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Dr. Markus Schinhärl, M.Eng.

Faculty of Mechanical Engineering and Mechatronics

Support Staff

Lab Engineer

C 210

0991/3615-374

Sortierung:
Journal article
  • Elmar Pitschke
  • Peter Sperber
  • R. Stamp
  • Rolf Rascher
  • L. Smith
  • M. Smith
  • Markus Schinhärl

Prediction of MRF polishing by classification of the initial error with Zernike polynomials.

In: Optical Manufacturing and Testing V vol. 5180 pg. 115-122

  • (2003)

DOI: 10.1117/12.507652

show abstract

The magnetorheological finishing (MRF) process makes use of a magnetically stiffened magnetorheological abrasive fluid to polish the surface of a workpiece in a precise fashion. The process may be used to finish the surface of high quality optical lenses. Investigations have been undertaken to quantify the operation of MRF and to identify those parameters key to an optimal operation of this lens production process. A correlation has been developed to relate the parameters important to the removal characteristics and to the precision of the polishing result and to the duration of polishing. A relationship to indicate the most appropriate MRF processing parameters for a lens is presented. In the examples discussed Fringe-Zernike polynomials are used to quantify the error on a lens.
Lecture
  • Elmar Pitschke
  • Peter Sperber
  • R. Stamp
  • Rolf Rascher
  • L. Smith
  • M. Smith
  • Markus Schinhärl

Prediction of MRF polishing by classification of the initial error with Zernike polynomials.

In: Optical Manufacturing and Testing V

San Diego, CA, USA

  • 03.08.2003 (2003)
Lecture
  • Elmar Pitschke
  • Peter Sperber
  • Rolf Rascher
  • R. Stamp
  • M. Smith
  • L. Smith
  • Markus Schinhärl

Lens production enhancement by adoption of artificial influence functions and a knowledge-based system in a magnetorheological finishing process.

In: Optical Manufacturing and Testing VII

San Diego, CA, USA

  • 03.08.2003 (2003)
Lecture
  • Markus Schinhärl
  • Elmar Pitschke
  • Rolf Rascher
  • Peter Sperber
  • R. Stamp
  • L. Smith
  • G. Smith

Temporal stability and performance of MR polishing fluid.

In: Current Developments in Lens Design and Optical Engineering V

SPIE, The International Society for Optics and Photonics San Diego, CA, USA

  • 2004 (2004)
Journal article
  • Elmar Pitschke
  • Markus Schinhärl
  • Peter Sperber
  • Rolf Rascher
  • R. Stamp
  • L. Smith
  • M. Smith
  • A. Hammer

Comparison of a new contact topographical measurement system for spherical and aspherical surfaces with interferometry.

In: Current Developments in Lens Design and Optical Engineering V vol. 5523 pg. 225-234

  • (2004)

DOI: 10.1117/12.558899

show abstract

Since end of 2003 the TII-3D - the new contact topography measuring device for measuring aspherical and spherical surfaces - is available on market. Due to its novel technology, the system is specified to measure a large range with λ/10 accuracy, therefore being a very flexible tool for pre- and post-measurements in high quality zonal polishing processes like MRF. At the University of Applied Sciences Deggendorf a testing series has been carries out to compare the results of the TII-3D with CGH-interferometric measurements on aspherical surfaces. An analysis of the measurement errors is shown and ranking of the different metrology systems for production processes of high quality aspherical lenses is given.
Journal article
  • Markus Schinhärl
  • Elmar Pitschke
  • Rolf Rascher
  • Peter Sperber
  • R. Stamp
  • L. Smith
  • G. Smith

Temporal stability and performance of MR polishing fluid.

In: Current Developments in Lens Design and Optical Engineering V vol. 5523 pg. 273-280

  • (2004)

DOI: 10.1117/12.558897

show abstract

The lifetime of standard magnetorheological (MR) polishing fluids, used for example in polishing machines for optical applications, is limited. Scanning electron microscope examinations as well as chemical analyses of the fluid had been undertaken in order to investigate reasons for limited lifetime. We found out that the removal rate decreases during the course of time. However, the usable fluid life is most limited by the point of time when the critical minimum amount of fluid, necessary to ensure circulation, is reached. The results in association with a new fluid conditioner show, that a standard MR polishing fluid may be used for longer periods than common periods of about 2 weeks.
Contribution
  • Elmar Pitschke
  • Markus Schinhärl
  • Rolf Rascher
  • Peter Sperber

Erzeugung hochpräziser Oberflächen auf optischen Bauelementen für die Präzisionsoptik mit magnetorheologischem Finishing (MRF).

In: Fünftes Symposium - Zukunft Glas - von der Tradition zum High-Tech-Produkt, page 8998. OTTI. pg. 89-98

  • (2004)
Lecture
  • Elmar Pitschke
  • Markus Schinhärl
  • Rolf Rascher
  • Peter Sperber

Erzeugung hochpräziser Oberflächen auf optischen Bauelementen für die Präzisionsoptik mit magnetorheologischem Finishing (MRF).

In: Fünftes Symposium - Zukunft Glas - Von der Tradition zum High-Tech-Produkt

Zwiesel

  • 17.06.2004 (2004)
Lecture
  • Elmar Pitschke
  • Markus Schinhärl
  • Peter Sperber
  • Rolf Rascher
  • R. Stamp
  • L. Smith
  • M. Smith
  • A. Hammer

Comparison of a new contact topographical measurement system for spherical and aspherical surfaces with interferometry.

