AN AUTOMATED APPROACH TO MANUFACTURABILITY ASSESSMENT OF DIE-CAST PARTS JATINDER MADAN. Doctor of Philosophy

Transcription

1 AN AUTOMATED APPROACH TO MANUFACTURABILITY ASSESSMENT OF DIE-CAST PARTS by JATINDER MADAN Mechanical Engineering Department Submitted in fulfillment of the requirement of the degree of Doctor of Philosophy to the INDIAN INSTITUTE OF TECHNOLOGY DELHI May 2007

2 ; tartii--4 )- r I T. DELMil LIRRARY A CD. 1 NoT±L.3 U 'D TH 6A1.7 1i 4' WO tsttpr3

3 Dedicated to Ily Parents & Fami(y

4 Certificate This is to certify that the thesis entitled "An Automated Approach to Manufacturability Assessment of Die-cast Parts" submitted by Jatinder Madan to the Indian Institute of Technology Delhi, New Delhi, India, for the award of the degree of Doctor of Philosophy, is a record of the original bonafide research work carried out by him under our guidance and supervision. The results contained in it have not been submitted in part or full to any other institute or university for the award of any degree/diploma. (Dr. P. V. Madhusudhan Rao) Associate Professor Mechanical Engineering Department Indian Institute of Technology Delhi New Delhi (Dr. T. K. Kundra) Professor Mechanical Engineering Department Indian Institute of Technology Delhi New Delhi

5 Acknowledgements This thesis is an important milestone in the journey of my life. I take this opportunity to express my sincere gratitude to my PhD supervisors Dr. P. V. M. Rao and Prof. T. K. Kundra, of Mechanical Engineering Department, IIT Delhi. I am grateful to my supervisors for their expert guidance and wise counsel that enabled me to enrich this exciting domain. My last four years of interaction with them was a great learning experience. Number of meetings during this period helped me in my research and motivated me to achieve targets. Besides being source of help and motivation they had been very kind and caring with great compassion towards me. I will forever cherish my close association with them and hope that the abilities they have nourished in me. continue to guide me throughout my life. I am also thankful to my SRC members Prof. S. Wadhwa, Prof. Ashok Gupta and Dr. D. Ravi Kumar for their valuable suggestions which were helpful in my research. I duly acknowledge the help which I received from Sh. Ram Chandar, In-charge of Integrated Design & Manufacturing Lab. Continuous discussions with fellow research scholars Dr. K. V. Ramana, Dr. V. S. Rao, Mr. Senthilkumaran K., Mr. T. C. Bera, Mr. Kaushal Desai and other M. Tech students working in the IDM Lab were quite useful and I am grateful to all of them for their support. I am also thankful to Mr. Madan Lal of IDM Lab. Thanks are also due to Sh. P. V. Mohan Rao of Tool Room and Training Centre, Govt. of Delhi, New Delhi and other industrial units, especially MINDA SM Technocast Ltd., Greater Noida, for providing required input in my research work. My sincere thanks are due to my parent institute Sant Longowal Institute of Engineering & Technology, Longowal, Punjab for sanctioning me study leave, without which my research work could not have been possible. I am also grateful to IIT Delhi for providing me opportunity to carry out this research work. I am also thankful to my friend Dr. Sukhwinder Singh for propping me up and extending help whenever there was a need. I am thankful to all my friends and colleagues for support to me and my family on many occasions. iii

6 I take this opportunity to express my deep sense of gratitude to my parents Kailash Madan and Inderjit Madan who gave me everything they could, to make me what I am today. I am thankful to all my family members for their love and support especially my brother Surinder Madan, sister Anu and my parents-in-law Mohan Lal Puri and Sudesh Puri for their encouragement, love and support. I am also thankful to my uncle Darshan Lal Budhiraja and aunt Saroj Budhiraja for their encouragement and support in my studies. Last but not the least; my whole hearted appreciations are due to my wife Monika Puri and, sons Vineet and Mudit, for their understanding, patience and cooperation, without which this work would not have been completed in time. They had to endure my absence from home for a long time and on many festivals and family occasions. Their touching care and love provided me the necessary strength to withstand the pressures which came in my way. JJAilt)j-i" (Jder Madan) iv

7 Abstract This thesis is about an automated approach to design for manufacturability analysis of parts made by pressure die-casting process. Design for Manufacturing or DFM is any aspect of design process in which issues involved in manufacturing the designed object are considered explicitly with a view to influencing the design (Dixon and Poli 1995). A significant work in the past has been done in the area of design for manufacturing in machining and sheet metal working domain while little attention has been given to die-casting. Pressure die-casting process has gained significance because of benefits associated with this process. Parts made with pressure die-casting require little or no machining, are light in weight and the process requires less energy and can be automated (NADCA 2007). In die-casting production lead times are particularly longer. This is due to die design and manufacturing, and process simulation and testing required before production is started. Introducing DFM in die-casting is therefore very important to reduce production lead time and product development cost. Part designer may not have requisite process related knowledge and competency to assess manufacturability. Manually performing DFM tasks with the help of a die-casting expert is quite cumbersome and lengthy. Automation of DFM assessment will reduce production lead time and increase savings in manufacturing cost. It has been observed that comprehensive automated manufacturability studies of die-cast parts, which account for product, process and manufacturing resource related considerations, are almost non-existent. Automation of both rule based and plan based aspects of manufacturability analysis for die-cast parts have been addressed in this work. In rule based

