Faculty of Manufacturing Engineering

Transcription

1 Faculty of Manufacturing Engineering EFFECT OF INJECTION MOULDING PARAMETERS ON WARPAGE DEFLECTION Siti Salmah Binti Mohd Sani Master of Science in Manufacturing Engineering 2015

2 EFFECT OF INJECTION MOULDING PARAMETERS ON WARPAGE DEFLECTION SITI SALMAH BINTI MOHD SANI A thesis submitted in fulfillment of the requirements for the degree of Master of Science in Manufacturing Engineering Faculty of Manufacturing Engineering UNIVERSITI TEKNIKAL MALAYSIA MELAKA 2015

3 DECLARATION I declare that this thesis entitled Effect of Injection Moulding Parameters on Warpage Deflection is the result of my own research except as cited in the references. The thesis has not been accepted for any degree and is not concurrently submitted in candidature of any other degree. Signature :... Name :... Date :...

4 APPROVAL I hereby declare that I have read this thesis and in my opinion this thesis is sufficient in terms of scope and quality for the award of Master of Science in Manufacturing Engineering. Signature :.... Supervisor Name :... Date :.....

5 DEDICATION To my beloved family

6 ABSTRACT Injection moulding is a process that can be characterised as their ability to produce high production rates with accurately product size and complex part shape. Generally, there are four elements affected the quality of injection moulded parts such as machine parameters, mould design, plastic materials and operator. In order to ensure quality of injection moulding parts can be produced at minimum cost and maximum productivity, the appropriate machine setting parameters are the priority should be achieved. Variation of process parameters are unavoidable in production of injection moulding and affected the quality of part because involved enormous process parameters. The purpose of this study is to analyze the effect of injection moulding parameters that are including cavity temperature, core temperature, mould temperature, melt temperature and cooling time. The main response of this study is to investigate the warpage deflection using simulation software and actual experimental method. The experiment was performed using injection moulding machine Arburg 420C while simulation was done using Moldflow TM Plastic Insight (MPI) software. Design of experiment (DOE) using Taguchi method was applied to design the experimental runs and it was used to analyze the significant factors that affected the warpage deflection. Three methods of investigation work were performed in this research. First investigation work was performed by compared the deviation percentage between simulation Moldflow TM software and actual experimental method using different core and cavity mould temperature gradient. Second and third investigation works focus on optimized parameters using whole cold mould and whole hot mould where both investigation works were performed using simulation Moldflow TM software. Analysis of variance (ANOVA) was used as statistical tools to get the percentage of contribution for each factor and to find the interaction between parameters involved. The average deviation percentage of warpage deflection by simulation software and actual experiment for first investigation work using different mould core and cavity temperature gradient was found 12.80%. The improvement of warpage deflection between those three investigation works shows that the warpage deflection is improved at 89.53% from mm to mm between first and third investigation work. Meanwhile, warpage reduction between first and second investigation is 83.52% and between second and third investigation is 35.31%. Result shows that the lower differences between core and cavity temperature contributes smaller warpage deflection. On the other hand hot mould temperature controlled contributes less warpage deflection as compared to cold mould. This study proved that with appropriate control parameters in injection moulding process can produce better plastic products quality. i

