Technology Lecture on Challenge to Defect-free Machining: One Step Beyond Precision
Date: 19 Mar 2009 - 19 Mar 2009
Venue: SIMTech Auditorium, Tower Block, Level 3
The purpose of this lecture is to generate industrial awareness on trends and applications of precision grinding and other abrasive processes for the precision engineering industry, particularly those engaged in machining. In this session, the speaker will provide clues as to how a well developed country like Japan remains relevant in manufacturing technology.
Precision grinding and abrasive processes are well suited for processing and machining hard-to-machine materials commonly used in high value-added sectors such as the medical technology and aerospace sectors. Although sophisticated equipment is used in today’s manufacturing, the fundamental principle of material removal is based on break-off of the chemical bonding between atoms which constitute materials of hard and sharp tools. As a result of violent destruction, the atom arrangement on the newly created surface and subsurface is different from its bulk materials. This phenomenon is described in many terminologies like “damaged layer”, “mosaic zone”, “work hardening”, “plastic flow”, “dislocation”, “residual stress” and so on.
This presentation consists of three parts. Part (1) gives generational information of background and current state in the field of ultra precision engineering. The information covers the properties of ductile and brittle materials, the basic material removal mechanisms in ductile-mode machining, micro/nano machining and high-speed machining, and the limitation and problems encountered in the current machining technologies. For most of the ductile materials like metals, the material removal takes place at the ductile regime accompanied by a larger amount of plastic flow. This plastic energy contributes more than 90% to the totally energy consumed in material removal, most of which is eventually converted into the heat and is a hazard to the tool, machine and workpiece. The plastic flow also turns the finished surface to undesirables including worse roughness, larger residual stress and greater work hardening.
Part (2) attempts to show how high-speed and high-acceleration machining technologies are applied to reduce the plastic flow and to improve in surface integrity.
Part (3) explores a new Chemo-Mechanical Grinding (CMG) technology for Si substrates to achieve a high degree of crystalline perfection. The single crystal Si ingot is first sawn into wafers, each of which then undergoes lapping, etching and several steps of polishing to remove the mechanical imperfection and to achieve mirror surfaces. An alternative process has been newly developed by effective use of solid-state reaction between the CeO2 abrasives and Si. Si is removed in a form of amorphous Ce-O-Si at a dry condition. The fabricated 300 mm Si wafers are examined on both surface and subsurface. The results have shown that (1) the surface is generated by fixed abrasives following grinding dynamics, (2) no defect or mechanical (structural) imperfection is introduced during fabrication; and (3) far better quality is achieved than that of CMP.
About the Speaker
Professor Zhou Libo received his Master of Science and PhD degrees in precision engineering from Tohoku University in Japan in 1988 and 1991 respectively. He began his academic career as an assistant professor at Tohoku University. He then moved on to join the Gintic Institute of Manufacturing Technology (now known as Singapore Institute of Manufacturing Technology, SIMTech) where he was promoted to the post of Senior Research Fellow to take part in research activities in precision grinding as well as to coordinate collaborative work, including the international joint research project on MEMS, industrial projects for aerospace industry and R&D planning for the precision machining group. Currently, he is a full professor with the Department of Intelligent System Engineering, National Ibaraki University . He is the editor of the Journal of Japan Society of Precision Engineering, the steering committee member of Japan Society of Mechanical Engineering and the Board member of Japan Society of Abrasive Technology. He holds 10 patents and has been actively involved in both local and international conferences, including ISAAT, ICPE, LEM21 as chairman and organising committee member.
Professor Zhou has published more than 50 referenced papers and 60 reviewed conference papers. He is the recipient of numerous national and international honours and awards. His research interest includes traditional and non-traditional machining processes for micro/nano and ultra-precision applications. He has a reputation for providing expertise in abrasive technology for semiconductor materials. He is also a visiting professor with Zhejiang University of Technology, “Haitian” scholar with Dalian University of Technology in China and Visiting Research Fellow with SIMTech.
2.00pm Welcome and Introduction of SIMTech
2.15pm Presentation (Part I) by Prof Zhou Libo
3.15pm Tea Break & Networking
3.30pm Presentation (Parts II & III) by Prof Zhou Libo
Who Should Attend
R&D managers, engineer, researchers and academic staff and students, particularly those engaged in machining.
Registration for the lecture is free of charge. Seats are available on a first-come, first-served basis.
For technical enquiries, please contact Dr Stephen Wan, Email: ymwan@SIMTech.a-star.edu.sg
For general enquiries, please contact Alice Koh, Email: firstname.lastname@example.org