1Technology Assessment

on

Current Advanced Research in Micro-Machining and Related Areas

AMT The Association For Manufacturing Technology

December 2004

2Published by:

AMT - The Association For Manufacturing Technology7901 Westpark Drive, McLean, VA 22102

Printed in the United States of America

Copyright 2004 AMT - The Association For Manufacturing Technology all rights reserved. No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without prior written permission of the publisher.

3A Report Compiled and Preparedby

Professors

Richard E. DeVor Kornel F. Ehmann Shiv G. KapoorUniversity of Illinois Northwestern University University of Illinois at Urbana-Champaign at Urbana-Champaign

with contributions from the following graduate research assistants:

Andrew Honegger, Martin Jun, George Langstaff, Xinyu Liu, Sunghyuk Park, Andrew Phillip, Johnson Samuel, Tim VanRavenswaay

University of Illinois at Urbana-Champaign

and

Kostyantyn Malukhin, Hankyu Sung, Hyung Suk Yoon, Wendy Xu, Huyue ZhaoNorthwestern University

for

AMT The Association for Manufacturing Technology

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5FORWARDFORWARD

This Technology Assessment Report was based on an extensive survey of the technical literature in micro-machining and related areas. The report was prepared by a team of faculty and graduate students from Northwestern University (NWU) and the University of Illinois at Urbana Champaign (UIUC). The team used best efforts to locate and access the most relevant and up-to-date articles on current research and development efforts worldwide in the area of micro-machining and related areas.

The report is presented as a collection of one-page synopses of the technical papers reviewed. They are grouped into seven chapters: 1. Micro-Manufacturing Processes and Systems, 2. Mechanics of Micro-machining, 3. Micro-Machining Machine Tool Development, 4. Micro-Tooling, 5. Micro-Machining Metrology, 6. Integration into Microfactories, and 7. Miscellaneous Papers of Interest. The groupings may, in places, appear loose because of the unavoidable overlap in papers across these areas, but we have tried to place the papers in the chapter that was deemed most relevant to the subject matter.

It is important for us at the outset of this report to clarify the precise meaning of the term Micro-Machining in this context since this term implies different things to different people. In the traditional mechanical/manufacturing engineering communities it implies material removal processes at a certain scale (not clearly defined), while for others including those who were the principal force behind the development of micro-electro-mechanical-systems (MEMS) technologies, this term encompasses the universe of silicon processing techniques for MEMS devices that were adopted or suitably modified from lithography-based techniques that are prevalent in integrated circuit manufacture.

6At this time, unfortunately, a convergence in terminology has not been forthcoming and, hence, a definition of the term Micro-Machining to be implied in the context of this assessment is in order.

In principle, one may take two viewpoints:

(1) The first viewpoint may define Micro-Machining as the collection of all cutting operations that are performed on micro/meso-scale components and products that fall into the 100 m to 10,000 m size range as shown in the figure below. The Micro-Machining regime is characterized by the requirement of producing high accuracy complex geometric features in a wide variety of materials in the above-defined size range. These requirements impose the use of considerably downsized tooling (micro-tools, e.g., endmills in the 50 to 500 micron diameter range), small undeformed chip thicknesses and feedrates (submicron to a few microns) and speed settings (50K to 200K RPM might not be uncommon) that would be considered technologically infeasible at the conventional macro-scale. As a consequence, the principal distinction between Macro-and Micro-Machining operations emerges and manifests itself as the dominance of ploughing and rubbing phenomena at the cutting edge over shearing and the necessity to take micro-structural effects into consideration.

(2) The second viewpoint approaches the definition of the Micro-Machining regime from the standpoint of the magnitude of the undeformed chip thickness being removed in the cutting process. It is difficult to define a clear-cut value of the undeformed chip thickness that would differentiate the macro-, micro/meso- and nano-scale cutting regimes since other factors such as grain-structure, cutting edge radius, etc., also come into play. The authors of this report would suggest the following classification:

7MICRO/MESOMICRO/MESO--SCALE SCALE MANUFACTURING DOMAINMANUFACTURING DOMAIN

8Macro-scale Machining: Operations performed at conventional regimes at undeformed chip thickness values that are larger (perhaps by an order of magnitude) than the cutting edge radius, hence dominated by shearing, and for which micro-structural effects can be neglected. Generally, the values of the undeformed chip thickness are larger than 10 mm.

Micro/meso-scale Machining: These operations are characterized by the dominance of ploughing, rubbing, plastic and elastic deformation effects in the cutting zone due to the fact that the radius of the tools cutting edge is on the same order as the undeformed chip thickness. These conditions give rise to phenomena usually encompassed by the term - size-effects. The values of the undeformed chip thickness fall into the submicron to a few microns range.

Nano-scale Machining (or Nanometric cutting): This term is customarily associated with ultraprecision machining by single point diamond tools usually used in diamond turning operations. The size of the workpiece can be very large, viz., large optical components, but the operation is performed under small undeformed chip thickness values that overlap or go below the range that characterizes micro/meso-scale machining. The fact that nanometer-sized chips can be removed is due to the possibility of having diamond tool cutting edge sharpness of the same order of magnitude.

9In closing this Forward, the authors wish to acknowledge their appreciation to the AMT -Association For Manufacturing Technology for the opportunity to work on this project and prepare this assessment.

Kornel F. EhmannEvanston, Illinois

Richard E. DeVorShiv G. KapoorUrbana, Illinois

December 2004.

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11

TABLE OF CONTENT 1. Micro-manufacturing Processes and Systems 13

2. Mechanics of Micro-machining 33

2.1 Cutting mechanisms; Chip formation and cutting forces 372.2 Influence of microstructure 552.3 Surface generation mechanisms 652.4 Machinability issues in micro-machining 71

3. Micro-Machining Machine Tool Development 833.1 Machine tool structures 893.2 Actuation and control 973.3 Spindle technology for micro-machining 1053.4 Fixturing and material handling issues 113

12

TABLE OF CONTENT 4. Micro-tooling 131

4.1 Tool geometry, design and fabrication 1354.2 Tool materials 1534.3 Tool wear and tool life 159

5. Micro-machining Metrology 171

6. Integration into Microfactories 1936.1 Microassembly 1976.2 Microfactory layout and applications 209

7. Miscellaneous Papers of Interest 223

13

CHAPTER 1.CHAPTER 1.

MicroMicro--manufacturing Systems manufacturing Systems and Processesand Processes

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15

1. Micro-manufacturing Processes and Systems

This chapter provides an overview of characteristic examples of systems and processes for micro/meso-scale manufacturing operations in various stages of development. Emphasis is placed on systems that are based on other than micro-cutting operations since these will be addressed, in detail, in the upcoming chapters.

The chapter begins with a few review articles that outline current and future trends in micro-manufacturing. These articles also define, to some extent, the size regime of these operations.

What follows next, is a collection of papers on micro-ECM, micro-EDM, rapid prototyping and other processes whose scaled-down versions are being developed for micro/meso-scale manufacturing. A common theme that seemingly permeates all the developments are the attempts to develop multi-functional machines that are capable of performing as many of the required operations as possible on a single piece of manufacturing equipment, including both processing and metrology, with minimal or perhaps no movement of the part. This trend has been viewed by many as necessity, given the difficulties in the handling of small components and loss of part feature registration caused by relocation of the part, both of which constitute significant problems in micro/meso-scale manufacturing.

16

Micro/meso-scale mechanical manufacturing, Miniaturized machines, Micro-factories

Micro/Meso-scale Mechanical Manufacturing: Opportunities and Challenges

Keywords

Title

JSME/ASME Materials and Processing Conference, Honolulu, Oct. 15-18

Ehmann, K. F., DeVor, R. E., Kapoor, S.G.

Citation

Author

AbstractThe overarching objective of this paper is to outline a vision for a plausible way for meeting the requirements of manufacturing high

accuracy micro/meso-scale components and devices (102 - 104m) in a broad range of materials. It is proposed that micro/meso-scale mechanical manufacturing methods, derived from their conventional macro-scale counterparts, performed on miniaturized equipment integrated in a massively parallel fashion into micro-factories of the future could meet the technological requirements (i.e., relative accuracy, geometric complexity, cost, etc.) and offer capabilities that are beyond those currently available. First, the rationale and justification for this concept is outlined followed by an account of the science and technology foundation needed and a synopsis of the scientific, technological and commercialization barriers that will have to be overcome in the course of the realization of the proposed concept.

Objectives of Research Define the micro/meso-scale manufacturing domain Identify opportunities for micro-manufacturing Identify modeling, device, and system development

challenges Identify scientific, technological, and

commercialization barriers

Approach Analyze current gaps in miniaturization research and

technology Survey literature in miniaturization sciences

Schematic of a possible architecture for a micro-factory of the futureKey findings No specifically developed manufacturing technologies exist for micro/meso-scale domain

(sizes between 10 and 10,000m and 10-3-10-5 relative tolerances) Machine volume does not currently decrease with part sizes below approximately 106

mm3 leading to increased machine cost and reduced efficiency.

