Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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  • Publication
    Comparison of binderless carbide with conventional carbide as a cutting material for milling
    ( 2023)
    Uhlmann, Eckart
    ;
    Hein, Christoph
    ;
    Dargin, Muzaffer
    In order to be able to use the resources more sustainably and at the same time reduce the costs of machining, it is important to identify new types of cutting materials. Up to now, tools made of carbide have often been used in machining. Carbide has a high hardness H and, compared to other tool materials, enables long tool life T. This has a positive effect on process reliability. Conventional carbide usually consists of tungsten carbide WC and cobalt Co. The tungsten carbide WC represents the hard material itself. The cobalt Co is a binder and ensures that the hard materials are kept together. This combination makes the carbide less hard than the pure hard materials. The reduction of the hardness H of the material also results in a reduction in the tool life T of the milling tool. Various approaches are being pursued to increase the tool life T of the milling tool. One approach is the reduction of the binder in carbides. The reduction of the binder increases the hardness H of the material and thus the tool life T of the milling tool. Conventional carbide has a cobalt content of 6% < Co < 10%. The new cutting material, the binderless carbide, on the other hand, has a cobalt content of 0.40 % < Co < 3 %. The complete elimination of a binder is not possible from a manufacturing point of view at this time. To validate the milling tool made of binderless carbide, it is compared with milling tools made of conventional carbide. The two milling tools have identical geometries. This is to ensure that the influence of the cutting material on the machining result can be identified. For this reason, the identical experimental milling tests are carried out with the milling tool made of binderless carbide and the milling tool made of conventional carbide. The following parameters are recorded during the experimental tests: - Mean roughness depth Rz depending on the cutting path lc - Arithmetic average roughness Ra depending on the cutting path lc - Cutting edge rounding rß depending on the cutting path lc The experimental results show that the increased hardness H of the material has increased the tool life T of the milling tool. This makes it possible to use the available resources more sustainably and efficiently. In addition, the increase in tool life T results in an increase in the economic efficiency of milling.
  • Publication
    Acoustic emission-based process monitoring in the milling of carbon fibre-reinforced plastics
    ( 2022)
    Uhlmann, E.
    ;
    Holznagel, Tobias
    Milling of fibre-reinforced plastics is a challenging task. The highly abrasive fibres lead to high tool wear and coating failures, which cause increasing process forces and temperatures. Machining with a worn tool, in turn, can result in unwanted workpiece damages such as delamination or fibre protrusion. Reliable monitoring of the process must therefore be able to detect damages to the milling tool and the workpiece alike. The presented process monitoring approach measures the acoustic emission generated by the milling tool cutting edge entering the workpiece with a sensor attached to the tool holder. Specific acoustic emission frequency spectra and waveforms are emitted in the cutting zone for different tool wear states. Coating failures as well as other acoustic emission events due to workpiece damages can be robustly detected and distinguished by feature extraction and signal processing as well. The developed setup, the monitoring parameterisation techniques and signal processing algorithms as well as experimental and monitoring results are presented and discussed in this paper.