The method of cnc high-speed turning trapezoidal thread

There are certain technical difficulties in machining trapezoidal threads on CNC lathes, especially in high-speed cutting. It is not easy to observe and control during machining, and the safety and reliability are also poor. This requires correct tool geometry and processing technology. An efficient and feasible processing method is introduced.
Whether on an ordinary lathe or on a CNC lathe, there is always a great technical difficulty in processing trapezoidal threads for students in secondary and higher vocational schools, especially in the high-speed turning of trapezoidal threads on a CNC lathe. Most books and textbooks do not introduce special topics. It is difficult for students to master their fine calculation and reasonable processing technology. The author will focus on the high-speed turning method of trapezoidal thread according to the examination questions of senior workers in Hunan Province in recent years and in combination with his own experience and experience.

1、 Selection of processing methods
As shown in Figure 1, when machining trapezoidal threads on the CNC lathe, the three jaw chuck adopts the method of one clamp and one top. For the convenience of tool setting and programming, the program origin is set at the center point of the right end face of the workpiece. In addition, a tool setting template is also made to facilitate the accuracy of the Z direction when changing tools in rough and fine turning. It should be pointed out that because of the high-speed machining of trapezoidal threads, cemented carbide tools are selected.
When turning trapezoidal thread at high speed, due to the excessive thread pitch, in order to prevent "knife pricking" and "blade breakage", it is required that the cutting force should not be too large when machining trapezoidal thread, and the tool should not cut on three sides at the same time. Through years of practice, the author has proved that the straight cutting method or straight grooving method can not be used for processing with thread cutting commands G32 and G92 on the economic NC lathe. Even though the method of using G92 combined with the left and right swing of subprogram introduced in many magazines in recent years is not the best method for layered cutting. Although this method theoretically can reduce the force during cutting, it ignores that most of our commonly used lathes are economic NC lathes, However, the control system of economical CNC lathe is semi closed loop, so that the servo system can not keep up with the numerical requirements of the CNC system when swinging left and right, thus changing the machining pitch. Considering the comprehensive programming and processing, combined with practical experience, I think it is a better, safe, reliable and easy method to use the thread cutting compound cycle command G76 to process.