Marcel Henerichs

Performance of Lasered PCD- and CVD-Diamond Cutting Inserts for Machining Carbon Fiber Reinforced Plastics (CFRP)

Carbon fiber reinforced plastics (CFRP) combine superior mechanical properties with a low weight. Consequently, this material is highly interesting for the aircraft as well as the automotive industry, leading to a massively increased application over the last years. However machining CFRP still faces different difficulties: The material is highly abrasive, most tool substrates and coatings face massive abrasive wear. Machining CFRP often results in many material defects like delamination, fiber pull-out, high surface roughness and burnt matrix material. Several technologies have been developed to combine ultra-hard tool surfaces and most adaptable cutting edge geometries. One of the most interesting approaches is laser machining of diamond cutting edges. The technology combines the wear resistance of thick layer diamonds with a geometrical flexibility so far known only for carbide tools. In the presented study, the wear resistance of different Polycrystalline Diamond (PCD) and Chemical Vapor Deposition (CVD)-Diamond grades machined with two different laser systems has been tested for machining CFRP. In comparison state-of-the-art grinded PCD cutting inserts are being tested. The comparison of machining characteristics is done by machining CFRP in a continuous turning process with a single fiber orientation. Machining forces are measured to evaluate tool wear. The resulting work piece quality is analyzed by measuring the surface roughness. The machined CFRP is a M21 resin system with an IMA-12K fiber from Hexcel

ELID dressing behaviour of fine grained bronze bonded diamond grinding wheels

The application of metal bonded grinding wheels generally results in high wear resistance and profile constancies of the grinding wheels. Especially bronze bonded grinding wheels can efficiently be used for the grinding tasks, as it is easier to modify their chemical composition - and therefore their bond hardness - to suit a specific grinding task. The combination of very small grained diamonds and a metal bond causes great difficulties for conventional dressing. In this paper, an assessment on the capabilities of ELID for dressing of bronze bonded diamond grinding wheels is presented. Distinct types of bronze-bonds with different chemical composition are investigated regarding their electrochemical dissolution and oxidation behaviour during ELID. Iron-based (Fe-Bz) and cobalt-based (Co-Bz) bronze-bond types showed good performance regarding oxide layer formation during the pre-dressing. An extensive oxide layer growth prevents the metal bond from a too fast anodic dissolution. In contrast, pure bronze type (Cu-Bz) showed no closed oxide layer formation resulting in an extensive anodic dissolution of the grinding wheel bond.