- Email: [email protected]
1985 Precision Engineering Conference
|°
PRE¢| Conference report 14-15
November
1985, Raleigh,
North
Carolina,
USA
1985 Precision Engineering Conference
Organized specifically to act as a forum for the exchange of ideas with a substantial visiting Japanese delegation, this meeting succeeded admirably. Ample time was allowed for discussion, both in the sessions and informally, of a programme which was less wide ranging than the conference title. The previous evening's welcome reception set just the right social tone for the meeting; Atkinson and Estler's report on accuracy testing and initial operating experience on LODTM did the same for the technical content*. The original tool positioning accuracy target for LODTM was 1.1 microinch rms, with a surface finish goal of 4.2 nm rms; Atkinson's synoptic comment on the current status was to describe it as 'a 2 to 4 microinch machine." Parts are being produced, although there are still a number of interesting technical questions to be addressed - - if and when production demands allow the time. Katsuki reviewed Toshiba's experience in the design and construction of diamond turning machines. Designs for friction drives, air bearing spindles, slideways and structures were discussed and examples of machines for machining discs, drums and polygon mirrors presented. Detailed finite element modelling of spindle growth showed good correlation with measurements for steady state at a range of spindle speeds. Another modelling application, presented later in the meeting, was Strenkowski's use of NIKE-2D to model chip formation. The presentation focused on shear band formation although the model clearly has potential to be developed to * For more details on the design and error budget for the Large Optics Diamond Turning Machine see, inter alia abstract from 3rd International Precision Engineering Seminar, Brown et al Proc SPIE 381, 1983
PRECISION ENGINEERING
address such issues as tool tip temperature and the detailed chip mechanics of diamond turning. Ueda, also from Toshiba, described the diamond turning of OFHCcopper master for moulding of plastic Fresnel lenses. Katsuki, in his presentation, had noted that active magnetic bearing spindles were available, but stated that they were too expensive for practical machines. His compatriot from Seiko offered a different prospect for the future; in discussing designs for ultra-high speed grinding spindles, he mentioned joint work with S2M (the French magnetic bearing innovators**) and stated that it was his 'responsibility to bring the price down'. One was left with little doubt of the probable outcome! Yokokura and Sumiya described their system for testing aspheric surfaces using electron beam written computer generated holograms. Maximum aspheric departure accepted is 1000;t and quoted accuracy is better than 0.1/~m. Cost considerations suggest that system applications are likely to be limited to larger batches. The capital costs will be non-trivial and the cost per surface for data compaction and e-beam writing were quoted as about $2500. Super smooth surface requirements in such devices as the ring laser gyro have driven the development of new evaluation techniques. Stowell described a system designed to measure extremely low level scatter and the application of that system in assessing surface and sub-surface damage in finishing operations. Brown followed this with a majestic review of polishing research which demonstrated both the progress in understanding the complex surface interactions and the level of mysteries still to be unravelled. A polishing process has been ** See Habermann and Liard, Precision Eng., 1980, 2 (3), 139-140
developed at Saitama University where the material removal process changes from mechanical to chemical as polishing progresses. Kasai included in his report, experience with the process: for example, roughness and flatness of 0.002/Jm and 10 #m respectively have been achieved on 50 mm GaAs wafers. Two papers focused on grinding machines. First, Chaloux described at attachment for Pneumo lathes to allow diamond grinding optical surfaces up to 50 mm diameter. Yoshioka et al took a rather broader approach ranging from wheel/workpiece interactions through such machine design ideas as hydraulic load compensated leadscrews to the details of surface and centreless grinders. Bifano and Dow's paper described their real time control scheme for a rolling element bearing spindle. The control algorithms may be of broader applicability than the spindle system. In addition to the presentations of technical papers, there were two round table discussions; "The Education of a Precision Engineer' and 'Organization of an American Precision Engineering Society'. Neither produced much in the way of concensus, although reports of Japanese experience in both areas offered some fascinating insights. Hocken, moderator of the round table bn education, set the tone by asking delegates what they wanted of 'new precision engineers' (by implication, new graduates at Master's level). The range of responses reflected the breadth of the subjec~ and the differing levels of importance attached to various aspects by different organizations; perhaps cloning is the only approach that will satisfy those doing the hiringT The discussion about the formation of a US based society had many similar characteristics; everyone agreed that it was a good idea and everyone had a different idea of what to do next. Finally it was agreed first that a new name was needed as the acronym for the American Precision Engineering Society was hardly flattering and second that a committee be formed to solicit further ideas and informationt. t The secretary of the committee is E. C. Teague. Any comments may be addressed to him at the Precision Engineering Division, NaUonal Bureau of Standards, Gaithersburg, Maryland 20899, USA
111
Optics and Laser Technology bridges the research~applications gap in the optics field. Established over 15 years ago and with subscribers in nearly 50 countries, this journal is a major source of information on the latest advances in optics and their applications worldwide. As well as full research papers, technical notes and letters to the editor, the journal contains conference reports, book reviews, a calendar of events and news on the latest commercial optical equipment throughout the world.
