Common excavator structures include power unit, working device, slewing mechanism, control mechanism, transmission mechanism, walking mechanism and auxiliary facilities.

The working device is a device that directly completes the excavation task. It is hinged by three parts: boom, stick and bucket. The boom take-off and landing, stick telescopic and bucket rotation are all controlled by reciprocating double acting hydraulic cylinders.

Standard excavators usually have 11 joint pivot pins, which are distributed on the boom, stick and bucket.

According to the installation position, There are bucket pins, arm pins, arm cylinder pins, coupling pins of boom and arm, boom cylinder pins and boom pins.

The pivot pin at the bottom of the boom is usually the longest pin. Except for the top pin of the boom cylinder, the cylinder pin of other parts are relatively short.

Usually, the top pin of the boom oil cylinder does not have a plate. It has a bolt hole at both ends or three screw holes on both side surfaces

In addition, the pins in other positions basically have plates, and the types of plates of different brands are different.