Common Faults and Treatments of Simple CNC Lathes

Simple CNC lathes are also called economical CNC lathes. They are developed on the basis of ordinary lathes. , Automatically complete the processing of parts. Therefore, the simple CNC lathe is still an electromechanical integration equipment, so when a failure occurs, it must be comprehensively analyzed from the two aspects of the mechanical structure and electrical control of the machine tool.

1. After the program runs, the stepper motor vibrates and does not turn.

This phenomenon is generally caused by the phase failure of the stepper motor or its control system. It is possible that the stepper motor itself is faulty or its drive circuit is faulty. First check whether the connecting plug of the stepper motor is in good contact. If the contact is good, you can replace the motor without failure to verify whether the motor is in good condition. If the motor still cannot work normally after replacing the motor, it means that its control part is not normal. You can focus on checking the high-power triode on the drive board and its protection component release diode. Under normal circumstances, these two components

2. The workbench stopped suddenly during the running of the program

This phenomenon is generally caused by a mechanical failure, but it may also be caused by a malfunction in the control system. At this time, the worktable can be returned to the origin first, and the processing program can be restarted. If the worktable always stops at a certain position, it should be that a certain part of the transmission system is damaged, deformed or stuck by foreign objects. First cut off the power, and then check whether the gap between the screw nut and the screw or the slide plate is too tight, whether there is any foreign matter in the ball guide groove of the ball screw, whether the screw is bent and deformed, whether the flexible gear in the stepper motor reducer is loose Or a foreign object 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.

3. Stepping 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 emphatically. When the high-voltage switch transistor is damaged, the high-voltage power supply cannot be connected, and the output torque of the stepping motor decreases at high speed and steps are lost. There may also be a mechanical failure somewhere, so the screw, screw nut, slide plate, stepper motor reducer, etc. should also be checked. When some 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 zero after the program runs.

Generally, it is a failure of the control system. When the tool is feeding or processing, the stepper motor runs at a low speed, and when the program returns to the zero point, it is required to return quickly. The stepper motor runs at high speed and uses a high-voltage drive power supply to increase the output torque. There is a switch triode that controls the output of the high-voltage drive power supply. When the switch triode is damaged, the high-voltage power supply cannot be turned on when returning to the zero point at high speed, 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 switch triode.

5. Offside when tool returns to zero

Generally, it is caused by too much running resistance of the mechanical transmission system. When cutting feed, the tool holder runs at low speed, driven by low voltage, and the stepping motor has a small operating torque, which is not enough to overcome the resistance and cause step loss. When returning to zero, the stepper motor is driven by high voltage, (source of information: with high speed, large torque, and no cutting resistance, so the stepper motor does not lose steps. In this way, if you lose your steps when you go and return normally, it will cause the phenomenon of not returning to zero. At this time, you can check whether there are iron filings and foreign objects on the transmission gear in the stepping motor reducer or the transmission gear between the stepping motor and the lead screw, or whether the slide plate is too tight to increase the running resistance.

6. The size error of the processed workpiece is very large

One possibility is that the screw or screw nut is loosely connected to the lathe. There is no knife resistance during idling, and the slide plate operates normally. Due to the increase of cutting resistance during processing, the connection between the screw or screw nut and the lathe is loose, resulting in the drift of the workpiece size. Tighten the connection part, and the fault can be eliminated. Another possibility is caused by the electric knife holder. If the tool holder cannot be automatically locked after the tool is changed, the tool deviates from the processing point during cutting, which will also cause the above phenomenon. At this time, check the tool holder locking device and the tool holder control box.

7. Partial dimensional error of the workpiece is large

It is mainly caused by the excessive gap between the nut and the lead screw. Since the nut and the lead screw have been running in a certain section for a long time, the gap in this section increases. At the beginning of the program, the measured lead screw clearance is compensated into the program, but it cannot be compensated in the wear section, so that the local dimensions of the workpiece are out of tolerance. The solution is to repair or replace the lead screw.


This is because when the program requires a certain number of tools, the electric tool post is transferring the tool, and when it rotates to this number of tools, there is no response signal, so that the tool post will not stop rotating and cannot be positioned. The Hall element on the electric knife holder should be checked. When the Hall element is damaged, the signal output is not detected when the desired tool is in place, resulting in the above phenomenon. Just replace the Hall element of the knife.

9. During program execution, return to monitoring status and work stops

Generally, it is caused by monitoring program failure or strong magnetic interference. For strong magnetic interference, it can be solved by grounding or shielding. If you do not execute the program or do not follow the execution command when starting the program, you will return to the monitoring state immediately. Generally, the monitoring program or computer hardware is faulty, and you can replace the suspicious chip, such as an off-chip program memory chip, a programmable interface chip or the single-chip microcomputer itself. Sometimes off-chip data memory failure can also cause this phenomenon. Otherwise, we have to find the manufacturer to re-adjust.

10. processingPrograms are often missing

If the machining program is lost after the control system is powered off, and the machining program is re-entered after the machine tool is powered on, the machine tool can process normally, it may be that the voltage of the backup battery is reduced or disconnected, causing the machining program in the data memory to be powered off on the machine tool Then it cannot be kept and lost. Just replace the backup battery. If the processing program is often partially or completely lost during processing, it is very likely that the data memory is faulty. At this time, the off-chip data memory or the single-chip microcomputer itself can be replaced.

In short, the simple CNC lathe is composed of mechanical and electrical parts. After a fault occurs, it must be analyzed from both mechanical and electrical aspects to determine whether it is a mechanical fault or an electrical fault, and then analyze in depth to find out the fault point.

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