Abstract: The span and length to diameter ratio of the large-scale crankshaft are big, and the structure and the distribution of crank pins are complex. Thus it is easier for crankshaft to generate biggish torsional deflection which finally influences the contour precision of the crank pin in tangential point tracing grinding. Based on the analyses of force and torsional deformation of the crankshaft under different crankshaft driving modes of the headstock and the tailstock, the relationship between torsional deformation and rotation angle error of the crankshaft in tangential point tracing grinding is discussed in this paper. According to crankshaft rotational motion and wheel frame coordinated motion in tangential point tracing grinding, contour error of the crank pin caused by torsional deflection is established under different crankshaft driving modes. The simulation results show that minimum contour error of the crank pin can be obtained when crankshaft is synchronously driven by both the headstock and the tailstock, and speed error does not exist in tangential point tracing grinding.

Key words: Crank pin, Torsional deflection, Rotation angle error, Contour precision