Publikationen Ultra-Precision Manufacturing Lab

Unsere Mitarbeitenden im Ultra-Precision Manufacturing Lab sind anerkannte Experten in ihrem Fachgebiet und publizieren regelmässig wissenschaftliche Arbeiten in Form von Papers, Präsentationen und Vorträgen.

Zudem unterstützen wir Studierende, die Interesse haben, ihre Studien-, Bachelor- oder Masterarbeit im Bereich der Präzisionsfertigung zu schreiben.

Unten finden Sie eine Auswahl der Publikationen.

Publikationen 2023

Hybrid laser and subtractive machining of reaction bonded silicon carbide

M. Groeb1 , R. Catrin1 , J. Groeb2

Published: March 15, 2023

The use of high-performance materials such as technical ceramics is rapidly increasing, as these materials have many advantageous properties. The high hardness, high resistance to chemical and abrasive wear, high young’s modulus and low weight are proving their use in creating complex, more precise and efficient machinery and mechanisms. The high hardness coupled with the low surface energy make mechanical finishing of these materials highly time consuming and therefore expensive. In this study, reaction bonded silicon carbide (RB-SiC) is pre-machined with an ultra-short pulse laser to create periodic fracture zones, enabling higher material removal modes. Finishing is performed in a ductile cutting regime, leading to better surface finishes, less breakouts and tighter tolerance control. For this, several experiments based on a Design of Experiments plan are undertaken, varying the pulse energy, dwell time of the laser, but also the cutting parameters of the milling tool such as median chip thickness and cutting speed. During the experiments, the specific cutting energy was monitored via a dynamometer. After the cutting trials, the surfaces were analysed via white light interferometry. A significant reduction in the specific cutting energy with laser pre-damage was achieved.

1RhySearch, Werdenbergstr. 4, 9471 Buchs, Switzerland 
2Independent Researcher, Darmstadt, Germany

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Publikationen 2022

Development of a methodology for evaluating the process window of ductile machining for brittle-hard materials

Oliver Fähnle1, Yannik Steimer1, Henrik Surberg1Niklas Sass2Marco Buhmann2, Thomas Liebrich2

Published online: 13 October, 2022

This paper presents a standardized methodology for determining the process window for ductile machining of brittle materials. Its application for CaF2 is reported, identifying an optimized process window for single-point diamond turning on UPM machines by determining optimized process parameters.

1 Eastern Switzerland University of Applied Sciences, Buchs, Switzerland
2 Rhysearch Institute, Buchs, Switzerland

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Parameter study on distortion during precision turning of additive manufactured half shells in Invar

Raoul Rotha(3), Rico Weberb, Jasmin Zanolaria, Kabil Ramadania, Adriaan Spieringsb(3), Mileva Pavlica-Patiglerc

Published online: August, 2022

Additive manufacturing (AM) allows a high degree of complexity and the creation of geometries that are not possible with conventional manufacturing methods. However, the quality and the accuracy of the parts are often not sufficient and a precise post-processing is inevitable. In the case of subsequent machining, especially of thin-walled and non-rotationally symmetrical components, residual stresses generated during additive manufacturing may result in distortions. In order to achieve the required accuracy a stress relief heat treatment may be required. If for other reason this is not possible the optimisation of the additive manufacturing procedure as well as the cutting process is necessary to reduce the distortion of the workpiece. In this paper the influence of different machining parameters is investigated for AM-manufactured cylindrical half shells made in Invar, and compared to non-additively manufactured and heat treated workpieces. A post-process stress relief annealing eliminates most distortions, whereas on the machining side a single deep cut is more beneficial for smaller distortions instead of several small cuts and higher cutting speed. By this, a decrease of 33% in distortion could be achieved. The results also show that different AM scanning strategies have no significant impact on the distortion of the workpiece.

RhySearch, Buchs SG, Swizerland
b inspire AG,  St.Gallen, Switzerland
c SwissOptic AG, Heerbrugg SG, Swizerland

*The full paper is available to CIRP members

Virtual Reality Extension for Digital Twins of Machine Tools

Valentin Holzwarth , Christian Hirt , Joy Gisler , and Andreas Kunz

Published: April 27, 2022

Digital twins (DTs) provide numerous opportunities for value creation in manufacturing. Services enabled by DTs include remote monitoring of assets’ conditions and predictive maintenance. In this paper, we introduce novel, previously unexplored services based on a fully virtualized machine tool, which are targeted at increasing machine operators’ productivity. This allows conducting procedures, such as operator training at a virtual machine tool, which results in the real machine tool being available for value adding activities. Beyond operator training, we envision further potential applications of the virtual machine tool including the run-in of new processes and collision detection.

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Point cloud based tool path generation for corrective machining in ultra‑precision diamond turning

Marco Buhmann1,2, Erich Carelli3, Christian Egger3, Klaus Frick3

Published online: April 20, 2022

The increasing demand for machining non-rotational optical surfaces requires capable and fexible cutting tool path generation methods for ultra-precision diamond turning. Furthermore, the recent interest in on-machine metrology and corrective machining requires efcient as well as accurate algorithms capable to handle point cloud based surface data. In the present work, a new computation method for the tool path generation is proposed that focuses on three-axes corrective machining. It is based on the principle of defning the surface to be machined by a point cloud of given density, since surface measurement data is usually available as point cloud. Numeric approximation techniques are used to compute the surface normal vectors and calculate the resulting positions of the cutting tool path preserving a uniform radial axis motion for face turning. Investigations are performed in order to quantify the error between the calculated tool path and the exact analytical solution. The error dependencies are analyzed regarding the local surface slope and numerical parameters. Error values below 1 nm are achieved. In addition, form deviation results prove the method’s capability for corrective diamond turn machining.

