NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenIPH TeisnachBeitrag (Sammelband oder Tagungsband)
Christian J. Trum, M. Jung, Beate Schmidbauer, Sebastian Sitzberger, E. Willenborg, Rolf Rascher
Hybrid-process-chain for polishing optical glass lenses – HyoptO
Proceedings of SPIE Optical Engineering + Applications (24 August - 04 September, 20208; Optical Manufacturing and Testing XIII; online conference), San Diego, United States, vol. 11487
2020
DOI: 10.1117/12.2568400
Abstract anzeigen
A number of process steps that build on one another are required to manufacture optical components from glass. The polishing steps are the most time-consuming and therefore cost-intensive parts of the process chain. Low removal rates and the depth of the Sub Surface Damage (SSD) to be removed contribute to this. An alternative for the complete removal of the SSD-penetrated material using contactless polishing methods such as Ion Beam Figuring (IBF) is the healing of the SSD. Due to the induced energy during laser-polishing, the material is remelted at the defects and the SSD are closed. However, laser-polishing is also associated with disadvantages in terms of shape accuracy and surface quality. The project HyoptO is therefore devoted to the development of a hybrid-process-chain consisting of laser processing and conventional polishing. It is expected that the healing times of the SSD can significantly reduce the process times in the subsequent polishing steps. However, there are a few questions to be answered regarding the economic use of the hybrid-process-chain. These include:
NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenIPH TeisnachBeitrag (Sammelband oder Tagungsband)
Simon Killinger, Johannes Liebl, Rolf Rascher
First steps towards an automated polishing process chain using one robot
Proceedings of SPIE 11478 (Seventh European Seminar on Precision Optics Manufacturing [8 July 2020; Teisnach]), Bellingham, WA, USA
2020
DOI: 10.1117/12.2564840
Abstract anzeigen
Manufacturing precision optics is a complex process chain, which requires many operations on different machines. This is combined with operator-dependent steps such as manual cleaning, loading and measuring. In order to realize this process chain on a smaller shop area and to achieve a higher level of automation we build an operator-independent polishing cell. In this cell, an ABB robot serves as the actuator handling the workpiece. We positioned the robot in the center of the polishing cell to operate several workstations, so the whole process chain works with one single actuator. This arrangement allows a smaller and cheaper system, since no additional handling is required.
NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenIPH TeisnachBeitrag (Sammelband oder Tagungsband)
Michael Benisch, O. Fähnle, Rolf Rascher, Werner Bogner
Force and pressure analysis during overarm polishing
Proceedings of SPIE 11478 (Seventh European Seminar on Precision Optics Manufacturing [8 July 2020; Teisnach]), Bellingham, WA, USA
2020
DOI: 10.1117/12.2564903
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The Preston-equation implies, that, besides the relative speed υrel and a specific constant KP, the pressure p plays a significant role for the removal rate when polishing an optical component. This paper demonstrates a possibility for a qualitative evaluation of the pressure distribution before the polishing process. A pressure-sensitive foil is used as a gauge for pressure measurement. The effectiveness of this measuring method is explained. Specific weaknesses and limitations in the use of these foils are discussed. A method for an integrated evaluation of the pressure on different spots of the polishing pad is proposed at the end of the paper.
NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenIPH TeisnachBeitrag (Sammelband oder Tagungsband)
M. Pohl, R. Börret, Olga Kukso, Rolf Rascher
Mid spatial frequency error prevention strategies for the grinding process
Proceedings of SPIE 11478 (Seventh European Seminar on Precision Optics Manufacturing [8 July 2020; Teisnach]), Bellingham, WA, USA
2020
DOI: 10.1117/12.2565261
Abstract anzeigen
This research is focused on the link between manufacturing parameters and the resulting mid-spatial frequency error in the manufacturing process of precision optics. The goal is to understand the generation mechanisms of mid-spatial frequency errors and avoid their appearance in the manufacturing process. Also, a simulation which is able to predict the resulting mid spatial frequency error from a manufacturing process is desired.
NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenIPH TeisnachBeitrag (Sammelband oder Tagungsband)
Olga Kukso, Rolf Rascher, M. Pohl, R. Börret
On the metrology and analysis of MSF error
Proceedings of SPIE 11478 (Seventh European Seminar on Precision Optics Manufacturing [8 July 2020; Teisnach]), Bellingham, WA, USA
2020
DOI: 10.1117/12.2566251
Abstract anzeigen
The aim of our research was to study middle spatial frequency errors (MSFE) on optical surfaces. We investigate the surfaces after manufacturing processes to find out the main affecting factors and to choose the proper processing parameters to minimize the size of the errors. To find an appropriate parameter window we have to be able not only to define the factors, which lead to MSFE, but also to analyze the change of the error after next following production steps.
NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenIPH TeisnachBeitrag (Sammelband oder Tagungsband)
M. Jung, Christian J. Trum, Beate Schmidbauer, E. Willenborg, Rolf Rascher
Non-ablative removal of sub surface damages in ground optical glass substrates by controlled melting of thin surface layers using CO2-laser radiation
Proceedings of SPIE 11478 (Seventh European Seminar on Precision Optics Manufacturing [8 July 2020; Teisnach]), Bellingham, WA, USA
2020
DOI: 10.1117/12.2564801
Abstract anzeigen
The form generation of optical surfaces by grinding and mechanical polishing results in small sub surface damages in the form of micro cracks that conventionally have to be removed by further removal of the damaged surface layers. In order to reduce process time and material cost non-ablative methods for removal of micro cracks are desired. Utilising the low optical penetration depths of less than 10 μm for CO2-laser radiation in glass, the laser energy can be used to heat up and melt thin surface layers. Using a 1.5 kW CO2-laser, a quasi-line focus formed by a scanner unit and a constant feed speed, it is possible to close all micro cracks present in the rough grinded test surfaces (max. SSD-depth ~ 63 μm), while achieving a process time of less than 2 seconds for a Ø 30 mm N-BK7 lens, respectively 7.5 seconds for fused silica. With a Sa as low as 50 nm and low distortion from the original shape the surfaces can directly be conventionally polished, further reducing the process chain complexity.
NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenIPH TeisnachBeitrag (Sammelband oder Tagungsband)
Sebastian Sitzberger, Johannes Liebl, Christian J. Trum, Rolf Rascher
Concept of a two-part clamping system for lenses in optical metrology
Proceedings of SPIE 11478 (Seventh European Seminar on Precision Optics Manufacturing [8 July 2020; Teisnach]), Bellingham, WA, USA
2020
DOI: 10.1117/12.2566547
Abstract anzeigen
The developed concept represents a universally applicable clamping system designed to fit in any measuring machine with
any measuring principle. The design ensures that, as long as the lens remains clamped, the measurement results are
reproducible. Form errors due to tension remain constant across all measuring and processing steps. The version presented
in this paper was developed especially for small lenses in the diameter range up to 40 mm. On the one hand, the design
allows for fast measurement of loose lenses. On the other hand, the device can also be used for measurement comparisons,
since lenses can also be mounted permanently. In the following, the concept and first results of measurement tests are
presented.
NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenIPH TeisnachBeitrag (Sammelband oder Tagungsband)
Armin Reif, Sebastian Sitzberger, Rolf Rascher
Cutting high-performance materials with ultrasonically modulated cutting speed
Proceedings of SPIE 11478 (Seventh European Seminar on Precision Optics Manufacturing [8 July 2020; Teisnach]), Bellingham, WA, USA
2020
DOI: 10.1117/12.2565757
Abstract anzeigen
The continuing trend towards lightweight construction and the associated machining rates of up to 95 % lead to an
increased use of high-performance materials. The ever growing demands on the strength and quality of components and
the associated use of materials which are hard to machine require the further development of new, economical machining
techniques. In ultrasonic-assisted machining, an additional high-frequency vibration is superimposed on the conventional
machining process. The vibration of the tool is usually excited axially or longitudinally to the workpiece, i.e. vertical to
the cutting direction. An additional vibration overlay around the rotation axis (torsional) of the tool is also possible. This
generates a vibration overlay in the cutting direction. The vibration initiation causes vibration amplitudes in the range of a
few micrometers at the tool cutting edge. This leads in turn to a high-frequency change in the cutting speed or feed rate.
Overall, an additional torsional vibration overlap can further reduce cutting forces, increase tool life and improve
workpiece quality.
In order for a grinding tool to generate a torsional vibration, a special tool was required that had to be designed by
simulation. The formation of a torsional vibration was achieved by helical slots in the sonotrode. Depending on the angle
of rotation and the length of the slots, a part of the axial vibration is converted into a torsional vibration by an axial
excitation of the sonotrode. The aim in designing the slots was to achieve the highest possible vibration amplitude.
Following the simulation, the slots were inserted into the tool in the corresponding optimum geometric position.
Afterwards, the specially designed grinding tool was validated by machining the brittle-hard glass-ceramic material
Zerodur. The first test results with the torsionally vibrating tool are presented in the following.
NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenIPH TeisnachBeitrag (Sammelband oder Tagungsband)
M. Pohl, U. Bielke, R. Börret, Rolf Rascher, Olga Kukso
MSF-error prevention strategies for the grinding process
Proceedings of SPIE 11171 (Sixth European Seminar on Precision Optics Manufacturing, 1117101 [9-10 April 2019, Teisnach]), Bellingham, WA, USA
2019
DOI: 10.1117/12.2526581
Abstract anzeigen
This research is focused on the link between manufacturing parameters and the resulting mid-spatial frequency error in the manufacturing process of precision optics. This third publication focuses on strategies of avoidance and generation mechanisms of the mid-spatial frequency errors from the grinding process. The Goal is to understand the generation mechanisms of the mid-spatial frequency errors and avoid their appearance in the manufacturing process.
NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenIPH TeisnachBeitrag (Sammelband oder Tagungsband)
Sebastian Sitzberger, Johannes Liebl, J. Reitberger, Rolf Rascher
Zero-point clamping systems in optical production
Proceedings of SPIE 11171 (Sixth European Seminar on Precision Optics Manufacturing, 1117101 [9-10 April 2019, Teisnach]), Bellingham, WA, USA
2019
DOI: 10.1117/12.2528774
Abstract anzeigen
Zero point clamping systems are an integral part of the manufacturing industry. They have only yet to find their way into the optical industry. This article compares the hydraulic expansion holder, a clamping system currently used in the optical industry with a zero-point clamping system. The achievable accuracies of both systems are compared over several measurement series. In addition, the process capability evaluation is used for the comparison. Finally, the results are summarized to provide every researcher and practitioner with a foundation for assessing whether zero point clamping systems meet the requirements for the use in optical manufacturing.
NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenIPH TeisnachBeitrag (Sammelband oder Tagungsband)
Simon Killinger, Johannes Liebl, Rolf Rascher
Mid-spatial frequency errors in feed direction occurring in ADAPT polishing
Proceedings of SPIE 11171 (Sixth European Seminar on Precision Optics Manufacturing, 1117101 [9-10 April 2019, Teisnach]), Bellingham, WA, USA
2019
DOI: 10.1117/12.2528114
Abstract anzeigen
Previous work shows the effectiveness of computer controlled polishing (CCP) with the ADAPT tool by Satisloh for correcting form errors in optics manufacturing. This method however has a risk of producing residual errors in the range of mid spatial frequency errors (MSFE). In order to prevent these errors the residual in feed direction is investigated as well as the behavior at different parameters.
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