Milling hole force of Quartz fiber-reinforced polyimide composite in cryogenic cooling

Abstract

The machinability of composites had close relationship with cutting force. A milling hole force model of quartz fiber-reinforced polyimide composites (QFRP) was constructed considering cutting microzone temperature. A series of cryogenic milling hole testes were carried out through a liquid nitrogen inner cooling cutting equipment. The surface morphology and cutting force performance at hole entry and exit were analyzed in detail. The results show that helical milling force is mainly related to the axial feed, tangential feed, and mechanical properties of composites in different temperatures and changed slowly with spindle speed. The influence of axial feed on force is larger than that of tangential one. Meanwhile the large cutting force at hole entry and the little force at hole exit have the main reasons of the crimping and delamination defects. After cryogenic is intervened, the milling force is significantly improved, and the defects are effectively restrained. Especially, the hole entry and exit accuracies can be reached 0.03 mm, and there are no low-speed tearing and high-speed ablation defects. Furthermore, the change of force is caused by the change of properties of matrix, and composite at low temperature is the main reason to restrain defects. The cooling medium can avoid the phenomenon of increasing cutting force caused by tool expansion, as well as restraining the ablative defect.