17

Miniaturization, History, MEMS, Micromachining

The Miniaturization Technologies: Past, Present and Future

Keywords

Title

IEEE Transactions on Industrial Electronics, 42(5), 1995, pp. 423-430

Frazier, A. B., Warrington, R. O., and Friedrich, C.

Citation

Author

AbstractMicroelectromechanical Systems (MEMS), Micro Systems Technologies (MST, primarily in Europe) and Micro-manufacturing are relatively

recent phrases that have become synonymous with the design, development, and manufacture of very small devices and systems. Thispaper overviews the history of the major technologies that are utilized in this field. After this brief historical overview of the technologies, a short description of MEMS technologies is presented. The current status of the MEMS effort worldwide is reviewed with emphasis on the United State, Japan, and the European community with particular emphasis placed on Germany, the Netherlands, and Switzerland. The future for the technology along with technology transfer and management is discussed from the standpoint of market pull. Bulk and surface micromachining of silicon, X-ray micromachining using the LIGA process, and the complementary processes such as laser and focused ion beam micromachining are reviewed.

Objectives of Research Review of selected micromanufacturing technologies Review of the major silicon and planar micromachining

technologies

Approach Historical and literature review of micro-drilling, surface and bulk micromachining,

MEMS, and LIGA technologies Survey of current micro-manufacturing materials, technologies, and facilities Analysis of projected market demand for miniaturization technologies

Key findings The miniaturization technologies continue to gain

momentum in both research and development funding as well as in high technology markets.

A brief history of the miniaturization technologies is given.

Initial applications of specific MEMS technologies are reviewed.

The current state of several miniaturization technologies is discussed as well as the future markets projected that could utilize these technologies. Micro-tools and micro-features

18

Micro-manufacturing, Micro-assembly, Integrated system

Construction of an Integrated Manufacturing System for 3D Microstructure Concept, Design, and Realization

Keywords

Title

Annals of CIRP, 46(1), 1997, pp. 313-318.

Hatamura, Y., Nakao, M., Sato, T.

Citation

Author

AbstractAn integrated manufacturing system for 3D microstructures was conceptualized, designed, and actually built. The system realized 3D

shaping by using fast atom beam etching (FAB) in combination with workpiece rotation, 3D assembly by using a concentric manipulator and observation by a multi-view scanning electron microscope. Through the demonstration of 3D micro manufacturing capabilities, it was shown that: (1) knowledge about conventional machining is applicable even in micro-manufacturing and can be applied for 3D zero reaction force shaping, constant monitoring and on-one-table operation, and (2) image based control is effective for integrated micro-manufacturing systems.

Objectives of Research Design and build an integrated micro-manufacturing system Determine applicability of macroscale manufacturing knowledge to

microscale

Approach Motivate necessity for micro-manufacturing Outline fundamental knowledge necessary for 3D micro-manufacturing Design and build desktop factory to meet micro-manufacturing requirements Use fast atomic beam (FAB) etching for material removal Test fabrication and assembly capabilities of the machine by using

architecture-inspired component shapes

Layout of integrated 3D micro-structure manufacturing system

Key findings 3D micro-fabrication and micro-assembly realized in a desktop factory Zero-reaction force shaping is important for micro-fabrication

(accomplished using FAB) Multiple view monitoring system eliminates need for axis scales or

encoders and simplifies micro-assembly

19

Micro-metal forming; Material behaviour; Processes

Microforming - From basic research to its realization

Keywords

Title

Journal of Materials Processing Technology, 50(2), 2001, p 445-462

Engel, U., Eckstein, R.

Citation

Author

AbstractThe production of miniature parts is gaining importance due to the trend of miniaturization which is increasingly determining the

development of products ranging from mobile phones and computers to medical products. The application of conventional manufacturing processes for the production of such microparts is possible, but there are problems that result from the small dimensions. This fact applies also in the field of metal forming, however, in the meantime many research projects in several countries could improve this situation. This paper gives a review of the problems associated with miniaturization, the way of solution starting from basic research, and the results showing the progress of microforming today.

Objectives of Research Review of the problem associated with miniaturization Show by means of examples the necessity of basic research to

realize the special application of metal forming at the micro-scale.

Forward rod-backward can extrusion

Approach Explanation of general size effects Case studies Research in progress

Key findings Research in the last 10 years has substantially contributed to the fundamental

insight into the peculiarities of the microforming process and an improved understanding of the mechanisms which are the basis to realize processes of industrial relevance.

Many problems require short-term solutions. However, some topics need long-term basic research and will only succeed when there are self-multiplying effects of scientific interest, industrial support and many widely distributed activities.

Effect of miniaturization on areas with open and closed lubricant pockets

20

Micro metal forming; Material, Equipment

Microforming

Keywords

Title

CIRP Annals - Manufacturing Technology, 50(2), 2001, pp. 445-462

Geiger, M.; Kleiner, M.; Eckstein, R.; Tiesler, N.; Engel, U.

Citation

Author

AbstractMicroforming is a well suited technology to manufacture very small metallic parts, in particular for mass production, as they are required in

many industrial products resulting from microtechnology. Compared to other manufacturing technologies microforming features specific economical and ecological advantages. Nevertheless, there are only some singular applications known until today. This paper tries to find out the reasons why, analyzing systematically the problems emerging in transferring the know-how on forming from the macro- to the microworld. Reviewing the state of the art in basic and applied research reveals that scaling effects do appear not only within the process but must be taken into account in all the other areas of the whole forming system as well, demanding finally new solutions especially for tool manufacturing and machine concepts. Recent progress, innovative ideas and new developments in these sectors represent a promising basis to exploit the inherent potential of microforming in the future.

Objectives of Research Review of the state of the art in microforming

Approach Application and limits of forming Identification of the size effects Basic research on these phenomena

Bent lead structure. Width of the leads 150 m, height 127 m

Key findings Due to the ongoing trend towards miniaturization, there is a huge

market for mechanical components and metallic microparts which have to be produced in large numbers

Forming technology is excellently suited to meet these demands, showing a high potential as a supplementary and even substituting technology with respect to economical and ecological factors andthose characterizing the quality of the final product in terms of accuracy, mechanical properties and reliability

A broad breakthrough of forming technology in the microsector is still missing

21

Electrochemical machining, Electrochemical micro-machining

Electromechanical Micro-Machining: New Possibilities for Micro-Manufacturing

Keywords

Title

Journal of Materials Processing Technology, 113, 2001, pp. 301-305

Bhattacharyya, B., Doloi, B., Sridhar, P.S.

Citation

Author

AbstractElectrochemical micro-machining (EMM) appears to be very promising as a future micro-machining technique since in many areas of

applications it offers several advantages. The paper highlights the design and development of an EMM system set-up which includes various components such as mechanical machining components, electrical systems and an electrolyte flow system, etc. A microprocessor controlled end-gap controlling system has also been developed for this purpose. The developed EMM set-up will open up many challenging possibilities for effective utilizations of the electrochemical material removal mechanism in micro-machining.

Objectives of Research Develop testbed for:

Conducting detailed research on the EMM process Attain adequate process control for micro-machining requirements

(accuracy on the order of microns)

Approach Identification of important process parameters Design and fabrication of a testbed comprised of:

Main machining body Tool feeding devices Work holding platforms Machining chamber Table for mounting machining chamber

Diagram of developed EMM testbed

Key findings Stepper motors and precision lead screws were used to attain precise

tool feeding motion Flow of electrolyte is one of the most important components of EMM Developed testbed is capable of controlled tool feed, controlled electrolyte

flow and pulsed power supply

22

Electrochemical micromachining, Side insulated electrode, Gap control, Pulsed current

Localized electrochemical micromachining with gap control

Keywords

Title

Sensors and Actuators, A108, 2003, pp. 144-148

Li Yong, Zheng Yunfei, Yang Guang, Peng Liangqiang

Citation

Author

AbstractAn approach to electrochemical micromachining is presented in which side-insulated electrode, micro gap control between the cathode and

anode and the pulsed current are synthetically utilized. An experimental set-up for electrochemical micromachining is constructed, which has machining process detection and gap control functions; also a pulsed power supply and a control computer are involved .Micro electrodes are manufactured by micro electro-discharge machining 9 EDM) and side insulated by chemical vapor deposition (CVD).A micro gap control strategy is proposed based on the fundamental experimental behavior of electrochemical machining current with the gap variance. Machining experiments on micro hole drilling, scanning machining layer-by-layer and micro electrochemical deposition are carried out. Preliminary experimental result show the feasibility of electrochemical micromachining and its potential capability for better machining accuracy and smaller machining sizes.