In: Current Developments in Lens Design and Optical Engineering V

Denver, CO, USA

  • 02.08.2004 (2004)
Journal article
  • Markus Schinhärl
  • Elmar Pitschke
  • Andreas Geiss
  • Rolf Rascher
  • Peter Sperber
  • R. Stamp
  • L. Smith
  • G. Smith

Comparison of different magnetorheological polishing fluids.

In: Optical Fabrication, Testing, and Metrology II vol. 5965 pg. 659-670

  • (2005)

DOI: 10.1117/12.656430

show abstract

Magnetorheological Finishing (MRF) is commonly used to finish high quality optical surfaces. The process is based on a magnetorheological fluid, which stiffens in a magnetic field and thus may be used as a polishing tool. The fluid removal characteristic depends on several parameters, for example the magnetic field strength or the relative velocity between workpiece and polishing tool. Another parameter is the fluid itself. Different compositions of polishing abrasives result in different removal characteristics. At the University of Applied Sciences Deggendorf, five different magnetorheological polishing fluids have been analysed. The results of the research are scanning electron microscope analyses as well as spectra analyses. The removal characteristic for each fluid has been determined for different glass materials. Finally, the fluid conditions during polishing have been analysed. For this purpose, the fluid flow rate, the fluid pressure and the fluid viscosity have been investigated.
Journal article
  • Elmar Pitschke
  • Markus Schinhärl
  • Peter Sperber
  • Rolf Rascher

Utilizing a TII aspherical measurement machine in a computer-controlled polishing process.

In: Optical Measurement Systems for Industrial Inspection IV vol. 5856 pg. 987-993

  • (2005)

DOI: 10.1117/12.612597

show abstract

The demand on quality of optical surfaces is increasing from year to year. Computer controlled polishing is one way to fulfill these demands. The process depends on the error-profile of the optical surface. In this paper the usage of the TII measurement machine is discussed to manufacture optical surfaces.
Journal article
  • Elmar Pitschke
  • Markus Schinhärl
  • Andreas Geiss
  • Peter Sperber
  • Rolf Rascher
  • R. Stamp
  • L. Smith
  • M. Smith

A new approach to predict computer-controlled polishing results.

In: Optical Manufacturing and Testing VI vol. 5869 pg. 94-102

  • (2005)

DOI: 10.1117/12.616780

show abstract

A novel approach to handle and quantify a computer controlled polishing process will be introduced. This approach will be compared to real data. This comparison indicates the correctness of this approach. Based on it a formula has been developed to predict the results of a computer controlled polishing process. The formula will be used to predict real polishing processes and the results will be compared to the real results. The limits when using this formula will be shown along with suggestions when the formula would be useful. This rough prediction of the computer controlled polishing results may be used to enhance the automation of a computer controlled polishing process. Also a way to improve the formula itself will be introduced. It is the opinion of the author that by further stabilizing of the whole computer controlled polishing process the whole system becomes more robust, the prediction more accurate and the whole system improves in reliability and the results become better.
Journal article
  • Markus Schinhärl
  • Elmar Pitschke
  • Andreas Geiss
  • Rolf Rascher
  • Peter Sperber
  • R. Stamp
  • L. Smith
  • G. Smith

New viscosity measurement for magnetorheological polishing fluid.

In: Optical Manufacturing and Testing VI vol. 5869 pg. 133-141

  • (2005)

DOI: 10.1117/12.616690

show abstract

In Magnetorheological Finishing (MRF) a magnetic field is applied to a stream of abrasive magnetorheological fluid, in order that the fluid behaves as the polishing tool. The process may be used to finish the surface of high quality optical lenses. The fluid viscosity is one important parameter the polishing tool characteristic depends on. At the University of Applied Sciences Deggendorf a new viscosity measurement, which uses the inductance of the fluid had been tested. The result of the research is a close relationship between viscosity and inductance. The new viscosity measurement is not an absolute, but a comparative system, based on inductance of the flowing fluid and the fluid age.
Journal article
  • Andreas Geiss
  • Markus Schinhärl
  • Elmar Pitschke
  • Rolf Rascher
  • Peter Sperber

Analysis of thermal sources in a magnetorheological finishing (MRF) process.

In: Optical Manufacturing and Testing VI vol. 5869 pg. 111-120

  • (2005)

DOI: 10.1117/12.616751

show abstract

Magnetorheological finishing (MRF) is a computer controlled polishing (CCP) technique for high quality surfaces. The process uses a magnetorheological fluid which stiffens in a magnetic field and thus acts as the polishing tool. At the University of Applied Sciences Deggendorf thermal sources in a MRF polishing unit have been analysed using an infrared camera. The result of the research is a warming of the fluid in the fluid conditioner caused by the mixer motor. The existing cooling is therefore essential, in order to ensure a constant polishing tool characteristic during polishing runs. A new fluid conditioner, which was developed at the University of Applied Sciences Deggendorf, with the aim of an extended fluid lifetime may be used without cooling, because an increase of the fluid temperature in the conditioner could not been detected. Furthermore, a warming of the workpiece during the polishing process was not ascertainable.
Lecture
  • Peter Sperber
  • Elmar Pitschke
  • Markus Schinhärl
  • Rolf Rascher

MRF in der Praxis – Optimierung der Wirtschaftlichkeit.

In: BayTech Optik Seminar

Deggendorf

  • 19.04.2005 (2005)
Lecture
  • Elmar Pitschke
  • Markus Schinhärl
  • Peter Sperber
  • Rolf Rascher

Utilizing a TII aspherical measurement machine in a computer-controlled polishing process.

