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Do you know what precautions should be taken for preventive maintenance of CNC machine tools?

Release time:2015/12/9
This article has been read:234time

If any CNC machine tool wants to work continuously and reliably for a long time, in addition to the quality factors of the machine itself, it is also closely related to correct maintenance, timely troubleshooting, and timely repair during use. From the perspective of improving the effectiveness of CNC machine tools, maintenance should include two aspects: one is daily maintenance (preventive maintenance), which is to extend the mean time between failures (MTBF) of the machine tool; On the other hand, it is fault maintenance, whose purpose is to minimize the Mean time to recovery (MTTR). Doing these two tasks well is the basic guarantee for fully utilizing equipment efficiency.

In order to give full play to the benefits of CNC machine tools, it is important to do a good job in Preventive maintenance, so that the CNC system will have fewer failures and improve the mean time between failures of the system. In addition, preparations for maintenance should be made at all times to promptly repair any system malfunctions, in order to minimize downtime and repair time. This requires familiarity with the structure and performance of the equipment, the composition and basic operation of the CNC system, understanding the detection points available for maintenance on the printed circuit board used in the system, and mastering their normal levels and waveforms for comparison and analysis when repairing faults. In addition, the technical data and original setting parameters of the CNC system and programmable logic controller (PLC), as well as commonly used typical part programs, should also be properly stored. According to actual usage, some vulnerable spare parts can be equipped appropriately, such as fuses, brushes, as well as transistor modules and printed circuit boards that are prone to malfunctions. For backup circuit boards, they should be regularly installed on the CNC system and powered on for operation to avoid malfunctions caused by long-term use.

The key to preventive maintenance is to strengthen daily maintenance and upkeep, which usually includes the following points:

1. The CNC system programming, operation, and maintenance personnel equipped with CNC machine tools should be familiar with the mechanical structure, CNC device, strong current equipment, hydraulic system, pneumatic circuit, and other characteristics of the equipment used, as well as the specified usage environment and processing conditions. And strictly follow the requirements of the machine tool and CNC device user manual to use the machine tool correctly and reasonably, and try to avoid malfunctions caused by improper operation.

2. Many systems use paper tape Reading machine as program input devices. System parameters, part processing programs and other paper tape information are all input into the CNC system through paper tape Reading machine. If the tape reading part of the tape Reading machine (that is, the light emitting and light receiving part of the reading head) has dirt, the read tape information will be wrong. Therefore, the surface of the reading head, the paper tape pressing plate, and the paper tape channel should be checked frequently to remove the dirt in time. The moving parts of the paper tape Reading machine, such as the driving wheel roller, the guide roller compaction roller, the tension arm roller, etc., should be regularly cleaned and well lubricated.

3. Regularly clean the air filter. When the air filter installed on the door of the CNC cabinet and electrical cabinet is dusty, it can cause poor cooling air circulation inside the cabinet. Prolonged use of this method can cause an increase in temperature inside the cabinet, making the system unable to work reliably. Therefore, regular inspections should be carried out according to the usage environment, and at least once every six months, dismantling and cleaning should be carried out. The specific method is to 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 fails, you can use neutral detergent (5% detergent) to wash, but not rub, and then place the filter element in a cool and ventilated place to dry.

Do you know what precautions should be taken for preventive maintenance of CNC machine tools?

4. Regularly maintain the battery. For CNC devices that use CMOS memory to store system parameters, in order to avoid parameter loss during shutdown and power outage, battery power supply is used to maintain it. When the battery voltage is lower than the CMOS holding voltage, the battery can automatically charge when the machine tool is turned on. Normally, the battery can ensure that the information is stored for more than 1000 hours after power outage. When the machine tool is shut down for a long time, it should also be regularly powered on and started according to the requirements of the manual to replenish the battery's power. If this type of CNC device displays a battery failure alarm on the CRT or with an indicator light, it indicates that the voltage is too low, the battery has failed, and a new battery needs to be replaced. In order to save the original data, the battery should be replaced with the power on and the polarity of the battery should not be reversed.