Objectives of Research Develop micro gap control strategy using the electrochemical machining current as a trigger. Develop means to constrain the region of reaction so as to achieve machining accuracy in the micro domain. Demonstrate the capability of the test bed for achieving better machining accuracy and smaller machining size.

Approach Design and build a ECM unit. Use of side insulated electrode, micro gap control and pulsed current to limit the area of reaction within 10-20 m Conduct machining experiments to demonstrate the feasibility of the test bed to achieve better machining accuracy and smaller machining size.

ECM setup & Current behavior with electrode gap

Key findings Experimental setup constructed has machining process detection and

gap control functions, in addition to pulsed power supply. Based on fundamental experimental behavior of electrochemical current

with the gap variance, a micro gap control strategy was proposed which constrained the machining gap between 10-20 m.

Machining experiments on micro hole drilling, scanning machining layer by layer and micro electrochemical deposition were carried out.

Preliminary experimental results show feasibility of the localized electrochemical micro machining.

Further work needs to be done on electrolyte, electrode insulation and systematic control of machining process.

23

Electrochemical micromachining, Ultra short pulses

Micro electrochemical milling

Keywords

Title

Journal of Micromechanics and Microengineering, 15, (2005), pp. 124-129

Bo Hyun Kim, Shi Hyoung Ryu, Deok Ki Choi and Chong Nam Chu

Citation

Author

Hemisphere with 60 m diameter machined with 45m electrode, 304 SS, 6V,60ns pulse on, 1s period

Key findings Micro structures were successfully machined by micro ECM. With ultra short pulses ( nano second duration) electrochemical reaction

is limited to the vicinity of the electrode. Low concentration electrolyte 0.1 M H2SO4,was found to yield good

surface quality for the structures.( Ra = 280 nm) For machining of 3D structures with large aspect ratios, a disc-type

electrode is used to prevent occurrence of taper.

AbstractIn this paper, electrochemical machining (ECM) for fabricating micro structures is presented. By applying ultra short pulses, dissolution of a

workpiece can be restricted to the region very close to an electrode. Using this method, 3 D micro structures were machined on stainless steel. Good surface quality of the structures was obtained in the low concentration electrolyte 0.1 M H2SO4.In ECM, when the machining depth increases, structures taper. To reduce the taper the disc type electrode is introduced. By electrochemical milling, various 3 D structures including a hemisphere with 60 m diameter were fabricated.

Objectives of Research Develop means to fabricate micro structures using ECM. Use the developed method to fabricate 3D micro structures to prove its applicability to the micromachining domain.

Approach Design and build a ECM unit. Use of ultra short pulses of nanosecond duration to limit the machining zone to a couple of micrometers. Machine 3D structures on stainless steel to demonstrate the capability of the process.

Disc-type electrode by EDM (54m. Neck diameter 22m)

24

Electrochemical machining, Micromachining

Experimental investigation into electrochemical micromachining (EMM) process

Keywords

Title

Journal of Materials processing technology, 140 (2003),pp 287-291

B. Bhattacharya, J. Munda

Citation

Author

Key findings ECM testbed successfully developed. Machining voltage in the range of 7-10 V gives appreciable MRR with

lower value of overcut for Cu Most effective zone of electrolyte concentration is 15-25 g/l resulting in

higher MRR with least overcut for Cu Parametric combination of 10V machining voltage and 15g/l electrolyte

concentration is best for machining thin Cu plate with high MRR and least overcut.

Abstract

Due to several advantages and wider range of applications, electrochemical micromachining (EMM) is considered to be one of the mosteffective advanced future micromachining techniques. A suitable EMM setup mainly consists of various components and sub-systems,e.g. mechanical machining unit, micro-tooling system, electrical power and controlling system and controlled electrolyte flow system etc.have been developed successfully to control electrochemical machining (ECM) parameters to meet the micromachining requirements.Investigation indicates most effective zone of predominant process parameters such as machining voltage and electrolyte concentration,which give the appreciable amount of material removal rate (MRR) with less overcut. The experimental results and analysis on EMM willopen up more application possibilities for EMM.

Objectives of Research

To study the factors affecting machinability in the ECM domain.

Approach Design and build a ECM unit. Conduct a series of planned experimentations on Cu plates to study the

effect of voltage and electrolyte concentration on the material removal rate (MRR) and the over cut.

EMM set up

SEM picture of micro hole machined by EMM with 15g/l electrolyte concentration, Machining voltage 10 V, pulse on time 15ms and frequency of pulsed power supply 50 Hz.

25

MEMS, Fabrication, Manufacturing, Packaging, Reliability, Assembly, CAD tools

Developments in Microelectromechanical Systems (MEMS): A Manufacturing Perspective

Keywords

Title

Transactions ASME, 125(4), 2003, pp.816-823

Tadigadapa, Srinivas A., Najafi, Nader

Citation

Author

AbstractThis paper presents a discussion of some of the major issues that need to be considered for the successful commercialization of MEMS products. The diversity of MEMS devices and historical reasons have led to scattered developments in the MEMS manufacturing infrastructure. A good manufacturing strategy must include the complete device plan including the package as part of the design and process development of the device. In spite of rapid advances in the field of MEMS there are daunting challenges that lie in the areas of MEMS packaging, and reliability testing. CAD tools for MEMS are starting to get more mature but are still limited in their overall performance. MEMS manufacturing is currently at a fragile state of evolution. In spite of all the wonderful possibilities, very few MEMS devices have been commercialized. In the authors opinion, the magnitude of the difficulty of fabricating MEMS devices at the manufacturing level is highly underestimated by both the current and emerging MEMS communities. A synopsis of MEMS manufacturing issues is presented here.

Objectives of Research Identify and expound on the major issues related to

MEMS and their commercialization

Approach Motivation for micromachining techniques Current micromachining processes (MEMS fabrication) Packaging techniques for MEMS devices Reliability testing and compensation issues Challenges in manufacturing of MEMS devices

Key findings Important to include package as part of the design

and process development of a MEMS device Many challenges still exist for MEMS packaging and

reliability testing Limited performance from CAD tools for these devices Highly understated difficulty in MEMS fabrication by

MEMS communities

26

ECM, Micro-EDM, 3D-Micro Structure, Finishing

Fine Surface Finishing Method for 3-Dimensional Micro Structures

Keywords

Title

Proceedings IEEE, 1996, pp.73-78

Takahata, K., Aoki S., Sato T.

Citation

Author

AbstractA new finishing method using advanced ECM (electrochemical machining) assisted by fine abrasive grains to finish surfaces of 3-D micro components used in MEMS was developed. With this method, fine surfaces at selected micro-areas, which cannot be obtained by micro-EDM (electrodischarge machining) nor conventional ECM, are created in a few minutes. An advanced machine, capable of producing complicated 3-D micro structures with fine surfaces by the combination of the micro-EDM and the developed finishing method, was also developed. The high performance was achieved by a sequential process without workpiece handling between the micro-EDM to the finishing process. Using the new machine, a high precision shaft with a mirror-like surface was created. The result is satisfactory and can be applied to make a cylindrical substrate for a rotor of micro wobble motor. The developed process is suitable for producing practical micro mechanical components.

Objectives of Research Develop a new surface finishing method for 3-D micro structures using advanced ECM Use experimental results to support the concept and show its performance Demonstrate ability to machine components with the developed machining process and machine

Approach New finishing method that uses ECM with abrasive grains (Al203) Process performance evaluated for different

methods and as a function of machining parameters Tested new process and machine

Key findings Developed new surface finishing method for

selected micro-areas and confirmed its applicability to components of the MEMS region

Sequential machining process from 3-D micro-EDM to the developed finishing possible through advanced machine

Demonstrated application of the sequential machining process to 3-D micro components

Comparison between machined surfaces obtained by different methods (304 SS)

27

Micro-EDM, Micro-machining, EDM accuracy, Nicro-holes

Micro-EDM Recent Developments and Research Issues

Keywords

Title

Journal of Materials Processing Technology 149, pp. 50-57, 2004

Pham, D. T., Dimov, S. S., Bigot, S., Ivanov, A., Popov, K.

Citation

Author

AbstractDue to the high precision and good surface quality that it can give, EDM is potentially an important process for the fabrication of micro-tools,

micro-components, and parts with micro-features. However, a number of issues remain to be solved before micro-EDM can become a reliable process with repeatable results and its full capabilities as a micro-manufacturing technology can be realized. This paper presents some recent developments in micro-EDM in its various forms (wire, drilling, milling, and die-sinking) and discusses the main research issues. The paper focuses on the planning of the EDM process and the electrode wear problem. Special attention is paid to factors and procedures influencing the accuracy achievable, including positioning approaches during EDM and electrode grinding.