7 ABSTRAK Pengacuan suntikan adalah satu proses yang dapat disifatkan mempunyai kemampuan untuk menghasilkan sesuatu produk dengan kadar pengeluaran yang tinggi, saiz produk yang tepat dan bentuk produk yang kompleks. Secara umumnya, terdapat empat elemen yang memberikan kesan ke atas kualiti pengacuan suntikan sesuatu produk seperti parameter mesin, reka bentuk acuan, bahan plastik dan operator. Bagi memastikan kualiti produk acuan suntikan boleh dihasilkan pada kos yang minimum dan produktiviti yang maksimum, tetapan parameter mesin yang sesuai adalah perkara pertama yang perlu dicapai. Variasi proses parameter tidak dapat dielakkan dalam pengeluaran acuan suntikan dan ianya memberi kesan kepada kualiti sesuatu produk kerana melibatkan proses parameter yang sangat banyak. Tujuan kajian ini adalah untuk menganalisa kesan parameter pengacuan suntikan seperti suhu rongga, suhu teras, suhu acuan, suhu leburan dan masa penyejukan. Respon utama kajian ini adalah untuk menyiasat kesan ledingan dengan menggunakan kaedah simulasi dan eksperimen. Eksperimen ini dijalankan dengan menggunakan mesin acuan suntikan Arburg 420C manakala simulasi dilakukan dengan menggunakan perisian Moldflow TM Plastic Insight (MPI). Rekabentuk eksperimen (DOE) menggunakan kaedah Taguchi telah digunakan untuk merancang eksperimen dan ianya digunakan untuk menganalisa faktor-faktor penting yang mempengaruhi ledingan. Tiga kaedah penyelidikan telah dijalankan dalam kajian ini. Kaedah penyelidikan pertama ialah melalui perbandingan peratusan sisihan antara perisian Moldflow TM simulasi dan kaedah eksperimen sebenar dengan menggunakan suhu acuan teras dan rongga yang berbeza. Kerja penyelidikan kedua dan ketiga memberi penekanan kepada mengoptimumkan parameter menggunakan simulasi perisian Moldflow TM. Analisa varians (ANOVA) digunakan sebagai alat statistik untuk mendapatkan peratusan sumbangan bagi setiap faktor dan mengenalpasti interaksi di antara parameter yang terlibat. Purata peratusan sisihan ledingan di antara perisian simulasi dan eksperimen sebenar untuk kaedah penyelidikan pertama bagi suhu acuan teras dan rongga berbeza adalah sebanyak 12.80%. Penambahbaikan nilai ledingan di antara ketiga-tiga kaedah penyelidikan menunjukkan bahawa ledingan bertambah baik sebanyak 89.53% dari mm kepada mm antara kaedah penyelidikan pertama dan ketiga. Sementara itu, pengurangan ledingan antara kaedah penyelidikan pertama dan kedua adalah 83.52% dan antara kaedah penyelidikan kedua dan ketiga adalah 35.31%. Keputusan menunjukkan bahawa perbezaan yang lebih rendah di antara suhu teras dan suhu rongga menyumbang ledingan yang lebih kecil dan acuan suhu panas menyumbang kurang ledingan berbanding acuan sejuk. Oleh itu, ia membuktikan bahawa dengan pengawalan parameter yang sesuai dalam proses suntikan plastik boleh menghasilkan produk plastik yang lebih berkualiti. ii

8 ACKNOWLEDGEMENTS First and foremost I thank to Allah S.W.T, the Almighty God for His will and grace for giving me patience and spirit throughout this research until the research is successfully completed. The highest appreciation to my principle supervisor, Dr. Mohd Amran bin Md Ali for his supervision, guidance, knowledge and valuable support in all moves during the course at my study. Special thank and gratefully acknowledge to all the Universiti Teknikal Malaysia Melaka (UTeM) staff especially at Faculty of Manufacturing Engineering (FKP) and Faculty of Technology (FTK) for providing research facilities, support, advice and assistance throughout my master project. I am also grateful to UTeM for the financial support through the short term grant PJP/2012/FKP (25B) S1028. Lastly, I would like to express my special thanks and appreciation to my beloved parents, family members and colleagues who continuous giving me patience and supports all the time. I offer my regards and blessings to all of those who supported me in any aspect during the completion of this project.. iii

9 DECLARATION DEDICATION ABSTRACT ABSTRAK ACKNOWLEDGEMENTS TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES LIST OF APPENDICES LIST OF ABBREVIATIONS LIST OF PUBLICATIONS TABLE OF CONTENTS PAGE i ii iii iv vi viii xi xii xiii CHAPTER 1. INTRODUCTION Background Problem Statement Objectives Scope Thesis Outline 7 2. LITERATURE REVIEW Injection Moulding Application Process Injection Moulding Parameters Melt Temperature Mould Temperature Cooling Time Mould Types of Mould Feeding System Mould Components Cooling Medium Plastic Defect Warpage Defect Plastic Material Polypropylene (PP) Computer Aided Engineering (CAE) Simulation Product Design Meshing Cooling System Warpage Analysis Design of Experiment (DOE) Taguchi Method Application of Taguchi Method 43 iv

10 2.8 Analysis of Variance (ANOVA) Summary METHODOLOGY Introduction Equipment, Tool and Material Machine Mould Plastic Material Warpage Measurement Mould Temperature Controller Mould Temperature Measurement Software Minitab TM Version Moldflow TM Plastic Insight (MPI) Experimental Setup Planning Matrix for Mould Temperature Gradient Planning Matrix for Cold Mould Planning Matrix for Hot Mould Warpage Analysis Using Moldflow TM Plastic Insight (MPI) Summary RESULT AND DISCUSSION Framework of Discussion Result Product Pre-Simulation and Meshing Statistics Mould Temperature Gradient Simulation Taguchi Analysis for Mould Temperature Gradient Analysis of Variance (ANOVA) for Mould Temperature Gradient Interaction Plot for Mould Temperature Gradient Comparison between Simulation and Experiment Cold Mould Temperature Simulation Taguchi Analysis for Cold Mould Analysis of Variance (ANOVA) for Cold Mould Interaction Plot for Cold Mould Hot Mould Temperature Simulation Taguchi Analysis for Hot Mould Analysis of Variance (ANOVA) for Hot Mould Interaction Plot for Hot Mould Summary CONCLUSION AND RECOMMENDATIONS 105 FOR FUTURE RESEARCH REFERENCES 108 APPENDICES 120 v