In: Optical Measurement Systems for Industrial Inspection IV

München

  • 13.06.2005 (2005)
Lecture
  • Andreas Geiss
  • Markus Schinhärl
  • Elmar Pitschke
  • Rolf Rascher
  • Peter Sperber

Analysis of thermal sources in a magnetorheological finishing (MRF) process.

In: Optical Manufacturing and Testing VI

San Diego, CA, USA

  • 31.07.2005 (2005)
Lecture
  • Markus Schinhärl
  • Elmar Pitschke
  • Andreas Geiss
  • Rolf Rascher
  • Peter Sperber
  • R. Stamp
  • L. Smith
  • G. Smith

New viscosity measurement for magnetorheological polishing fluid.

In: Optical Manufacturing and Testing VI

SPIE, The International Society for Optics and Photonics San Diego, CA, USA

  • 31.07.2005 (2005)
Lecture
  • Elmar Pitschke
  • Markus Schinhärl
  • Andreas Geiss
  • Peter Sperber
  • Rolf Rascher
  • R. Stamp
  • L. Smith
  • M. Smith

A new approach to predict computer-controlled polishing results.

In: Optical Manufacturing and Testing VI

San Diego, CA, USA

  • 31.07.2005 (2005)

show abstract

A novel approach to handle and quantify a computer controlled polishing process will be introduced. This approach will be compared to real data. This comparison indicates the correctness of this approach. Based on it a formula has been developed to predict the results of a computer controlled polishing process. The formula will be used to predict real polishing processes and the results will be compared to the real results. The limits when using this formula will be shown along with suggestions when the formula would be useful. This rough prediction of the computer controlled polishing results may be used to enhance the automation of a computer controlled polishing process. Also a way to improve the formula itself will be introduced. It is the opinion of the author that by further stabilizing of the whole computer controlled polishing process the whole system becomes more robust, the prediction more accurate and the whole system improves in reliability and the results become better.
Lecture
  • Markus Schinhärl
  • Elmar Pitschke
  • Andreas Geiss
  • Rolf Rascher
  • Peter Sperber
  • R. Stamp
  • L. Smith
  • G. Smith

Comparison of different magnetorheological polishing fluids.

Jena

  • 12.09.2005 (2005)
Journal article
  • Elmar Pitschke
  • Markus Schinhärl
  • Peter Sperber
  • Rolf Rascher
  • R. Stamp
  • M. Smith
  • L. Smith

Correlation between influence- function quality and predictability of a computer-controlled polishing process.

In: Optical Engineering vol. 45 pg. 063401 ff.

  • (2006)

DOI: 10.1117/1.2213630

show abstract

A mathematical method has been developed to analyze influence functions that are used in a computer-controlled polishing process. The influence function itself is usually generated by some kind of calibration where the exact procedure is dependent on the process used. The method is able to determine asymmetries in an influence function. Application of this method yields a value that may be used to judge the quality of an influence function. That quality is also an indicator of the variance of the evolving surface error profile, since a close relationship between it and the polishing process exists. On the basis of an ideal, theoretical process, a model to handle and quantify the result of a real polishing process is described. Practical application of this model demonstrates the effect of influence-function quality on the polishing result. Based on this model, the predictability of the polishing result is evaluated. This initiative to judge influence functions by their quality is an important contribution to the development of computer-controlled polishing. Due to improved process reliability, the reject rate will decrease, and the result will be more economic manufacture.
Journal article
  • Markus Schinhärl
  • Andreas Geiss
  • Rolf Rascher
  • Peter Sperber
  • R. Stamp
  • L. Smith
  • G. Smith
  • Elmar Pitschke

Coherences between influence function size, polishing quality and process time in the magnetorheological finishing.

In: Current Developments in Lens Design and Optical Engineering VII vol. 6288 pg. 62880Q ff.

  • (2006)

DOI: 10.1117/12.678720

show abstract

Magnetorheological finishing (MRF) is a computer controlled polishing process (CCP), which is commonly used in the field of high quality optical lens production. The process uses the material removal characteristic of the polishing tool (influence function) and the surface error-profile to calculate individual, surface error-profile dependent polishing sequences. At the University of Applied Sciences Deggendorf a testing series with a magnetorheological finishing machine has been performed, and effects of the influence function size and its removal capacity on the polishing quality and the process time have been investigated. The result of the research shows that the influence function size has a major effect on the process time, whereas the polishing quality is nearly independent of the influence function size. During the testing series the process time was significantly reduced using an appropriate influence function size. The process time decreased about 9% relating to the original influence function.
Lecture
  • Markus Schinhärl

Coherences between spot size, process time and polishing quality in MRF.

In: QED Users Group Meeting

Rochester, NY, USA

  • 2006 (2006)
Contribution
  • Andreas Geiss
  • Markus Schinhärl
  • Elmar Pitschke
  • Rolf Rascher
  • Peter Sperber
  • J. Slabeycius

Deposits and damages on high precision surfaces of advanced materials.

In: Proceedings of the 5th Youth Symposium on Experimental Solid Mechanics, Puchov, Slowakei.

  • (2006)
Journal article
  • Andreas Geiss
  • Markus Schinhärl
  • Elmar Pitschke
  • Rolf Rascher
  • Peter Sperber
  • J. Slabeycius

Sedimentations on high-precision surfaces of advanced materials by magnetorheological finishing.

In: Current Developments in Lens Design and Optical Engineering VII vol. 6288 pg. 62880R ff.

