01、Layered multiple metalworking method
When there are multiple cavities on aluminum alloy plate parts to be processed, if one cavity is processed one cavity in turn, it is easy to make the cavity wall tangled and deformed due to uneven force. The solution is to take the layered metalworking method, that is, to process all the cavity at the same time, but not a metalworking, but a number of levels, layer by layer metalworking to the required size. In this way, the force of the parts will be more uniform, and the probability of deformation is smaller.
02、Appropriate selection of cutting parameters
Selecting proper cutting parameters can effectively reduce cutting force and cutting heat in the process of cutting. In the process of machining, the cutting quantity is too large to lead to the cutting force of a cutting tool, which is easy to cause the deformation of parts, and the rigidity of the machine tool spindle and the durability of the tool will be affected. In the various elements of cutting parameters, the cutting force is affected by the amount of back cutting tool. Supposedly, reducing the amount of back cutting is beneficial to ensure that the parts do not deform, but at the same time will reduce the metalworking efficiency. CNC machining high speed milling can solve this problem, only need to reduce the amount of back cutting at the same time, increase the feed accordingly, and improve the speed of the machine tool, you can reduce the cutting force, but also to ensure the efficiency of metalworking.
03、Improve the cutting ability of the tool
Tool material, geometric parameters have an important impact on the cutting force, cutting heat, the correct selection of tools, to reduce parts metalworking deformation is very important.
① Reasonable selection of tool geometric parameters.
Front Angle: under the condition of maintaining the strength of the blade, the front Angle is appropriate to choose a larger, on the one hand, can grind out a sharp edge, but also can reduce the cutting deformation, smooth chip removal, and then reduce the cutting force and cutting temperature. Never use a knife with a negative front Angle.
Back Angle: The size of the back Angle has a direct effect on the wear of the back tool surface and the quality of the machined surface. The cutting thickness is an important condition for selecting the back Angle. Rough milling, due to large feed, heavy cutting load, large heat, the requirements of the tool heat dissipation conditions, therefore, the back Angle should be selected smaller. In finishing milling, the cutting edge is required to be sharp, reduce the friction between the tool surface and the machining surface, and reduce the elastic deformation. Therefore, the rear Angle should be selected larger.
Helix Angle: In order to smooth milling and reduce milling force, helix Angle should be selected as large as possible.
Main deflection Angle: Appropriately reducing the main deflection Angle can improve the heat dissipation conditions, so that the average temperature of the metalworking zone will decrease.
② Improve the tool structure.
Reduce the number of cutter teeth and increase the chip space. Due to the large plasticity of aluminum alloy material, large cutting deformation in metalworking, the need for larger chip space, so the bottom radius of the chip groove should be larger, the number of milling cutter teeth is less. For example, the milling cutter below φ20mm adopts two cutter teeth; The milling cutter of φ30 ~ φ60mm is better with three cutter teeth to avoid the deformation of thin-walled aluminum alloy parts caused by chip blockage.
Fine grinding teeth: the roughness value of the cutting edge of the tool teeth should be less than Ra=0.4um. Before using a new knife, a fine whetstone should be used in the front and back of the knife teeth for a few times to eliminate residual burrs and slight serrated lines when sharpening the knife teeth. In this way, not only can reduce the cutting heat and cutting deformation is relatively small.
Strictly control the tool wear standard: After the tool wear, the workpiece surface roughness value increases, the cutting temperature rises, the workpiece deformation increases. Therefore, in addition to the selection of tool materials with good wear resistance, the tool wear standard should not be greater than 0.2mm, otherwise it is easy to produce debris nodules. When cutting, the workpiece temperature generally do not exceed 100℃, in order to prevent deformation.
04、Pay attention to the order of cutting
Rough and finish machining should use a different cutting sequence. Rough machining requires to cut the excess material on the blank surface in a short time at a fast cutting speed to form the geometric profile required for finishing. Therefore, the emphasis is on machining efficiency, the pursuit of material removal rate per unit time, should be used in reverse milling. And the finishing to the machining precision and surface quality requirements more adjust the machining quality, should be used down milling. Because the cutting thickness of the cutter teeth gradually decreases to zero during the down milling process, the work hardening phenomenon will be reduced, and the deformation of the parts will be inhibited to a certain extent.
05、The thin-walled parts are pressed twice
When metalworking aluminum alloy thin-walled parts, the clamping force is also an important cause of deformation, which is inevitable even if the machining accuracy is improved. In order to reduce the deformation of the workpiece due to clamping, the pressed parts can be loosened to release the pressing force before the finishing reaches the size, so that the parts can be freely restored to the original state, and then slightly pressed again. The operation point of the secondary pressing is on the supporting surface, and the clamping force should act in the direction of good rigidity of the workpiece. The size of the clamping force should be based on the strength of the clamping workpiece without loosening, which has high requirements on the experience and hand feel of the operator. The compression deformation of the parts processed in this way is small.
06、Drilling and milling machining method
In the metalworking of parts with cavity, if the milling cutter directly down into the parts will cause poor chip removal because of the lack of cutting-containing space of the milling cutter, which leads to the accumulation of a lot of cutting heat, and the expansion of deformation, and even may cause the collapse of the knife, broken knife and other accidents. The method is to drill before milling, that is, to drill the cutter hole with a drill bit no smaller than the size of the milling cutter, and then use the milling cutter to reach into the cutter hole to start milling, which can effectively solve the problems mentioned above.
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