11 LIST OF TABLES TABLE TITLE PAGE 2.1 Market segment for injection molded products Commonly used parameters and responses in injection moulding process Melt temperature range recommendation Mould temperature range recommendation Function of each component Comparison of crystalline and amorphous material Standard orthogonal array for Taguchi method Optimization and modelling application of Taguchi method Summarization of ANOVA Mechanical properties of P20 tool steels Thermal properties of P20 tool steels Properties of polypropylene Working procedure of warpage measurement Properties oil as coolant fluid medium Properties water as coolant fluid medium Constant pressure parameters Process parameters and working levels mould temperature gradient Planning matrix for gradient mould temperature Process parameters and working levels cold mould Planning matrix for cold mould Process parameters and working levels hot mould Planning matrix for hot mould Mesh statistics 76 vi

12 4.2 Simulation result of warpage deflection for mould temperature gradient Signal to noise (S/N) ratio for mould temperature gradient Response table (S/N) ratio for mould temperature gradient Analysis of variance (ANOVA) of mould temperature gradient Simulation result of warpage deflection for cold mould Signal to noise (S/N) ratio for warpage deflection of cold mould Response table S/N for warpage deflection of cold mould ANOVA for warpage deflection of cold mould Simulation result of warpage deflection for hot mould Signal to noise (S/N) ratio for warpage deflection of hot mould Response table S/N for warpage deflection of hot mould ANOVA for warpage deflection of hot mould Percentage of improvement warpage deflection using Taguchi method Percentage of improvement warpage deflection between mould condition 104 vii

13 LIST OF FIGURES FIGURE TITLE PAGE 1.1 Development of television commercialization Cyclic process injection moulding Injection unit of injection moulding machine Ishikawa cause-effect diagram of injection moulding process parameters Investigated process parameters in injection moulding of plastic Investigated responses in injection moulding of plastic Two plate mould Types of injection mould Feeding system Components of mould Example of warpage deflection Types of polymer Break down of US themoplastic production into common types Location, distance, and diameter of cooling channels Flow chart of Taguchi sequence Methodology outline Injection moulding machine Mould plate (a) core (b) cavity Dumbbell part Horizontal optical comparator Heater mould temperature controller Chiller mould temperature controller 57 viii

14 3.8 Infrared thermometer Mould temperature measurement for first investigation work Mould temperature measurement for first investigation work Overall Taguchi approach Example of mesh statistics Example of process setting wizard Overview framework of discussion result D solid modelling using solid work software Meshing process Visualization of minimum warpage deflection for mould temperature gradient Visualization of maximum warpage deflection for mould temperature gradient Warpage of injection moulded part due to different mould temperature Assymmetrical flow front due to different mould temperature S/N response diagram of mould temperature gradient Prediction suggested for optimization by Taguchi method in minitab TM software for mould temperature gradient Result prediction optimization of Taguchi method for mould temperature gradient Interaction plot of core and cavity temperature for mould temperature gradient Comparison between simulation and experimental warpage deflection for mould temperature gradient Visualization of minimum warpage deflection for cold mould temperature Visualization of maximum warpage deflection for cold mould temperature S/N response diagram for warpage deflection of cold mould temperature Prediction of optimization by Taguchi method for cold mould Result prediction of Taguchi method for cold mould Interaction plot of mould and melt temperature for cold mould Visualization of minimum warpage deflection for hot mould temperature Visualization of maximum warpage deflection for hot mould temperature S/N response diagram for warpage deflection of hot mould temperature Prediction of optimization by Taguchi method for hot mould 100 ix

15 4.23 Result prediction of Taguchi method for hot mould Interaction plot for hot mould 102 x

16 LIST OF APPENDICES APPENDIX TITLE PAGE A Specification of injection moulding Arburg 420 C B Dumbbell part drawing 121 C Visualization warpage for mould temperature gradient 122 D Visualization warpage for cold mould temperature 128 E Visualization warpage for hot mould temperature 134 F Raw data warpage experimental Y-axis 140 xi

17 LIST OF ABBREVIATIONS DOE - Design of experiment ANOVA - Analysis of variance MPI - Moldflow TM plastic insight OA - Orthogonal array CAE - Computer aided engineering PP - Polypropylene US - United State RSM - Response surface method S/N - Signal to noise SS - Sum of square DF - Degree of freedom MS - Mean square s - Second mm - Millimeter ºC - Degree celcius xii

