1, Process measures to reduce processing deformation
1. Reduce the internal stress of the blank

2. Improving the cutting ability of cutting tools

1) Reasonably select the geometric parameters of the cutting tool.




2) Improve tool structure.

② Fine grinding of blade teeth. The roughness value of the cutting edge of the cutter teeth should be less than Ra=0.4um. Before using a new knife, a fine oilstone should be used to gently grind the front and back of the blade teeth a few times to eliminate any remaining burrs and slight serrations when grinding the blade teeth. In this way, not only can cutting heat be reduced, but cutting deformation is also relatively small.
③ Strictly control the wear standards of cutting tools. After tool wear, the surface roughness value of the workpiece increases, the cutting temperature rises, and the deformation of the workpiece increases accordingly. Therefore, in addition to selecting tool materials with good wear resistance, the tool wear standard should not exceed 0.2mm, otherwise it is easy to produce chip deposits. During cutting, the temperature of the workpiece should generally not exceed 100 degree to prevent deformation.
3. Improving the clamping method of workpieces
For thin-walled aluminum parts with poor rigidity, the following clamping methods can be used to reduce deformation:
① For thin-walled liner parts, if a three jaw self centering chuck or spring chuck is used to clamp radially, once loosened after processing, the workpiece will inevitably deform. At this point, the method of compressing the axial end face with good rigidity should be used. Using the internal hole of the part for positioning, make a threaded through shaft and insert it into the internal hole of the part. Use a cover plate to press the end face tightly and then tighten it with a nut. When processing the outer circle, clamping deformation can be avoided, thus achieving satisfactory machining accuracy.
② When processing thin-walled thin plate workpieces, it is best to use vacuum suction cups to obtain evenly distributed clamping force, and then use smaller cutting amounts to process, which can effectively prevent workpiece deformation.
Additionally, the stuffing method can also be used. To increase the process rigidity of thin-walled workpieces, media can be filled inside the workpiece to reduce deformation during clamping and cutting processes. For example, injecting urea melt containing 3% to 6% potassium nitrate into the workpiece, and after processing, immersing the workpiece in water or alcohol can dissolve and pour out the filler.
4. Reasonably arrange the process
During high-speed cutting, due to large machining allowance and intermittent cutting, the milling process often generates vibration, which affects machining accuracy and surface roughness. Therefore, the CNC high-speed cutting process can generally be divided into rough machining, semi precision machining, corner cleaning machining, precision machining and other processes. For parts with high precision requirements, sometimes secondary semi precision machining is required, followed by precision machining. After rough machining, the parts can be naturally cooled to eliminate the internal stress generated by rough machining and reduce deformation. The margin left after rough machining should be greater than the deformation, generally 1-2mm. During precision machining, the surface of the parts should maintain a uniform machining allowance, generally ranging from 0.2 to 0.5mm, to keep the cutting tool in a stable state during the machining process. This can greatly reduce cutting deformation, achieve good surface machining quality, and ensure the accuracy of the product.
2, Operational skills for reducing machining deformation

1. For parts with large machining allowance, in order to have better heat dissipation conditions during the machining process and avoid heat concentration, symmetrical machining should be used during machining. If there is a 90mm thick sheet metal that needs to be machined to 60mm, if one side is milled and the other side is milled immediately, and the flatness reaches 5mm when machining to the final size in one go; If repeated feed symmetric machining is used, each side is machined twice to the final size, ensuring a flatness of 0.3mm.
2. If there are multiple cavities on the sheet metal part, it is not advisable to use the sequential processing method of one cavity for each cavity during processing, as this can easily cause uneven stress on the part and deformation. Adopting multiple layers of processing, each layer is processed simultaneously to all cavities as much as possible, and then the next layer is processed to make the parts uniformly stressed and reduce deformation.
3. Reduce cutting force and cutting heat by changing the cutting amount. Among the three elements of cutting parameters, the back feed has a significant impact on cutting force. If the machining allowance is too large and the cutting force of a single pass is too large, it will not only cause deformation of the parts, but also affect the rigidity of the machine tool spindle and reduce the durability of the tool. If the amount of back cutting is reduced, it will greatly reduce production efficiency. However, high-speed milling is commonly used in CNC machining to overcome this challenge. While reducing the amount of back cutting, as long as the feed rate is correspondingly increased and the machine speed is increased, the cutting force can be reduced while ensuring machining efficiency.
4. The order of cutting also needs to be carefully considered. Rough machining emphasizes improving machining efficiency and pursuing a cutting rate per unit time. Generally, reverse milling can be used. Cut off excess material on the surface of the blank at the fastest speed and in the shortest time possible, and basically form the geometric contour required for precision machining. Precision machining emphasizes high precision and quality, and it is advisable to use forward milling. Because the cutting thickness of the cutter teeth gradually decreases from maximum to zero during forward milling, the degree of work hardening is greatly reduced, while also reducing the degree of deformation of the parts.
5. Thin walled workpieces undergo deformation during machining due to clamping, which is difficult to avoid even during precision machining. To minimize the deformation of the workpiece, the clamping part can be loosened before the final size is reached during precision machining, allowing the workpiece to freely return to its original state. Then, it can be slightly tightened to ensure that the workpiece is firmly clamped (completely based on hand feel), which can achieve the desired machining effect. In short, it is best for the clamping force to act on the supporting surface, and the clamping force should act in the direction of good workpiece rigidity. On the premise of ensuring that the workpiece is not loose, the smaller the clamping force, the better.
6. When processing parts with a cavity, it is advisable not to let the milling cutter directly penetrate the part like a drill bit, resulting in insufficient chip space for the milling cutter, unsmooth chip removal, overheating, expansion, tool breakage, and other adverse phenomena. First, use a drill bit of the same size or one size larger than the milling cutter to drill the tool hole, and then use the milling cutter to mill it. Alternatively, CAM software can be used to produce spiral cutting programs.