Correct use of CNC end mills

When milling complex workpieces on the milling center, the following problems should be noted in the use of CNC end mills: 1. The end mills for end mills are mostly spring clip clamps, which are in cantilever state. During the milling process, sometimes the end mill may gradually protrude from the tool holder or even fall completely, causing the workpiece to be scrapped. The reason is generally because the inner hole of the tool holder and the outer diameter of the end mill shank are between There is an oil film, resulting in insufficient clamping force. End mills are usually coated with anti-rust oil when they are shipped out. If non-water-soluble cutting oil is used for cutting, the inner hole of the tool holder will also adhere to a misty oil film. When there is oil film on the tool holder and the tool holder, the tool holder It is difficult to firmly clamp the shank, and the end mill is easy to loosen and fall during machining. Therefore, before the end mill is clamped, the end of the end mill and the inner hole of the tool holder should be cleaned with a cleaning solution, and then dried before being clamped. When the diameter of the end mill is large, even if the shank and the tool holder are clean, a knife-off accident may occur. In this case, a shank with a flattened notch and a corresponding side locking method should be used. Another problem that may arise after the end mill is clamped is that the machined neutral cutter breaks at the tool holder port. The reason is generally because the tool holder has been used for too long and the tool holder port has been worn into a tapered shape. The vibration of the knife is due to the slight gap between the end mill and the holder, so the knife may vibrate during machining. The vibration will make the circumferential cutting edge of the end mill uneven, and the amount of cut and enlargement will increase than the original value, which will affect the machining accuracy and tool life. However, when the width of the groove is small, the tool can be purposefully vibrated, and the required groove width can be obtained by increasing the amount of cut, but in this case, the maximum amplitude of the end mill should be limited to 0.02 mm or less. Otherwise, stable cutting is not possible. The smaller the vibration of the end mill in normal machining, the better. When tool vibration occurs, consider reducing the cutting speed and feed rate. If there is still a large vibration after both have been reduced by 40%, you should consider reducing the amount of knife. If the resonance occurs in the processing system, the cause may be due to excessive cutting speed, small feed speed, insufficient rigidity of the tool system, insufficient workpiece clamping force, and workpiece shape or workpiece clamping method. Measures such as increasing the amount of the tool system, increasing the feed rate, and increasing the feed rate. 3. The end cutting of the end mill is cut in the numerical control milling of the workpiece cavity such as the mold. When the cut point is a concave part or a deep cavity, the extension amount of the end mill needs to be lengthened. If a long-edge end mill is used, it is easy to generate vibration and cause tool breakage due to the large deflection of the tool. Therefore, in the process of machining, if only the cutting edge near the end of the tool is required to take part in the cutting, it is better to use a short-blade long-shank type end mill with a long total tool length. When machining a workpiece with a large-diameter end mill on a horizontal CNC machine tool, due to the large deformation caused by the tool's own weight, more attention should be paid to the problem that the end edge cutting is prone to occur. In the case where a long edge end mill must be used, the cutting speed and feed rate must be greatly reduced. 4. Selection of cutting parameters The choice of cutting speed depends mainly on the material of the workpiece to be machined; the choice of feed speed depends mainly on the material of the workpiece to be machined and the diameter of the end mill. Tool samples from some foreign tool manufacturers are attached with a tool cutting parameter selection table for reference. However, the selection of cutting parameters is affected by many factors such as the machine tool, the tool system, the shape of the workpiece to be machined, and the clamping method. The cutting speed and feed rate should be adjusted according to the actual situation. When the tool life is a priority, the cutting speed and the feed rate can be appropriately reduced; when the cutting edge of the chip is not good, the cutting speed can be appropriately increased. 5. The choice of cutting method adopts down-cut milling to prevent the blade from being damaged and improve the tool life. However, there are two points to note: 1 If using ordinary machine tools, try to eliminate the gap of the feed mechanism; 2 When the surface of the workpiece remains with an oxide film or other hardened layer formed by casting or forging, it is advisable to use up-cut milling. 6. The use of carbide end mills The use range and use requirements of high-speed steel end mills are relatively wide, even if the selection of cutting conditions is slightly inappropriate, there will not be too much problem. While the carbide end mill has good wear resistance during high-speed cutting, it is not used in a wide range of high-speed steel end mills, and the cutting conditions must strictly meet the requirements of the tool.

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