Coverage includes: • Lasers • Fibre optics • •
Holography Interferometry
• Integrated optics • High speed photography • Infra-red and ultra-violet • Optics in medicine
For further details or a sample copy, please write to:
Mrs. Sheila King, Butterworth Scientific Ltd., PO Box 63, Westbury House, Bury Street, Guildford, Surrey GU2 5BH,
U.K.
112
APRIL 1986 VOL 8 NO 2
PIt|¢15 In summary, this was an enjoyable and informative meeting. It suggested that there is a need for an easily accessible, low cost forum for the continuously expanding US precision engineering community.
C. Evans Gaithersburg, Maryland, USA
Papers presented A t k i n s o n D. and Esler T. Results of accuracy testing and initial operating experience of the LODTM.
~,atsuki M. Design and applications of ultraprecision diamond turning machine. Y o k o k u r a T. Interferometry with computer-generated holograms for strong aspheric surface testing. S t o w e l l K. Damage effects identified by scatter evaluation of supersmooth surfaces. B r o w n N. Polishing research.
Yoshioka J., H a s h i m o t o F., Kanai A., M i y a s h i t a M . , A b o T. and Daito M . Ultraprecision grinding technology for brittle materials. Ota M . Design and applications of ultra high-speed internal grinding head--200 000 rpm.
Ueda K. Micro-grooving for plastic grating lens with CNC diamond lathe.
Bifano T. and D o w T. Correction of spindle accuracy.
22-24 April 1985, Hanover, FRG
M o t o r - C o n 85
PRECISION ENGINEERING
Chaloux L. Diamond grinding of optical surfaces on brittle materials.
Kasai T. Application of P-MAC polishing to Si wafers.
Conference report
The 7th Motor-Con conference was held in conjunction with the Hanover trade fair. The conference covered motors, their drive systems and control systems, ranging from small stepper motors to large industrial drives. The conference consisted of 13 sessions spread over three days. Several of the papers given were of limited interest to precision engineering, these mainly covering large AC motors, control of drives for AC motors by microprocessor and the use of new power devices for their drives. The first session dealt with stepper motors and contained papers describing methods of obtaining position information by evaluating the BEMF of a stepper motor. Also covered was the cause of parametric resonance in stepper motors and an alternative to choosing between stepper and PC motors. The second session covered brushless DC servo motors and included papers reporting new types of brushless motors and methods of increasing the torque-speed range of motors. The topic of evaluating motors for a particular requirement with particular emphasis on brushless DC motors was also dealt with. The
S t r e n k o w s k i J. An analysis of shear band behaviour in diamond turning.
subject of sensors was covered, with emphasis on Hall effect sensors, in particular their use in commutating brushless DC motors. A new type of position and velocity transducer with a high temperature range was presented. The session covering motor drives was of great interest, with three papers given on the use of power MOSFETSin amplifiers. It included designs for driving centrifuges and a novel form of switch mode amplifier using both MOSFETS and thyristors, to increase the reliability of the servo amplifier. Also presented was a paper showing showing a new power MOSFET-based switching amplifier with a switching frequency of 50 kHz and a low pass filter across the motor to produce a low ripple drive signal. The subject of motion control was discussed with the main emphasis being given to microprocessor control of motion system. The interfacing of microprocessor control to the drive system, and what standards should be applied (if any), were discussed at length, but no real conclusion was reached. The subject of motion control by microprocessor was also discussed, with papers on
adaptive control of servo systems and a description of a complete motion control system consisting of two special ics which contain most of the hardware needed. The last session of the conference included papers showing how people dealt with problems associated with motion control. The conference ranged from PC servo motors to very large threephase AC motors and drives, and therefore covered a very large area of motion control. It was of great interest because of the large area it covered, but only a fraction of this wide range could truthfully be described as "Precision Engineering'!
D. Stoddart Cranfield Institute of Technology, Bedford, UK
Papers presented Schneider S.M.O.L. About parametric resonance in stepper motors. Edmond R. Direct and cartesian coordinate stepping motors. Werner S. Self-synchronization of permanent magnet energized stepper motor with detection of position by evaluation of the BEMF. Hofer K. Speed controlled 4Q-Dc drives without current or speed feedback. Oudet C. and Ettelman D.J. An alternative to choosing between DC and stepper motors. Tomasek J. Velocity and position feedback in brushless DC servo systems. Brosnan i . and Barber N.T. Rare-earth high performance brushless drives and their application.
