When milling complex workpieces on a CNC machining center, the following points should be noted when installing and using CNC end mills:

1. Installation of CNC end mill

Most end mills used in CNC machining centers are clamped by spring clamps and are in a cantilever state when used. 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 is between the outer diameter of the end mill shank. There is an oil film between the parts, resulting in insufficient clamping force. End mills usually come with anti-rust oil when they leave the factory. If non-water-soluble cutting oil is used during cutting, a mist-like oil film will also adhere to the inner hole of the tool holder. When there is an oil film on both the CNC tool holder and the tool holder, the tool It is difficult for the clamp to firmly clamp the tool holder, and the end mill can easily loosen and fall off during machining. Therefore, before clamping the end mill, the end mill handle and the inner hole of the tool holder should be cleaned with cleaning fluid and dried before clamping.

When the diameter of the end mill is large, even if the tool holder and tool holder are clean, a tool drop accident may still occur. In this case, a tool holder with a flat notch and a 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 holder port. The reason is generally that the tool holder has been used for too long and the tool holder port has been worn into a tapered shape. At this time, it should be Replace the tool holder with a new one.

2. Vibration of CNC end mills

Since there is a small gap between the end mill and the tool holder, the CNC tool may vibrate during the machining process. Vibration will make the cutting amount of the end mill's circumferential edge uneven, and the cutting expansion amount will increase than the original value, affecting the machining accuracy and tool service life. However, when the width of the processed groove is too small, the tool can also be vibrated purposefully to obtain the required groove width by increasing the cutting expansion amount. However, in this case, the maximum amplitude of the end mill should be limited to less than 0.02mm. , otherwise stable cutting cannot be performed. The smaller the vibration of the end mill during normal machining, the better.

When tool vibration occurs, you should consider reducing the cutting speed and feed speed. If there is still large vibration after both have been reduced by 40%, you should consider reducing the amount of tool engagement.

If resonance occurs in the machining system, the reason may be due to factors such as excessive cutting speed, low feed speed, insufficient rigidity of the tool system, insufficient workpiece clamping force, workpiece shape or workpiece clamping method. At this time, adjustments should be made to the cutting Measures such as dosage, increasing the stiffness of the CNC tool system, and increasing the feed speed.

3. End cutting of CNC end mills

In CNC milling of workpiece cavities such as molds, when the cut point is a concave part or a deep cavity, the extension of the end mill needs to be lengthened. If a long-edged end mill is used, due to the large deflection of the CNC tool, it is easy to vibrate and cause the CNC tool to break. Therefore, during the machining process, if only the cutting edge near the end of the CNC tool is required to participate in cutting, it is best to use a short-edge, long-shank end mill with a longer total length of CNC tool. When using large-diameter end mills to process workpieces on horizontal CNC machine tools, due to the large deformation caused by the tool's own weight, more attention should be paid to the problems that are prone to occur in end-edge cutting. When a long-blade end mill must be used, the cutting speed and feed rate need to be significantly reduced.

4. Selection of cutting parameters

The selection of cutting speed mainly depends on the material of the workpiece to be processed; the selection of feed speed mainly depends on the material of the workpiece to be processed and the diameter of the end mill. Tool samples from some foreign tool manufacturers include CNC tool cutting parameter selection tables for reference. However, the selection of cutting parameters is also affected by many factors such as machine tools, CNC tool systems, shape of the workpiece to be processed, and clamping methods. The cutting speed and feed speed should be appropriately adjusted according to the actual situation.

When the life of the CNC tool is the priority, the cutting speed and feed speed can be appropriately reduced; when the chip separation condition is not good, the cutting speed can be appropriately increased.

5. Selection of cutting method

The use of down milling can help prevent blade damage and improve the life of CNC tools. However, there are two points to note: ① If ordinary machine tools are used for processing, efforts should be made to eliminate the gap in the feed mechanism; ② When there is an oxide film or other hardened layer formed by the casting or forging process remaining on the surface of the workpiece, reverse milling should be used.