Objectives of Research Identify key issues that are problematic for micro-EDM Investigate sources of errors in the micro-EDM process

Approach Categorize micro-EDM processes Investigate problematic areas for micro- EDM (part handling, preparation, machining

process, measurement) Analyze contributions of different process

errors (machine, electrode, fixturing, wear)

Key findings All aspects of the process need to be

considered when assigning process tolerances for micro-EDM parts

Process optimization is mainly based on empirical methods

A strategy for micro-EDM milling is proposed to compensate for electrode wear Problematic areas for micro-EDM

28

Miniaturization, MEMS, Micromachining

Microelectrodischarge Machining for MEMS Applications

Keywords

Title

IEEE Seminar on Demonstrated Micromachining Technologies for Industry, 2000, 6/1-4

Allen, D. M.

Citation

Author

AbstractThe fabrication of miniature devices for MEMS has relied heavily in the past on bulk and surface etching of silicon and metal films

deposited in vacuum or electrochemically. However, some materials such as stainless steels, titanium and shape memory alloys require high aspect ratio holes through foils up to 200 m thick when etching technology may not be practical or economical. Industrial MEMS applications include ink jet printing heads containing hundreds of accurately aligned, identical, round nozzles about 50 m in diameter. With the aid of an EPSRC Equipment Grant, the potential of using microelectrodischarge machining (micro-EDM) to fabricate such nozzles has been investigated.

Objectives of Research Study of the accuracy of micro-hole production using micro-EDM

Approach Experimental observation of micro-holes made by Micro-EDM for ink jet printer nozzles

Key findings The accuracy of micro-hole production is dependent on the

way in which micro-electrode production is carried out There are problems with material microdefects that are

becoming significant in microengineered products made from multicrystalline metals

The quality of printer head is dependent not only on the micromachining processes involved in its fabrication but also on the quality of the material from which it is made

The micro-EDM process is excellent for its precision and resolution capabilities but major challenges are

wear of the micro-electrode during the machining of the nozzles

the very slow machining rate due to the low pulse energy used for individual discharges

Accuracy of individual holes of ink jet nozzles made by micro-EDM

29

Rapid prototyping, Micro-component, Micro-feeding, Micromachining

Micro Rapid Prototyping System for Micro Components

Keywords

Title

Thin Solid Films, 420 421, 2002, pp. 515523

Li, X., Choi, H., Yang, Y.

Citation

Author

AbstractSimilarities between silicon-based micro-electro-mechanical systems (MEMS) and Shape Deposition Manufacturing (SDM) processes are obvious: both integrate additive and subtractive processes and use part and sacrificial materials to obtain functional structures. These MEMS techniques are two-dimensional (2-D) processes for a limited number of materials while SDM enables the building of parts that have traditionally been impossible to fabricate because of their complex shapes or of their variety in materials. This work presents initial results on the development of a micro rapid prototyping system that adapts the SDM methodology to micro-fabrication. This system is designed to incorporate microdeposition and laser micromachining. In the hope of obtaining precise microdeposition, an ultrasonic-based micro powder-feeding mechanism was developed in order to form thin patterns of dry powder that can be cladded or sintered onto a substrate by a micro-sized laser beam. Furthermore, experimental results on laser micromachining using a laser beam with a wavelength of 355 nm are also presented. After further improvement, the developed micromanufacturing system could take computer-aided design (CAD) output to reproduce 3-D heterogeneous microcomponents from a wide selection of materials.

Objectives of Research Develop system for micro rapid prototyping Enable heterogeneous material composition using micro powderfeeding mechanism

Approach Assess capabilities and limitations of current micro rapid prototyping techniques Develop and characterize ultrasonic-based micro-feeding device for deposition

of micro powders Study laser micro machining process attributes

Top and side views of a laser micromachined channel

Key findings Incorporating micro-deposition and laser micromachining can extend rapid

prototyping technology to micro components Micro powders can be deposited using an capillary tube excited by a

piezoelectric plate (Rayleigh wave mechanism) Drilling depth depends on number of laser pulses, laser fluence, and focal plane Moving velocity of the substrate affects shape and depth of machined channels

30

Laser; micro-stereolithography, lamination, laser sintering, microcladding and rapid prototyping

Overview of Laser Based Prototyping in Microdomain

Keywords

Title

Proceedings of SPIE, Vol. 4157, 2001, pp. 129 134.

Kathuria , Y.P.

Citation

Author

AbstractIn the emerging field of microrobotics and micro-electromechanical systems, the requirement of complex mechanical parts is gaining much

importance. On one hand, the overall size and shape of the product is becoming smaller and more complex, whereas on the other hand the demand/offer for new products is dramatically increasing. In order to overcome this problem, new organizational structures for the complete process for product development as well as for new technologies is necessary. This paper highlights the various processes, viz., micro-streolithography of polymer resin, selective laser sintering of metallic powder as well as melting processes using lasers for the rapid prototyping of three dimensional parts in the microdomain.

Objectives of Research Overview of the four laser baser rapid prototyping processes in the microdomain Discuss the quality of the parts made by the laser based rapid prototyping Compare the laser based prototyping processes with the LIGA processes

Approach Apply four laser based rapid prototyping techniques to generate complex

3D microparts made of of polymers, metal and metal-matrix composites intended forrapid product development

Use UV and Nd-YAG lasers in the rapid prototyping processes

Key findings Two phonon microstereolithography can produce 3D microstructures with

submicron resolution Beam interaction time plays a crucial role in the microcladding process The line width of metallic structures is limited by the particle size, molten

droplet and surface tension effects

Microturbine made by laser stereolithography

Helical microstructure made by microcladding

31

Laser ablation; Material processing; Short-pulse laser

Short-pulse laser ablation of solid targets

Keywords

Title

Optics Communications

Momma, C.; Chichkov, B.N.; Nolte, S.; Alvensleben, F.; Tunnermann, A.; Welling, H.; Wellegehausen, B.

Citation

Author

AbstractLaser ablation of solid targets by Ti:sapphire laser radiation is studied. The solid targets are irradiated by 0.2-5000 ps laser pulses in the

intensity range of 109 - 51016 W/cm2. Dependences of the ablation depth on the laser pulse energy and pulse duration are discussed. Advantages of sub-picosecond laser radiation for precise material processing are demonstrated.

Objectives of Research Discussion of the characteristic features of the short-pulse laser induced ablation of solid targets. Explanation and demonstration of the advantages of short-pulse lasers for material processing.

Approach Description of the physical processes and characteristics in case of sufficiently high-intensity laser Discussion of experimental setup and results Discussion and experimental results on the laser ablation in a low fluence regime

Key findings Investigations of laser ablation are performed in a very broad range of laser parameters In the high fluence regime, short-pulse lasers do not provide considerable advantages for

material processing in comparison with long-pulse lasers. Real advantages of short-pulse lasers for material processing exist at low fluences. In this

regime, very pure ablation of metal targets in vacuum are demonstrated. The advantages of short-pulse lasers are very promising and inviting for precise material

processing.

Hole drilled in a copper plete (0.5 mm) with short laser pulses

Schematic of short-pulse laser ablation in a low fluence regime

32

Allen, D. M. Microelectrodischarge Machining for MEMS Applications. IEEE Seminar on Demonstrated Micromachining Technologies forIndustry, 2000, 6/1-4

Bhattacharyya, B., Doloi, B., Sridhar, P.S. Electromechanical Micro-Machining: New Possibilities for Micro-Manufacturing. Journal of Materials Processing Technology, 113, 2001, pp. 301-305

Bhattacharya, B., J. Munda, Experimental investigation into electrochemical micromachining (EMM) process. Journal of Materials processing technology, 140 (2003),pp 287-291

Ehmann, K. F., DeVor, R. E., Kapoor, S.G. Micro/Meso-scale Mechanical Manufacturing: Opportunities and Challenges. JSME/ASME Materials and Processing Conference, Honolulu, Oct. 15-18

Engel, U., Eckstein, R. Microforming - From basic research to its realization, Journal of Materials Processing Technology, 50(2), 2001, p 445-462

Frazier, A. Bruno, Warrington, R. O., Friedrich, C. The Miniaturization Technologies: Past, Present, and Future. IEEE Transactions on Industrial Electronics, 42(5), 1995, pp. 423-430

Geiger, M.; Kleiner, M.; Eckstein, R.; Tiesler, N.; Engel, U. Microforming, CIRP Annals - Manufacturing Technology, 50(2), 2001, pp. 445-462 Hatamura, Y., Nakao, M., Sato, T. Construction of an Integrated Manufacturing System for 3D Microstructure Concept, Design, and

Realization. Annals of CIRP, 46(1), 1997, pp. 313-318 Kathuria , Y.P., Overview of Laser Based Prototyping in Microdomain, Proceedings of SPIE, Vol. 4157, 2001, pp. 129 134. Kim, B.H., Ryu, S.H., Choi, D.K., Chu, C.N., Micro electrochemical milling.Journal of Micromechanics and Microengineering, 15, (2005), pp.

