In actual processing, the types of threads generally include: ordinary single thread, trapezoidal thread, special thread, special-shaped thread, etc. Among them, ordinary threads are the most widely used. Coarse threads are mostly used for connection, while fine threads are used for the connection of thin-walled parts or parts subject to variable load, vibration and impact load, and can also be used for mechanism fine-tuning. When machining ordinary threads, it is necessary to pay attention to the need for multiple cycle feeds during cutting, and the cutting depth must be reduced in accordance with a certain proportion each time.plastic machining
If the cutting depth of each tool is the same, the force on the cutting edges on both sides of the thread turning tool will increase sharply as the material removal rate increases, resulting in a decrease in thread accuracy and tool damage. In the competition, internal threads and external threads are relatively common, and the processing is generally less difficult. The main attention should be paid to the calculation of the bottom of the thread.
Compared with ordinary threads, trapezoidal threads have longer length, larger pitch, deeper cutting depth, greater cutting force, higher precision requirements, and greater processing difficulties. The thread cutting methods of CNC lathes generally include: straight approach, oblique approach, staggered cutting, and grooving rough CNC cutting.
(1) Straight forward method. Refers to when the lathe is cutting, the Z-direction does not change when the linear motion is performed, and the X-direction feeds a cutting depth in stages. It is characterized by convenience, quickness, and high efficiency. Generally, ordinary threads with a small pitch can be used. However, because the two edges of the turning tool are cutting at the same time, the chip removal is not smooth, and the force is large, the cnc turning tool is easy to wear, and the chips will scratch the thread surface.
(2) Inclined method. It refers to the Z-direction feed and the X-direction also has linkage, forming a diagonal feed mode. At this time, the thread turning tool always has only one cutting edge to participate in the cutting, the chip removal is smoother, and the force and heat are less than the straight forward method. But when the thread depth is deep and the pitch is large, the phenomenon of knife sticking is easy to occur.
(3) Staggered cutting method. The thread turning tools are staggered in the direction parallel to the left and right side of the thread, respectively, until the bottom of the thread. It is very suitable for large thread cutting, but the programming is more complicated.
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(4) Grooving rough cutting method. First, use a grooving tool smaller than the width of the thread turning tool head to rough cut a groove, and then use the thread turning tool for thread processing. Large-pitch threads are often used, but the operation and programming are extremely cumbersome.