  • (2006)

show abstract

Magnetorheological finishing (MRF) is a computer controlled polishing (CCP) technique for high precision surfaces. The process uses a magnetorheological fluid which stiffens in a magnetic field and thus acts as the polishing tool. A standard MR fluid consists of magnetic carbonyl iron (CI) particles, nonmagnetic polishing abrasives and liquid. To delaying oxidation of the iron particles and avoiding agglomeration the liquid consists of water completed with stabilizers. For the material removal and smoothing of the surface mostly cerium oxide or diamond is used. The materials to be polished may tend toward to different sedimentations of the MR fluid on the machined surface. These sedimentations result from the machining and may develop a polishing layer with MR fluid components. At the University of Applied Sciences Deggendorf analysis of the machined surface are made by the scanning electronic microscope (SEM) to determine the sedimentations of the finishing. The results of the research display the influence for the surface properties due to developing polishing layer by magnetorheological finishing.
Contribution
  • Andreas Geiss
  • Markus Schinhärl
  • Elmar Pitschke
  • Rolf Rascher
  • Peter Sperber

Rauhigkeitsentwicklung bei der Bearbeitung von Komponenten für die Präzisionsoptik mit Diamantwerkzeugen.

In: Sechstes Symposium - Zukunft Glas - von der Tradition zum High-Tech-Produkt, OTTI, Zwiesel.

  • (2006)
Lecture
  • Markus Schinhärl
  • Andreas Geiss
  • Rolf Rascher
  • Peter Sperber
  • R. Stamp
  • L. Smith
  • G. Smith
  • Elmar Pitschke

Coherences between influence function size, polishing quality and process time in the magnetorheological finishing.

In: Current Developments in Lens Design and Optical Engineering VII

San Diego, CA, USA

  • 2006 (2006)
Contribution
  • Andreas Geiss
  • Markus Schinhärl
  • Elmar Pitschke
  • Rolf Rascher
  • Peter Sperber

Rauhigkeitsentwicklung bei der Bearbeitung von Komponenten für die Präzisionsoptik mit Diamantwerkzeugen.

In: Sechstes Symposium - Zukunft Glas - von der Tradition zum High-Tech-Produkt, OTTI, Zwiesel. pg. 143-153

  • (2006)
Journal article
  • Elmar Pitschke
  • Markus Schinhärl
  • Rolf Rascher
  • Peter Sperber
  • L. Smith
  • R. Stamp
  • M. Smith

Simulation of a complex optical polishing process using a neural network.

In: Robotics and Computer-Integrated Manufacturing vol. 24 pg. 32-37

  • (2006)

DOI: 10.1016/j.rcim.2006.07.003

show abstract

Most modern manufacturing processes change their set of parameters during machining in order to work at the optimum state. But in some cases, like computer-controlled polishing, it is not possible to change these parameters during the machining. Then usually a standard set of parameters is chosen which is not adjusted to the specific conditions. To gather the optimum set of parameters anyway simulation of the process prior to manufacturing is a possibility. This research illustrates the successful implementation of a neural network to accomplish such a simulation. The characteristic of this neural network is described along with the decision of the used inputs and outputs. Results are shown and the further usage of the neural network within an automation framework is discussed. The ability to simulate these advanced manufacturing processes is an important contribution to extend automation further and thus increase cost effectiveness.
Lecture
  • Andreas Geiss
  • Markus Schinhärl
  • Elmar Pitschke
  • Rolf Rascher
  • Peter Sperber
  • J. Slabeycius

Deposits and damages on high precision surfaces of advanced materials.

In: 5th Youth Symposium on Experimental Solid Mechanics

Puchov, Slowakei

  • 10.-13.05.2006 (2006)
Lecture
  • Andreas Geiss
  • Markus Schinhärl
  • Elmar Pitschke
  • Rolf Rascher
  • Peter Sperber
  • J. Slabeycius

Sedimentations on high-precision surfaces of advanced materials by magnetorheological finishing.

In: Current Developments in Lens Design and Optical Engineering VII

San Diego, CA, USA

  • 13.08.2006 (2006)
Journal article
  • Markus Schinhärl
  • G. Smith
  • Andreas Geiss
  • L. Smith
  • Rolf Rascher
  • Peter Sperber
  • Elmar Pitschke
  • R. Stamp

Calculation of MRF influence functions.

In: Optical Manufacturing and Testing VII vol. 6671 pg. 66710Y ff.

  • (2007)

show abstract

Magnetorheological finishing (MRF) is a commonly used computer-controlled polishing (CCP) technique for high precision optical surfaces. The process is based on a magnetorheological abrasive fluid, which stiffens in a magnetic field and may be employed as a sub-aperture polishing tool. Dependent upon the surface error-profile of the workpiece and the polishing tool characteristic (influence function) an individual polishing procedure is calculated prior to processing. However, determination of the influence function remains a time consuming and laborious task. A user friendly and easy to use software tool has been developed, which enables rapid computation of MRF influence functions dependent on the MRF specific parameters, such as, magnetic field strength or fluid viscosity. The software supersedes the current cumbersome and time consuming determination procedure and thus results in considerably improved and more economical manufacture. In comparison with the conventional time period of typically 20 minutes to ascertain an influence function, it may now be calculated in a few seconds. An average quality improvement of 57% relating to the peak-valley (PV) value, and approximately 66% relating to the root-mean-square (RMS) of the surface error-profiles was observed during employment of the artificial computed influence functions for polishing.
Journal article
  • Elmar Pitschke
  • Peter Sperber
  • Rolf Rascher
  • R. Stamp
  • M. Smith
  • L. Smith
  • Markus Schinhärl

Lens production enhancement by adoption of artificial influence functions and a knowledge-based system in a magnetorheological finishing process.

