Analysis of machining strategies for fiber reinforced plastics with regard to process force direction

Mechanical machining of composites, especially the machining of holes for bolts or rivets, poses challenges due to the anisotropic material structure. Machining forces may damage the workpiece permanently. Chipping or delamination are severe damages, primarily occurring at the workpiece's surface layers. Prior research has shown that machining induced damages can be significantly reduced by using machining strategies, which aim at directing the resultant process force vectors toward the center of the workpiece. This article presents detailed analyses of two such machining strategies with regard to the process force direction. A combined process of circular and spiral milling as well as five-axial wobble milling is analyzed. The influences of process and workpiece parameters (feed, tool inclination, tool spiral angle, cutting edge radius) on the resultant machining force vector are determined.