8 manufacturability analysis, designed part is checked for any rule violations against vast number of die-casting process rules and knowledge of industrial best practices. Violations if any are reported to the designer as an advice in the form of redesign suggestions. Designer can take note of these suggestions to alter or change design keeping in view functional aspects of the part. Manufacturing time and cost estimation has been used as a means of plan based manufacturability assessment. Determining manufacturing time and cost also depends on vast number of variables influenced by part geometry and manufacturing resources utilized for producing the part. In the proposed method, automation of this aspect has been achieved which significantly reduced time required for cost estimation and for preparing quotations. Cost estimation obtained is more realistic as it not only considers part geometrical information but manufacturing resources also, like die-casting machine and multi-cavity tooling etc. Significant level of automation has been achieved in this work as most of the information is extracted from the part CAD model. Automated feature recognition module recognizes die-casting features from CAD model of the part. It can recognize a wide variety of features including interacting and nested features. Withdrawal directions of die-casting features are evaluated using global visibility aspects instead of local visibility. Whether a feature can be moulded using two die-halves across the parting surface is also checked. This makes proposed algorithm very close to industrial practice. As selection of parting direction and parting line is required for any DFM analysis in die-casting, an automated parting direction and parting line determination module is developed. Parting line for the part is determined automatically using process vi

9 considerations and priorities. Eleven significant influencing factors like number of undercuts, draw distance, projected area etc. are accounted for while deciding most suitable parting direction. Automation of manufacturability assessment of a given design is a key requirement to realize integration of design and process planning activities. Proposed system would be quite helpful in reducing product development time as it will require less iterations between design and manufacturing, before design of a die-cast part is finalized. Manufacturing time and cost estimation at the desktop of the designer would provide important input to the designer. Combined affect of using this manufacturability assessment system would be increased efficiency of decision making at design as well as manufacturing stage. Proposed work contributes significantly in the direction of automation of diecasting feature recognition, parting direction and parting line determination, rule based manufacturability assessment and manufacturing cost estimation of parts made by pressure die-casting (PDC) and is very close to industrial practice. Results obtained by using proposed system for a number of typical die-cast industrial components have been validated with those from industry. vii

10 Table of contents Caption Page No. Certificate Acknowledgements Abstract Table of contents List of Figures List of Tables i iii v ix xiii xvii Chapter 1: Introduction Die-casting process Research motivation Research objectives Brief methodology Thesis organization 10 Chapter 2: Literature review Introduction Some definitions and concepts Automated die-casting feature recognition Automated parting direction and parting line determination Automated design for manufacturability analysis Automated manufacturing time and cost estimation Research gaps and need for present research 39 Chapter 3: Automated die-casting feature recognition Introduction 45 ix

11 3.2 Protrusion and depression features recognition Depressions with single/double withdrawal direction/s Isolated symmetrical protrusion features Isolated generic undercut and protrusion Outside undercuts Interacting undercut features Candidate parting direction selection Results Feature recognition results for an Automotive Die-cast Part Feature recognition results for Socket Housing Concluding remarks 72 Chapter 4: Automated parting direction and parting line determination Introduction Parting line determination Parting direction determination Pahl and Beitz method Factors affecting parting direction determination Parting direction evaluation Results Concluding remarks 97 Chapter 5: Automated Design for Manufacturability Analysis Introduction Process constraints and design guidelines 101

12 5.2.1 Part geometry limitations Overall part attributes Industrial best practices Manufacturability of individual features Part attributes and feature recognition Non-manufacturable features Features requiring side-cores Part attributes Wall thickness Sharp edges Rib features Manufacturability evaluation system Implementation and results Concluding remarks 118 Chapter 6: Automated manufacturing cost estimation Introduction Tooling cost estimation Mould die-material cost Die manufacturing cost Trim die-cost Cycle time and processing cost Die-casting cycle time and processing cost Trimming cycle time and processing cost Material and energy cost 131 xi

13 6.4.1 Material cost Energy cost Machine selection and constraint checks Machine constraints vs. cavity requirements Determining number of cavities Feature cost sensitivity analysis Machine loading Implementation and results Concluding remarks 148 Chapter 7: Industrial case studies Introduction Industrial case study (Socket Housing) Industrial case study (Counterweight) Discussion Concluding remarks 163 Chapter 8: Conclusions Summary Major contributions Scope of future work 169 References 171 Research publications from the present work 183 Resume 185 Annexure 'A' 187