In: Optical Manufacturing and Testing VII vol. 6671 pg. 66711J ff.

  • (2007)

DOI: 10.1117/12.761356

show abstract

High quality optical lenses are usually finished by magnetorheological finishing (MRF). In this process an abrasive fluid, with the ability to stiffen in a magnetic field, is used as the polishing tool in a computer-controlled machine tool. Although the machine is automated it is necessary for a skilled operator to set the machine and make judgments with regard to its operation. An investigation has been under way to examine the detailed operation of the MRF process, and the information that is necessary to establish best practice. This has resulted in the incorporation of a knowledge based system (KBS) into the machine control regime, and a methodology for the creation of artificial polishing tool characteristics, the machine influence function. The incorporation of the these elements has been instrumental in the operation of an enhanced MRF machine. This has been subject to extensive test procedures, and it has been demonstrated that the production process may be enhanced significantly and consistently. Batch production time may be significantly reduced, a figure in excess of a 50% reduction was met consistently during prolonged operation. Furthermore the incorporation of the KBS is instrumental in increasing the automation of the MRF process, reducing the levels of manual input necessary to manage machine operation.
Contribution
  • K. Fathima
  • Andreas Geiss
  • Rolf Rascher
  • Peter Sperber
  • Markus Schinhärl
  • Elmar Pitschke

Design and development of a novel computer-controlled power device for electrical-assisted optical grinding.

In: Optifab 2007: Technical Digest, volume TD04. pg. TD0406-1 ff.

  • (2007)
Journal article
  • Markus Schinhärl
  • Rolf Rascher
  • R. Stamp
  • G. Smith
  • L. Smith
  • Elmar Pitschke
  • Peter Sperber

Filter algorithm for influence functions in the computer-controlled polishing of high-quality optical lenses.

In: International Journal of Machine Tools and Manufacture vol. 47 pg. 107-111

  • (2007)

show abstract

Computer controlled polishing (CCP) is widely used in the production of high-quality optical lenses. CCP enables surface error-profile-dependent calculation of polishing sequences prior to processing, and facilitates the cost-effective manufacture of high-quality optical surfaces. Calculation of an individual polishing sequence requires knowledge of the surface error-profile in addition to knowledge of the material removal characteristic (influence function) of the polishing tool. Measurement errors during both determination of the surface error-profile, and the influence function, may lead to an incorrect polishing sequence calculation, which in turn may result in an inadequate product quality. A new method has been developed which minimises the effects of measurement errors on the influence function. The resulting algorithm renders an influence function symmetrical and filters noisy data. Practical polishing tests with magnetorheological finishing have been performed to verify this new technique. The improvement of the peak-valley (PV) value of the surfaces polished with the symmetrical rendered influence function was observed to average 14% greater than that which related to the PV value improvement of those surfaces which were polished with the unmodified influence function. The algorithm developed is based on software and is easily implemented. Thus, artificial enhancement of an influence function is a straightforward technique to improve the result of the polishing process.
Contribution
  • Andreas Geiss
  • Markus Schinhärl
  • Elmar Pitschke
  • K. Fathima
  • Rolf Rascher
  • Peter Sperber
  • J. Slabeycius

Correcting silicon carbide and silicon nitride moulds by Magnetorheological Finishing.

In: Proceedings of the 7th euspen International Conference, Bremen, Vol. 2. pg. 360-363

  • (2007)
Lecture
  • Markus Schinhärl
  • G. Smith
  • Andreas Geiss
  • L. Smith
  • Rolf Rascher
  • Peter Sperber
  • Elmar Pitschke
  • R. Stamp

Calculation of MRF influence functions.

In: Optical Manufacturing and Testing VII, SPIE

San Diego, CA, USA

  • 2007 (2007)
Contribution
  • Andreas Geiss
  • Markus Schinhärl
  • Elmar Pitschke
  • Rolf Rascher
  • Peter Sperber
  • K. Fathima
  • J. Slabeycius

Subsurface damages detecting on standard optical glass by dimple method.

In: Proceedings of the 12th International Conference on Problems of Material Engineering, Mechanics and Design, Jasna, Slowakei. pg. 13 ff.

  • (2007)
Lecture
  • Andreas Geiss
  • Markus Schinhärl
  • Elmar Pitschke
  • Rolf Rascher
  • Peter Sperber
  • K. Fathima
  • J. Slabeycius

Subsurface damages detecting on standard optical glass by dimple method.

In: The 12th International Conference on Problems of Material Engineering, Mechanics and Design

Jasna, Slowakei

  • 29.-31.08.2007 (2007)
Lecture
  • Markus Schinhärl

Schneller und genauer - Optimale Polierstrategie durch variable Abtragsfunktion.

In: BayTech Optik Seminar

Deggendorf

  • 2008 (2008)
Journal article
  • Markus Schinhärl
  • Rolf Rascher
  • R. Stamp
  • L. Smith
  • G. Smith
  • Peter Sperber
  • Elmar Pitschke

Utilisation of time-variant influence functions in the computer-controlled polishing.

