Angewandte Naturwissenschaften und WirtschaftsingenieurwesenElektrotechnik und MedientechnikHochschulleitung und -einrichtungenMaschinenbau und MechatronikZeitschriftenartikel
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
Precision Engineering, vol. 32, no. 1, pp. 47-54
DOI: 10.1016/j.precisioneng.2007.04.005
Abstract anzeigen
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.
Angewandte Naturwissenschaften und WirtschaftsingenieurwesenElektrotechnik und MedientechnikHochschulleitung und -einrichtungenMaschinenbau und MechatronikZeitschriftenartikel
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
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.
Angewandte Naturwissenschaften und WirtschaftsingenieurwesenElektrotechnik und MedientechnikHochschulleitung und -einrichtungenMaschinenbau und MechatronikZeitschriftenartikel
Markus Schinhärl, Elmar Pitschke, Rolf Rascher, Peter Sperber, R. Stamp, L. Smith, G. Smith
Temporal stability and performance of MR polishing fluid
Current Developments in Lens Design and Optical Engineering V, vol. 5523, pp. 273-280
DOI: 10.1117/12.558897
Abstract anzeigen
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.
Angewandte Naturwissenschaften und WirtschaftsingenieurwesenElektrotechnik und MedientechnikHochschulleitung und -einrichtungenMaschinenbau und MechatronikZeitschriftenartikel
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
Current Developments in Lens Design and Optical Engineering V, vol. 5523, pp. 225-234
DOI: 10.1117/12.558899
Abstract anzeigen
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.
Angewandte Naturwissenschaften und WirtschaftsingenieurwesenElektrotechnik und MedientechnikHochschulleitung und -einrichtungenMaschinenbau und MechatronikZeitschriftenartikel
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
Robotics and Computer-Integrated Manufacturing, vol. 24, no. 1, pp. 32-37
DOI: 10.1016/j.rcim.2006.07.003
Abstract anzeigen
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.
Angewandte Naturwissenschaften und WirtschaftsingenieurwesenElektrotechnik und MedientechnikHochschulleitung und -einrichtungenMaschinenbau und MechatronikZeitschriftenartikel
Markus Schinhärl, Elmar Pitschke, Andreas Geiss, Rolf Rascher, Peter Sperber, R. Stamp, L. Smith, G. Smith
Comparison of different magnetorheological polishing fluids
Optical Fabrication, Testing, and Metrology II, vol. 5965, pp. 659-670
DOI: 10.1117/12.656430
Abstract anzeigen
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.
Angewandte Naturwissenschaften und WirtschaftsingenieurwesenElektrotechnik und MedientechnikHochschulleitung und -einrichtungenMaschinenbau und MechatronikZeitschriftenartikel
Markus Schinhärl, Elmar Pitschke, Andreas Geiss, Rolf Rascher, Peter Sperber, R. Stamp, L. Smith, G. Smith
New viscosity measurement for magnetorheological polishing fluid
Optical Manufacturing and Testing VI, vol. 5869, pp. 133-141
DOI: 10.1117/12.616690
Abstract anzeigen
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.
Angewandte Naturwissenschaften und WirtschaftsingenieurwesenElektrotechnik und MedientechnikHochschulleitung und -einrichtungenMaschinenbau und MechatronikZeitschriftenartikel
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
Optical Manufacturing and Testing VII, vol. 6671, no. September
DOI: 10.1117/12.761356
Abstract anzeigen
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.
Angewandte Naturwissenschaften und WirtschaftsingenieurwesenElektrotechnik und MedientechnikHochschulleitung und -einrichtungenMaschinenbau und MechatronikZeitschriftenartikel
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
Current Developments in Lens Design and Optical Engineering VII, vol. 6288
DOI: 10.1117/12.678720
Abstract anzeigen
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.
Angewandte Naturwissenschaften und WirtschaftsingenieurwesenElektrotechnik und MedientechnikHochschulleitung und -einrichtungenMaschinenbau und MechatronikZeitschriftenartikel
Andreas Geiss, Markus Schinhärl, Elmar Pitschke, Rolf Rascher, Peter Sperber, J. Slabeycius
Sedimentations on high-precision surfaces of advanced materials by magnetorheological finishing
Current Developments in Lens Design and Optical Engineering VII, vol. 6288
Abstract anzeigen
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.
Angewandte Naturwissenschaften und WirtschaftsingenieurwesenElektrotechnik und MedientechnikHochschulleitung und -einrichtungenMaschinenbau und MechatronikZeitschriftenartikel
Andreas Geiss, Markus Schinhärl, Elmar Pitschke, Rolf Rascher, Peter Sperber
Analysis of thermal sources in a magnetorheological finishing (MRF) process
Optical Manufacturing and Testing VI, vol. 5869, pp. 111-120
DOI: 10.1117/12.616751
Abstract anzeigen
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.
Angewandte Naturwissenschaften und WirtschaftsingenieurwesenElektrotechnik und MedientechnikHochschulleitung und -einrichtungenMaschinenbau und MechatronikZeitschriftenartikel
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
Optical Manufacturing and Testing VI, vol. 5869, pp. 94-102
DOI: 10.1117/12.616780
Abstract anzeigen
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.
Version: 2.1.2-qf2