1 RhySearch, Buchs SG, Switzerland
2 Institute of Machine Tools and Manufacturing (IWF), Swiss Federal Institute of Technology, Zurich, Switzerland
3 Institute for Computational Engineering (ICE), Eastern Switzerland University of Applied Sciences, Buchs SG, Switzerland

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Publikationen 2021

Alignment, calibration and data post‐processing for on‐machine metrology on ultra‐precision diamond turning machines

Marco Buhmann1,2, Thomas Liebrich1 , Raoul Roth1 , Lars Gloor2 , Konrad Wegener2 

Published: June 2021

Implementing on‐machine measurements on ultra‐precision diamond turning machines follows the principle of measuring close to the machining process without reclamping the workpiece and sets up a closed‐loop process consisting of machining and measuring. The probe integration into the machine tool inevitably comes along with measurement errors due to alignment, probe system and kinematic imperfections as well as varying scanning conditions. In order to reduce these errors an approach is presented to align the optical axis of an interferometric one‐dimensional optical probe parallel to the machine tool spindle axis, necessary to reduce the cosine error caused by misalignment. Furthermore, the approach allows to determine the gain error of the probe system. The machine tool’s X‐axis straightness deviations in Z‐direction are measured and compensated by post‐processing of the measurement data. An experimental validation method is presented and yields to a maximum measurement error range of about 45 nm for a measurement of a non‐rotational symmetric freeform surface with a diameter of 20 mm.

1 RhySearch, Buchs SG, Switzerland
2 Institute of Machine Tools and Manufacturing (IWF), ETH Zurich, Switzerland

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Investigation on probe positioning errors affecting on-machine measurements on ultra-precision turning machines

Marco Buhmanna,b, Erich Carellic, Christian Eggerc, Raoul Rotha, Thomas Liebricha

Published: 2021

The measurement of machined surfaces directly on ultra-precision turning machines yields to notable advantages, e.g. in correcting formdeviations without re-clamping. In the present work, a one-dimensional probe is moved by the machine axes to optically scan the workpiece. The integration and positioning methodology of the probe within the machine tool coordinate system as well as a measurement simulation model are presented. Simulations and experiments are conducted to identify the influence of positioning errors of the probe regarding the measurement results. The measurement error along the spindle axis, which mainly affects the measured form deviation, depends on the gradient of the geometry to be measured.

a RhySearch, Buchs SG, Switzerland
b Institute of Machine Tools and Manufacturing (IWF), ETH Zurich, Switzerland
c Institue for Computational Engineering (ICE), University of Applied Science NTB Buchs, Switzerland

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Publikationen 2020

New positioning procedure for optical probes integrated on ultra-precision diamond turning machines

Marco Buhmann1, Raoul Roth, Thomas Liebrich, Klaus Frick2, Erich Carelli2, Michael Marxer3

Published: 12 May, 2020

The ability to verify the geometrical quality of a machined workpiece on the machine tool itself can be a crucial advantage in ultra-precision diamond turning. This paper presents a new positioning procedure for optical one-dimensional (1D) probes integrated on diamond turning machines with two horizontal linear axes and one rotational axis. A tilted flat, mounted onto the spindle, is used to determine the offsets between the probe and the spindle axis in order to minimize measurement deviations referred to probe alignment errors. An estimation of the positioning uncertainty, which can be specified to be less than 0.3 µm, is given.

1Institute of Machine Tools and Manufacturing (IWF), ETH Zurich, Switzerland

2Institute for Computational Engineering (ICE), University of Applied Science NTB Buchs, Switzerland

3Institute for Production Metrology, Materials and Optics (PWO), University of Applied Science NTB Buchs, Switzerland

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Automatisierung in der Präzisionsfertigung

Thomas Liebrich

Published: 2020

Poster Industrie 2025 F&E Konferenz

Publikationen 2019

Testing procedure for optical probes integrated on ultra-precision diamond turning machines

euspen SIG Meeting: Micro/Nano Manufacturing

M. Buhmann1,2, T. Liebrich1, R. Roth1

Published: 2019

The ability to verify the geometrical quality of a workpiece on the machine tool itself can be a crucial advantage in ultra‑precision diamond turning. This work presents a test procedure for single point distance measuring optical probes integrated on diamond turning machines (DTMs). To be able to specify the probe´s characteristics a strategy using the axis of the DTM itself is developed.

Figure 1 shows the experimental setup consisting of a measurement target mounted on the z‑axis and the probe mounted on the x‑axis of the DTM. The flat metallic diamond turned surface used as measurement target is positioned orthogonal to the z‑axis. While running a NC program, which commands a specific trajectory, for example a sinusoidal path, the glass scale signal of the DTM and the probe´s distance signal is recorded with a frequency of up to one kilohertz. By analyzing the glass scale signal the actual movement of the z‑axis can be extracted and used as a nominal value to evaluate the quality of the probe signal and its characteristics. An estimation of deviations caused by misalignment of the probe and measurement target is described. Besides that, effects caused by a possible time delay, temperature drifts and dynamic effects of the machine axis are taken into account and strategies to contain these effects are shown.

By adjusting the programmed trajectory the probe´s measuring range to be tested can be varied. Furthermore, by tilting the probe in regard to the measurement target´s surface (see Figure 1 (b)), the important behavior in non‑orthogonal measurements on high reflective surfaces can be investigated. In the present work an interferometric probe is employed. The obtained deviations slightly differ depending on the probe´s tilt and distance value. With a linear compensation for a measuring range of four micrometers the maximum error can be reduced by fifty percent to residual deviations of less than twenty nanometers.

1RhySearch, The Research and Innovation Centre Rheintal, Buchs, Switzerland

2Institute of Machine Tools and Manufacturing (IWF), Swiss Federal Institute of Technology (ETH), Zurich, Switzerland

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