In: Precision Engineering vol. 32 pg. 47-54

  • (2008)

DOI: 10.1016/j.precisioneng.2007.04.005

show abstract

In the computer controlled polishing, a polishing tool moves in a well-defined manner across the workpiece surface in order to individually remove the surface error-profile. The commonly used technique to calculate the moving of the polishing tool is the dwell time method. Based on a constant (time-invariant) removal characteristic of the polishing tool (influence function) the amount of material to be removed is controlled via the dwell time. The longer the polishing tool is in contact with a particular area of the workpiece, the more material is removed at this position. Mathematical basics to calculate dwell time-profiles are shown, and a new approach considering time-variant influence functions for the computer controlled polishing is introduced. The results point out that time-variant influence functions may contribute to further decrease the process time, and thus to make a computer controlled polishing process more efficient. The reduction of the process time was observed to approximately 35% using a combination of the dwell time method with time-variant influence functions.
Journal article
  • Markus Schinhärl
  • G. Smith
  • R. Stamp
  • Rolf Rascher
  • L. Smith
  • Elmar Pitschke
  • Peter Sperber
  • Andreas Geiss

Mathematical modelling of influence functions in computer-controlled polishing. Part I.

In: Applied Mathematical Modelling vol. 32 pg. 2888-2906

  • (2008)

show abstract

Computer-controlled polishing (CCP) is commonly used to finish high-quality surfaces, such as optical lenses. Based on magnetorheological finishing (MRF), a mathematical model to calculate the polishing tool characteristic (influence function) was developed and verified experimentally. The first part of this paper introduces the model to predict the size and shape of an influence function. The second part of this paper describes the calculation of the distribution of material removal within the size of an influence function. The model supersedes the current cumbersome procedure for determining an influence function and thus results in considerably improved and more economical manufacture. Furthermore, the model enables the quality of the final surface to be enhanced when polishing complex, for example aspherical or free-form, workpiece geometries and provides the first step in the application of time-variant influence functions.
Contribution
  • Christian Schopf
  • K. Fathima
  • Andreas Geiss
  • Markus Schinhärl
  • Christian Vogt
  • Rolf Rascher
  • Peter Sperber

Ultraschallunterstütztes Schleifen von Linsen.

In: Siebtes Symposium - Zukunft Glas - von der Tradition zum High-Tech-Produkt. pg. 191-203

  • (2008)
Journal article
  • Markus Schinhärl
  • G. Smith
  • R. Stamp
  • Rolf Rascher
  • L. Smith
  • Elmar Pitschke
  • Peter Sperber
  • Andreas Geiss

Mathematical modelling of influence functions in computer-controlled polishing. Part II.

In: Applied Mathematical Modelling vol. 32 pg. 2907-2924

  • (2008)

show abstract

Computer-controlled polishing (CCP) is commonly used to finish high-quality surfaces, such as optical lenses. Based on magnetorheological finishing (MRF), a mathematical model to calculate the polishing tool characteristic (influence function) was developed and verified experimentally. The second part of this paper describes the calculation of the distribution of material removal within the size of an influence function and is based on Preston’s fundamental polishing equation. The complete influence function model was implemented using MATLAB. The result is a user-friendly and easy-to-use software tool that enables fast computation of MRF influence functions without the current cumbersome determination procedure, and thus gives improved and more economical production of high-quality surfaces.
Journal article
  • Elmar Pitschke
  • Markus Schinhärl
  • Rolf Rascher
  • Peter Sperber
  • L. Smith
  • R. Stamp
  • M. Smith

Simulation of a complex optical polishing process using a neural network.

In: Robotics and Computer-Integrated Manufacturing vol. 24 pg. 32-37

  • (2008)

DOI: 10.1016/j.rcim.2006.07.003

show abstract

Most modern manufacturing processes change their set of parameters during machining in order to work at the optimum state. But in some cases, like computer-controlled polishing, it is not possible to change these parameters during the machining. Then usually a standard set of parameters is chosen which is not adjusted to the specific conditions. To gather the optimum set of parameters anyway simulation of the process prior to manufacturing is a possibility. This research illustrates the successful implementation of a neural network to accomplish such a simulation. The characteristic of this neural network is described along with the decision of the used inputs and outputs. Results are shown and the further usage of the neural network within an automation framework is discussed. The ability to simulate these advanced manufacturing processes is an important contribution to extend automation further and thus increase cost effectiveness.
Contribution
  • Andreas Geiss
  • K. Fathima
  • J. Slabeycius
  • L. Hajduchova
  • Rolf Rascher
  • Peter Sperber
  • Markus Schinhärl

Examination of surface and subsurface damages on silicon wafers using dimple polishing.

In: Proceedings of the 13th International Conference on Problems of Material Engineering, Mechanics and Design, Rajeke, Slowakei, 26.-29.08.2008.

  • (2008)
Journal article
  • Andreas Geiss
  • Rolf Rascher
  • J. Slabeycius
  • Markus Schinhärl
  • Peter Sperber
  • K. Fathima

Material removal study at silicon nitride molds for the precision glass molding using MRF process.

In: Current Developments in Lens Design and Optical Engineering IX vol. 7060 pg. 706007 ff.

