Brunimento flexível de cilindros de blocos de compressores herméticos: avaliação do efeito da granulometria e do número de golpes da ferramenta na rugosidade

Abstract

The objective of this work is to evaluate the effect of the two cutting parameters (grain size and number of tool strokes) on the values of roughness (Ra, Rq, Rp, Rt, Rv, Rk, Rpk, Rvk, Mr1, Mr2 and CV) in flexible honed crankcase cylinder of hermetic compressors. The study was based on a full factorial design 2¹ e 3¹, where the grain size factor was investigated in two levels (400 and 800 mesh) and the number of tool strokes in three (1, 3 and 5). The flexible honing process was carried out to cylinders previously machined by the conventional honing in the production line of EMBRACO. The flexible honing was conducted at UFU using a CNC milling machine and the Silicon Carbide flex hone tools. An electromechanical surface roughness tester was used to carry out roughness measurements. The measurement uncertainty was assessed using the GUM method. The Analysis of Variance (ANOVA) technique was applied, and it was observed that the factor tool grain size caused statistically significant effects on Ra, Rq, Rp, Rpk, Rk and Mr2, while the number of strokes affected the parameters Ra and Rpk. The interaction between these factors affected the parameters Ra, Rq, Rp and Rk. The results indicated that the flexible honing process using 800 mesh tool grain size and 5 strokes gave the best surface finish considering the functionality of the cylinders. The application of these cutting conditions allowed the obtaining of surfaces very similar to the ones resulting from the plateau honing process, which can increase the field of application of this process. The flexible honing using the 800 mesh tool grain size and 1 stroke allowed obtaining a finish similar to that achieved with the 400 mesh tool grain size and 3 strokes, reducing the machining time.