1、 What is up milling and up milling of CNC milling machine
The rotation direction of the contact part between the milling cutter and the workpiece is the same as the feed direction of the workpiece, and vice versa. There is always a large or small gap between the nut and the lead screw of the milling machine. With the change of the horizontal milling component force, the table and the lead screw will move left and right. This periodic movement makes the table movement very unstable and easy to cause damage to the cutter teeth. However, the vertical milling component force of the forward milling presses the workpiece to the worktable, and the sliding and friction phenomenon between the cutter tooth and the machined surface is small, which reduces the friction The tool tooth wear, reducing work hardening and surface roughness are favorable. Therefore, when the clearance between the screw and nut of the worktable is adjusted to less than 0.03mm or when milling thin and long workpieces, it is better to use the down milling. In reverse milling, the workpiece is lifted up by the vertical force of milling, and the friction between the cutter tooth and the machined surface is increased. However, the horizontal force of milling is helpful for screw and nut to stick tightly, so that the table movement is more stable, and the cutter tooth wear caused by milling casting and forging is also small. Therefore, the general milling is usually up milling.
2、 Characteristics of down milling and up milling of CNC milling machine
Features of down milling:
In down milling, the cutting thickness of each tool changes gradually from small to large. When the cutter tooth is just in contact with the workpiece, the cutting thickness is zero. Only when the cutter tooth slides over a certain distance on the cutting surface left by the previous cutter tooth, and the cutting thickness reaches a certain value, the cutter tooth can really start cutting. Up milling makes the cutting thickness change from large to small, and the sliding distance of cutter teeth on the cutting surface is also very small. Moreover, the distance of the cutter teeth on the workpiece is shorter than that of the reverse milling. Therefore, under the same cutting conditions, the tool is easy to wear when using up milling. In down milling, the cutter teeth are cut from the surface of the workpiece each time, so it is not suitable for processing the workpiece with hard skin. The average cutting thickness is large and the cutting deformation is small during the down milling, and the power consumption is less than that of the up milling.
Features of up milling:
Because the horizontal cutting force acting on the workpiece by the milling cutter is opposite to the feed movement direction of the workpiece, the screw rod and nut of the worktable can always keep one side of the thread tightly fit. However, it is not the case in down milling. Because the direction of horizontal milling force is consistent with the direction of workpiece feed motion, when the force of cutter teeth on the workpiece is large, due to the existence of the gap between the table screw rod and nut, the table will move, which not only destroys the stability of the cutting process, but also affects the processing quality of the workpiece, and in serious cases, it will damage the cutter. Due to the large friction between the cutter teeth and the workpiece, the cold and hard phenomenon on the machined surface is serious.
Conclusion: both forward milling and reverse milling have their own advantages and determination. The specific milling method should be based on the requirements of the workpiece to be processed. If the surface smoothness is required to be high, the forward milling should be used, and the reverse milling should be used.
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