design of a 15 mm x 20 mm x 1 mm microfluidic platform using Cyclic Olefin Copolymer (COC), a common polymer.

The demoulding force was measured during the micro injection moulding process. The sixteen trials were repeated ten times to incorporate process variation, systematic and random noise in the experimental procedure. The results were analysed using Taguchi method to identify the influence of the process parameters upon the demoulding force and their sensitivity to noise. In addition, the results also indicated either the presence or absence of the two level interactions between these process parameters. This study has contributed to understanding the characteristics of these process parameters in terms of their main effects, interactions and sensitivity to noise and to tune them for their optimal performance. Design of experiment using Taguchi L16 Orthogonal Array has been conducted with four process parameters namely, mould temperature, barrel temperature, holding pressure, and injection speed in order to understand the effect of these parameters during the micro injection moulding process. The analysis was carried out using Minitab16. Two criteria for S/N were used. This study has shown that the most significant parameters are mould temperature and holding pressure. Different polymers will

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Experimental Analysis and Optimization of Process Parameters of Plastic Injection Moulding for the Material Polypropylene (IJSRD/Vol. 4/Issue 05/2016/265)

be used in the future to study the effects of these process parameters upon different materials.

IV. PROPOSED METHODOLOGY The Experimental Set-up (Injection moulding machine), work piece material, tensile and flexural sample specifications, process parameters (input and output) and measuring instruments.

A. Materials Used In the Process The tensile specimens are made by using Polypropylene (PP).

B. Polypropylene PP- Homopolymer 110MA is a natural coloured grade produced by Spheripol II Technology. The grade is high flow & high rigidity and excellent gloss. This grade contains antistatic agent that reduces static charge built up in products.

Recommended Processing Temperature: 150 – 260 0C C. Input Parameters Plasticizing Temperature It is the change in the thermal and mechanical properties of a given polymer which involves:  Lowering of rigidity at room temperature;  Increase of the elongation to break at room temperature;  Increase of the toughness (impact strength) down to the lowest temperature of service ability.

D. Injection Pressure Injection pressure is defined as the pressure on the face of the injection screw when melt material was injected into the mould. With an increase in injection pressure shrinkage decreases.

E. Cooling Time Cooling time is commonly defined as the time from the end of packing stage toward ejection. The criticality of cooling time in terms of shrinkage was confirmed also by considering techniques different from injection moulding.

F. Response Parameters 1) Tensile Strength Tensile Strength determines the behaviour of materials under axial stretch loading. Data from test are used to determine elastic limit, elongation, modulus of elasticity, proportional limit, reduction in area, tensile strength, yield point, yield strength and other tensile properties. Methods for tensile tests of plastics are outlined in ASTM D-638.

2) Tensile Specimen The tensile specimens are manufactured on the injection moulding machine. The dimensions of the tensile samples are ASTM D 638-2010 Dumbbell 127×12.7×3.2mm

Fig. 3: Tensile Specimen Mould Insert V. SIMULATION/EXPERIMENTAL RESULTS In this paper, the experimental results were obtained by conducting experiments based on DOE by Response surface methodology’s (RSM) Central composite design using Minitab 16 software.

Tensile Plasticizing Injection Pressure Cooling Time Strength Temp N/mm2 185 38.1821 30 36.4681 200 65 25 36.0536 185 55 30 35.8148 185 55 30 35.8148 170 65 25 36.235 185 55 30 35.8148 159.773 55 30 30.5641 185 71.8179 30 35.6791 200 45 25 35.5225 210.227 55 30 34.9761 185 55 21.591 35.6791 185 55 30 35.8148 170 45 35 35.8511 185 55 30 35.8148 200 65 35 35.3525 185 55 38.409 36.5637 170 45 25 36.6477 185 55 30 35.8148 170 65 35 37.0451 200 45 35 36.1281 Table 1: Polypropylene input and output parameters values in RSM

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Experimental Analysis and Optimization of Process Parameters of Plastic Injection Moulding for the Material Polypropylene (IJSRD/Vol. 4/Issue 05/2016/265)

A. Central Composite Design for Tensile Strength of Polypropylene Surface Plot of Tensile Strength vs Injection Pressu, Plasticizing Tem Hold Values Cooling Time 38.41

C*C -0.0014 0.0043 -0.315 0.759 A*B 0.0001 0.0009 0.093 0.928 A*C -0.0084 0.0018 -4.725 0.001 B*C 0.006 0.0027 2.254 0.048 Table 2: Estimated Regression Coefficients for Tensile Strength S = 0.3786 R-Sq = 88.4% R-Sq(adj) = 77.9% Residual Plots for Tensile Strength Normal Probability Plot of the Residuals

36

Percent

T ensile Str ength

70

34 160

180

200

40

50

Residuals Versus the Fitted Values

99

2

90

1

Residual

38

50 10

60 Injection P r essur e

1

P lasticizing T emp

0 -1 -2

-2

-1

0 Residual

1

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33

2

6

1

4 2

Tensile Strength < 34.5 34.5 - 35.0 35.0 - 35.5 35.5 - 36.0 36.0 - 36.5 36.5 - 37.0 37.0 - 37.5 > 37.5

70

Injection Pressure

65 60 55

36

37

0 -1 -2

0

Contour Plot of Tensile Strength vs Injection Pressu, Plasticizing Tem

35 Fitted Value

Residuals Versus the Order of the Data

8

Residual

Fig. 4: Surface Plot of Tensile Strength vs Injection Pressure, Plasticizing Temperature, Cooling Time

