Nine key points of preventive maintenance of precision CNC machine tools
In order for any precision CNC machine tools to work continuously and reliably for a long time, in addition to the quality factors of the machine tool itself, it is also closely related to the correct maintenance, timely troubleshooting and timely maintenance during use.
The key to preventive maintenance is to strengthen daily maintenance and maintenance, usually the following points should be done:
1. Professional maturity of technical personnel. The numerical control system programming, operation and maintenance personnel equipped for numerical control machine tools should be familiar with the mechanical structure, numerical control device, strong electrical equipment, hydraulic system, gas circuit and other characteristics of the equipment used, as well as the specified operating environment and processing conditions. And use the machine tool correctly and rationally in strict accordance with the requirements of the machine tool and numerical control device instruction manual, and try to avoid malfunction caused by improper operation.
2. Daily maintenance of the paper tape reader. Many systems use a tape reader as the input device of the program. The tape information such as system parameters and part processing programs must be input into the CNC system through the tape reader. If the tape reading part of the paper tape reader (ie the light-emitting and light-receiving parts of the reading head) is dirty, the read tape information will be wrong. It should be checked frequently and the dirt should be removed in time. The moving parts of the paper tape reader, such as the driving wheel roller, the guide roller, the pressing roller, the tension arm roller, etc., should be cleaned frequently and ensured that they are well lubricated.
3. Clean the air filter regularly. When the air filter installed on the CNC cabinet and the electrical cabinet door has a lot of dust, it will cause the cooling air in the cabinet to have poor circulation. For a long time, it will cause the temperature in the cabinet to rise, making the system unable to work reliably. Therefore, it should be checked regularly according to the use environment, and it should be removed and cleaned at least every six months. The specific method is: first remove the fastening screws, take out the inner core of the air filter, and use compressed air to blow off the dust on the filter element from the inside out. If the filter is dirty, you can also gently vibrate the filter at the same time. If the above method does not work, you can use a neutral detergent (the proportion of detergent is 5%) to rinse, but do not rub, and then put the filter element in a cool and ventilated place to dry Just dry.
4. Regular battery maintenance. For the numerical control device that uses CMOS memory to save system parameters, in order to avoid the loss of parameters when the machine is shut down and power off, the battery is used for power supply to keep it. When the battery voltage is lower than the CMOS holding voltage, the battery can be automatically charged when the machine is turned on. Under normal circumstances, the battery can ensure that the information is stored for more than 1000 hours after the power failure. When the machine tool is shut down for a long time, it should be powered on regularly according to the requirements of the manual to make the battery replenish power. If this kind of numerical control device displays a battery failure alarm on the CRT or with an indicator light, it means that the voltage is too low, the battery has failed, and a new battery needs to be replaced. In order to preserve the original data, the battery should be replaced when the power is turned on, and the polarity of the battery should not be reversed.
5. The DC servo motor should be checked and cleaned regularly. The DC servo motor has brushes, which gradually wear out due to contact and friction with the commutator during operation. Excessive wear of the brushes will affect the performance of the motor and even cause damage to the motor, so it must be checked and replaced regularly. For general machine tools such as CNC lathes, CNC milling machines and machining center machine tools, it can be checked once a year; for machine tools that frequently perform acceleration and deceleration work, such as punch presses, it should be checked every two months. The inspection should be carried out when the power supply of the CNC system is disconnected and the motor has been completely cooled. First, remove the brush cover, take out the brush, and measure its length, generally speaking. When the brush is worn to half of its original length, it should not be used any more, and a new brush of the same type must be replaced. In the second step, carefully check whether there are deep grooves or cracks on the arc-shaped contact surface of the brush and the commutator, and whether the brush spring has spark marks. If the above phenomenon occurs, you must carefully check the surface of the commutator. If the commutator is normal, you can replace the new brush, and check again after a month; if the above phenomenon still occurs, it is necessary to consider whether the working conditions of the motor are too bad and cause the motor itself to fail. Before installing a new brush, clean the brush hole with clean compressed air that does not contain metal powder and moisture, and be sure to blow off the brush powder that sticks to the hole wall. If it is difficult to blow out, you can use tools such as a screwdriver to assist in cleaning until the hole wall is completely clean. But be careful not to damage the surface of the commutator and the hole wall with the tip of the screwdriver. Finally, put in the new brush, tighten the brush cover, and let the servo motor run dry for a period of time, so that the surface of the new brush matches the commutator.
6. Pay attention to the closed CNC cabinet door. Under normal circumstances, it should be avoided to open the CNC cabinet door at will, especially for long-term open door operation. The air filter should be cleaned in time. And never use the method of opening the cabinet door to dissipate heat, otherwise it will not be worth the loss. Because there is a lot of dust, oil mist and metal powder floating in the air in the workshop, these sundries fall on the printed circuit board and electronic components, which is easy to cause the insulation resistance of the components to drop and cause failure, and even make the components and printed circuit board. The circuit board is damaged and scrapped. Especially for CNC machine tools with the spindle control system installed in the strong electric cabinet, if the strong electric cabinet door is not closed tightly or the seal is not good, it is easy to damage the electrical components and cause the spindle control to fail.
7. Regularly clean the cooling device to enhance the heat dissipation effect. Some servo motors or spindle motors are equipped with a forced cooling device on the casing. If the protective net or heat sink of the cooling device is dirty, the air circulation will be affected, and the cooling capacity will inevitably be reduced, resulting in failure due to heat loss. Therefore, these cooling devices should be cleaned regularly. The specific method is: if the ventilation is hindered by the accumulation of dust on the protective net, it can be removed for cleaning; And so deep into the middle of the heat sink to sweep the dust. However, care should be taken during operation, and the heat sink should not be squeezed and deformed and overlapped, so as not to affect the heat dissipation effect. The above cleaning cycle is generally once every six months, and can also be shortened appropriately according to specific circumstances.
8. For CNC machine tools that are not used for a long time, the CNC system should be energized frequently, and the machine tool should be idling when it is locked and not moving. In the rainy season in the south where the air becomes more humid, electricity should be turned on every day, and the heat generated by the electrical components themselves should be used to drive off the moisture in the CNC cabinet. To ensure stable and reliable circuit performance. Practice has proved that the machine tools that are not in use are often prone to various failures after passing through Huangmeitian. If the CNC machine tool has been idle for more than half a year, the brushes of the DC servo motor should be taken out to avoid corrosion on the surface of the commutator due to chemical action, deterioration of the commutation performance, and even damage to the motor.
9. For the parts that move frequently on the machine tool, both mechanically and from the control drive, should be checked regularly as a key point. For example, in order to ensure the reliability of the machine tool on CNC machine tools, many limit switches are used to limit the movement position. The reliability of these travel switches directly affects the working reliability of the whole machine. In addition, the mechanical and electrical structure of the automatic tool changer on the machine tool is relatively complex, and it is prone to failure. Therefore, the electrical system that controls the tool selection and positioning of the tool magazine and the working condition of the travel switch that detects the operating position of the manipulator should be checked frequently. in order to ensure the normal operation of the machine.
After a long-term operation of any CNC machine tool, wear and failure will inevitably occur, but extending the working life of components, prolonging the wear cycle of machine tool components, preventing the occurrence of unexpected and malignant accidents, and striving for the machine tool to work reliably for a long time is a daily task. The purpose of preventive maintenance and maintenance of machine tools.