Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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Increased efficiency and accuracy in ultra-precision machining through adapted CAM software

2020 , Uhlmann, Eckart , Polte, Julian , Hein, Christoph , Kuche, Yves , Dörr, Martin

CAM software is widely used through the last 40 years for a broad field of applications. The networkability of machine tools and the digitally integrated production as an existing trend for the next years and exponentially increasing computing power enable direct data transfer between CAD/CAM software and machine tool. Increments ar < 5 nm are common in ultra-precision CNC codes and are not supported by most traditional CAM software. Therefore, ultra-precision machining often remains a manufacturing process with high manual effort in the machine setting and the generation of CNC codes. In order to increase the degree of automation in ultra-precision machining, machine manufacturers are developing their own, customised CAM software. The studies presented in this paper investigate the influence of different process preparation on relevant parameters during ultra-precision face turning of an n surface with monocrystalline diamond tools. Machine-specific CAM software is com pared with manual CNC code creation from a point cloud. The influence on the workpiece characteristics dimensional accuracy GF and average roughness depth Ra is investigated. The influence of the chosen strategy for the generation of the CNC code on the machining time tm is examined to compare the economics of the strategies. In order to keep the comparison significant, the cutting parameters cutting depth ap and feed f are kept constant in all strategies. Decreasing machining time tm increases efficiency in comparison to manual CNC code creation.

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Tool wear prevention in ultra-precision polymer machining

2020 , Uhlmann, Eckart , Fang, F. , Polte, Julian , Hein, Christoph , Lai, M. , Dörr, Martin , Jahnke, Christian

Polymers become more relevant in the field of optical components as their optical properties, like refractive index n and wavelength dependent dispersion n = f(λ), can be adjusted easily by additives. Due to their low density Ï polymeric optics are lightweight compared to glasses. The demand for ultra-precision machined polymer lenses is increasing. Small series and individualised components can only be produced economically by using ultra-precision machining. Within theses studies the influence of different measures to reduce diamond tool wear occurring during ultra-precision diamond face turning of polycarbonate (PC) and polysulfone (PSU) will be investigated. Continuous and interrupted face turning experiments are conducted to analyse the effects from separation of the diamond tool and workpiece. Results show increasing tool wear in interrupted cutting. Changes of the environmental conditions in the cutting process show an influence of increasing humidity H on diam ond tool wear. This contribution gives a qualitative and quantitative overview on the influencing factors on diamond tool wear in ultra-precision turning of polymers and gives an outlook on strategies to avoid its occurrence.

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