Frequency

Histogram of the Residuals

34

-2

-1 0 Residual

1

2

4

6

8 10 12 14 Observation Order

16

18

20

Fig. 6: Residual Plots for Tensile Strength

Hold Values Cooling Time 38.41

50 45 40 160

170

180 190 Plasticizing Temp

200

210

Fig. 4: Contour Plot of Tensile Strength vs Injection Pressure, Plasticizing Temperature, Cooling Time Overlaid Contour Plot of Tensile Strength Tensile Strength 30.5641 37.0451

70

Injection Pressure

65

Hold Values Cooling Time 38.41

60

VI. CONCLUSION

55 50 45 40 160

Fig. 7: Response Optimiser for Tensile Strength Global solution after response optimization Plasticizing Temperature:- 195.76990C Injection Pressure :- 71.8150 bar Coling Time :- 21.6190 sec The maximum value of Tensile Strength is 37.0435N/mm2

170

180 190 Plasticizing Temp

200

210

Fig. 5: Overlaid Contour Plot of Tensile Strength Term Coef SE Coef T P Constant 27.7454 21.8707 1.269 0.279 Plasticizing 0.1084 0.1814 0.598 0.034 Temp(A) Injection Pressure(B) -0.643 0.2131 -3.018 0.013 Cooling Time(C) 1.1982 0.4449 2.693 0.023 A*A 0.0004 0.0004 0.789 0.448 B*B 0.0041 0.001 4.187 0.002

In present work, experimental analysis and optimization of process parameters of plastic injection moulding has been reported. Response surface methodology (RSM) has been utilized to investigate the influence of three important input parameters â&#x20AC;&#x201C; plasticizing temperature, injection pressure and cooling time on two performance characteristics-Tensile Strength of materials Polypropylene (PP). Centered central composite design was employed to conduct the experiments and to develop a correlation between the process parameters and performance characteristics. The analysis of experimental work is performed using MINITAB 16 statistical software. The important conclusions that can be drawn from the present research work are summarized as follows:Response surface methodology (RSM) was applied for developing the mathematical models in the form of regression equation.

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Experimental Analysis and Optimization of Process Parameters of Plastic Injection Moulding for the Material Polypropylene (IJSRD/Vol. 4/Issue 05/2016/265)

    

The influence of all factors has been identified which can play a key role in increasing Tensile Strength of PP. Surface plots and Contour plots have been plotted for studying combined effect of two factors while keeping other factor at their least-values.

The optimized value of input parameters was obtained to achieve maximum values of Tensile strength for the material PP From ANOVA it is clear that:For Polypropylene to achieve maximum Tensile Strength injection pressure is the most significant factor followed by cooling time and plasticizing temperature.

VII. FUTURE SCOPES

Although investigation has been done for process parameters still there is scope for further improvement. The following suggestions may prove useful for future work: 1) Any other mechanical or electrical property of the material can be measured as a response parameter 2) Efforts can be taken to investigate the effects of process parameters on shrinkage and warpage of the materials.

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[3] Amit Kumar, et.al, Time-Based Optimization of Injection Moulding Process Using Response Surface Methodology, 2015 [4] Anand K. Dwiwedi, et.al, Practical application of Taguchi method for optimization of process parameters of injection molding machine for PP material, International Research journal of engineering and technology, 2015.

[5] Michael Packianather, et.al, Micro injection moulding process parameter tuning, ScienceDirect, 2015.

[6] Daniel Annicchiarico & Jeffrey R. Alcock Review of Factors that Affect Shrinkage of Molded part in Injection Molding, , Taylor & Francis, 2014.

[7] D.Bhattacharya & B.Bepari, Feasibility study of recycled polypropylene through multi response optimization of injection moulding parameters using grey relational analysis, ScienceDirect , 2014.

[8] Sanjay Lahoti, et.al, Optimization of Critical Processing Parameters for Plastic Injection Molding for Enchance Productivity and reduced time for development, International Journal of Advanced Engg Research and studies, 2014.

[9] Wie Gua, et.al, Influence of processing parameters on microcellular injection molding, ScienceDirect, 2014.

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[11] Kingsun Lee & Jui Chang Lin,Optimization of Injection Molding Parameters for LED Lamshade, , ICETI ,2013.

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[14] Nik M. Mehat, et.al, Reducing the shrinkage in plastic injection moulded gear via Grey-Based-Taguchi optimization method, World Congress of Engg, 2012.

[15] Stefan Moser, Effective Run-In and Optimization of injection molding process , InTech, 2012.

[16] Alireza & Sadeghi, Parameter study in plastic injection molding process using stastistical methods and IWO algorithm, International Journal of Modeling and Optimization 2011.

[17] M.Stanek, et.al, Optimization of Injection Molding Process, International Journal of Mathematics and Computers n Simulation, 2011 [18] S.Kamaruddin, Zahid A.Khan & S.H. Foong , Application of Taguchi Method in the Optimization of Injection Moulding Parameters for Manufacturing products from Plastic Bend, International Journal of Engg and Technology, 2010.

[19] Chung-Neng Huang, Chong-Ching Chang, Determination of Optimal Manufacturing Parameters for Injection Mold by Inverse Model Basing on MANFIS, 2010.

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