With the improvement of the durability requirements of the excavator, the hardness and diameter of the shaft sleeve of its working device are increasing, the interference of the shaft sleeve is gradually increasing, and the theoretically calculated pressing force is also large. It is necessary to select the shaft sleeve assembly process. The assembly process of several interference fit bushings is described below.
The hammering process is flexible in operation and strong in adaptability, but the process is labor-intensive, and the assembly guidance is not well controlled. The hammering process is mainly used for bushings with small interference on the mating surface and short lengths.
Using a press to implement the press-fitting process has uniform force, easy-to-control assembly orientation, high production efficiency, and can adapt to a large amount of interference, but it is necessary to make press-fitting tooling, customized hydraulic cylinders, Configure the hydraulic pump station. Our company has many models of excavators and various types of bushings. It is necessary to design different tooling and configure hydraulic cylinders and hydraulic pump stations with different structures according to different excavators and bushings in different positions.
Using the thermal expansion characteristics of metal, first heat the bushing seat hole to expand and increase the diameter of the inner hole, change the interference fit between the seat hole and the bushing into a clearance fit, and then insert the bushing into the seat hole, after the hole is cooled become an interference fit.
Contrary to the hot-loading process, this process freezes the bushing, and the bushing can be easily put into the hole of the structural member after being frozen and shrunk. When the bushing returns to the normal temperature size, an interference fit can be obtained. However, when the amount of interference is large, the amount of freezing shrinkage is not enough, and it needs to be assembled with hammering. If the amount of interference is large, it needs to be combined with a press for press-fitting.