124-129 Li, X., Choi, H., Yang, Y. Micro Rapid Prototyping System for Micro Components. Thin Solid Films, 420 421, 2002, pp. 515523 Li Y., Zheng Yunfei, Yang Guang, Peng Liangqiang. Localized electrochemical micromachining with gap control. Sensors and Actuators,

A108, 2003, pp. 144-148 Momma, C.; Chichkov, B.N.; Nolte, S.; Alvensleben, F.; Tunnermann, A.; Welling, H.; Wellegehausen, B., Short-pulse laser ablation of solid

targets, Optics Communications, v 129, n 1-2, Aug 1, 1996, p 134-142 Pham, D. T., Dimov, S. S., Bigot, S., Ivanov, A., Popov, K. Micro-EDM Recent Developments and Research Issues. Journal of Materials

Processing Technology 149, pp. 50-57, 2004 Tadigadapa, Srinivas A., Najafi, Nader. Developments in Microelectromechanical Systems (MEMS): A Manufacturing Perspective.

Transactions ASME, 125(4), 2003, pp.816-823 Takahata, K., Aoki S., Sato T. Fine Surface Finishing Method for 3-Dimensional Micro Structures. Proceedings IEEE, 1996, pp.73-78

Citations

33

CHAPTER 2.CHAPTER 2.

Mechanics of MicroMechanics of Micro--machiningmachining

34This page was intentionally left blank

35

2. Mechanics of Micro-machining

Material removal processes exhibit significantly different behavior and characteristics at the micro/meso-scales than at the conventional macro-scale. These differences are primarily the consequence of the relative scaling between the principal constituents of the cutting operations performed. Micro-cutting operations are frequently used to produce features with reduced sizes and tolerances that necessitate the use of tools such as small diameter endmills that themselves have features, e.g., the cutting edge radius, that are comparable in size to the cutting parameters, viz., the feedrate, owing to current limitations in tool manufacture. As a consequence, the mechanisms of chip formation may have significant ploughing as well as shearing effects, which will influence cutting forces, vibrations, process stability and part surface finish in ways quite different than in conventional, macro-machining.

A second significant factor in micro-machining is the need to consider the inhomogeneity of the material at the scale of micro-machining since the characteristic grain size, except for single crystal materials, is on the order or even larger than the chip thickness/cut crossection and frequently on the order of the tool diameter, e.g., in drilling or endmilling. Even for single crystal materials, the crystallographic orientation plays a significant role in cutting performance at the micro-scale.

The first section of this chapter presents results pertaining to the size effect, energy considerations and basic cutting mechanics considerations in micro/meso-scale-machining. The modeling methods presented range from continuum mechanics and molecular dynamics approaches to mechanistic modeling.

36

The second section of this chapter is devoted to work performed to ascertain the influence of the work materials microstructure on the cutting force system and other process outcomes. Finite element and mechanistic modeling approaches are presented, followed by work on the influence of crystallographic orientation.

The last two sections of this chapter are devoted to the few available results that relate to the important but theoretically-difficult issue of surface generation in micro-machining and more pragmatic machinability issues in micro-cutting, respectively. There are at least two reasons why surface generation in micro-machining should receive increased attention. First, as size scales down, surface-to-volume ratios for components tend to increase and surface effects, e.g., surface tension, surface roughness, become more critical to component performance. Second, in micro-scale machining the factors related to the machining process that significantly influence surface roughness become many and their effects become quite complex relative to macro-level machining where the surface roughness is primarily influenced by kinematic/geometric factors, viz., feedrate and tool geometry. At the micro-scale machining process dynamics, tool vibrations, the ploughingphenomenon and associated elastic/plastic deformation, material side-flow, and burr formation at grain boundaries in multi-phase materials all can have order of magnitude larger influence on the roughness of the machining surface than the classical kinematic/geometric factors. The last section of this chapter gives a collection of practical developments and application examples of micro-cutting.

37

2. Mechanics of Micro-machining

2.1 Cutting mechanisms; Chip formation and cutting forces

38

AbstractEven though grinding is recognized as a form of cutting, gaps exist between the cutting theory and the grinding theory. In this paper the

components of energy consumption in metal cutting are re-examined. The energy consumed due to plastic flow in the subsurface layer of the machined surface is found to be important when the depth of cut is decreased. This plastic flow in the subsurface layer increases the hardness, residual stresses and chemical activity of the layer. Size effect phenomena are studied by machining brass at a very slow cutting speed of 0.1 m/min and using undeformed chip thickness values in the range of 2 m and 40 m.

Objectives of Research To study the factors contributing to the size effect phenomenon, while machining at low undeformed chip thickness values in the range of 2

to 40 m.Approach

Analytical quantification of the energies consumed in metal cutting namely, surface energy W1, shear deformation work in the shear zone W2 , friction energy on rake face W3 , friction energy on tool flank W4 and kinetic energy of the chip W5 .

Experiments involving measurement of cutting edge profile and machining tests on brass, measuring the cutting and the thrust forces.

Analyzing the machining data to identify important energy consumption areas to account for the size effect at low depths of cut.

Key findings Of the several components of energy involved in metal cutting which are

usually neglected in metal-cutting analyses, the energy to cause plastic flow in the subsurface layer of the workpiece was found to be the first one to become important with decrease in undeformed chip thickness.

The main cause of this plastic flow is the extension of the shear zone below the machined surface. Friction between the tool flank and the machined surface is responsible only for a small part of the plastic flow.

A size effect for the shear stress on the shear plane was not found in these tests. Though the minimum depth of cut was 2 m the area of the shear plane or the volume of the shear zone might not be small enough to indicate the size effect.

Size effect, Plastic flow

Size Effect in Metal-Cutting Force

Keywords

Title

Journal of Engineering for Industry, 1968, pp.119-126.

Nakayama. K and Tamura.K

Citation

Author

Deformation and energy consumption during metal cutting

39

Machining, size-effect, specific shear energy, strain gradients, dislocation processes

An explanation for the size-effect in machining using strain gradient plasticity

Keywords

Title

JSME/ASME Int. Conf. On Materials and Processing 1, 2002, pp. 318-323

Joshi, S. and Melkote, S.

Citation

Author

AbstractMaterial length scales expressed in terms of strain gradients have been successfully incorporated into constitutive models to explain the size-effect in indentation, bending and torsion. Deformation in machining involves large strain gradients and is known to demonstrate a comparatively larger size-effect. This paper attempts to explain the size-effect in the Primary Deformation Zone (PDZ) of an orthogonal cutting process by developing a strain gradient plasticity based model. Considering a parallel-sided configuration of the PDZ, models are formulated for the strain gradient, density of geometrically necessary dislocations, shear strength and the specific shear energy. The analysis shows that for deformation in the PDZ, the length of the shear plane represents the material length scale. The model also provides an estimate of the lower bound on the size-effect observed in the specific shear energy. Trends in the predicted specific shear energy match well with experimental values obtained form the literature.

Objectives of Research To develop a more realistic model of micro-level material removal

phenomena for improved understanding of the size-effect in machining To develop a model for the size-effect in a deformation process using

the strain gradient plasticity theory where the strength is considered a function of the strain gradient

Approach Model of the Primary Deformation Zone (PDZ) using strain gradient

plasticity Determination of the geometry of the strain field Evaluation of the strain gradient Evaluation of density of dislocations Evaluation of material strength as a function of material length scale

Key Findings Models were formulated for the strain gradient, density of geometrically necessary dislocations, shear strength of material in the PDZ

and the specific energy As the length of the shear plane reduces, strain gradient increases leading to increase in the shear strength A lower bound on the size-effect in specific shear energy can be predicted using the model, which is capable of capturing the trend in

the experimental values. The predicted values of specific energy were found to match closely with the experimental values for

40

Micro-cutting, steel, process optimization

An evaluation of ploughing models for orthogonal machining

Keywords

Title

Journal of Manufacturing Science and Engineering, 121(1999), pp. 550-558

Waldorf, D. J., DeVor, R. E., and Kapoor, S. G.

Citation

Author

AbstractAn analytical comparison is made between two basic models of the flow of workpiece material around the edge of an orthogonal cutting tool

during steady-state metal removal. Each has been the basis for assumptions in previous studies which attempt to model the machining process, but no direct comparison had been made to determine which, if either, is an appropriate model. One model assumes that aseparation point exists on the rounded cutting edge while the other includes a stable build-up adhered to the edge and assumes a separation point at the outer extreme of the build-up. Theories of elastic-plastic deformation are employed to develop force predictions based on each model, and experiments are performed on 6061-T6 aluminum alloy to evaluate modeling success. The experiments utilize unusually large cutting edge radii to isolate the edge component of the total cutting forces. Results suggest that a material separation point on the tool itself does not exist and that the model that includes a stable build-up works better to describe the experimental observations.

