Analysis of the grain shape influence on the chip formation in grinding

•With a new single grain scratching method the chip formation was observed in situ.•This enabled to detect the transition of chip formation phases for the first time.•Specific grain engagement depths at the transition points were determined.•These are influenced by the grain shape in and cross to the direction of motion.•A quantitative chip formation model was derived, considering the grain shape.

In grinding many qualitative models for chip formation have been developed so far, which divide different phases of chip formation. A newly developed experimental single grain scratching method is presented, which enables to observe the chip formation in situ by means of a high speed video camera. Hence, it was possible to detect the transition of the chip formation phases for the first time and to determine specific grain engagement depths at the transition points. Based on experimental investigations using CBN grains and workpieces made of hardened steel 100Cr6 (AISI 52100) the influence of the 3D grain shape on the chip formation was analysed on the basis of characteristic values. Finally, a quantitative chip formation model was derived, which takes account of the 3D grain shape as well as the cutting speed and the status of lubrication. Although the influencing quantity of the different grain shape characteristic differs, it has to be stated that the grain shape in direction of motion as well as in transversal direction has significant influence on the chip formation in grinding.