The roughness characterization in cylinders obtained by conventional and flexible honing processes

Crankcase cylinders of hermetic compressors are produced in large numbers for refrigerators of domestic use. They are, usually, machined by using a three-stage honing process (roughing, semi-finishing, and finishing), and for their characterization during the quality control, an evaluation of roughness is carried out. Although the roughness represents a peerless factor to characterize the honed surfaces, its implementation is a challenge for scientists and technicians in general due to the difficulty of detecting the difference between the surface finish on different honing stages. This paper assesses the roughness of parts obtained by flexible honing applied after conventional honing process by using a portable surface roughness tester and an interferometer in white light mode (chromatic length aberration-CLA). An extensive evaluation of roughness was made using several roughness parameters, graphics, and curves that include the following: roughness profile, topographies, amplitude parameters, Rk family parameters, volume, and feature parameters. The measurement uncertainty associated with all roughness parameters was estimated by applying the methods proposed in the JCGM 101. The results obtained after flexible honing were compared with those found in parts machined by conventional honing. This experimentation showed that flexible honing process when applied after the conventional honing provided an essential improvement of the surface finish and an increase of the repeatability and the quality of honed parts. The volume and the feature parameters can be used as alternative to appropriately characterizing honed surfaces, because they were able of detecting the changes caused on the surface by different stage of honing process.