Principle of thread processing in CNC lathe

Update:22-06-2020
Summary:

Thread is one of the common geometrical features in mec […]

Thread is one of the common geometrical features in mechanical engineering and is widely used. There are many thread processing technologies, such as rolling and thread rolling based on plastic deformation, turning, milling, tapping and threading based on cutting, thread grinding, thread grinding, etc. Among them, thread turning is one of the commonly used processing methods for single-piece or small batch production. As a CNC lathe, thread turning is one of its basic functions.

 

Thread turning characteristics

 

Thread CNC machining is different from contour machining, and its characteristics are as follows: thread machining belongs to forming machining. The cutting edge is long at the same time, and it is prone to bite and pierce. Generally, multiple cutters are required to complete the cutting. In order to ensure the lead (or pitch) ) Accurate, there must be a suitable cut-in and cut-out length. The tooth shape and tooth angle of thread processing are basically guaranteed by the shape of the tool. Therefore, the shape and correct installation of the tool directly affect the quality of the thread shape. The thread feed rate and spindle speed must maintain a strict transmission ratio, that is, F = Ph(mm/r), therefore, constant linear speed control is prohibited during machining. The cutting speed of thread cutting is generally not high, based on the principle that there is no built-up edge or plastic damage to the tool.

 

In the process of thread turning, it is often necessary to reinstall the tool-to-tool due to thread tool wear and chipping. The quality of the tool-to-tool installation directly affects the accuracy of the thread turning, especially the repair of the thread. The second tool setting restricts the machining efficiency of the CNC lathe for threading. When the thread precision is high, if the trapezoidal thread needs to be finished on both sides, it needs to be roughed before changing the finishing tool for finishing. If the problem of tool setting and tool setting during the process cannot be solved well, the CNC turns the thread Will not be well applied.

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Principle of thread processing in CNC lathe

 

The CNC turning thread is very different from the ordinary lathe thread. The ordinary lathe is turned through the mechanical transmission of the gear and the screw, that is, each time the spindle rotates, the tool holder moves the lead of a thread. During the entire threading process This drive chain cannot be disconnected, otherwise it will buckle in disorder.

 

CNC turning is to send a pulse signal to the CNC system through the encoder installed on the spindle. There is a CNC system to perform arithmetic control, and a command is sent to control the servo motor to control the tool to move through the ball screw to achieve thread turning. In order to prevent thread turning during multiple passes, the starting position of the thread is controlled by detecting the pulse signal. When the program processing starts, the spindle rotates and the tool waits for the spindle encoder to send a synchronization signal (zero signal). Carry out a turning movement, then when turning the second tool thread, the tool returns to the starting point of the previous turning, or waits for the synchronization signal (zero signal) to be received and then turn again, so that the turning thread is always on the same spiral, so it is not There will be a buckle phenomenon.

 

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