Estudo de desvios geométricos causados na furação e alargamento do ferro fundido vermicular com diferentes valores de sobremetal

Abstract

The seek for greater competitiveness, reduction in losses and better profit guarantee has led the metal work industry to invest more money in research and methods to reduce costs and attempt of increase productivity efficiency, mainly in manufacture of metal components. Into this context, specifically in machining sector for production of holes, any benefit, whether on the increase of tool life, efficiency of chip removal process, reducing the machining time or improvement on dimensional and geometric quality (surface finish) of holes, would be significant achievement. This work aims to investigate the quality 10 mm diameter cylindrical holes performed by drilling process with special designed carbide drills in a compacted graphite cast iron. Machining trials were also carried out with straight flute carbide reamers for comparison in terms of production of tight tolerances holes. For reaming process, holes were previously machined with solid carbide twist drills with diameters of 9.5 and 9.7mm. Rejection criterion was based on the number of 25 holes for conditions investigated. All experimental trials were carried out in dry condition machining. The surface roughness (Ra parameter) and roundness deviation were used as output parameters to evaluate the performance of special designed drills. The results showed that the roundness deviation obtained on machining with special drills was slightly higher than those generate by the reamers. Regarding the roughness values, it is observed that they were satisfactory when machined with special drills, thereby indicating that special drills can be an alternative tool to reamers for the production of holes with tight tolerances under the conditions investigated in this work.