DESIGN AND DEVELOPMENT OF MICRO- INJECTION MOLDING MACHINE FOR METAL INJECTION MOLDING (MIM)

Transcription

1 DESIGN AND DEVELOPMENT OF MICRO- INJECTION MOLDING MACHINE FOR METAL INJECTION MOLDING (MIM) A dissertation Submitted in partialfulfiffment for the award of the degree of MASTER OF TECHNOLOGY in PRODUCTION ENGINEERING Su6mitted 6y VIKASH KUMAR 2004MEP2498 Vlicr the guidance of Dr. Naresh Bhatnagar DEPARTMENT OF MECHANICAL ENGINEERING INDIAN INSTITUTE OF TECHNOLOGY, DELHI MAY 2006

2 0E467E101TE This is to certify that the report entitled "Design and Development of Micro- Injection Molding Machine for Metal Injection Molding", being submitted by Mr. Vikash Kumar to the Indian institute of Technology, Delhi, in partial fulfillment of the award of the Master of Technology degree in Production Engineering. Mr. Vikash Kumar has working under my guidance and has fulfilled the requirements for the submission of the report, which is to our knowledge, has the requisite standard. The works carried out in this report have not been submitted in part or in full, to any other university or Institute for the award of any degree or diploma during the year Place: New Delhi Date: 20th May 2006 Supervisor, Dr. Naresh Bhatnagar Associate Professor, Dept. of Mech. Engg. IIT, Delhi

3 Acknowledgements First, I would like to thank my Supervisor, Dr. Naresh Bhatnagar, Associate Professor, Department of Mechanical Engineering, IIT-Delhi, who provided me this opportunity and blessed with infinite patience. For every stumble and fail use as I tried to find my way, I was given a chance to find out the answer. It goes without saying that his technical advice was always flawless and timed perfectly. My foremost, thanks are due to my parents for their encouragement, support, love and affection, which keep me going always. I also acknowledge the help of Dr. P. V.Madhusudhan Rao, Associate Professor, Dr. R.Sagar, Professor and Dr. Pulak Mohan Pandey, Assistant professor, Department of Mechanical Engineering, IIT-Delhi, for their invaluable suggestions and encouragement at every stage of my work, without which I could not have accomplished my task. I am very thankful to Mr. P. Selvakumar, Research scholar and Ms. Parvin, Research scholar, Mr. D.C. Kushwaha, Mr. Tulsiram, Mr. Shrichand Sharma for their kind help and cooperation throughout my project. I would also like to thank all the staff members and technicians especially of Production Lab, NC lab and Machine Tool Laboratory for their kind cooperation in carrying out my experiments. I also thank all those people who helped me directly or indirectly but have gone unnoticed. New Delhi 20th May 2006 Vikash Kumar 2004MEP2498 ii

4 ABSTRACT Metal injection molding (MIM) is a metalworking technology for costeffectively producing small, complex, precision metal parts in high run volumes. Metal Injection Molding or MIM, also called Powder Injection Molding or PIM, is a net-shape process for producing solid metal parts that combines the design freedom of plastic injection molding with material properties near that of wrought metals. With its inherent design flexibility, MIM is capable of producing an almost limitless array of highly complex geometries in many different alloys ranging from stainless steels, alloy steels, and soft magnetic materials, controlled expansion materials and custom alloys. [1] In this process metals involves mixing a very high volume of metal powder with organic binders to produce a feedstock. A bonded metal 'green' part is then molded. Careful removal of the binders leaves a skeleton of metal, which is then subjected to high temperature sintering. After sintering, full density can be realized and for that reason the mechanical properties of MIM components are generally superior to those of traditional powder metallurgy parts. MIM components have properties similar to wrought materials and dimensional tolerances superior to investment casting. As most of these products are complex and small, the use of conventional injection molding machine is not advocated therefore the metal injection molding is a very complex area of research. The objective of present work was to design and develop a Micro-Injection Molding Machine for Metal Injection in order to manufacture a high quality tensile and flexure specimen. Keywords: Metal injection molding, Debinding, Sintering, Binders, Mold, Metal powder, Microstructure. iii

5 Table of contents CERTIFICATE ACKNOWLEDGEMENTS ABSTRACT TABLE OF CONTENTS LIST OF FIGURES LIST OF TABLES LIST OF DRAWING NOMENCLATURE & ABBREVIATIONS ii iii iv- vi vii- viii ix xi CHAPTER-1: INTRODUCTION Metal Injection Molding Background How Does PMIM Work? MIM Process Outline Feedstock Preparation and mixing Molding Debinding Sintering: Basic Attributes of MIM Process Feedstock Characteristics Molds Characteristics Part Characteristics Part Tolerances Tools for metal injection moulding Advantages of the MIM process Process limitations Metal Injection Molding Vs Other Production Technologies Application of MIM Product Status 16 iv

6 CHAPTER-2: LITERATURE REVIEW AND MOTIVATION International Status Motivation Problem definition objective 24 CHAPTER-3: MATERIALS AND METHODOLOGY Metal Powder & Binder Furnaces Environment for debinding and sintering process: Design Parameters Part Size Range Part Section Thickness Weight Range of Parts Density / Porosity of Parts Part Tolerances Surface Finish of Parts Part complexity Feedstock Shrinkage Design Mold Plate Design and manufacturing Mold plate Material selection Gate Design Runner Design Ejection system Venting Fabrication of Mold Various stages followed in the manufacture of mold Stage 1: Finishing the impression: Stage 2: Aligning cavity and core Stage 3: Bedding down Stage 4: Fitting of ejector system Stage 5: Sprue bush and registering fitment Stage 6: Tryout and hardening 41

7 3.8 Mold Design 42 CHAPTER-4: EXPERIMENTAL SETUP Experimental Setup Measurement of Particle Size of Iron Powder Preparation of Feedstock Preparation of iron powder and polyethylene glycol Preparation of copper powder and polypropylene Preparation of specimen for tension test and flexural test 45 CHAPTER-5: RESULTS AND DISCUSSIONS Specimen produced through iron powder feedstock Mechanical Properties of mixture of Copper powder with PP Microstructure of specimens made from mixture of copper and PP Development of Micro Injection Molding Machine Working of modified injection molding machine 50 CHAPTER-6: RESULTS AND CONCLUSIONS 53 REFERENCES APPENDIX-A: CNC codes for milling impression on mold plate APPENDIX-B: The detailed drawings of the modified MIM APPENDIX-C: Various fabricated parts for Modified injection molding machine 71 vi