  • (2008)

DOI: 10.1117/12.794583

show abstract

High-technology applications which are using high precision optic components in high and medium quantities have increased during recent years. One possibility to mass-produce e.g. such lenses is the precision glass molding (PGM) process. Especially for aspheric and free-form elements the PGM process has certain advantages. Premise is to manufacture accurate press molds, which have to feature smaller figure errors as the required lenses and may be made of materials, which are difficult to machine, like silicon nitride ceramics. These work pieces have to be machined in economical and steady process chains. However, due to the complex shapes and the corresponding accuracy an error dependent polishing is required. The Magnetorheological Finishing (MRF) as a high precision computer controlled polishing (CCP) technique is used and will further be presented in this work. To achieve the postulated demands a previous study of the material removal at selected machining parameters is needed. Changing machining parameters modify the removal, which is presented through values like the peak and volume removal rate. The value changes during the controlled variation of process parameters are described and discussed. Magnetorheological Finishing (MRF) provides one of the best methods to finish PGM molds that are relatively inaccurate to high precision in an economical, steady and efficient way. This work indicates the MRF removal selection and removal interference for the correction and finishing of precise silicon nitride molds for the precision glass molding.
Contribution
  • K. Fathima
  • Christian Schopf
  • Andreas Geiss
  • Markus Schinhärl
  • Christian Vogt
  • Rolf Rascher
  • Peter Sperber

Precision finishing of aspherical optical components using ELID grinding.

In: Siebtes Symposium - Zukunft Glas - von der Tradition zum High-Tech-Produkt. pg. 191-203

  • (2008)
Contribution
  • Andreas Geiss
  • J. Slabeycius
  • Rolf Rascher
  • Markus Schinhärl
  • Peter Sperber
  • K. Fathima

Material influence of silicon nitride at Magnetorheological Finishing (MRF).

In: Proceedings of the 12th International Research/Expert Conference ”Trends in the Development of Machinery and Associated Technology” TMT 2008, Istanbul, Türkei, 26.-30.08.2008.

  • (2008)
Contribution
  • Markus Schinhärl
  • Christian Vogt
  • Andreas Geiss
  • R. Stamp
  • Peter Sperber
  • L. Smith
  • G. Smith
  • Rolf Rascher

Forces acting between polishing tool and workpiece surface in magnetorheological finishing.

In: Proceedings of SPIE, Volume 7060, Current Developments in Lens Design and Optical Engineering IX (Optical Engineering + Applications, San Diego, CA, USA; August 10-14, 2008). vol. 7060 pg. 706006 ff.

  • Eds.:
  • P. Mouroulis
  • W. Smith
  • R. Johnson

  • (2008)

DOI: 10.1117/12.794196

show abstract

Magnetorheological finishing is a computer-controlled polishing technique that is used mainly in the field of high-quality optical lens production. The process is based on the use of a magnetorheological polishing fluid that is able, in a reversible manner, to change its viscosity from a liquid state to a solid state under the control of a magnetic field. This outstanding characteristic facilitates rapid control (in milliseconds) of the yield stress, and thus the pressure applied to the workpiece surface to be polished. A three-axis dynamometer was used to measure the forces acting between the magnetorheological fluid and the workpiece surface during determination of the material removal characteristic of the polishing tool (influence function). The results of a testing series using a QED Q22-X MRF polishing machine with a 50 mm wheel assembly show that the normal forces range from about 2 to 20 N. Knowledge of the forces is essential, especially when thin workpieces are to be polished and distortion becomes significant. This paper discusses, and gives examples of, the variation in the parameters experienced during a programme of experiments, and provides examples of the value of this work.
Journal article
  • Markus Schinhärl
  • R. Stamp
  • Elmar Pitschke
  • Rolf Rascher
  • L. Smith
  • G. Smith
  • Andreas Geiss
  • Peter Sperber

Advanced techniques for computer-controlled polishing.

In: Current Developments in Lens Design and Optical Engineering IX vol. 7060

  • (2008)

DOI: 10.1117/12.808036

show abstract

Computer-controlled polishing has introduced determinism into the finishing of high-quality surfaces, for example those used as optical interfaces. Computer-controlled polishing may overcome many of the disadvantages of traditional polishing techniques. The polishing procedure is computed in terms of the surface error-profile and the material removal characteristic of the polishing tool, the influence function. Determinism and predictability not only enable more economical manufacture but also facilitate considerably increased processing accuracy. However, there are several disadvantages that serve to limit the capabilities of computer-controlled polishing, many of these are considered to be issues associated with determination of the influence function. Magnetorheological finishing has been investigated and various new techniques and approaches that dramatically enhance the potential as well as the economics of computer-controlled polishing have been developed and verified experimentally. Recent developments and advancements in computer-controlled polishing are discussed. The generic results of this research may be used in a wide variety of alternative applications in which controlled material removal is employed to achieve a desired surface specification, ranging from surface treatment processes in technical disciplines, to manipulation of biological surface textures in medical technologies.
Contribution
  • Andreas Geiss
  • Markus Schinhärl
  • Rolf Rascher
  • Peter Sperber
  • J. Slabeycius
  • K. Fathima
  • Christian Vogt

Magnetorheological Finishing of silicon nitride moulds.

In: Proceedings of the 10th Anniversary International Conference of the European Society of Precision Engineering and Nanotechnology, Zürich, Schweiz, Volume 2.

  • (2008)
Lecture
  • K. Fathima
  • Christian Schopf
  • Andreas Geiss
  • Markus Schinhärl
  • Christian Vogt
  • Rolf Rascher
  • Peter Sperber

Precision finishing of aspherical optical components using ELID grinding.

In: Siebtes Symposium - Zukunft Glas - von der Tradition zum High-Tech-Produkt

OTTI e.V., Zwiesel Zwiesel

  • 04.-05.06.2008 (2008)
Lecture
  • Christian Schopf
  • K. Fathima
  • Andreas Geiss
  • Markus Schinhärl
  • Christian Vogt
  • Rolf Rascher
  • Peter Sperber

Ultraschallunterstütztes Schleifen von Linsen.

