The box body is the core part of the construction machinery transmission system. The main processing content is the plane and the hole system. The processing quality of the workpiece determines the assembly accuracy and working performance of the machine. The following introduces the processing skills and practical experience of box-type parts from the aspects of processing equipment, tooling and tool selection, etc., to provide reference for the processing of other similar parts.
The box body is a polyhedron structure with an internal cavity, thin wall and uneven distribution of wall thickness, and is made of gray cast iron HT250 material. Gray cast iron has good machinability, wear resistance and vibration absorption [1], which can meet the strength and rigidity requirements of the whole machine.

The structure of box-like parts is complex and irregular. With the rear shell structure, one clamping cannot complete the milling and drilling of the large bottom plane, and two clampings affect the machining accuracy of the plane. After the box structure, when the workpiece is positioned and the bottom of the processing position is large, the workpiece is easily deformed due to the thin wall, so the flatness of the large plane and the position of the pin hole are out of tolerance. At the same time, when processing such workpieces, the accuracy requirements for the position and coaxiality of each hole should also be guaranteed.

When compiling the processing technology, the craftsman should fully understand the performance of the workshop equipment, and select the appropriate processing equipment according to the external dimensions of the workpiece and the processing capacity of the equipment. Vertical lathes are used for rough machining; CNC vertical lathes are used for semi-finishing and finishing machining, vertical machining centers are used for both ends of the machining, and horizontal machining centers or horizontal milling and boring machines are used for the side machining. For machining centers, the runout of the spindle should be checked periodically. For horizontal machining centers, the minimum rotation scale unit of the worktable should also be considered. The angle between the centerline of some radial holes and the centerline of the workpiece is half a degree, and the processing equipment with the minimum rotation scale unit of an integer degree cannot meet the requirements of such holes. of machining accuracy. When preparing the processing technology, the worktable should rotate clockwise or counterclockwise for one cycle to complete the processing content of all the peripheral surfaces of the workpiece, which helps to maintain the rotation accuracy of the horizontal machining center and improve the service life of the equipment.