1. Symmetrical processing method
For parts with large machining allowance, in order to make them have better heat dissipation conditions during the machining process and avoid heat concentration, symmetrical machining should be adopted during machining. If a 90mm thick aluminum sheet needs to be processed to 60mm, if one side is milled and the other side is milled immediately, and the final size is processed at one time, the flatness will reach 5mm; if it is processed symmetrically with repeated feeding, each side is processed twice to The final dimension can guarantee a flatness of 0.3mm.
2. Layered multiple processing method
If there are multiple cavities on the sheet part, as shown in the picture below. When processing, it is not suitable to use the sequential processing method of one cavity and one cavity, which will easily cause uneven stress on the parts and cause deformation. Multi-layer processing is adopted, and each layer is processed to all the cavities at the same time, and then the next layer is processed to make the parts evenly stressed and reduce deformation.
3. Proper selection of cutting amount
The cutting force and cutting heat can be reduced by changing the cutting amount. Among the three elements of cutting amount, the amount of back-engagement has a great influence on the cutting force. If the machining allowance is too large, the cutting force of one pass is too large, which will not only deform the parts, but also affect the rigidity of the machine tool spindle and reduce the durability of the tool. If the amount of knives to be eaten by the back is reduced, the production efficiency will be greatly reduced. However, high-speed milling is used in CNC machining, which can overcome this problem. While reducing the amount of back cutting, as long as the feed is increased accordingly and the speed of the machine tool is increased, the cutting force can be reduced and the processing efficiency can be guaranteed at the same time.
4. Pay attention to the order of cutting
Roughing and finishing should use different pass sequences. Rough machining emphasizes improving machining efficiency and pursuing the removal rate per unit time. Generally, up-cut milling can be used. That is, the excess material on the surface of the blank is removed at the fastest speed and the shortest time, and the geometric contour required for finishing is basically formed. While finishing emphasizes high precision and high quality, it is advisable to use down milling. Because the cutting thickness of the cutter teeth gradually decreases from the maximum to zero during down milling, the degree of work hardening is greatly reduced, and the degree of deformation of the part is also reduced.
5. Secondary compression of thin-walled parts
Thin-walled workpieces are deformed due to clamping during processing, and even finishing is unavoidable. In order to reduce the deformation of the workpiece to a minimum, you can loosen the pressing piece before finishing the final size, so that the workpiece can freely return to its original state, and then slightly press it, as long as the workpiece can just be clamped, so that The ideal processing effect can be obtained. In short, the action point of the clamping force is preferably on the support surface, and the clamping force should act in the direction of the workpiece with good rigidity. On the premise of ensuring that the workpiece is not loose, the smaller the clamping force, the better.
6. Drilling and then milling
When machining parts with a cavity, try not to let the milling cutter plunge directly into the part like a drill when machining the cavity, which will result in insufficient space for the milling cutter to accommodate chips and poor chip removal, resulting in overheating, expansion, and chipping of the parts. Unfavorable phenomena such as broken knife. First drill the hole with a drill of the same size as the milling cutter or one size larger, and then mill it with the milling cutter. Alternatively, CAM software can be used to produce helical rundown programs.