113
PRE¢| Conference report 14-15
November
1985, Raleigh,
North
Carolina,
USA
1985 Precision Engineering Conference
Organized specifically to act as a forum for the exchange of ideas with a substantial visiting Japanese delegation, this meeting succeeded admirably. Ample time was allowed for discussion, both in the sessions and informally, of a programme which was less wide ranging than the conference title. The previous evening's welcome reception set just the right social tone for the meeting; Atkinson and Estler's report on accuracy testing and initial operating experience on LODTM did the same for the technical content*. The original tool positioning accuracy target for LODTM was 1.1 microinch rms, with a surface finish goal of 4.2 nm rms; Atkinson's synoptic comment on the current status was to describe it as 'a 2 to 4 microinch machine." Parts are being produced, although there are still a number of interesting technical questions to be addressed - - if and when production demands allow the time. Katsuki reviewed Toshiba's experience in the design and construction of diamond turning machines. Designs for friction drives, air bearing spindles, slideways and structures were discussed and examples of machines for machining discs, drums and polygon mirrors presented. Detailed finite element modelling of spindle growth showed good correlation with measurements for steady state at a range of spindle speeds. Another modelling application, presented later in the meeting, was Strenkowski's use of NIKE-2D to model chip formation. The presentation focused on shear band formation although the model clearly has potential to be developed to * For more details on the design and error budget for the Large Optics Diamond Turning Machine see, inter alia abstract from 3rd International Precision Engineering Seminar, Brown et al Proc SPIE 381, 1983
PRECISION ENGINEERING
address such issues as tool tip temperature and the detailed chip mechanics of diamond turning. Ueda, also from Toshiba, described the diamond turning of OFHCcopper master for moulding of plastic Fresnel lenses. Katsuki, in his presentation, had noted that active magnetic bearing spindles were available, but stated that they were too expensive for practical machines. His compatriot from Seiko offered a different prospect for the future; in discussing designs for ultra-high speed grinding spindles, he mentioned joint work with S2M (the French magnetic bearing innovators**) and stated that it was his 'responsibility to bring the price down'. One was left with little doubt of the probable outcome! Yokokura and Sumiya described their system for testing aspheric surfaces using electron beam written computer generated holograms. Maximum aspheric departure accepted is 1000;t and quoted accuracy is better than 0.1/~m. Cost considerations suggest that system applications are likely to be limited to larger batches. The capital costs will be non-trivial and the cost per surface for data compaction and e-beam writing were quoted as about $2500. Super smooth surface requirements in such devices as the ring laser gyro have driven the development of new evaluation techniques. Stowell described a system designed to measure extremely low level scatter and the application of that system in assessing surface and sub-surface damage in finishing operations. Brown followed this with a majestic review of polishing research which demonstrated both the progress in understanding the complex surface interactions and the level of mysteries still to be unravelled. A polishing process has been ** See Habermann and Liard, Precision Eng., 1980, 2 (3), 139-140
developed at Saitama University where the material removal process changes from mechanical to chemical as polishing progresses. Kasai included in his report, experience with the process: for example, roughness and flatness of 0.002/Jm and 10 #m respectively have been achieved on 50 mm GaAs wafers. Two papers focused on grinding machines. First, Chaloux described at attachment for Pneumo lathes to allow diamond grinding optical surfaces up to 50 mm diameter. Yoshioka et al took a rather broader approach ranging from wheel/workpiece interactions through such machine design ideas as hydraulic load compensated leadscrews to the details of surface and centreless grinders. Bifano and Dow's paper described their real time control scheme for a rolling element bearing spindle. The control algorithms may be of broader applicability than the spindle system. In addition to the presentations of technical papers, there were two round table discussions; "The Education of a Precision Engineer' and 'Organization of an American Precision Engineering Society'. Neither produced much in the way of concensus, although reports of Japanese experience in both areas offered some fascinating insights. Hocken, moderator of the round table bn education, set the tone by asking delegates what they wanted of 'new precision engineers' (by implication, new graduates at Master's level). The range of responses reflected the breadth of the subjec~ and the differing levels of importance attached to various aspects by different organizations; perhaps cloning is the only approach that will satisfy those doing the hiringT The discussion about the formation of a US based society had many similar characteristics; everyone agreed that it was a good idea and everyone had a different idea of what to do next. Finally it was agreed first that a new name was needed as the acronym for the American Precision Engineering Society was hardly flattering and second that a committee be formed to solicit further ideas and informationt. t The secretary of the committee is E. C. Teague. Any comments may be addressed to him at the Precision Engineering Division, NaUonal Bureau of Standards, Gaithersburg, Maryland 20899, USA
111
Optics and Laser Technology bridges the research~applications gap in the optics field. Established over 15 years ago and with subscribers in nearly 50 countries, this journal is a major source of information on the latest advances in optics and their applications worldwide. As well as full research papers, technical notes and letters to the editor, the journal contains conference reports, book reviews, a calendar of events and news on the latest commercial optical equipment throughout the world.
