Analysis Of Common Failures And Maintenance Of CNC Machining Centers

1. Common Fault Types Of CNC Machining Centers

1.1 System Failure

System failure is a relatively common type of failure in CNC machining centers, mainly due to the failure of its own conditions and related components that do not meet the standards used. If the cooling system leaks, after long-term use, it will cause a lot of pressure on the cooling system. Under a heavy load environment, it is easy to leak, and then the CNC machining center will generate heat during the operation, causing the system to respond slowly And the slowness will also have a great impact on the accuracy of the processing. If it becomes serious, it will cause the machining center to alarm and automatically stop. At the same time, the machining center may move beyond the specified range when different axes are moving. Under such over-limit conditions, an over-travel alarm will occur.

1.2 Random Failure

Compared with system failures, random failures do not occur much in the operation of CNC machining centers, but they are more common. This type of failure is often accidental and only appears under corresponding conditions. Faced with this type of failure, it is often impossible to analyze and judge the cause of the failure in advance during the operation of a CNC machining center, and can only implement some preventive treatment. The occurrence of random failures is generally closely related to some important parameter settings, also related to the environmental conditions of the operation, and also related to the actual operating procedures and skills of the operators. For example, in the operation of the connectors and connecting components, they are not locked due to negligence, the position of the contacts of the relays and the socket positions of various switches are changed, and the requirements are not met and the CNC machining center fails.

1.3 Alarm Display Failure

For CNC machining centers, it is generally constituted by a variety of hardware and software. If its software and hardware fail, an alarm will appear. Often the hardware and software equipment are equipped with automatic alarm devices. When the hardware and software equipment have abnormal failures or exceed the specified value, the related alarm equipment of the hardware and software equipment will be triggered, and the warning light will light up. Or flashing. If there is an error in the processing program of the system or the parameter setting of the system is lost, and the computer calculation error occurs, the automatic alarm device will be triggered to prompt the failure, which will cause the concern of relevant personnel. If this type of failure exists, relevant personnel can handle the failure according to the corresponding alarm prompts. But there is still a kind of fault that is often difficult to diagnose, that is, when the hardware and software equipment of the system fails, there is no clear display of the indicator light. If you want to quickly judge such faults, you often need to quickly delineate the fault area. , And combined with the state before and after the system failure to implement the fault judgment, so as to find the fault location.

2. Common fault diagnosis and maintenance of CNC machining center

2.1 Tool magazine failure

Common tool magazine faults include the tool magazine cannot rotate or rotate incorrectly, the tool holder cannot clamp the tool, and the tool holder is not in place. The tool magazine cannot be rotated or rotated incorrectly may be due to the loose coupling used to connect the motor shaft and the worm shaft, the fault of the frequency converter, the tightness of the mechanical connection, the low voltage of the power grid and the error of the transmission mechanism Wait for the situation, which requires a comprehensive inspection and repair. The inability of the tool holder to clamp the tool may be due to the lack of clamping force due to the loosening of the tool holder adjusting screw, loose spring, etc., which requires performance inspection, and fixing and repairing to ensure the firmness of the screw and spring . The improper position of the knife cover may be caused by improper adjustment of the device, excessive machining error, etc., which leads to inaccurate position of the shift fork, or improper installation of the limit switch, which leads to an error in the feedback signal.

2.2 Inaccurate spindle positioning affects automatic tool change

After positioning the spindle, it is found that there is a certain deviation in its position. The drive system of the spindle is checked. There is no alarm, and the structure of the mechanical part is relatively simple. The positioning of the machine tool is implemented through the encoder, and the positioning action It has good accuracy, so the possibility of its malfunction due to electrical problems is very small. Then consider the mechanical department that caused the fault. It may be caused by the connection problem of the encoder. After checking the connection part, it is found that the connection sleeve screw on the encoder is loose, which leads to the connection between the encoder and the spindle. If there is too much gap in the area, the screws need to be well fixed according to the requirements.

2.3 There is no display failure in the CNC machining center

If the CNC machining center is in use and debugging, and the fault area is not displayed, the system can continue to run, but the display fails, and the fault disappears after restarting the operation. In the face of such failures of CNC machine tools, relevant maintenance personnel need to perform judgments through experience and check the performance of various components to determine whether the failure occurs due to poor contact, and also need to check the display board. During the check, you can check one by one in manual mode to diagnose the fault.

2.4 Unbalanced movement of machining center

The unbalanced motion of the machining center is mainly due to the vibration and crawling of the coordinate axis. This situation is often closely related to a variety of reasons. It may be due to the problem of the mechanical transmission system or the adjustment of the servo feed system. And set improper circumstances. In diagnosing this fault, first set the operation mode of the airport to manual mode, and control the Y axis feed through the hand pulse generator. It is found that the Y axis vibrates, and the Y axis is moved for a long time. The speed unit alarm light of the axis is on, which indicates that the Y-axis servo drive has an over-current alarm. The cause of the failure may be excessive load of the motor, poor mechanical transmission system, excessive gain of the position loop, and The servo motor is malfunctioning, etc. In troubleshooting, the interchange method can be used to confirm the cause of the failure.

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