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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.

F: Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen F: Maschinenbau und Mechatronik I: Hochschulleitung und -einrichtungen

Beitrag (Sammelband oder Tagungsband)

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

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)

2008

DOI: 10.1117/12.794196

Abstract anzeigen

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.

F: Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen F: Maschinenbau und Mechatronik I: Hochschulleitung und -einrichtungen

Zeitschriftenartikel

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

Current Developments in Lens Design and Optical Engineering IX, vol. 7060, no. August

2008

DOI: 10.1117/12.794583

Abstract anzeigen

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.

F: Maschinenbau und Mechatronik

Vortrag

Andreas Geiss

Vom µm zu lamda/20 - MRF bei advanced materials

BayTech Optik Seminar, Deggendorf

2008

F: Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen F: Maschinenbau und Mechatronik I: Hochschulleitung und -einrichtungen

Beitrag (Sammelband oder Tagungsband)

Andreas Geiss, J. Slabeycius, Rolf Rascher, Markus Schinhärl, Peter Sperber, K. Fathima

Material influence of silicon nitride at Magnetorheological Finishing (MRF)

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

F: Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen F: Maschinenbau und Mechatronik I: Hochschulleitung und -einrichtungen

Beitrag (Sammelband oder Tagungsband)

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

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

2008

F: Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen F: Maschinenbau und Mechatronik I: Hochschulleitung und -einrichtungen

Beitrag (Sammelband oder Tagungsband)

Andreas Geiss, Markus Schinhärl, Rolf Rascher, Peter Sperber, J. Slabeycius, K. Fathima, Christian Vogt

Magnetorheological Finishing of silicon nitride moulds

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

2008

F: Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen F: Elektrotechnik und Medientechnik F: Maschinenbau und Mechatronik I: Hochschulleitung und -einrichtungen

Zeitschriftenartikel

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

Applied Mathematical Modelling, vol. 32, no. 12, pp. 2907-2924

2008

Abstract anzeigen

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.

F: Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen F: Elektrotechnik und Medientechnik F: Maschinenbau und Mechatronik I: Hochschulleitung und -einrichtungen

Zeitschriftenartikel

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

Applied Mathematical Modelling, vol. 32, no. 12, pp. 2888-2906

2008

Abstract anzeigen

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.

F: Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen F: Elektrotechnik und Medientechnik F: Maschinenbau und Mechatronik I: Hochschulleitung und -einrichtungen

Vortrag

Markus Schinhärl, G. Smith, Andreas Geiss, L. Smith, Rolf Rascher, Peter Sperber, Elmar Pitschke, R. Stamp

Calculation of MRF influence functions

Optical Manufacturing and Testing VII, SPIE, San Diego, CA, USA

2007

F: Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen F: Elektrotechnik und Medientechnik F: Maschinenbau und Mechatronik I: Hochschulleitung und -einrichtungen

Zeitschriftenartikel

Markus Schinhärl, G. Smith, Andreas Geiss, L. Smith, Rolf Rascher, Peter Sperber, Elmar Pitschke, R. Stamp

Calculation of MRF influence functions

Optical Manufacturing and Testing VII, vol. 6671

2007

Abstract anzeigen

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.

F: Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen F: Elektrotechnik und Medientechnik F: Maschinenbau und Mechatronik I: Hochschulleitung und -einrichtungen

Vortrag

Andreas Geiss, Markus Schinhärl, Elmar Pitschke, Rolf Rascher, Peter Sperber, K. Fathima, J. Slabeycius

Subsurface damages detecting on standard optical glass by dimple method

The 12th International Conference on Problems of Material Engineering, Mechanics and Design, Jasna, Slowakei

2007

F: Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen F: Elektrotechnik und Medientechnik F: Maschinenbau und Mechatronik I: Hochschulleitung und -einrichtungen

Beitrag (Sammelband oder Tagungsband)

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

Optifab 2007: Technical Digest, volume TD04

2007