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Common Faults and Analysis of Simple CNC Lathe (Part 1)

Sep. 03, 2020

Heavy duty lathe Exporter shares this article with you.

CNC lathe, also known as economical CNC lathe, is developed on the basis of ordinary lathes. Its automatic control system is mainly composed of single-chip microcomputers. Through control programs, it controls the longitudinal and transverse feed devices and tool change devices of the machine tool. , Automatically complete the processing of parts. Therefore, simple CNC lathes are still mechatronics equipment, so when a failure occurs, a comprehensive analysis must be made from the mechanical structure and electrical control of the machine tool.

1. After the program runs, the stepper motor shakes and does not rotate

This phenomenon is generally caused by a phase failure of the stepper motor or its control system. It may be a failure of the stepper motor itself or a failure of its drive circuit. First check whether the connecting plug of the stepper motor is in good contact. If the contact is good, the motor without fault can be replaced to verify whether the motor is in good condition. If the motor still fails to work normally after changing the motor, it means that its control part is not normal. You can focus on checking the high-power transistor on the drive board and its protective component release diode. Generally, these two components.

2. The workbench stops suddenly while the program is running

This phenomenon is generally caused by a mechanical failure, but it may also be caused by a failure of the control system. At this time, you can first return the worktable to the origin and restart the processing program. If the worktable always stops when it runs to a certain position, it should be that a certain part of the transmission system is damaged, deformed or blocked by foreign objects. Turn off the power first, and then check whether the gap between the screw nut and the screw or the slide plate is too tight, whether there are foreign objects in the ball guide groove of the ball screw, whether the screw is bent or deformed, and whether the flexible gear in the stepper motor reducer is loose Or foreign matter is stuck, etc. If there is no abnormality in the manual cranking, it means that the control system is faulty and should be checked according to fault 1.

CNC Lathe

CNC Lathe

3. Stepper motor loses steps at high speed

It may be that the drive power supply voltage is reduced, which reduces the output torque of the stepper motor. The driving power supply part should be checked. When the high-voltage switch transistor is damaged, the high-voltage power supply is turned on, and the output torque of the stepping motor decreases at high speed and loses steps. There may also be a mechanical failure, so you should also check the lead screw, nut, slide, stepper motor reducer, etc. When parts are bent, deformed, or there are foreign objects, the running resistance will increase. The phenomenon is not obvious when running at low speed, but the running resistance cannot be completely overcome at high speed.

4. The tool does not return to the zero point at the end of the program

Usually it is a control system failure. When the tool is feeding or processing, the running speed of the stepper motor is low, and when the program returns to the zero point, a quick return is required. The stepping motor runs at high speed and adopts high voltage drive power to increase the output torque. There is a switching transistor that controls the output of the high-voltage drive power supply. When the switching transistor is damaged, the high-voltage power supply cannot be turned on during the high-speed zero return, and the output torque of the stepping motor is not enough, so that the tool does not return to the zero point. It can be eliminated by replacing the switching transistor.


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