Guarantee Of Machining Accuracy Of Thin-Walled Plate-Shaped Die Castings Based On Deformation Control

With the rapid development of the manufacturing industry, the requirements for specific strength and specific stiffness of mechanical parts are getting higher and higher, and thin-walled plate-shaped structural parts are widely used. Such structural parts generally have the problem of poor casting and machining processability. The blank is easy to deform during casting production, and the parts are also easy to deform during machining due to residual stress and improper support clamping methods, resulting in machining size and position tolerance, and even affecting fatigue life and working intensity. This topic takes the middle plate as an example to describe how to ensure the machining accuracy of thin-walled plate-shaped die castings by suppressing deformation during die casting and machining.
Graphic results
The middle plate is a key part used to fix the motors on both sides in a certain automobile gearbox. It weighs about 1.2kg and is made of ADC12 die-cast aluminum alloy. The appearance is shown in Figure 1. It is a typical thin-walled plate-shaped part, disc-shaped, with an outer size of about φ340mm. The wall thickness of the middle connection part is 5mm. In order to make the design lightweight, there is a large area of ​​hollowing, which greatly reduces the rigidity of the part and increases the difficulty of its die casting and machining.

Figure 1 Appearance of the middle plate

Figure 2 Schematic diagram of parts with strict precision requirements

Figure 3 Fixture for middle plate solution 2
1. Press head 2. U-axis tailstock 3. Tailstock L plate 4. Fixture bottom plate 5. Diamond pin 6. Floating support 7. Fixed support 8. Pre-positioning guide column 9. Round pin
Due to the poor rigidity of the middle plate, a small clamping torque can also produce a lever effect, causing local deformation of the workpiece, rebound after processing, and reduce the processing accuracy. Therefore, the clamping point and support point of such parts must be set point to point, and the clamping force arm must be 0 as much as possible. The action sequence is: put the workpiece in place → clamp the fixed support → float the floating support → clamp the floating support clamping point.

Figure 4 Z3-2 hole Y-axis coordinate offset fluctuation diagram

Figure 5 X/Y thermal offset of vertical machining center
First, the deformation of the blank should be controlled within a reasonable range to provide a relatively reliable positioning rough reference for machining. The amount of blank machining allowance is determined by its dimensional accuracy. The higher the accuracy, the smaller the allowance can be. For thin-walled plate-shaped workpieces, the design and manufacturing quality of the fixture are crucial. After qualified commissioning, daily maintenance should also be taken seriously. The thermal deformation of the machine tool has little effect on the milling flatness, but sometimes has a very large impact on the hole position, so it is necessary to try to compensate.