There are many reasons for the deformation of aluminum parts, which are related to materials, part shapes, production conditions, and so on. There are mainly the following aspects: deformation caused by internal stress of the blank, deformation caused by cutting force, cutting heat, and deformation caused by clamping force.
Process measures to reduce deformation of aluminum parts
1. Reduce the internal stress of the blank
The natural stress of the blank can be partially eliminated by natural or artificial aging and vibration treatment. Pre-processing is also an effective process. For the blank of the big head of the fat head, due to the large margin, the deformation after processing is also large. If the excess portion of the blank is processed in advance and the remaining amount of each part is reduced, not only the processing deformation in the subsequent process can be reduced, but also a part of the internal stress can be released after being pre-processed for a certain period of time.
2, improve the cutting ability of the tool
The material and geometric parameters of the tool have an important influence on the cutting force and the cutting heat. The correct selection of the tool is essential for reducing the deformation of the part.
(1) Reasonable selection of tool geometry parameters.
1 Front angle: Under the condition of maintaining the strength of the cutting edge, the front angle is appropriately selected. On the one hand, the sharp cutting edge can be ground, and the cutting deformation can be reduced, the chip removal can be smoothed, and the cutting force and the cutting temperature can be reduced. Never use a negative rake cutter.
2 Back angle: The size of the back angle has a direct influence on the flank wear and the quality of the machined surface. Cutting thickness is an important condition for selecting the back angle. In rough milling, due to the large feed rate, the cutting load is heavy, the heat generation is large, and the heat dissipation condition of the tool is required. Therefore, the back angle should be selected to be smaller. When finishing milling, the edge is required to be sharp, the friction between the flank and the machined surface is reduced, and the elastic deformation is reduced. Therefore, the back angle should be selected to be larger.
3 helix angle: In order to make the milling smooth and reduce the milling force, the helix angle should be as large as possible.
4 lead angle: Properly reducing the lead angle can improve the heat dissipation condition and reduce the average temperature of the processing area.
(2) Improve the tool structure.
1 Reduce the number of milling cutter teeth and increase the chip space. Due to the large plasticity of the aluminum material, the cutting deformation during processing is large, and a large space for chipping is required. Therefore, the bottom radius of the chip groove should be large, and the number of teeth of the milling cutter is small.
2 fine grinding teeth. The roughness value of the cutting edge of the cutter is less than Ra = 0.4 um. Before using a new knife, you should use a fine stone to grind a few times in front of and behind the teeth to eliminate residual burrs and slight zigzag when sharpening the teeth. In this way, not only the cutting heat can be reduced but also the cutting deformation is relatively small.
3 Strictly control the wear standard of the tool. After the tool wears, the surface roughness of the workpiece increases, the cutting temperature increases, and the workpiece deformation increases. Therefore, in addition to the choice of tool materials with good wear resistance, the tool wear standard should not be greater than 0.2mm, otherwise it will easily lead to built-up edge. When cutting, the temperature of the workpiece should not exceed 100 °C to prevent deformation.