Objectives of Research Compare two basic models of the flow of workpiece material

around the rounded edge of an orthogonal cutting tool.. Determine which model is an appropriate model

Approach Analytical modeling using indentation to approximate ploughing Experimental verification

Key findings The model which considered a stable build-up was more

successful than the one assuming the separation point directly on the edge in matching the trend and magnitudes of the experimental results.

When cutting with a large edge radius tool on 6061-T6 aluminum, a stable build-up adheres to the cutting edge and influences the cutting forces considerably.

Large ploughing forces compared to shearing forces are expected when feedrate is at or below the value of the edge radius.

Cutting with material separation point on edge

Cutting with a stable build-up on edge

41

AbstractAn experimental study of the effect of single crystal diamond tool edge geometry on the resulting cutting and thrust forces and specific

energy in the ultraprecision orthogonal flycutting of Te-Cu was made. The effects of both the nominal rake angle and tool edge profile was investigated over uncut chip thicknesses from 20 m down to 10 nm. Characterization of the tool edge was performed with the use of the atomic force microscopy. Both the nominal rake angle and tool edge profile (effective rake angle) were found to have significant effects on the resulting forces and energies.

Objectives of Research To study the effect of tool edge geometry on the resulting forces and energies in the ultraprecision orthogonal fly cutting of TE-Cu.

Approach Characterization of A) tool edge using atomic force microscope,

B) rake and clearance angles using optical microscope. Orthogonal fly cutting: flat nosed single crystal diamond tool rotates,

Te-Cu work piece held stationary. Experimental assessment of the resulting specific energies

made by measuring the cutting and thrust forces.

Key findings Both the nominal rake angle and the tool edge profile were found to

have significant effects on the resulting forces and energy dissipated over uncut chip thickness from 20 m to 10 nm.

When the uncut chip thickness is large relative to the extent of the tool edge profile, the resulting forces and energies are governed by the nominal rake angle.

When the uncut chip thickness approaches the size of the edge contour, effective rake angle appears to determine the resultingforces.This is predominantly shown by the study of the direction of the resultant force vector with respect to the uncut chip thickness. At small uncut chip thicknesses the effective rather than nominal rake angle dictates the direction of the resultant force.

Cutting,Cutting forces,Diamond

Effect of Tool Edge Geometry on Energy Dissipation in Ultraprecision Machining

Keywords

Title

Annals of the CIRP, 42(1), 1993, pp.83-86.

Lucca, D. A,Seo Y.W and Komanduri, R.

Citation

Author

Direction of resultant force vector v/s uncut chip thickness for various rake angles. ( Notice how at low uncut chip

thicknesses the rotation angle changes)

42

AbstractAn experimental investigation was conducted to examine the dissipation of mechanical energy when machining at depths of cut less than

several micrometers. Cutting and thrust forces which resulted in orthogonal ultra-precision fly cutting of Al 6061-T6 were measured over a range of depths of cut 20 m down to 0.01 m at a cutting speed of 0.8 m sec-1. Measurement of the tool-work piece contact length indicated that it may become the characteristic length scale when machining at sub-micrometer depths of cut. Evidence suggests that the process maybe viewed as transitioning from a cutting dominant to plowing/sliding indentation dominant process. Tool edge condition was seen to have a significant effect on the resulting forces when the depth of cut was below the tool edge radius.

Objectives of Research To quantify the dissipation of mechanical energy in the ultra precision machining of ductile materials (Al 6061-T6)

Approach Orthogonal fly cutting: flat nosed single crystal diamond tool rotates and work piece held stationary. Experimental assessment of the

resulting specific energies made by measuring the cutting and thrust forces. The range of possible contact lengths at the work piece interface was bracketed by using two methods: 1) Upper Bound: coating the

diamond tool with a thin layer of AuPd, cutting at a given depth of cut and then observing the region of worn-off coating at the flank face(using SEM) and 2) Lower Bound: using the measured thrust force and an interface pressure equal to the plain flow stress of the workpiecematerial to predict a contact length.

Orthogonal cutting geometry at small depths of cut

Key findings Overall trends in the cutting forces and energies for Al 6061-T6

agree well with previously reported results for copper. Bracketing of the tool workpiece contact length by two methods

indicates that it may become a characteristic length when machining at sub micrometer depths of cut.

Rotation of the measured resultant force vector and the increased significance of the tool-workpiece contact length suggest that the process may be viewed as a transition from a cutting dominated to a plowing/sliding indentation dominant process.

Tool edge condition seen to have a significant effect on the resulting forces when the depth of cut was below the tool edge radius.

Ultra-precision machining, Specific energy

Energy Dissipation and Tool-Workpiece Contact in Ultra-Precision Machining

Keywords

Title

Tribology Transactions, 37(3), 1994, pp.651-655.

Lucca, D.A., Seo, Y.W. and Rhorer, R.L.

Citation

Author

SEM picture of the flank face showing worn-off Au-Pd coating

43

Minimum chip thickness, atomistic cutting model

Minimum thickness of cut in micromachining

Keywords

Title

Nanotechnology, 3, 1992, pp. 6-9

Ikawa, N., Shimada, S., and Tanaka, H.

Citation

Author

AbstractThis paper discusses the significance of the minimum thickness of cut (MTC) which is defined as the minimum undeformed thickness of the chip removed from a work surface at a cutting edge under perfect performance of a metal cutting system. Following a brief look at the relation between MTC and the extreme machining accuracy attainable for a specific cutting condition, it is shown that a very fine chip with an undeformed thickness of the order of a nanometer can be obtained from experimental face turning of electroplated copper by a well-defined diamond tool. To understand the nanometric metal cutting process, a computer simulation using an atomistic model is proposed.

Objectives of Research Outline the significance of the minimum thickness of cut Carry out experiments to cut undeformed thickness on the order

of a nanometer with a well-defined diamond tool Better understand the chip removal process in micromachining

Approach Face turning of electroplated copper with a diamond tool Atomic cutting model to simulate the chip removal process

Key Findings Under the combination of a specially prepared

diamond cutting edge and free machining of electroplated copper as a work material, a very thin chip nominally of the order of 1 nm has been experimentally produced

A hypothetical atomistic cutting model supports its feasibility

SEM micrographs of chips

Atomistic model of micromachining

44

AbstractA generalized hypothesis for the brittle to ductile transition in micromachining and microindentation of brittle materials is proposed. By the

hypothesis, complicated transition phenomena observed in practical machining processes are well explained. Experimental results on microturning, ELID grinding of monocrystalline Si and LiNbO3 support the applicability of the hypothesis. Microindentation testing is shown to evaluate the intrinsic ductility and critical scale of machining for ductile mode machining. To analyze the machining process at extremely small scales, molecular dynamics computer simulations of microindentation and cutting are made on a defect free surface. These results suggest that any material, in spite of their ductility, can be machined in ductile mode under sufficiently small scale of machining.

Objectives of Research To study the brittle-ductile transition phenomena in microindentation and micromachining.

Approach Hypothesis about possible mechanisms for brittle-ductile transition phenomena. Diamond turning and ELID grinding of Si(100) and LiNbO3 surfaces and microindentation of fine polished Si and LiNbO3 surfaces carried

out to test the validity of the hypothesis. Molecular dynamics (MD) computer simulation of microindentation and cutting were conducted to analyze the material removal process in

the nanometer or atomic scale.

Key findings The mode of material removal, brittle or ductile depends on the dominance of two criteria: the resolved tensile stress on cleavage plane or

shear stress on slip plane exceeds a certain critical value for each stress levels under a particular machining condition. The dominance of the criteria depends on the size of the stress field in which the unit process of the particular machining takes place. For larger than micrometer scale machining the brittle mode material removal is the predominant criteria. Since the critical tensile strength, which is sensitive to pre-existing defects, shows a remarkable size effect, the ductile mode process is

favorable in the micrometer to sub-micrometer scale of machining. Experimental results on machining of mono-crystalline Si and LiNbO3support the applicability of this criteria.

Microindentation experiments are useful in evaluating the intrinsic ductility and critical scale of machining for ductile mode machining. MD simulations suggest that any material, regardless of its brittleness, can be machined in the ductile mode under a sufficiently small scale

of machining, say nanometer level or less.

Micromachining, Ductile transition, Brittle material

Brittle-Ductile Transition Phenomena in Microindentation and Micromachining

Keywords

Title

Annals of the CIRP, 44(1), 1995, pp. 523-526.

Shimada, S.,Ikawa, N.,Inamura, T. , Ohmori, H. and Sata, T.

