Aluminum parts processing deformation of many reasons, and material, parts shape, production conditions have a relationship. Mainly the following aspects: rough deformation caused by the blank, cutting force, cutting heat caused by deformation, clamping force caused by deformation.
To reduce the processing of deformation of the process measures
1 to reduce the internal stress of the blank
With natural or artificial aging and vibration treatment, can be part of the blank to eliminate the internal stress. Pre-processing is also an effective process. On the fat head of the rough, due to the margin, so after processing deformation is also large. If the excess part of the blank is machined in advance, the margin of each part is reduced, not only the processing deformation of the subsequent process can be reduced, but also a part of the internal stress can be released after being pre-processed for a period of time.
2 to improve the cutting capacity of the tool
Tool material, geometric parameters on the cutting force, cutting heat has an important impact, the correct choice of tools, to reduce the deformation of parts is essential.
(1) a reasonable choice of tool geometry parameters.
① front angle: to maintain the strength of the blade under the conditions of the rake angle appropriate to choose a larger, on the one hand can wear a sharp edge, the other can reduce the cutting deformation, so that chip removal, and thus reduce the cutting force and cutting temperature. Avoid using negative rake tool.
② rear angle: the size of the horn on the flank wear and processing surface quality has a direct impact. Cutting thickness is an important condition for selecting the rear corner. Roughing, due to the large feed, cutting load weight, heat a large amount of requirements, the tool cooling conditions are good, so the horn should be selected smaller. Fine milling, the requirements of sharp edges, reduce the flank face and the processing of the surface friction, reduce the elastic deformation, therefore, after the choice of larger.
③ helix angle: In order to make the milling smooth, reduce the milling force, the helix angle should be selected as much as possible.
④ main declination: appropriate to reduce the main declination can improve the cooling conditions, so that the average temperature of the processing area.
(2) to improve the tool structure.
① reduce the number of milling cutter, increase the chip space. As the aluminum material plasticity larger, large deformation in the processing of cutting, the need for larger chip space, so the bottom of the tank should be a large radius, the number of milling cutter less.
② fine grinding teeth. The roughness value of the cutting edge of the knife is less than Ra = 0.4um. Before using the new knife, you should use fine stone in the knife before the teeth, gently grinding a few times to eliminate the blade when the teeth of the remaining burrs and slightly sawtooth. In this way, not only can reduce the cutting heat and cutting deformation is relatively small.
③ strict control of the tool wear standards. After the tool wear, the workpiece surface roughness value increases, the cutting temperature increases, the workpiece deformation increases. Therefore, in addition to the use of good wear resistance of the tool material, the tool wear standards should not be greater than 0.2mm, or prone to BUE. Cutting, the workpiece temperature is generally not more than 100 ℃, to prevent deformation.
3 to improve the workpiece clamping method
For less rigid thin-walled aluminum parts, the following clamping method can be used to reduce deformation:
① For thin-walled bushing parts, if you use a three-jaw self-centering chuck or spring chuck to clamp from the radial, once the work is released, the workpiece must be deformed. At this point, should be used to improve the rigidity of the axial end of the method of compression. To the parts of the hole positioning, made a threaded thread through the mandrel, into the parts of the hole, with a cover on the end of its face and then tighten the nut tight. Machining the outer circumference can avoid clamping deformation, so as to obtain satisfactory machining accuracy.
② the thin-walled sheet workpiece processing, the best choice of vacuum sucker, in order to obtain uniform distribution of clamping force, and then a smaller amount of cutting to the processing, can be very good to prevent deformation of the workpiece.
In addition, you can also use the packing method. In order to increase the rigidity of the thin-walled workpiece, the medium can be filled with the medium to reduce the workpiece during the clamping and cutting process. For example, to the workpiece filled with 3% to 6% potassium nitrate urea melt, after processing, the workpiece immersed in water or alcohol, the filler can be dissolved and poured out.
4 reasonable arrangements for the process
High-speed cutting, due to large processing margin and intermittent cutting, so the milling process often produce vibration, affecting the processing accuracy and surface roughness. Therefore, the NC high-speed machining process can be divided into: rough processing - semi-finishing - Qing angle processing - finishing and other processes. For parts with high precision requirements, it is sometimes necessary to perform secondary semi-finishing and then finish the finishing. After roughing, the parts can be naturally cooled to eliminate the internal stress generated by roughing and reduce the deformation. Rough after leaving the margin should be greater than the amount of deformation, usually 1 ~ 2mm. Finishing, the parts of the finishing surface to maintain a uniform processing margin, generally 0.2 ~ 0.5mm is appropriate, so that the tool in the processing process in a stable state, can greatly reduce the cutting deformation, access to good surface processing quality, to ensure that Product accuracy.