18 LIST OF PUBLICATIONS Mohd Amran, Siti Salmah, Mohd Zaki, Raja Izamshah, Mohd Hadzley, Sivarao Subramonian, Mohd Shahir, Mohd Amri, The Effect of Pressure on Warpage of Dumbbell Plastic Part in Injection Moulding Machine. Advanced Materials Research, Vol. 903 (2014), pp Mohd Amran, Siti Salmah, Abdul Faiz, Raja Izamshah, Mohd Hadzley, Manshoor Bukhari, Mohd Shahir, Mohd Amri, Effect of Injection Moulding Machine Parameters on the Warpage by Applying Taguchi Method. Applied Mechanics and Materials, Vol. 699 (2015), pp Mohd Amran, Siti Salmah, Zolkarnain Marjom, Umar Al-Amani, Raja Izamshah, Mohd Hadzley, Zulkeflee Abdullah, Mohd Sanusi, Warpage Analysis Verification between Simulation and Experimental of Dumbbell Plastic Part in the Injection Moulding Process. International Symposium on Research in Innovation and Sustainability, Vol. 26 (4), pp Mohd Amran Ali, Siti Salmah, Zulkeflee Abdullah, Liew Pay Jun, Mohd Razali Muhamad, Raja Izamshah, Mohd Hadzley, Abu Abdullah, Zolkarnain Marjom, Effect of Cold and Hot Mould on Warpage using Mouldflow Insight Analysis. Proceeding of International Conference on Design and Concurrent Engineering (idecon 2014). September Melaka: Universiti Teknikal Malaysia Melaka (UTeM). Mohd Amran, Siti Salmah, Raja Izamshah, Mohd Shahir, Mohd Amri, Effendi Mohamad, Zolkarnain Marjom, Hambali Boejang, Umar Al-Amani, Mohd Kamal Musa, Warpage Analysis of Different Number Cooling Channels for Dumbbell Plastic Part in Injection Moulding. Proceeding of International Conference on Design and Concurrent Engineering (idecon 2014). September Melaka: Universiti Teknikal Malaysia Melaka (UTeM). xiii

19 CHAPTER 1 INTRODUCTION This chapter describes the background of the project research, problem statement, scope of study, objectives and the overall organization of the contents in this thesis. 1.1 Background Plastic industry is one of the fastest growing major industries in the world. Usage of plastic materials increases from time to time. Life without plastics is rather hard to imagine. Every day, human rely on plastic items such as household, automotive parts, medical devices and others. Department of Skills Development Ministry of Human Resources (2013) reported that Malaysia produces more than 60% of the products is manufactured from plastic materials. There are varieties of processing method that can be used to convert the plastic raw materials into end product. Common plastic processes involved are extrusion, injection moulding, blow moulding, compression moulding, transfer moulding and rotational moulding. However, injection moulding is one of the most important polymer processing operations in plastic industry. Zhou (2013) reported that among, all plastic products about one third are produced by injection moulding process. Meanwhile, Kittisorn (2004) stated that injection moulding accounts around 47% of all plastic products manufactured. This is 1

20 because of injection moulding process having many advantages such as can produce complex shape of plastic parts, ability to produce good dimensional ability, mass production, short cycle operation time etc. Subsequently, injection moulding is widely used for manufacturing a variety of plastic parts, from the smallest component to entire body panels of cars (Wolf, 2012). Four elements that affected the quality of injection moulded parts are machine setting parameters, mould conditions, type of plastic materials and human error during handling the injection moulding operations. Further, contributions of each element approximately are type of plastic materials 10%, human error 10%, mould conditions 20% and machine setting parameters 60% (Kamal et al., 2009). Nevertheless, it is difficult to control injection machine setting parameters due to many parameters involved in injection moulding process. Thus, several approaches have been applied in injection moulding to study about the process parameters such as using trial and error method, simulation using software and optimizing process parameter by design of experiment (DOE). Trial and error method has insufficiently to support the plastic polymer product development due to increasing demand for high quality product and short production time (Fuh et al., 2004). Simulation of polymer processing is getting more applicable in industry because it helps to forecast the problems that may occur, study of process parameters control and optimized processing conditions. In addition, DOE approached enables to gaining an in-depth knowledge of the process interaction. Therefore, simulation method and DOE approached are more preferred in injection moulding due to their capability to lead toward fast, cost effective and reliability. Although, injection moulding is an important process for plastic production, possibility getting various defects can be found due to complex processing involved. 2

