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September 3, 2019
Many reasons cause aluminium parts deformation, which are related to the material quality, the parts shape and the production conditions.
There are 3mainly reasons:
Technological Measures for Reducing Aluminum Deformation .
The internal stress of rought part can be partly eliminated by natural or artificial aging and vibration treatment. Pre-processing is also an effective process. For big rough aluminum part, the deformation after machining is also large. If cut the extra aluminum material from rought part, get precise tolerance the deformation can be improved. Also a part of internal stress can be released after stay for a period of time.
Material and geometric parameters of cutting tools have an important influence on cutting force and heat. Correct selection of cutting tools is very important to reduce machining deformation of parts.
For Thin-walled Aluminium workpieces with poor rigidity, the following clamping methods can be used to reduce deformation:
aluminum machined part
In high-speed cutting, because of large machining allowance and intermittent cutting, milling process often produces vibration, which affects the processing accuracy and surface roughness. Therefore, the NC high-speed cutting process can be generally divided into roughing, semi-finishing, angle clearing and finishing processes. For parts requiring high precision, it is sometimes necessary to finish them twice and half, and then finish them. After rough machining, the parts can be cooled naturally to eliminate the internal stress and reduce the deformation. The allowance left after roughing should be greater than the deformation, generally 1-2 mm. When finishing, the surface of parts should be kept uniform. Generally, 0.2-0.5mm is the best way to keep the tool in a stable state during the process of finishing, which can greatly reduce the cutting deformation, obtain good surface processing quality and ensure the accuracy of the product.
Except the above reasons, the operation method is also very important in the actual operation.
In order to make them have better heat dissipation conditions and avoid heat concentration in machining, symmetrical processing should be adopted. If a 90 mm thick sheet needs to be processed to 60 mm, if the other side is milling immediately after milling one side, and the flatness reaches 5 mm once to the final dimension. If the repeated feed symmetrical processing is used, each side is processed to the final dimension twice, the flatness can be guaranteed to reach 0.3 mm.
The sequential processing method of one cavity and one cavity should not be adopted in the processing, which is easy to cause uneven force and deformation of the parts. Layered multi-processing is adopted, each layer is machined to all the cavity at the same time, and then the next layer is machined, so that the parts are uniformly stressed and the deformation is reduced.
Among the three factors of cutting parameters, back feed has a great influence on cutting force. If the machining allowance is too large and the cutting force of the tool is too large. Not only will the parts be deformed, but also will affect the rigidity of the machine tool spindle and reduce the tool durability. If we reduce the amount of knives eaten by the back, the production efficiency will be greatly reduced. However, high-speed milling can overcome this problem in NC machining. At the same time, the cutting force can be reduced and the processing efficiency can be guaranteed as long as the feed is increased correspondingly and the speed of the machine tool is increased.
Rough milling emphasizes the improvement of processing efficiency and the pursuit of cutting rate per unit time. Reverse milling can be generally used. That is to say, the superfluous material on the surface of the blank is removed at the fastest speed and in the shortest time, and the geometric contour required for finishing is basically formed. Precision machining emphasizes high precision and high quality, and it is advisable to use forward milling. Because the cutting thickness of the cutter teeth decreases gradually from the maximum to zero, the degree of work hardening is greatly reduced, and the degree of deformation of the parts is also reduced.
In order to minimize the deformation of the workpiece, it is possible to loosen the pressing part before finishing is about to reach the final dimension, so that the workpiece can be freely restored to its original state, and then slightly compressed, whichever is rigid enough to hold the workpiece (completely by hand), so as to achieve the desired processing effect. In a word, the point of action of clamping force is best on the supporting surface. The clamping force should be applied in the direction of good rigidity of the workpiece. The smaller the clamping force, the better, on the premise of ensuring that the workpiece is not loose.
When machining the parts with cavity, try not to let the milling cutter penetrate directly into the parts like a drill bit, resulting in inadequate chip space and unsmooth chip removal of the milling cutter, resulting in overheating, expansion of the parts, tool breaking and other adverse phenomena. First drill the hole with a bit of the same size or size as the milling cutter, and then milling with the milling cutter. Alternatively, the spiral downcutter program can be produced with CAM software.
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