When milling complex workpieces on the milling machining center, the use of CNC end mills should pay attention to the following issues.
1. Clamping of end mills: Most of the end mills used in machining centers are clamped in a spring clamp set and are in a cantilevered state when in use. In the milling process, sometimes the end mill may gradually extend from the tool holder, or even completely fall off, resulting in the scrapping of the workpiece, which is generally due to the presence of oil film between the inner hole of the tool holder and the outer diameter of the shank of the end mill, resulting in insufficient clamping force. End mill cutters are usually coated with anti-rust oil, if cutting with non-water-soluble cutting oil, the inner hole of the tool holder will also be attached to a layer of foggy oil film, when the shank and the tool holder are on the oil film, the tool holder is difficult to firmly clamp the shank, in the processing of the end mill cutter is easy to loosen and fall off. Therefore, before clamping the end mill, the shank of the end mill and the inner hole of the tool holder should be cleaned with cleaning liquid and dried before clamping. When the diameter of the end mill is large, even if the shank and the tool holder are clean, it may still happen that the tool is dropped, then the shank with the cutting notch and the corresponding side locking method should be used. Another problem that may occur after the end mill is clamped is that the end mill is broken at the tool clamp port during processing, the reason is generally because the tool clamp has been used for too long, the tool clamp port has worn into a cone.
2. Vibration of the end mill: Because there is a small gap between the end mill and the tool holder, the tool has the possibility of vibration during the machining process. Vibration will make the end mill circumferential edge of the eating amount is not uniform, and the cutting expansion than the original value increases, affecting the machining accuracy and tool life. However, when the groove width is small, it is possible to make the tool vibrate purposely to obtain the required groove width by increasing the cutting and expanding volume, but the maximum amplitude of the end mill should be limited to less than 0.02mm in this case, otherwise stable cutting cannot be carried out. The smaller the vibration of the end mill in normal machining, the better. When the tool vibration occurs, consider reducing the cutting speed and feed rate, if both have been reduced by 40% there is still a large vibration, then consider reducing the amount of tool eating. If resonance occurs in the machining system, the reason may be that the cutting speed is too large, the feed rate is small, the tool system is not rigid enough, the workpiece clamping force is not enough and the shape of the workpiece or the workpiece clamping method, etc. At this time, measures should be taken to adjust the cutting amount, increase the rigidity of the tool system, and improve the feed rate.
3. End mill end-edge cutting in the mold and other workpiece cavity CNC milling processing, when the cutting point for the lower concave part or deep cavity, the need to extend the end mill extension. If a long end mill is used, the deflection of the tool will cause vibration and tool breakage. Therefore, in the process of machining, if only the cutting edge near the end of the tool is required to participate in the cutting, it is best to use a short-edge long-shank end mill with a longer total tool length. In horizontal CNC machine tools using large diameter end mills when processing the workpiece, due to the deformation generated by the weight of the tool is larger, more attention should be paid to the end of the cutting edge is prone to problems. In the case of a long-edge end mill must be used, it is necessary to significantly reduce the cutting speed and feed rate.
4. The choice of cutting parameters: the choice of cutting speed depends mainly on the material of the workpiece being machined; the choice of feed rate depends mainly on the material of the workpiece being machined and the diameter of the end mill. But the choice of cutting parameters at the same time by the machine tool, tool system, the shape of the machined workpiece and clamping method and other factors, should be adjusted according to the actual situation of the appropriate cutting speed and feed rate. When the tool life as a priority factor, can be appropriate to reduce the cutting speed and feed rate; when the chip off-edge condition is not good, it can be appropriate to increase the cutting speed.
5. The choice of cutting mode: the use of smooth milling is conducive to preventing damage to the cutting edge, which can improve the tool life. But there are two points need to pay attention to: ① such as the use of ordinary machine tool processing, should try to eliminate the clearance of the feed mechanism; ② when the workpiece surface residual casting, forging process formed by the oxide film or other hardening layer, it is appropriate to use the reverse milling.
6. The use of carbide end mills: the use of high-speed steel end mills and the use of the requirements of a broader range, even if the cutting conditions are slightly improper selection, it is not too big a problem. While carbide end mills have good wear resistance when cutting at high speed, but its range of use is not as wide as that of HSS end mills, and the cutting conditions must be strictly in line with the requirements of the tool.
Post time: Aug-19-2021