Avaliação do desgaste de brocas na furação de material de atrito

Abstract

The machining of composite materials presents a number of challenges depending on the nature of these materials. This work presents a study on the evaluation of wear of drill bits in the drilling of friction materials, a composite material composed of polymers, ceramics and metals used in the manufacture of brake linings for commercial vehicles. The evaluation of drill wear in the drilling process is important from the moment that there is a large production demand, with diversified formulations and with limited productive capacity, demanding a high productivity, but preserving the quality of the product. In the case of drilling, the quality of the drill depends on the conditions of the drill used and, therefore, the evaluation of the wear behavior of the drill becomes important competitive factor both in observing the technical requirements of the product design and economically. In this study, the evolution of the wear of drill bits of hard metal and polycrystalline synthetic diamond (PCD) in the drilling of two different formulations of friction material, A and B, is analyzed. The results obtained indicate a more rapid wear of the metal- hard drill bit in relation to PCD drills, where the metal-hard bit used in material B showed higher wear than the metal-hard drill bit used in material A, while for the PCD drills wear was similar for both formulations. The predominantly abrasive wear mechanism was observed for the hard metal drills and the occurrence of chipping for the PCD drills. It was verified that the end-of-life criterion of the tools is related to the VBmax of the second stage due to the rounding caused in the region of the corner formed by the main edge and its respective secondary edge. Based on the results obtained, PCD drills are the most suitable for this application, a result that is in line with other similar research related to the drilling of composite materials and contributes to the scarce existing literature on the machining of friction material. Among the opportunities for future research, studies with hard-metal drills of grades with higher abrasion resistance are suggested as a possible more economical alternative (sic).