The crankshaft is the most important part of the engine. It bears the force transmitted by the connecting rod and turns it into torque to output through the crankshaft and drive the other accessories on the engine. The crankshaft is subjected to the combined action of the centrifugal force of the rotational mass, the inertia force of the periodic change and the reciprocating inertia force, so that the crankshaft is subjected to the bending torsion load. Therefore, the crankshaft is required to have sufficient strength and stiffness, and the neck surface needs to be wear-resistant, uniform and well balanced.