21 Defects such as warpage, short shot, flashing, burn marks, sink marks, shrinkage, and weld line are the common problems that impact product quality in injection moulding process. Warpage defect becomes a common pitfall in injection moulding process especially for thin plastic parts. Warpage can be defined as dimensional distortion from the intended shape of the plastic part in a moulded product after it was ejected from the mould in injection moulding process (Fischer, 2012). It causes a part to bend or twist out of shape and alters dimensions as well as the contours and angles of the part (Alfreda, 2006). Consequently, the warpage part can cause failure to surface quality and poor part assembly. Therefore, the ability to reduce the amount of warpage in plastic is very useful in all stages of the product life cycle. Knowing how process setting parameters contribute to warpage phenomenon and minimize them becomes increasingly important. Therefore, this research studies the effect of injection moulding parameters on the warpage of dumbbell product. The simulation method using Moldflow TM software and experimental operation are performed through input various process parameters; melt temperature, mould temperature, cooling time, core and cavity temperature. Then, warpage deflection is investigated as output response. Mould temperature was controlled using water for cold mould and oil for hot mould. Then, Taguchi method and analysis of variance (ANOVA) were performed as statistical tools. 3

22 1.2 Problem Statement Nowadays, electronic product such as handphone, remote control, digital watch, laptop, note book, camera, video cam, television etc. are design to become lighter, thinner and smaller to fulfil market demand. Figure 1.1 shows the example of product development for television from era 1930 to 2010 century. It is obviously shown that the development of the television becomes lighter and thinner. One way to ensure lighter and thinner plastic part produce is by reduces the wall thickness. However, producing a lighter, thinner and smaller part was the challenges to the plastic industry because it can produce higher of warpage deflection (Huang and Tai 2001). Ranran and Huimin (2013) investigate the defect of warpage on the washing machine control panel using moldflow software and found that mould having unbalanced gate location produce higher warpage deflection. Wang et al., (2012) reveal that automobile dashboard having higher warpage due to the limitation of the gating system. Furthermore, Sun et al., (2011) found that warpage deformation was minimized after analyse using orthogonal experiment designation. Figure 1.1: Development of Television Commercialization (Lia, 2013) 4

23 As well know that, warpage defect is one of the big issues in injection moulding process (Subramanian, 2011). This defect will impact the final of the product and will cause the product to be rejected. Therefore, it s become motivation to many researchers to find the best combination of plastic materials, optimum process setting parameters and prediction using simulation study. Simulation method become essential due to many parameters involved in injection moulding process. In injection moulding process, plastic material is heated until molten, injected into the mould, cooled rapidly and then ejected from the mould. Normally, the mould temperature is lower than hot melt plastic temperature during injected. Consequences, the skin touching of hot melt plastic and mould surface lead the temperature of the mould wall instantaneously causing enormous temperature change between them. The exchange of heat adding with as well as thickness and pressure variations throughout the structure, cause the component to have a non-uniform shrinkage rate. The non-uniform shrinkage is one from the most contribution causes of warpage which involved many process parameters. Hence, knowing the process parameters that contribute to warpage defect becomes increasingly important. In order to minimize the formation of warpage defect, studies about how process parameters affect on the warpage is very significant. Then, this research focuses on the effect of melt temperature, mould temperature, cooling time, core and cavity temperature on warpage deflection based on past researcher summarization and importance of those parameters selected towards warpage deflection as discussed in literature review. 5

24 1.3 Objectives The main objective of this research is to study the effect of injection moulding parameters on warpage deflection. To achieve main objective, three sub objectives are outline as follows: 1. To investigate the effect of injection moulding parameters such as melt temperature, mould temperature, cooling time, core and cavity temperature on warpage deflection. 2. To identify the percentage of deviation warpage deflection between simulation software and actual experiment. 3. To determine the smallest warpage deflection between three investigation works that are different core and cavity mould temperature gradient, whole cold mould and whole hot mould. 1.4 Scope This project focuses on study the effect of injection moulding process parameters on warpage deflection. Injection moulding machine Arburg 420C was used as main equipment in this research. It is due to availability of this machine in Polymer Laboratory, Faculty of Manufacturing Engineering, Universiti Teknikal Malaysia Melaka (UTeM). Injection moulding parameters that investigated were melt temperature, mould temperature, cooling time, core and cavity temperature. The mould used in this research was two-plate dumbbell injection mould. Horizontal optical comparator was used as measurement equipment the warpage deflection. There were three investigation work of research study. The first investigation work was performed using different mould temperature gradient between cold at mould core side and hot at mould cavity side using simulation software and experiment operation approach. The second investigation work 6