Citation

Author

45

AbstractThe paper describes a microplasticity model for analyzing the variations in the cutting force in ultra-precision diamond turning. The model

takes into account the effect of material anisotropy due to the changing crystallographic orientation of the workpiece being cut. A spectrum analysis technique is deployed to extract the features of the cutting force patterns. The model has been verified through a series of cutting experiments conducted on aluminum single crystals with different crystallographic cutting planes. The results indicate that the model can predict well the patterns of the cutting force variation. It is also found that there exists a fundamental cyclic frequency of variation of the cutting force per revolution of the workpiece. Such a frequency is shown to be closely related to the crystallographic orientation of the materials being cut. The successful development of the microplasticity model provides a quantitative means of explaining periodic fluctuation of the micro-cutting force in diamond turning of crystalline materials.

Objectives of Research To develop a micro-plasticity model for studying cutting force variations in ultra-precision diamond turning taking into account the effect of

material anisotropy due to changing crystallographic orientation of the workpiece being cut.

Approach Analytical model development for shear angle and

cutting force variation with crystallographic orientations Model validation using machining experiments

and spectrum analysis

Key findings Variation of microcutting forces in diamond turning of

crystalline materials is analyzed based on a microplasticity model and spectrum analysis technique. The model takes into account the effect of crystallographic orientation of work materials being cut.

Experimental results validate the proposed model. The variation of the cutting forces is closely related to

the crystallographic orientation of the crystals being cut. As the depth of cut increases the effect of the

crystallographic orientation of single crystal materials on microcutting forces was found to be pronounced.

Micro-cutting, Microplasticity, Ultraprecision

A Microplasticity Analysis of Micro-Cutting Force Variation in Ultra-Precision Diamond Turning.

Keywords

Title

Journal of Manufacturing Science and Engineering, 124, 2002, pp.170-177.

Lee, W.B. and Cheung, C.F. and To, S.

Citation

Author

Predicted variation of the shear angle with crystal orientations on (001) and (111) planes.

Predicted variation of the cutting forces with crystal orientations on (001) and (111) planes.

46

AbstractTheoretical and experimental analyses of orthogonal micromachining of copper are presented to promote fundamental understanding of

ultraprecision metal cutting processes. A method is proposed by applying rigid-plastic FEM to analyze the mechanics of the steady state orthogonal, micromachining process of copper taking into consideration the roundness of the tool edge. An FEM model is also developed to analyze the flow of cutting heat and the temperature distribution within both the workpiece and the tool based on the calculated stress and the material flow within the workpiece. Orthogonal micromachining experiments are carried out by employing both a micromachining equipment installed within a SEM (Scanning Electron Microscope) and an ultraprecision fly cutting machine. The results of the FEM analysis are compared with the experimental results.

Objectives of Research To study and analyze the mechanics of steady state, orthogonal, micromachining of copper

Approach Use of FEM to analytically study the stress, strain, material flow and cutting heat in the orthogonal micromachining of copper. Experimental validation using: A) orthogonal micromachining equipment installed inside a SEM, for direct observation of the micromachining process, and B) Ultraprecision fly cutting machine, for measuring the cutting heat.

Cutting, Micromachining, Finite element method

Combined Stress,Material Flow and Heat Analysis of Orthogonal Micromachining of Copper

Keywords

Title

Annals of the CIRP, 42(1), 1993, pp.75-78.

Moriwaki, T.,Sugimura, N. and Luan, S.

Citation

Author

Key findings The results from the FEM are in good agreement with the experimental

results. The cutting ratio (ratio of depth of cut to the chip thickness) decreases with an

increase in the ratio of the tool edge radius (R) to the depth of cut (D). The nominal specific cutting resistance increase as the R/D ratio increases.

The FEM analysis shows that the affected zone within the workpiece is expanded as the R/D ratio increases. Based on the distribution of the maximum shear stress calculated by the FEM analysis, the chip is found to separate from the workpiece just under the tool edge.

The measured cutting temperature reaches about 270K higher than the mean temperature of the workpiece when Cu is cut at cutting speed of 4.3m/s and the depth of cut is 1 m. The cutting temperature increases with an increase in the cutting speed.

From the calculated temperature distribution within the workpiece it is seen that the temperature gradient in the workpiece becomes larger in front of the cutting edge due to the material flow relative to the cutting tool.

Temperature distribution obtained by FEM analysis

47

Cutting, micromachining, accuracy

An atomic analysis of nanometric chip removal as affected by tool-work interaction in diamond turning

Keywords

Title

Annals of the CIRP, 40, 1991, pp. 551-554

Ikawa, N., Shimada, S., Tanaka, H., and Ohmori, G.

Citation

Author

AbstractThis paper discusses the significance of the minimum thickness of cut which is defined as the minimum uncut thickness of chip removed from the worksurface at a cutting edge under perfect performance of a metal cutting system. Following a brief look at the relation between the minimum thickness of cut and extreme machining accuracy attainable for a specific cutting condition, it is shown that a very fine chip the uncut chip thickness of which is on the order of 1 nm is obtained in experimental face turning by a well-defined diamond tool. To understand the nanometric chip removal process, a computer simulation using an atomistic model is made. The analysis of the experimental results aided by the computer simulation shows that, while the minimum thickness of cut is affected by the tool-workmaterial interaction to a certain degree, it is more strongly affected by the sharpness of the cutting edge and that the minimum thickness of cut may be on the order of 1/10 of the cutting edge radius.

Objectives of Research Understand the effect of cutting edge sharpness and tool-work interaction on the

minimum thickness of cut through an atomistic cutting model for computer simulation Estimate the minimum thickness of cut from the SEM observation of nanometric chips

obtained in the experimental face turning of electroplated copper, oxygen free high conductivity copper, and commercially pure aluminum

Approach Experimental face turning with a well-defined diamond tool SEM observations of the chips to estimate the minimum thickness of cut Atomistic cutting model to simulate and study significance of cutting parameters on the

minimum thickness of cut

Key Findings The minimum thickness of cut is one of the most important factors to determine the

machining accuracy attainable for a specific set of cutting conditions The minimum thickness of about 1 nm can be obtained in facing of Cu and Al. Extreme accuracy can be attained if the cutting edge sharpness is maintained at few nm The minimum thickness of cut is more strongly affected by the sharpness of cutting

edge than by the tool-work interaction The minimum thickness of cut may be at the order of 1/10 of the cutting edge radius

Atomistic model of nanometric cutting

48

AbstractBased on the method of transformation from an atomic model to a corresponding continuum model, the stress and strain distributions in

nanoscale cutting have been evaluated. These results show that a workpiece is subjected to concerted compressive and shear strain in the primary shear zone, though the area along the rake face of the tool is strained in tension. The results also show that the interior of the workpiece is exposed to a high, almost constant compressive stress. A possible mechanism of these different stress and strain distributions is discussed as well as its interpretation at the macroscale.

Objectives of Research To evaluate the stress and strain distribution in nanoscale cutting and to investigate the relationship between the mechanics of microscale

cutting and that of macroscale cutting using an atomic/continuum transformation.

Approach Molecular dynamic simulations and analysis.

Key findings A method of transformation from an atomic model to an equivalent

continuum model is presented together with its various interpretations. Workpiece material is subjected to concentrated compressive and shear

strain during cutting. However, the area along the rake face of a tool is subjected to tensile strain due to the adhesive forces between the tool and workpiece.

Stress distribution in the workpiece during cutting is very complex with regard to its direction, indicating the initiation of a kind of buckling deformation. The interior region of the workpiece including the area of primary shear is not exposed to any concentrated shear stress but exposed to relatively constant and high compressive stress.

The difference between the stress and strain distributions in the workpiece during cutting cannot be explained either by the theory of plastic deformation on the macroscale or by the theory of plastic deformation for a monocrystal. The mechanism of deformation in the primary shear zone seems to be related to buckling due to severe compression in that area.

Simulations, Micromachining, Cutting

On a Possible Mechanism of Shear Deformation in Nanoscale Cutting.

Keywords

Title

Annals of the CIRP, 43 (1), 1994, pp.47-50

Inamura, T.,Takezawa,N., Kumaki,Y. and Sata,T.

Citation

Author

Magnitude of the maximum shear stress and strain in the workpiece during cutting

49

AbstractThe physics of the micro-cutting process at very small depths of cut (1m or less) is not well understood despite the successful

development of ultra-precision machining technology. Sliding along the clearance face of the tool due to the elastic recovery of the workpiece and plowing due to the tool edge radius may become important in the micro-cutting range. To obtain a clear understanding of these two factors, an orthogonal cutting model the so-called RECM (round edge cutting model) is suggested,

Objectives of Research To develop an orthogonal cutting model considering the cutting edge radius and the elastic recovery of the material and to quantify the

plowing along the rounded edge and sliding on the clearance face.

Approach Analytical model development, model validation by comparing against published experimental results and comparison with Merchants

sharp edge cutting model (SECM).

Key findings The size effect is unaccountable for in Merchants SECM model. In micromachining as the depth of cut becomes of the same order as the tool edge radius the assumption that the tool edge is perfectly

sharp is no longer valid. As a consequence, micro machining may involve significant sliding along the clearance face of the tool due to elastic recovery of the workpiece material and plowing due to the large effective negative rake angle resulting from the tool-edge radius.