Coverage includes: • Lasers • Fibre optics • •
Holography Interferometry
• Integrated optics • High speed photography • Infra-red and ultra-violet • Optics in medicine
For further details or a sample copy, please write to:
Mrs. Sheila King, Butterworth Scientific Ltd., PO Box 63, Westbury House, Bury Street, Guildford, Surrey GU2 5BH,
U.K.
112
APRIL 1986 VOL 8 NO 2
PIt|¢15 In summary, this was an enjoyable and informative meeting. It suggested that there is a need for an easily accessible, low cost forum for the continuously expanding US precision engineering community.
C. Evans Gaithersburg, Maryland, USA
Papers presented A t k i n s o n D. and Esler T. Results of accuracy testing and initial operating experience of the LODTM.
~,atsuki M. Design and applications of ultraprecision diamond turning machine. Y o k o k u r a T. Interferometry with computer-generated holograms for strong aspheric surface testing. S t o w e l l K. Damage effects identified by scatter evaluation of supersmooth surfaces. B r o w n N. Polishing research.
Yoshioka J., H a s h i m o t o F., Kanai A., M i y a s h i t a M . , A b o T. and Daito M . Ultraprecision grinding technology for brittle materials. Ota M . Design and applications of ultra high-speed internal grinding head--200 000 rpm.
Ueda K. Micro-grooving for plastic grating lens with CNC diamond lathe.
Bifano T. and D o w T. Correction of spindle accuracy.
22-24 April 1985, Hanover, FRG
M o t o r - C o n 85
PRECISION ENGINEERING
Chaloux L. Diamond grinding of optical surfaces on brittle materials.
Kasai T. Application of P-MAC polishing to Si wafers.
Conference report
The 7th Motor-Con conference was held in conjunction with the Hanover trade fair. The conference covered motors, their drive systems and control systems, ranging from small stepper motors to large industrial drives. The conference consisted of 13 sessions spread over three days. Several of the papers given were of limited interest to precision engineering, these mainly covering large AC motors, control of drives for AC motors by microprocessor and the use of new power devices for their drives. The first session dealt with stepper motors and contained papers describing methods of obtaining position information by evaluating the BEMF of a stepper motor. Also covered was the cause of parametric resonance in stepper motors and an alternative to choosing between stepper and PC motors. The second session covered brushless DC servo motors and included papers reporting new types of brushless motors and methods of increasing the torque-speed range of motors. The topic of evaluating motors for a particular requirement with particular emphasis on brushless DC motors was also dealt with. The
S t r e n k o w s k i J. An analysis of shear band behaviour in diamond turning.
subject of sensors was covered, with emphasis on Hall effect sensors, in particular their use in commutating brushless DC motors. A new type of position and velocity transducer with a high temperature range was presented. The session covering motor drives was of great interest, with three papers given on the use of power MOSFETSin amplifiers. It included designs for driving centrifuges and a novel form of switch mode amplifier using both MOSFETS and thyristors, to increase the reliability of the servo amplifier. Also presented was a paper showing showing a new power MOSFET-based switching amplifier with a switching frequency of 50 kHz and a low pass filter across the motor to produce a low ripple drive signal. The subject of motion control was discussed with the main emphasis being given to microprocessor control of motion system. The interfacing of microprocessor control to the drive system, and what standards should be applied (if any), were discussed at length, but no real conclusion was reached. The subject of motion control by microprocessor was also discussed, with papers on
adaptive control of servo systems and a description of a complete motion control system consisting of two special ics which contain most of the hardware needed. The last session of the conference included papers showing how people dealt with problems associated with motion control. The conference ranged from PC servo motors to very large threephase AC motors and drives, and therefore covered a very large area of motion control. It was of great interest because of the large area it covered, but only a fraction of this wide range could truthfully be described as "Precision Engineering'!
D. Stoddart Cranfield Institute of Technology, Bedford, UK
Papers presented Schneider S.M.O.L. About parametric resonance in stepper motors. Edmond R. Direct and cartesian coordinate stepping motors. Werner S. Self-synchronization of permanent magnet energized stepper motor with detection of position by evaluation of the BEMF. Hofer K. Speed controlled 4Q-Dc drives without current or speed feedback. Oudet C. and Ettelman D.J. An alternative to choosing between DC and stepper motors. Tomasek J. Velocity and position feedback in brushless DC servo systems. Brosnan i . and Barber N.T. Rare-earth high performance brushless drives and their application.
113