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Sebastian Sitzberger, M.Eng.

Wissenschaftlicher Mitarbeiter

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ITC2 2.23

0991/3615-387


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Vortrag

  • Sebastian Sitzberger
  • M. Zäh
  • Rolf Rascher

Untersuchungen zu einer durchgängigen Werkstückaufnahme für die Herstellung von Hochpräzisionsoptiken

In: 3. Ko-op Symposium

Graduate Center der Munich School of Engineering Garching

  • 26.11.2020 (2020)
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
  • TC Teisnach Optik
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Beitrag (Sammelband oder Tagungsband)

  • Armin Reif
  • Sebastian Sitzberger
  • Rolf Rascher

Cutting high-performance materials with ultrasonically modulated cutting speed

Bellingham, WA, USA

  • (2020)

DOI: 10.1117/12.2565757

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.
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Zeitschriftenartikel

  • Armin Reif
  • P. Rinck
  • Sebastian Sitzberger
  • Rolf Rascher
  • M. Zäh

Zerspanung von Hochleistungswerkstoffen mit ultrasonisch modulierter Schnittgeschwindigkeit

In: ZWF - Zeitschrift für wirtschaftlichen Fabrikbetrieb vol. 115 pg. 2-5.

  • (2020)

DOI: 10.3139/104.112255

Die steigenden Anforderungen an die Festigkeit und die Qualität von Bauteilen und die damit verbundene Verwendung hochfester Materialien erfordert die Weiterentwicklung neuer wirtschaftlicher Zerspanungstechniken. Durch eine werkzeugseitige Schwingungsüberlagerung können bei der Bearbeitung von schwer zerspanbaren Werkstoffen die Zerspankräfte und der Werkzeugverschleiß reduziert sowie die Oberflächenqualität verbessert werden.
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Beitrag (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

pg. 114871L.

San Diego, United States

  • (2020)

DOI: 10.1117/12.2568400

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:
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Beitrag (Sammelband oder Tagungsband)

  • Sebastian Sitzberger
  • Johannes Liebl
  • Christian J. Trum
  • Rolf Rascher

Concept of a two-part clamping system for lenses in optical metrology

pg. 114780G.

Bellingham, WA, USA

  • (2020)

DOI: 10.1117/12.2566547

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.
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Beitrag (Sammelband oder Tagungsband)

  • Sebastian Sitzberger
  • Johannes Liebl
  • J. Reitberger
  • Rolf Rascher

Zero-point clamping systems in optical production

pg. 111710J1-111710J10.

Bellingham, WA, USA

  • (2019)

DOI: 10.1117/12.2528774

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.
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Vortrag

  • Sebastian Sitzberger
  • J. Reitberger
  • Rolf Rascher

Clamping system for optical components for adaptation in optical production

In: 10th HLEM 2019 - High Level Expert Meeting Asphere Metrology on Joint Investigations

Physikalisch-Technische Bundesanstalt Braunschweig

  • 19.-20.03.2019 (2019)
  • TC Teisnach Optik
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Vortrag

  • Christian J. Trum
  • Sebastian Sitzberger
  • Rolf Rascher

Improved performance of CMP processes through targeted adjustment of polishing slurry and polish pad

In: SPIE Optical Engineering + Applications 2018

San Diego, CA, USA

  • 2018 (2018)
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
  • TC Teisnach Optik
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Beitrag (Sammelband oder Tagungsband)

  • Sebastian Sitzberger
  • Christian J. Trum
  • Rolf Rascher
  • M. Zaeh

Workpiece self-weight in precision optics manufacturing: compensation of workpiece deformations by a fluid bearing

pg. 108290A.

  • (2018)

DOI: 10.1117/12.2318577

The effects, the extent and the importance of workpiece deformations, particularly lenses, caused by the weight of the workpiece itself, were examined in a previous paper1 . The considered deformations are in the single-digit to two-digit nanometer range. The investigation was carried out by FEM calculations. The conclusion of the previous aper was that a full-surface support of a workpiece in the processing of one surface presumably produces the best results. Furthermore, it was found that if the second functional surface is not to be touched in the process, a full contact lens mounting on its circumference is advisable. An alternative method for fixing precision lenses is therefore desirable. This can be accomplished in two steps. As a first step, the lens must be gripped at its periphery so that none of the optically functional surfaces of the lens is compromised. However, the complete circumference has to be fixated gaplessly because a punctual fixation has the disadvantage of deforming the lens surface asymmetrically. As a second step, the freely hanging lens surface should be supported to minimize deformation. An approach had to be found that supports the surface like a solid bearing but at the same time does not touch it. Therefore, the usage of an incompressible fluid as a hydrostatic bearing for full-surface support is pursued. For this purpose, the bottom side of the lens has to be stored on water. The results of the FEM simulation showed that with a fluid bearing the resulting deformations can be drastically reduced in comparison to a freely hanging surface. Furthermore, under the right conditions, a resulting deformation comparable to a full surface solid support can be achieved. The content of this paper is a test series under laboratory conditions for a first validation of the theoretical results. Therefore, a prototype model to test a lens fixation with a fluid bearing was developed and manufactured. The resulting deformations were measured with an interferometer and the effects are discussed.
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Beitrag (Sammelband oder Tagungsband)

  • Christian J. Trum
  • Christian Vogt
  • O. Fähnle
  • Sebastian Sitzberger
  • Rolf Rascher

First experiences with Filled-Up-Microscopy (FUM) to evaluate the depth of sub-surface damages on ground surfaces

  • (2018)
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
  • TC Teisnach Optik
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  • DIGITAL
Patent

  • Christian J. Trum
  • Sebastian Sitzberger

Kühlsystem für eine Ultraschall-Bohrmaschine

  • 06.12.2018 (2018)
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
  • TC Teisnach Optik
  • NACHHALTIG
Beitrag (Sammelband oder Tagungsband)

  • P. Rinck
  • Sebastian Sitzberger
  • M. Zaeh

Actuator design for vibration assisted machining of high performance materials with ultrasonically modulated cutting speed

pg. 103260C.

  • (2017)

DOI: 10.1117/12.2272133

  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
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Beitrag (Sammelband oder Tagungsband)

  • Johannes Liebl
  • Horst Linthe
  • Sebastian Sitzberger
  • Rolf Rascher

Interferometric measurement of highly accurate flat surfaces

  • (2016)

DOI: 10.1117/12.2235525

The most important part in manufacturing precision optics is a reliable measurement procedure which provides results a few times more accurate than the quality to be produced. In general two specific values are important, the repeatability of several measurements which are done in a row and the absolute accuracy which is mostly defined by the systematical error of the measurement device. The repeatability can be improved relatively simple, by increasing the number of measurements and a following averaging step. To increase the absolute accuracy of a measurement device in the field of precision optics is far more challenging. In this paper several interferometer absolute testing methods to measure flat surfaces are compared. The main objective was to name a value for the achievable accuracy. Therefor four different methods were analyzed: 1. The three flat test, a method which is already used several decades to determine the quality of a flat surface. As a result, two absolute measured profiles, horizontal and vertical, can be calculated. 2. The multi rotation test, an extension of the classical three flat test. The big advantage of this method is a fully three dimensional map of the systematical error. 3. The systematical error calculated by the SSI-A. Hereby several subapertures are measured over the whole surface. The redundant information’s of the overlapping regions can be used to calculate the systematical error of the system. 4. The rotation of the transmission flat relatively to the interferometer. Thereby the rotation unsymmetrical errors can be calculated and subtracted. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
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