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Cnc Machining Aluminum Prototype

The equipment that can be used in the machining of industrial aluminum profiles includes cnc machining equipment and CNC equipment, which can realize deep machining operations such as cutting, drilling, tapping, and slot milling. Many aluminum profile manufacturers can process aluminum profiles, but they do not necessarily use CNC equipment. Because the CNC equipment occupies a relatively large area, it needs professional personnel to control it, which will undoubtedly increase the cost investment for small enterprises. However, if you want high-precision machining, you must use CNC equipment, which can ensure that the error is within the smallest range.

CNC machine tool is an automatic machine tool equipped with a degree control system. Usually there are CNC machining machine tools, CNC machining milling machines, CNC machining boring and milling machines, etc. CNC machining of aluminum profiles is a new machining technology. Its advantage lies in that the precision of the processed aluminum profile parts is quite high, and the surface gloss is bright, which can meet the requirements of most enterprises for the precision of aluminum profiles, and can improve the machining efficiency of aluminum profile manufacturers. efficiency in the process, as well as reducing the defect rate, saving production costs and shortening the delivery time.

1. Process measures to reduce machining deformation

1Reduce the internal stress of the blank

Natural or artificial aging and vibration treatment can partially eliminate the internal stress of the blank. Pre-machining is also an effective process method. For the blank with fat head and big ears, due to the large allowance, the deformation after machining is also large. If the excess part of the blank is pre-processed and the allowance of each part is reduced, it can not only reduce the machining deformation of the subsequent process, but also release a part of the internal stress after pre-machining for a period of time.

2Improve the cutting ability of the tool

The material and geometric parameters of the tool have an important influence on the cutting force and cutting heat. The correct selection of the tool is very important to reduce the machining deformation of the part.

(1) Reasonable selection of tool geometric parameters.

Rake angle: Under the condition of maintaining the strength of the blade, the rake angle is appropriately selected to be larger, on the one hand, a sharp edge can be ground, and on the other hand, the cutting deformation can be reduced, the chip removal can be smooth, and the cutting force and cutting temperature can be reduced. Never use tools with negative rake angle.
Relief angle: The size of the relief angle has a direct impact on the wear of the flank and the quality of the machined surface. The cutting thickness is an important condition for selecting the clearance angle. During rough milling, due to the large feed rate, heavy cutting load, and large heat generation, the tool requires good heat dissipation conditions. Therefore, the clearance angle should be selected to be smaller. When fine milling, the cutting edge is required to be sharp, the friction between the flank face and the machined surface is reduced, and the elastic deformation is reduced. Therefore, the clearance angle should be larger.

Helix angle: In order to make the milling smooth and reduce the milling force, the helix angle should be as large as possible.
Main declination angle: Properly reducing the main declination angle can improve the heat dissipation conditions and reduce the average temperature of the machining area.

(2) Improve the tool structure.

Reduce the number of milling cutter teeth and increase the chip space. Due to the large plasticity of the machining aluminum material and the large cutting deformation during machining, a large chip space is required, so the bottom radius of the chip groove should be large and the number of milling cutter teeth should be small.
Finely ground teeth. The roughness value of the cutting edge of the cutter teeth should be less than Ra=0.4um. Before using a new knife, you should use a fine oil stone to lightly sharpen the front and back of the knife teeth a few times to eliminate the burrs and slight serrations left when sharpening the teeth. In this way, not only can the cutting heat be reduced, but also the cutting deformation is relatively small.

Strictly control the wear standard of the tool. After the tool is worn, the surface roughness value of the workpiece increases, the cutting temperature rises, and 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 built-up edge. When cutting, the temperature of the workpiece should generally not exceed 100 ℃ to prevent deformation.

3Improve the clamping method of workpieces

For thin-walled aluminum workpieces with poor rigidity, the following clamping methods can be used to reduce deformation:
For thin-walled bushing parts, if the three-jaw self-centering chuck or spring chuck is used for radial clamping, once it is released after machining, the workpiece will inevitably deform. At this time, the method of pressing the axial end face with better rigidity should be used. Position the inner hole of the part, make a threaded mandrel, insert it into the inner hole of the part, press the end face with a cover plate on it, and then tighten it with a nut. When machining the outer circle, clamping deformation can be avoided, so as to obtain satisfactory machining accuracy.
When machining thin-walled and thin-plate workpieces, it is best to use vacuum suction cups to obtain evenly distributed clamping force, and then process with a small amount of cutting, which can well prevent workpiece deformation.

