Precise alignment method of the large-scale crankshaft during non-circular grinding

A large-scale crankshaft of internal-combustion engine is easy to bend and twist when clamped onto the grinding machine. The deviation of workpiece axis from its optimal machining axis has a significant influence on machining accuracy of angle, eccentric throw, and diameter and contour of the heavy crankshaft in non-circular grinding. To reduce the consumption of manual labor and setting-up time, an automatic alignment approach and apparatus is proposed and integrated into the non-circular grinder. The on-machine gauge senses X and Y components of deviation of crank journal axis and feed them back to the computerized numerical control system. The motor-driving steady rests based on slider-crank mechanism are controlled to compensate for the deviation. The algorithm with self-correcting ability for compensation value is employed to make up for the finite contact stiffness of workpiece and steady rest. The results of three alignment tests are compared, which demonstrates the better effect on alignment precision and efficiency of the self-correcting compensation.