Clamping of the milling cutter
Most of the milling cutters used in machining centers are clamped in a spring clamp set and are in a cantilever shape when used. In the process of milling, sometimes the milling cutter may gradually stretch out from the tool holder, so that the whole is lost, so that the workpiece is scrapped, and the reason is generally due to the oil film stored between the inner hole of the tool holder and the outer diameter of the milling cutter handle, and the clamping force is not enough. The milling cutter is generally coated with anti-rust oil when leaving the factory, if the non-water-soluble cutting oil is used during cutting, the inner hole of the tool holder will also be attached to a layer of mist oil film, when the tool holder and the tool holder are stored in the oil film, the tool holder is difficult to clamp the tool holder firmly, and the milling cutter is loosened and lost during processing. Therefore, before the milling cutter is clamped, the milling cutter shank and the inner hole of the cutter holder should be cleaned with cleaning solution, and then clamped after drying.
When the diameter of the milling cutter is large, even if the shank and cartridge are clean, there is still a possibility of missing tools, in which case the shank with the notched and the corresponding side locking method should be used.
Another problem that may occur after the milling cutter is clamped is that the milling cutter is broken at the cartridge port during machining, and the reason is generally due to the cartridge being used for too long, and the cartridge port has been worn into a conical shape, so the new cartridge should be replaced at this time.
Vibration of the milling cutter
Since there is a small gap between the milling cutter and the tool holder, there is a possibility that the tool may vibrate during machining. The vibration will make the eating amount of the circumferential edge of the milling cutter uneven, and the cutting expansion amount will be larger than the original value, which will affect the machining accuracy and tool service life. However, when the groove width is small, the tool can be purposefully vibrated to obtain the required groove width by increasing the cutting expansion, but in this case, the maximum amplitude of the milling cutter should be below 0.02mm, otherwise stable cutting can not be carried out. The smaller the vibration of the milling cutter in normal machining, the better.
When tool vibration occurs, consideration should be given to reducing the cutting speed and feed rate, and if there is still a large vibration after both have been reduced by 40%, then a reduction in the amount of knives should be considered.
If there is resonance in the machining fragments, the cause may be that the cutting speed is too large, the feed speed is just too small, the tool fragmentation is not enough, the workpiece clamping force is not enough, and the workpiece shape or workpiece clamping essentials and other factors are caused, at this time, measures such as adjusting the cutting amount, adding the fragmented stiffness of the tool, and improving the feed rate should be adopted.
End cutting of the milling cutter
In the CNC milling process of the workpiece cavity such as a mold, when the cutting point is a concave part or a deep cavity, it is necessary to extend the protrusion of the milling cutter. If a long-edge milling cutter is used, it is easy to cause vibration and tool breakage due to the large deflection of the tool. Therefore, in the process of machining, if only the cutting edge with similar tool ends is required to participate in the cutting, it is best to choose a short-edged long-shank milling cutter with a long tool length. When a large-diameter milling cutter is used to machine a workpiece on a horizontal CNC machine, due to the large deformation caused by the weight of the tool, it is necessary to pay more attention to the title of the excellent end cutting edge. In the case where it is necessary to use a long-edge milling cutter, the cutting speed and feed rate need to be significantly reduced.
Selection of cutting data
The selection of cutting speed mainly depends on the material of the workpiece to be machined, and the selection of feed speed mainly depends on the material of the workpiece to be machined and the diameter of the milling cutter. The tool samples of some foreign tool manufacturers are attached to the tool cutting parameter selection table for reference. However, the selection of cutting parameters is also affected by many factors such as machine tools, tool fragments, the shape of the workpiece to be machined and the clamping method, and the cutting speed and feed rate should be adjusted according to the practical situation.
When tool life is a priority, the cutting speed and feed rate can be appropriately reduced, and when the chip leaving condition is not good, the cutting speed can be appropriately increased.
Selection of cutting methods
Adoption of climb milling is beneficial for defending against edge protection and can improve tool life. However, there are two points to focus on:
(1) If ordinary machine tool processing is accepted, the gap of the feed mechanism should be eliminated;
(2) When there is an oxide film or other hardened layer composed of casting and forging processes on the appearance of the workpiece, conventional milling should be accepted.
