Efeito do tratamento da microgeometria de ferramentas com revestimento diamantado no fresamento de eletrodo de grafite

Abstract

The rising need for manufacturing molds with increasingly smaller deadlines and costs is demanding from the toolmakers to customize and enhance their fabrication processes. One of the ways to achieve that is by improving their electrode machining, since this process will affect directly in the result of the dimensional precision and production time of the mold. The usage of graphite as raw material for electrodes is known to be highly satisfactory since the graphite has the advantage of machining faster and allowing a great variety of geometrical forms, however, its main disadvantage is that the graphite also has a high level of wearing during the machining process. The cutting edge preparations are used in order to reduce the effects of this problem, increasing the durability of the tools. In that interest, this paper has researched the effect of edge preparations on the wear of tools with polycrystalline diamond coating (PCD), in the milling of graphite electrodes. Therefore, experimental tests were performed with untreated tools, tools polished with abrasive brushes and tools treated by the polishing method with drag finishing. The tests consisted in machining electrodes with defined parameters and checking the wear generated on the cutters every 200 meters of machined length. Analysis of roughness, characterization of the tools after the treatments, characterization of the media and the brush used in the polishes and characterization of the machined graphite were also performed. The findings indicate that the edge preparation results in modifications on the coating surface, reducing the roughness value by a mean of 23%, and in the case of drag finishing process, a variation of the values reduction, since this process is more reliable and reproducible. The media and brush characterization indicated the silicon presence as an abrasive material, which may characterize a silicon carbide material. With regard to the tools wear, due to their life curve, gains such as reduction of flank wear and a length-machined increase of up to 63% were noticed, in comparison to the original tools. All tools passed through Stages I and II of Wear Curve, and did not reach Stage III, known as Catastrophic Wear. Abrasion was, apparently, the most present wear mechanism in the process, presenting as characteristics the flank wear, crater wear and notch wear. In conclusion, the two polishing processes showed gains and demonstrated their potential to be applied in tools production.