In recent years, with the rapid development of CNC machining, there are more and more CNC machine tools, and many CNC machine tools gradually show failures. With the development of microelectronic technology and computer technology, numerical control technology is also developing synchronously, and the degree of intelligence is getting higher and higher. Therefore, the practical application and maintenance of CNC technology in production are also constantly changing. Due to the complexity, diversity, and variability of maintenance technology and the constraints of some objective environmental factors, a mature and complete theoretical system has not been formed in the maintenance technology of CNC machine tools.

Due to the advanced nature of CNC machine tools and the instability of failures, most of the failures appear in the form of comprehensive failures, so the maintenance of CNC machine tools is more difficult. In order to standardize CNC maintenance work, improve the use-value of CNC machine tools, improve the quality of CNC equipment maintenance, and make CNC maintenance work adapt to the development of the manufacturing industry, we should standardize the maintenance of CNC machine tools.

CNC machining center

What Are CNC Machine Tools?

CNC machine tool is an automatic machine tool equipped with a program control system that integrates new technologies in various fields such as computer technology, automation technology, servo drive, precision measurement, and precision machinery. The control system can logically process the program specified by the control code or other symbolic instructions, and then express it in code, and then input it into the numerical control device through the information carrier. After the operation and processing, the numerical control device sends out control signals to control the action of the machine tool and automatically processes the parts according to the shape and size required by the drawing.

CNC machine tools can process complex, precise, small-batch, and multi-variety parts. CNC machine tool is a high-efficiency automatic machine tool with good economic performance and high production efficiency. As a typical mechatronic product, the CNC machine tool is the development direction of modern machine tool control technology.

The maintenance of the machine tool can greatly extend the life of the machine tool and improve the processing efficiency of the machine tool.

A Record of the Situation at the time of the Fault

When a CNC machine tool fails, the operator should first stop the machine tool to protect the site, record the failure as detailed as possible, and notify the maintenance personnel in time.

  1. Record the model of the machine that has failed, the model of the control system used, the software version number of the system, and the operating mode of the system.
  2. Record the phenomenon of failure and the location where the failure occurred.
  3. If the fault occurs in the automatic mode, the processing program number when the fault occurs, the block number in which the fault occurs, and the tool number used for processing should be recorded.
  4. In case of faults such as excessive machining accuracy or excessive contour error, the unqualified workpiece should be retained.
  5. When a fault occurs, if the system has an alarm display, record the alarm display status and alarm number of the system.
  6. Record the value of the position following the error of each coordinate axis when a fault occurs. Record the moving speed, moving direction, spindle speed, direction, etc. of each coordinate axis when a fault occurs.
  7. The cycle of failure and environmental conditions.

Confirm the Cause of the Fault

Before repairing the fault, the maintenance personnel should confirm the cause of the fault according to the fault record and fault phenomenon.

When the numerical control equipment fails, the first thing to do is to find out the fault phenomenon. The operator can understand the situation when the fault occurs, observe the process of the fault, and observe the specific occurrence of the fault. After inquiring to the operator of the machine, make a visual inspection, touch whether the various lines of the machine are in good condition, and check whether there is a short circuit. Power on again to detect the signal and alarm device of the machine, interface status, parameter adjustment, etc., until the problem of the machine tool is detected. The fault inspection includes an inspection of the operation and working conditions of the CNC machine tool, an inspection of the connection between the machine tool and the system, and an outer inspection of the CNC device.

Maintenance personnel should carefully analyze the cause of the failure. When analyzing the fault, the maintenance personnel should not be limited to the CNC part but should make a detailed inspection of the machine tool’s strong electrical, mechanical, hydraulic, pneumatic, and other aspects, and make a comprehensive judgment to achieve the purpose of confirming the cause of the fault. Fault inspection is the premise of CNC machine tool maintenance. Only when the problem is found correctly can it be repaired in a targeted manner.

Maintenance Methods of CNC Machine Tools

The maintenance methods of CNC machine tools are very important. The maintenance methods that are often used are as follows:

CNC machining for machine tool
CNC machining for machine tool

1. Observation Method

The maintenance personnel carefully identify various parts of the system by observing various abnormal phenomena of the surrounding environment such as light, sound, and smell when the fault occurs, and narrow the fault range to one module for repair.

2. Self-Diagnostic Function Method

The self-diagnosis function of the CNC system can monitor the working status of the CNC system at any time. If an abnormal situation occurs, an alarm message will be displayed on the CRT or a light-emitting diode will be used to indicate the approximate cause of the failure, which is the most effective maintenance method.

3. Functional Program Testing Method

The function program test method is to compile the common functions and special functions of the numerical control system into a function test program by manual programming or automatic programming and send it to the numerical control system. Then let the CNC system run this test program to check the accuracy and reliability of the machine tool to perform these functions, and then determine the possible cause of the failure.

4. Spare Parts Replacement Method

The so-called spare parts replacement method is to replace the suspicious parts with spare templates, integrated circuit chips, or components after analyzing the general cause of the failure. Replacing the faulty circuit board with a good spare part, and doing the corresponding initialization, so that the machine tool can be put into normal operation quickly, is the most commonly used troubleshooting method at present.

5. Principle Analysis Method

According to the composition principle of CNC, the characteristic parameters are analyzed logically, starting from the working principle of each component of the system, to determine the maintenance method of the faulty part.

6. Parameter Correction Method

System parameters are the basis for determining system functions. When the CNC system finds faults, it should check the system parameters in time. Incorrect parameter settings may cause system failure, directly affect the performance of the machine tool, and even make the machine tool unable to work normally. External interference or insufficient battery voltage will cause system parameters to be lost or changed and cause confusion. The system search function can be used to check and correct all errors to ensure the normal operation of the machine tool.

7. Improve the Power Supply Quality Method

Power supply fluctuations will affect the normal operation of the machine tool, and a regulated power supply can be used. Capacitive filtering can be used for high-frequency interference.

8. Initialization Method

If the system fails due to power failure or battery under voltage, the system should be initialized. Care should be taken to copy the data records before clearing.

9. Maintenance Information Tracking Method

Some large manufacturing companies can improve system software or hardware according to unexpected failures in actual work. Maintenance personnel needs to constantly update these data.

After the fault is detected, a suitable maintenance plan should be selected for repair, and then the maintenance plan should be adjusted accordingly. The records of each repair should also be recorded so that the next time the same situation is encountered, it can be dealt with quickly.


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