A cutting model called the RECM is suggested to quantify the above effects.

The cutting force predicted by RECM is a better fit to the experimental values than by SECM.

Analysis of the components of the cuttingforce establishes that the effect of the clearance face and the rounded edge of the tool dominate the cutting force system for under 1m depths of cut.

Cutting, Cutting forces, Diamond

Theoretical Analysis of Micro-Cutting Characteristics in Ultra-precision Machining

Keywords

Title

Journal of Materials Processing Technology, 49, 1995, pp.387-398.

Kim, J.D. and Kim, D.S.

Citation

Author

Cutting models of orthogonal cutting

50

Cutting edge radius, Minimum chip thickness, Surface integrity, Ultraprecision machining

Effect of diamond tool sharpness on minimum cutting thickness and cutting surface integrity in ultraprecision machining

Keywords

Title

Journal of Materials Processing Technology 62(1996) 327-330

Yuan, Z. J., Zhou, M., and Dong., S.

Citation

Author

AbstractThe diamond tools sharpness is a primary factor affecting the cutting deformation and the machined surface quality in the diamond cutting

process. In this paper, the relationship between the cutting edge radius and the minimum cutting thickness was analyzed. Cutting tests of aluminum alloys with diamond tools of different sharpness were performed in order to investigate the effect of cutting edge sharpness on the machined surface integrity. Experimental results show that the surface roughness, microhardness, residual stress and the dislocation density of the machined surface layer vary with the cutting edge radius.

Objectives of Research Analyze the relationship between the cutting edge sharpness and

the minimum cutting thickness. Study the influence of the cutting edge radius on the machined

surface integrity.

Approach Theoretical analysis Diamond turning experimentations

Key findings The minimum chip thickness value was derived as a function of

the force ratio Fy/Fx and the friction coefficient between the tool and workpiece. (0.249 ~0.322 )

With the cutting edge radius of =0.20.6 m, the attainable minimum cutting thickness was found to be 0.05~0.2 m.

The diamond tool edge radius has a considerable influence on the machined surface integrity. As the edge radius increases, the surface roughness increases, the microhardness increases, the residual stress increases and the dislocation density of the subsurface layer increases.

=0.3 m

=0.6 m

51

Micro-milling, minimum chip thickness, chip formation

Experimental analysis of chip formation in micro-milling

Keywords

Title

NAMRI/SME, 30, 2002, pp. 247-254

Kim, C., Bono, M., and Ni, J.

Citation

Author

AbstractThis study investigates the mechanism of chip formation when milling 360 brass with a 2-flute flat end-mill of diameter 635 m. Experiments reveal how chips are formed in the micro-milling process, which differs from conventional milling in that the feed per tooth is often smaller than the cutting edge radius of the tool. Several slots are milled using a speed of 80,000 rpm and feeds per tooth ranging from 0.188 m to 6 m. For each set of cutting conditions, the volumes of the resulting chips and the feed marks on the machined workpiece surface were analyzed.

Objectives of Research To investigate the mechanism of chip formation in

micro-milling

Approach Analysis of the volume of the resulting chip and

the feed marks on the machined workpiece surface

Comparison between the volume of the chips and the nominal volume.

Comparison between the feed mark spacing and the feed per tooth

Key Findings For micro-milling system with a particular stiffness

and cutting edge radius, the mechanism of chip formation varies with the feed per tooth

If the feed per tooth of the milling cutting is relatively small compared to the cutting edge radius of the tool, a chip may not form in each pass of the tool. Instead, the tool can rotate several times without performing any cutting, meaning that chips are produced intermittently.

A chip may also not form in each pass of the tool if the stiffness of the system is small.

52

Cutting edge radius, Minimum chip thickness, Cutting force, Slip-line field, Micro-endmilling

On the modeling and analysis of machining performance in micro-endmilling, Part II: cutting force prediction

Keywords

Title

Journal of Manufacturing Science and Engineering, in print

Vogler, M. P., DeVor, R. E., and Kapoor, S. G.

Citation

Author

AbstractIn this paper, a cutting force model for the micro-endmilling process is developed. This model incorporates the minimum chip thickness

concept in order to predict the effects of the cutter edge radius on the cutting forces. A new chip thickness computation algorithm is developed to include the minimum chip thickness effect. A slip-line plasticity force model is used to predict the force when the chip thickness is greater than the minimum chip thickness, and an elastic deformation force model is employed when the chip thickness is less than the minimum chip thickness. Orthogonal, microstructurre-level finite element simulations are used to calibrate the parameters of the force models for the primary metallurgical phases, ferrite and pearlite, of multi-phase ductile iron workpieces. The model is able to predict the magnitudes of the forces for both the ferrite and pearlite workpieces as well as for the ductile iron workpieces within 20%.

Objectives of Research Modeling the cutting forces in micro-milling accounting for

the effect of minimum chip thickness

Approach Slip-line plasticity modeling the cutting forces FE simulation to determine the minimum chip thickness values.

Key findings For a twelve fold increase in the chip load, the magnitude of the

cutting forces increased less than threefold for the range of cutting conditions tested.

The frequency spectra of the forces were found to contain a component that is a subharmonic of the tooth passing frequency at feedrates less than the minimum chip thickness and appears as a stepping behavior of the forces in the time domain. A decomposition of the simulated forces showed that the stepping behavior is the result of the interference between the tool and workpiece increasing during subsequent revolutions until the instantaneous chip thickness is greater than the minimum chip thickness.

The forces are more sensitive to the edge radius when machining more ferrite than when machining pearlite, due to both minimum chip thickness and the increased ductility of the ferrite that increases the ploughing forces.

ft = 0.25 m/flute

ft = 3.0 m/flute

53

Micro burr, Micro machining

An Experimental Study on Burr Formation In Micro Milling Aluminum and Copper

Keywords

Title

Transactions of NAMRI/SME,2002,pp.255-262.

Lee, K. and Dornfeld, D. A

Citation

Author

AbstractMicro-machining by mechanical machine tools or micro mechanical machining, is an emerging fabrication technology that broadens the

applicable material range for miniature workpieces to more metals and plastics. One of the problems in micromachining, however is burr formation.Experimental studies on micro-burr formation in milling aluminum 6061-T6 and copper 110 have been carried out. A range of different cutting chip loads and depths of cut using 127m, 254m and 635m tool diameters were considered. Different burr formation between micro milling and conventional milling was discussed. Flag-type, rollover-type, wavy-type and ragged-type burrs were observed in milling aluminum and copper.The influence of cutting parameters, axial depth of cut and feed rate, on burr size and burr type was considered. A case study of micro milling using the results of this study is presented.

Objectives of Research Study and characterize the different types of burr formations seen while conducting slotting experiments on aluminum and copper. Study experimentally the effect of varying machining parameters like

speed, feed rate and depth of cut on burr formations in aluminum and copper. To use findings of the study to generate tool paths resulting in

minimum burr formation

Approach Micro milling aluminum and copper using WC-Co , two flute

end mills with diameters of 127m, 254m and 635m Scanning electron microscopy for studying burr formations

Schematic view of burr definition in milling: shape and location

Key findings Flag-type burr, rollover-type burr,wavy-type burr and ragged-type burr are

observed.The rollover-type burr on tool entrance and flag-type burr on tool exit are bigger than in conventional milling processes.

For top burr, up-milling produces a smaller burr than down milling. As the depth of cut and feedrate increase, burr size increases. Run-out in micro-milling causes a big wavy-type burr and form error. The information gained can be used in tool path planning for micro-

machined components.

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55

2. Mechanics of Micro-machining

2.2 Influence of microstructure

56

Microstructure-level modeling, machining, ductile iron, simulation

Microstructure-level Modeling of Ductile Iron Machining

Keywords

Title

ASME J. Manufacturing Science and Engineering, 124, 2002, pp. 162-169

Chuzhoy, L, DeVor, R. E., Kapoor, S. G., and Bammann, D. J.

Citation

Author

AbstractA microstructure-level model for simulation of machining of cast irons using the finite element method is presented. The model explicitly

combines ferritic and pearlitic grains with graphite nodules to produce the ductile iron structure. The behaviors of pearlite, ferrite, and graphite are captured individually using an internal state variable model for the material model. The behavior of each phase is dependent on strain, strain rate, temperature, and amount of damage. Extensive experimentation was conducted to characterize material strain rate andtemperature dependency of both ferrite and pearlite. The model is applied to orthogonal machining of ductile iron. The simulation results demonstrate the feasibility of successfully capturing the influence of microstructure on machinability and part performance. The stress, strain, temperature, and damage results obtained from the model are found to correlate well with experimental results found in the literature. Furthermore, the model is capable of handling various microstructures in other heterogeneous materials such as steels.

Objectives of Research Simulates the material behavior of h