In: Siebtes Symposium - Zukunft Glas - von der Tradition zum High-Tech-Produkt

OTTI e.V., Zwiesel Zwiesel

  • 04.-05.06.2008 (2008)
Lecture
  • Christian Vogt
  • R. Stamp
  • G. Smith
  • Rolf Rascher
  • Peter Sperber
  • Florian Schneider
  • Roland Maurer
  • Markus Schinhärl

Strategies for grinding optical free-forms using ball-shaped grinding wheels.

In: SPIE Optifab

SPIE - The International Society for Optical Engineering Rochester, NY, USA

  • 11.05.2009 (2009)

show abstract

The demand for non-spherical surfaces and free-forms is steadily growing. Aspherical lenses can reduce the number of necessary lenses in optical systems e.g. used for lithographic devices for production of microprocessors. Parabolic mirrors can be used to focus light beams highly efficiently because of low absorption rates without colour distortion. Combined optical devices with included mechanical functions for assembly reduce necessary production steps. The most common pre-machining method for small numbers of high-precision lenses and mirrors is grinding. Depending on the required shape there are different options for generating surfaces e. g. spheres, parabolic mirrors or combined forms. The most flexible ones are grinding with (i) workpiece and ball-shaped tool rotating and (ii) fixed workpiece with ball-shaped tool rotating. In this manuscript grinding strategies dealing with meander and spiral tool paths are investigated in order to define which strategy works best for machining off-axis parabolic mirrors.
Contribution
  • Markus Schinhärl
  • Florian Schneider
  • Rolf Rascher
  • Christian Vogt
  • Peter Sperber

Relationship between influence function accuracy and polishing quality in magnetorheological finishing.

In: Proceedings of the 5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Advanced Optical Manufacturing Technologies (Dalian, China; April 26-29, 1010). pg. 76550Y ff.

  • Eds.:
  • L. Zhang
  • S. To
  • J. Sasian
  • L. Xiang

  • (2010)

DOI: 10.1117/12.865508

show abstract

Magnetorheological finishing is a typical commercial application of a computer-controlled polishing process in the manufacturing of precision optical surfaces. Precise knowledge of the material removal characteristic of the polishing tool (influence function) is essential for controlling the material removal on the workpiece surface by the dwell time method. Results from the testing series with magnetorheological finishing have shown that a deviation of only 5% between the actual material removal characteristic of the polishing tool and that represented by the influence function caused a considerable reduction in the polishing quality. The paper discusses reasons for inaccuracies in the influence function and the effects on the polishing quality. The generic results of this research serve for the development of improved polishing strategies, and may be used in alternative applications of computer-controlled polishing processes that quantify the material removal characteristic by influence functions.
Contribution
  • Florian Schneider
  • Markus Schinhärl
  • Christian Vogt
  • Roland Maurer
  • Peter Sperber
  • Rolf Rascher
  • R. Stamp
  • G. Smith

Effects of mechanical inaccuracies on the measurement result in metrology systems.

In: Proceedings of the 5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical Test and Measurement Technology and Equipment. vol. 7656 pg. 765611 ff.

  • (2010)
Contribution
  • Markus Schinhärl
  • Christian Vogt
  • Florian Schneider
  • Peter Sperber
  • Rolf Rascher

Investigations on Magnetorheological Finishing of High-Quality Optical Surfaces with Varying Influence Function (Proceedings of Optical Fabrication and Testing 2010; Jackson Hole, WY, USA; June 13-17, 2010).

In: Optical Fabrication and Testing on CD-ROM. pg. OWD3 ff.

Washington, DC, USA

  • (2010)

DOI: 10.1364/OFT.2010.OWD3

Contribution
  • Christian Vogt
  • Markus Schinhärl
  • Florian Schneider
  • Peter Sperber
  • Rolf Rascher

Investigations on Grinding Tools for Silicon Carbide Based Advanced Materials.

In: International Optical Design Conference 2010 (13-17 June 2010, Jackson Hole, WY, USA). (Proceedings of SPIE. 2004-) pg. OWD2 ff.

  • Eds.:
  • J. Bentley
  • R. Youngworth
  • G. Anurag

SPIE Bellingham

  • (2010)
Thesis
  • Markus Schinhärl

Prediction and control techniques for sub-aperture polishing of high-quality optical lenses.

University of the West of England Bristol, Großbritannien

  • 2010 (2010)
Lecture
  • Markus Schinhärl
  • Rolf Rascher

Relationship between influence function accuracy and polishing quality in magnetorheological finishing.

In: 5th SPIE International Symposium on Advanced Optical Manufacturing and Testing Technologies

Dalian, China

  • 26.-29.04.2010 (2010)
Contribution
  • Roland Maurer
  • Florian Schneider
  • Christian Vogt
  • Markus Schinhärl
  • Peter Sperber
  • Rolf Rascher

Physical marker based stitching process of circular and non-circular interferograms.

In: Proc. SPIE 8083, Modeling Aspects in Optical Metrology III (SPIE Optical Metrology; May 20122; Munich, Germany).

  • Eds.:
  • B. Bodermann

  • (2011)

DOI: 10.1117/12.889491

Lecture
  • Florian Schneider
  • Markus Schinhärl
  • Christine Wünsche
  • et al.

3D Scale - A system to reduce and compensate the influence of multiple axis errors of rotational axes.

In: SPIE Photonics West, Optoelectronic Materials and Devices, SPIE 2013

  • 2013 (2013)