The cutting amount in the CNC turning process of the CNC lathe includes the amount of back cutting a. , spindle speed s or cutting speed” (for constant linear speed cutting), feed speed or feed amount fo these parameters should be selected within the allowable range given by the machine tool.
Whether the turning amount (aP, ,, “) is selected reasonably has a very important role in whether the potential of the machine tool and the cutting performance of the tool can be fully utilized, and the realization of high quality, high yield, low cost and safe operation. The selection principle of the amount of turning is: rough turning When , first consider choosing the largest possible amount of back cut, secondly, choose a larger feed, and finally determine a suitable cutting speed.” Increasing the back-feed amount a of the CNC lathe can reduce the number of tool passes and increase the feed, which is conducive to chip breaking.
When finishing turning, the machining accuracy and surface roughness are required to be high, and the machining allowance is not large and uniform. Therefore, when choosing the cutting amount of finishing turning, we should focus on how to ensure the processing quality, and on this basis, do our best to improve productivity. Therefore, a small (but not too small) back-cut amount a and feed f should be selected during finishing, and high-performance tool materials and reasonable geometric parameters should be selected to increase the cutting speed v as much as possible.
(1) Spindle speed. The spindle speed should be determined according to the diameter of the machined part on the part and the cutting speed allowed by the material and processing properties of the part and tool. In addition to calculation and table look-up selection, the cutting speed can also be determined according to practical experience. It should be noted that the low-speed output torque of the AC variable frequency speed control CNC lathe is small, so the cutting speed cannot be too low.
(2) Spindle speed when threading. When CNC lathes process threads, due to the change of the transmission chain, in principle, the rotational speed should not be restricted as long as it can ensure that the tool can be displaced by one pitch in the direction of the main feed axis (mostly the z-axis) when the spindle rotates once. However, when the CNC lathe turns threads, it will be affected by the following aspects.
① The pitch value commanded in the thread machining block is equivalent to the feed amount
(mm/r) represents the feed rate F, if the spindle speed of the machine tool is selected too high, the converted feed rate (mm/min) must greatly exceed the normal value.
②The CNC lathe tool will be constrained by the frequency of the servo drive system and the interpolation operation speed of the numerical control device throughout the displacement process. Because the frequency of the rise and fall cannot meet the processing needs and other reasons, it may be caused by the main feed movement. “Leading” and “lag” lead to part of the thread pitch does not meet the requirements.
③The thread turning must be realized by the synchronous running function of the spindle, that is, the thread turning needs a spindle pulse generator (encoder). When the spindle speed is selected too high, the positioning pulse sent by the encoder (that is, a reference pulse signal sent out for each revolution of the spindle) may be caused by “overshoot” (especially when the quality of the encoder is unstable) Cause the workpiece thread to produce random lines (commonly known as “rotten teeth”).
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- CNC machining can create very similar parts to series parts. It is often more efficient and faster than other rapid prototyping technologies for the manufacture of a quantity of prototypes between 1 and 10 parts . We also recommend CNC machining for parts with large sizes (greater than 600 mm).