5. The DC servo motor should be regularly inspected and cleaned. The DC servo motor is equipped with an electric brush, which gradually wears out due to contact and friction with the commutator during operation. After excessive wear and tear of the electric brush, it can affect the working performance of the motor and even cause damage to the motor. Therefore, regular inspection and replacement are necessary. For general machine tools such as CNC lathes, CNC milling machines, and machining center machines, they can be inspected once a year; For machine tools that frequently engage in acceleration and deceleration work, such as punching machines, they should be inspected every two months. When checking, it is necessary to disconnect the power supply of the CNC system and ensure that the motor has completely cooled down. Firstly, remove the brush cover, take out the brush, and measure its length. Generally, this is the case. When the brush is worn to half its original length, it should no longer be used and must be replaced with a new brush of the same model. The second step should be to carefully inspect the arc-shaped contact surface between the brush and the commutator for deep grooves or cracks, as well as the brush spring for any signs of ignition. If there are any of the above phenomena, the surface of the commutator must be carefully inspected. If the commutator is normal, it can be replaced with a new brush and rechecked after one month; If the above phenomenon still occurs, it is necessary to consider whether the working conditions of the motor are too harsh, causing the motor to malfunction. Before installing a new brush, clean the brush hole with clean compressed air that does not contain metal powder or moisture, and be sure to blow out the brush powder adhering to the hole wall. If it is difficult to blow clean, tools such as a screwdriver can be used to assist in cleaning until all the hole walls are clean. But be careful to avoid damaging the commutator surface and hole wall with the screwdriver tip. Install a new brush, tighten the brush cover, and let the servo motor run idle 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. In general, it should be avoided to open the CNC cabinet door arbitrarily, especially for long-term open door operation. The air filter should be cleaned in a timely manner. 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 large amount of dust, oil mist, and metal powder floating in the air of the workshop, these impurities fall on printed circuit boards and electronic components, which can easily cause a decrease in insulation resistance of components and cause malfunctions, and even damage and scrap of components and printed circuit boards. Especially for CNC machine tools that install the spindle control system in a strong current cabinet, if the door of the strong current cabinet is not tightly closed or the seal is poor, it can easily cause damage to electrical components and cause spindle control failure.

7. Regularly clean the cooling device to enhance the heat dissipation effect. Some servo motors or spindle motors have forced cooling devices installed on the casing. If the protective mesh or heat sink of the cooling device is dirty, it will affect the air circulation and inevitably reduce the cooling capacity, leading to faults due to heat loss. Therefore, these cooling devices should be cleaned regularly. The specific method is: if the ventilation is hindered due to excessive dust accumulation in the protective mesh, it can be removed for cleaning; When there is a lot of dust accumulation in the heat sink, compressed air can be used to blow it clean, or a thin rod can be used to sweep the dust deep into the middle of the heat sink. But during operation, be careful not to compress or deform the heat dissipation fins, overlapping them together to avoid affecting the heat dissipation effect. The cleaning cycle mentioned above is generally once every six months, and can be appropriately shortened according to specific circumstances.

8. For CNC machine tools that have not been used for a long time, the CNC system should be regularly powered on and left idle when the machine tool is locked. In the southern rainy season where the air humidity changes greatly, it is more important to turn on electricity every day to use the heat generated by the electrical components themselves to drive away the moisture inside the CNC cabinet. To ensure stable and reliable circuit performance. Practice has proven that machine tools that are not in use are often prone to various malfunctions after passing through Huangmei. If the CNC machine tool is idle for more than half a year, the brush of the DC servo motor should be removed to avoid corrosion of the commutator surface due to chemical action, deterioration of commutation performance, and even damage to the motor.

9. For components that frequently move on machine tools, both mechanical and control driven, regular inspections should be a key focus. In order to ensure the reliability of CNC machine tools, many travel switches are used to limit the movement position. The reliability of these travel switches directly affects the working reliability of the entire machine. In addition, the Automatic tool changer on the machine tool has complex mechanical and electrical structures, which 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 to ensure that the machine tool can operate normally.

Any CNC machine tool will inevitably suffer from wear and failure after long-term operation, but it is the purpose of daily Preventive maintenance and maintenance for the machine tool to extend the working life of components, prolong the wear cycle of machine tool components, prevent accidents and malignant accidents, and strive for the machine tool to work reliably for a long time. General machine tool user manuals have specific requirements for maintenance and inspection, and operations should be strictly carried out in accordance with regulations.


Do you know what precautions should be taken for preventive maintenance of CNC machine tools?
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