Comparison of Ground and Laser Machined Polycrystalline Diamond (PCD) Tools in Cutting Carbon Fiber Reinforced Plastics (CFRP) for Aircraft Structures

The extended use of carbon reinforced plastics (CFRP), especially in aircraft industries, requires efficient machining solutions due to superior mechanical properties with a lower weight compared to metals. This material is highly abrasive, requiring very hard cutting materials and additionally only a sharp cutting edge provides a sufficient surface quality on the workpiece. Ultrashort laser pulses and the focusability of high brilliance laser systems enable diamond processing without relevant graphitization or other material deteriorating effects for polycrystalline diamond (PCD). This study focuses on a comparison of conventional and laser machined PCD cutting tool inserts and a characterization of their machining characteristics. Conventional processing of the PCD tools is done using grinding processes on five axis machining centers. Laser manufacturing is done using a five axis CNC machine with additional three axes for beam delivery. Comparable values in terms of surface roughness on flank and rake face as well as edge curvature radii are achieved. The comparison of machining characteristics is done machining CFRP in a continuous turning process with a single fiber orientation at cutting velocities of 200 m/min. Machining forces and the cutting edge radii are measured to evaluate tool wear. The resulting work piece quality is analyzed by measuring surface roughness and integrity using tactile surface roughness measurement (Taylor Hobson PGI 1240) and scanning electron microscopy (SEM).