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Repair size method is a common method to repair the wear and tear of matching auxiliary parts

by:JNSN     2021-12-24

Qingdao Ruijing Electromechanical Equipment Co., Ltd.

A crankshaft whose journal diameter is less than 80mm and whose roundness and cylindricity error exceeds 0.025mm, or whose diameter is over 80mm and whose roundness and cylindricity error exceeds 0.040mm or Imported bearings should be ground according to the specified size (repair size). When the journal wear is severe and the repairing effect cannot be achieved by the repair size method, the coating technology should be used for repair and then ground to the specified size or repair size.

What is the crankshaft repair size method?

The repair size method is a common method for repairing the wear and tear of the mating pair. It is to restore a part of the mating pair to be repaired to the correct shape and obtain a new repair size by machining. Then choose another part with the corresponding size to match it, a repair method to restore the mating nature. For crankshafts with little wear, grinding can be used to bring them to repair size.

Before grinding, the crankshaft with bending deformation must be corrected first. Grinding of the crankshaft is usually carried out on a crankshaft grinder. In addition to the dimensional accuracy and surface roughness of the journal surface, the grinding of the crankshaft must meet the requirements of the geometric tolerance: when grinding the crankshaft, it is necessary to ensure the coaxiality of the main journal and the shaft journal of the connecting rod. The parallelism between the two axis lines limits the crank radius error and ensures the accuracy of the angle between the connecting rod journals.

Eccentric grinding method and concentric grinding method can be used for connecting rod journal. The concentric grinding method is to keep the axial position of the connecting rod journal unchanged after grinding, that is, the crank radius and distribution angle remain unchanged. Crankshaft grinding of diesel engines often adopts the concentric method. The eccentric grinding method is to position and grind according to the worn connecting rod journal surface. At this time, the centerline position of the journal and the crank radius have changed. Generally, the crank radius after grinding is larger than the original crank radius, which increases the compression ratio, and the change of each cylinder is uneven, and at the same time, the mass center of the entire crankshaft is not in the crankshaft. The centerline of the main journal causes the crankshaft to be unbalanced, resulting in additional dynamic load during rotation. Therefore, when grinding the connecting rod journal, the increase in crank radius should be minimized to ensure that the concentricity error of the shaft journal of the connecting rod journal is not more than ±0.10mm to ensure the balance of the crankshaft during operation.

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