In addition, the packing method can also be used. In order to increase the process rigidity of thin-walled workpieces, a medium can be filled inside the workpiece to reduce the deformation of the workpiece during clamping and cutting. For example, urea melt containing 3% to 6% potassium nitrate is poured into the workpiece. After machining, the workpiece can be immersed in water or alcohol, and the filler can be dissolved and poured out.

4Reasonable arrangement of processes

During high-speed cutting, due to the large machining allowance and interrupted cutting, the milling process often generates vibration, which affects the machining accuracy and surface roughness. Therefore, the CNC high-speed cutting process can generally be divided into: roughing-semi-finishing-corner-clearing-finishing and other processes. For parts with high precision requirements, it is sometimes necessary to perform secondary semi-finishing and then finishing. After rough machining, the parts can be cooled naturally, eliminating the internal stress caused by rough machining and reducing deformation. The allowance left after rough machining should be greater than the deformation, generally 1 to 2 mm. During finishing, the finishing surface of the parts should maintain a uniform machining allowance, generally 0.2 ~ 0.5mm, so that the tool is in a stable state during the machining process, which can greatly reduce cutting deformation, obtain good surface machining quality, and ensure Product accuracy.

The operation skills to reduce the machining deformation

In addition to the above reasons, the parts of aluminum parts are deformed during machining. In actual operation, the operation method is also very important.

  1. For parts with large machining allowance, in order to make them have better heat dissipation conditions during the machining process and avoid heat concentration, symmetrical machining should be adopted during machining. If a 90mm thick sheet needs to be processed to 60mm, if one side is milled and the other side is milled immediately, and the final size is processed at one time, the flatness will reach 5mm; if it is symmetrically processed by repeated feeding, each side is processed twice to The final dimension can guarantee a flatness of 0.3mm.
  2. If there are multiple cavities on the plate parts, it is not suitable to use the sequential machining method of one cavity and one cavity during machining, which will easily cause the parts to be deformed due to uneven stress. Multi-layer machining is adopted, and each layer is processed to all the cavities at the same time, and then the next layer is processed to make the parts evenly stressed and reduce deformation.
  3. Reduce the cutting force and cutting heat by changing the cutting amount. Among the three elements of laser cutting amount, the amount of back-engagement has a great influence on the cutting force. If the machining allowance is too large, the cutting force of one pass is too large, which will not only deform the parts, but also affect the rigidity of the machine tool spindle and reduce the durability of the tool. If the amount of knives to be eaten by the back is reduced, the production efficiency will be greatly reduced. However, high-speed milling is used in CNC machining, which can overcome this problem. While reducing the amount of back cutting, as long as the feed is increased accordingly and the speed of the machine tool is increased, the cutting force can be reduced and the machining efficiency can be ensured at the same time.
  4. The order of knife moves should also be paid attention to. Rough machining emphasizes improving machining efficiency and pursuing the removal rate per unit time. Generally, up-cut milling can be used. That is, the excess material on the surface of the blank is removed at the fastest speed and the shortest time, and the geometric contour required for finishing is basically formed. While finishing emphasizes high precision and high quality, it is advisable to use down milling. Because the cutting thickness of the cutter teeth gradually decreases from the maximum to zero during down milling, the degree of work hardening is greatly reduced, and the degree of deformation of the part is also reduced.
  5. Thin-walled workpieces are deformed due to clamping during machining, and even finishing is unavoidable. In order to reduce the deformation of the workpiece to a minimum, just before the finishing is about to reach the final size, loosen the pressing piece to make the workpiece free to return to its original state, and then press it slightly, as long as the workpiece can just be clamped (completely). According to the hand feel), so that the ideal machining effect can be obtained. In a word, the action point of the clamping force is preferably on the supporting surface, and the clamping force should be applied in the direction of good rigidity of the workpiece. On the premise of ensuring that the workpiece is not loose, the smaller the clamping force, the better.
  6. When machining parts with a cavity, try not to let the milling cutter plunge directly into the part like a drill when machining the cavity, resulting in insufficient space for the cnc milling cutter to accommodate chips and poor chip removal, resulting in overheating, expansion and collapse of the parts. Knives, broken knives and other unfavorable phenomena. First drill the hole with a drill of the same size as the milling cutter or one size larger, and then mill it with the milling cutter. Alternatively, CAM software can be used to produce helical rundown programs.
    The main factor affecting the machining accuracy and surface quality of aluminum parts is that such parts are prone to deformation during the machining process, which requires the operator to have certain operating experience and skills.