How to avoid deformation in CNC aluminum machining
Aluminum alloy is an important industrial raw material. Due to its relatively small hardness and large thermal expansion coefficient, it is easy to deform in the machining of thin-walled and thin-plate parts. In addition to improving the performance of the tool and eliminating the internal stress of the material by pre-aging treatment, from the perspective of processing technology, some measures can also be taken to reduce the processing deformation of the material as much as possible.
1. Symmetric Machining
For aluminum alloy parts with large machining allowance, in order to create better heat dissipation conditions and reduce thermal deformation, it is necessary to avoid excessive heat concentration as much as possible. The method that can be taken is symmetrical machining.
2. Stratified Multiple Machining
When there are multiple cavities to be processed on aluminum alloy plate parts, if one cavity and one cavity are processed sequentially, it is easy to cause the cavity wall to be deformed due to uneven force. The best solution is to adopt a multi-layered processing method, that is, to process all the cavities at the same time, but not to complete the processing at one time, but to divide into several layers and process them to the required size layer by layer. In this way, the force of the parts will be more uniform, and the probability of deformation is small.
3. Get an Appropriate Cutting Parameter
Selecting the appropriate cutting amount can effectively reduce the cutting force and cutting heat during the cutting process. In the machining process, the excessive cutting amount will lead to excessive cutting force in one pass, which can easily cause deformation of the parts, and affect the rigidity of the machine tool spindle and the durability of the tool. Among the various elements of the cutting amount, the one that has the greatest impact on the cutting force is the amount of back engagement. It is said that reducing the amount of back cutting is beneficial to ensure that the parts are not deformed, but at the same time, it will reduce the processing efficiency. The high-speed milling of CNC machining can solve this problem. It only needs to increase the feed rate and increase the speed of the machine tool while reducing the amount of back-engagement, which can not only reduce the cutting force, but also ensure the processing efficiency.
4. Cutting Sequence
Roughing and finishing should use different pass sequences. Roughing requires the fastest cutting speed to remove excess material on the surface of the blank in the shortest time to form the geometric contour required for finishing. Therefore, the emphasis is on processing efficiency, and in pursuit of the material removal rate per unit time, up-cut milling should be used. However, finishing has higher requirements on machining accuracy and surface quality, emphasizing machining quality, and down milling should be used. Since the cutting thickness of the cutter teeth gradually decreases from the maximum to zero during down milling, the phenomenon of work hardening will be greatly reduced, and the deformation of the parts will also be inhibited to a certain extent.
5. Secondary Compression of thin-walled parts
When machining aluminum alloy thin-walled parts, the pressing force during clamping is also an important cause of deformation, which is unavoidable even if the machining accuracy is improved. In order to reduce the deformation of the workpiece due to clamping, before the finishing reaches the final size, the compressed parts can be loosened, the pressing force is released, the parts can be freely returned to their original shape, and then slightly compressed again. The action point of the secondary pressing is preferably on the supporting surface. The clamping force should act in the direction of good rigidity of the workpiece. The amount of the pressing force is based on the fact that the workpiece can be clamped without loosening. This is for the operator's experience and feel. There are higher requirements. The compression deformation of the parts processed in this way is small.6. Drilling before Milling
When machining parts with a cavity, if the milling cutter is directly plunged into the part, it will cause poor chip removal due to the insufficient chip space of the milling cutter, which will cause the part to accumulate a lot of cutting heat, expand and deform, and even Accidents such as knife breakage and knife breakage may occur. The best method is to drill first and then mill, that is, first use a drill bit not smaller than the milling cutter to drill the tool hole, and then use the milling cutter to extend into the tool hole to start milling.
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