Ductile ultra-precision machining of brittle materials by processes with defined diamond cutting

• Applicant: Professor Dr.-Ing. Eckart Uhlmann
• Subject Area: Metal-Cutting and Abrasive Manufacturing Engineering
• Term: since 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 320151403

The manufacturing of micro-optics for use in the medical sector, e.g. in general and visceral surgery for the realisation of high-precision and high-resolution laparoscopic examinations is subject to continuously increasing requirements. In this context, the demand on materials, which enable the near- and mid-infrared range, is growing and gallium phosphide (GaP) represents a suitable material. For the application in the general and visceral surgery, micro-optics made of GaP with a surface roughness Ra ≤ 10 nm are necessary. The Ultra-precision cutting concerning single crystal diamonds (SCD) enables the optical machining of GaP. Regarding economical machining technologies and using low rounded cutting edge radius rβ as well as a ratio of the chip thickness to the rounded cutting edge radius of h > rβ results in high tensile stresses σts in the workpiece. Reaching a material-dependent critical value leads to cracks and outbreaks in the material, which not allow surface roughness values of Ra ≤ 10 nm. To address the current challenges, ultra-sonic assisted systems are applied for a ductile machining of GaP. Using the ultra-sonic machining leads to compressive stresses σc, which achieve a plastic deformation without a crack development. The aim of the research project is the ductile machining of GaP to realise the requirements of application-specific micro-optics for use in the medical sector concerning surface roughness values, tool wear as well as economic efficiency. The scientific research hypothesis shows that using both the conventional and the ultra-sonic assisted ultra-precision cutting enables the ductile machining of GaP without crack development and with surface roughness values of Ra ≤ 10 nm for the direct manufacturing of micro-optics. To realise the research project with regard to the scientific research hypothesis, the specific material properties of GaP will be characterised as well as fundamental cutting mechanism will be identified. Based on this, detailed investigations concerning both the conventional and the ultra-sonic assisted ultra-precision turning will be carried out as well as the influences of the surface roughness values will be analysed. Furthermore, the wear behaviour of the used SCD as well as the influences of the crack development and the scientific research hypothesis will be detailed investigated. The results of the research project include detailed knowledge for the research hypothesis, both the conventional and the ultra-sonic assisted ultra-precision turning process as well as the wear behaviour of the used SCD for machining GaP.

• DFG Programme: Research Grants