Observation of machined surface and subsurface structure of hinoki (Chamaecyparis obtusa) produced in slow-speed orthogonal cutting using X-ray computed tomography

Abstract

X-ray computed tomography (CT) was applied to non-destructive observation of machined surface and subsurface structure of hinoki (Chamaecyparis obtusa) produced in slow-speed orthogonal cutting. The cutting experiments were conducted under several cutting conditions and the chip formations were observed with a high-speed camera to be classified into four chip types. The difference in the quality of the machined surfaces produced in four types of chip formation was investigated. During type 0 chip formation, the workpiece was cut almost exactly at the path of the cutting edge, so no deformation was found on and beneath the machined surface. During type I chip formation, the direction of the fore-split, which is dependent on the arrangement of cells, determined the machined surface. During type II chip formation, the cutting tool sometimes tore part of the workpiece below the path of the cutting edge and the tore part was then compressed by the tool, remaining on the machined surface. During type III chip formation, part of the workpiece above the path of the cutting edge was compressed by the tool, instead of being removed as a chip, so the compression occurred in wide area. The relationship between the formation of the machining defects such as torn grain or the compressed cells and the way chip is separated, deformed, or removed was clarified in this study.