With the rapid development of manufacturing industry, the requirements for the specific strength and stiffness of mechanical parts are becoming increasingly high, and thin-walled plate-like structural components are widely used. Such structural components generally suffer from poor casting and mechanical processing technology. The blank is prone to deformation during casting production, and the parts are also prone to deformation during machining due to residual stress and improper support clamping methods, resulting in processing dimensions and positional deviations, and even affecting fatigue life and working strength. This topic takes the intermediate plate as an example to explain how to ensure the machining accuracy of thin-walled plate-shaped die-casting parts by suppressing deformation during die-casting and machining processes.
Graphic and textual results
The middle plate is a key component used to fix the motors on both sides in a certain car gearbox. It weighs about 1.2kg and is made of ADC12 die cast aluminum alloy. Its appearance is shown in Figure 1. It is a typical thin-walled plate-shaped part, with a disk shape and an outer dimension of about φ 340mm. The wall thickness of the middle connecting part is 5mm. In order to make the design lightweight, there is a large area of hollow out, which greatly reduces the rigidity of the part and increases the difficulty of die casting and processing.

1. Pressure head 2. U-axis tailstock 3. Tailstock L-plate 4. Fixture base plate 5. Diamond pin 6. Floating support 7. Fixed support 8. Pre positioning guide column 9. Circular pin
Due to the poor rigidity of the intermediate plate, even a small clamping torque can generate a lever effect, causing local deformation of the workpiece, rebound after processing, and reducing processing accuracy. Therefore, the clamping and supporting points for such parts must be set point-to-point, and the clamping force arm should be set to 0 as much as possible. The sequence of actions is: workpiece placement → fixed support clamping → floating support floating up → floating support clamping point clamping.

Firstly, the deformation of the blank should be controlled within a reasonable range to provide a relatively reliable positioning rough reference for machining. The reserved amount of blank machining allowance depends on its dimensional accuracy, and the higher the accuracy, the smaller the allowance can be. The design and manufacturing quality of fixtures are crucial for thin-walled plate-like workpieces. After passing the debugging, daily maintenance should also be taken seriously. The thermal deformation of the machine tool has little effect on the milling flatness, and sometimes has a significant impact on the hole position. It is necessary to find ways to compensate for it.

Author of this article:
Huang Zhiwei and Li Shan
College of Mechanical and Electrical Engineering, Lingnan Normal University
This article comes from: "Special Casting and Nonferrous Alloys" magazine, "Die Casting Weekly" strategic partner