In addition to the quality factors of the machine tool, any CNC machine tool must be closely related to the correct maintenance, timely troubleshooting and timely maintenance in addition to the quality factors of the machine tool itself. From the point of view of improving the effectiveness of CNC machine tools, maintenance should include two aspects: on the one hand, daily maintenance (preventive maintenance), which is to extend the MTBF of the machine tool; on the other hand, it is fault maintenance. The purpose is to minimize the mean repair time MTTR. Doing these two tasks well is the basic guarantee for giving full play to the effectiveness of the equipment.
In order to give full play to the benefits of CNC machine tools, it is important to do preventive maintenance so that the CNC system will have fewer failures and improve the system's average time between failures. In addition, preparations for maintenance should be done at any time. When the system fails, it can be repaired in time to minimize downtime and repair time. This requires that you must be familiar with the structure and performance of the equipment, be familiar with the composition and basic operation of the CNC system, understand the available inspection points for the printed circuit board used in the system, and master its normal level and waveform so that it can be compared and analyzed during maintenance failures. . In addition, the technical data and original setup parameters of the CNC system and programmable controller (PLC) should be properly preserved, as well as the typical typical part programs. According to the actual use, some fragile spare parts can be properly equipped, such as fuses, brushes, fault-prone transistor modules and printed circuit boards. For the standby circuit board, the power supply must be installed on the CNC system periodically to avoid failure due to long-term use.
The key to preventative maintenance is to strengthen daily maintenance and maintenance. Usually the following points should be achieved:
1. The CNC programming, operation and maintenance personnel equipped with numerical control machine tools should be familiar with the characteristics of the mechanical structure, numerical control device, strong electrical equipment, hydraulic system, gas circuit, etc. of the equipment used, as well as the specified use environment and processing conditions. Wait. In addition, the machine tool must be used correctly and reasonably according to the requirements of the operating instructions of the machine tool and the numerical control device, and failures caused by improper operation should be avoided as much as possible.
2. Many systems use paper tape reader as the input device of the program. The paper tape information such as system parameters and part processing programs must be input into the CNC system through a paper tape reader. If the tape reading section of the tape reader (ie, the light emitting and receiving parts of the reading head) is dirty, the read tape information may be incorrect. Therefore, the surface of the reading head, the tape pressing plate, the tape passage surface Always check and remove dirt in a timely manner. The moving parts of the paper tape reader, such as the driving roller, the guide roller pressing roller, the tensioning roller, etc., should be cleaned regularly to ensure good lubrication.
3. Clean the air filter regularly. When the air filter installed on the numerical control cabinet and the electrical cabinet door has a large amount of dust, the cooling air in the cabinet may be unfavorably circulated. If this is done for a long time, the temperature inside the cabinet will rise, and the system cannot work reliably. Therefore, it should be checked regularly according to the use environment and at least once every six months. The specific method is: first remove the fastening screw, remove the core of the air filter, and blow the dust on the filter core from the inside out with compressed air. If the filter is dirty, you can also gently vibrate the filter at the same time. When the above method fails to work, you can use a neutral detergent (cleaning agent ratio 5%) to wash, but can not be rubbed, and then put the filter element in a cool and ventilated place to dry You can do it.
4, regular battery maintenance. For numerical control devices that use CMOS memory to save system parameters, in order to avoid loss of parameters when the power is turned off, battery power is used to maintain them. When the battery voltage is lower than the CMOS hold 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 is cut off. When the machine tool is stopped for a long time, it should be periodically powered on according to the requirements of the manual, so that the battery can be supplied with power. If such a numerical control device displays a battery failure alarm on the CRT or with an indicator lamp, 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 while the power is on, and the polarity of the battery cannot be reversed.
5, DC servo motor should be regularly checked and cleaned. The DC servo motor is equipped with a brush and gradually wears off when it contacts with the commutator during operation. Excessive brush wear can affect the performance of the motor and even damage the motor. Therefore, it must be checked and replaced regularly. For general machine tools such as CNC lathes, CNC milling machines and machining center machine tools, etc., they can be checked once a year; for machines that frequently perform acceleration and deceleration, such as punch presses, they should be checked every two months. When checking, it is necessary to disconnect the CNC power supply and the motor is completely cooled. First remove the brush cover, take out the brush and measure its length. Under normal circumstances. When the brush wears to half of its original length, it should not be used again, and the same type of new brush must be replaced. The second step should carefully check whether the brush contact with the commutator arc contact surface whether there is a deep groove or cracks, and whether the brush spring ignition traces, if the above phenomenon, you must carefully check the surface of the commutator. If the commutator is normal, the new brush can be replaced and checked again after one month; if the above phenomenon still occurs, it is necessary to consider whether the motor's working condition is too bad and the motor itself is faulty. Before installing a new brush, clean the brush holes with clean compressed air that does not contain metal powder and moisture. Be sure to blow off the brush powder that adheres to the hole walls. If it is difficult to blow the net, use a screwdriver or other tools to assist in cleaning until the wall is completely clean. However, care must be taken to avoid damage to the commutator surface and hole wall by the screwdriver tip. Finally, a new brush is installed, the cover is tightened, and the servo motor runs idle for a period of time so that the new brush surface matches the commutator.
6. Pay attention to the closed CNC cabinet door. Under normal circumstances should avoid opening the CNC door, especially long-term open door operation. The air filter should be cleaned in time. However, it is not possible to use the method of opening the door to dissipate heat. Otherwise, it will not be worth the candle. Because there is a lot of dust, oil mist and metal powder floating in the air in the workshop, these debris fall on the printed circuit board and electronic components, which may cause the insulation resistance of the components to drop and cause failure, and even make the components and printing. Circuit board damage is scrapped. Especially for CNC machine tools where the spindle control system is installed in a power cabinet, such as a strong cabinet door that is not closed or has a poor seal, it is easy to cause damage to the electrical components to disable the spindle control.
7. Clean the cooling device regularly to enhance the cooling effect. Some servomotors or spindle motors have a forced cooling device on the casing. If the protection network or heat sink of the cooling device is dirty, it will affect the circulation of air, which will inevitably reduce the cooling capacity and cause failure due to heat loss. Therefore, these cooling devices should be regularly cleaned. The specific method is: if the dust in the protection network interferes with the ventilation, it can be removed for cleaning; when the heat dissipation fins are a lot of dust, it can be blown with compressed air, or with a thin rod Into the middle of the heat sink to remove dust. However, be careful when handling. Do not squeezing and deforming the heat sinks and overlap them so as not to affect the heat dissipation effect. The above cleaning cycle is generally once every six months, and may also be shortened as appropriate.
8. For CNC machine tools that are not used for a long period of time, the CNC system should always be powered on, and the machine tool should be kept running when the machine tool is locked. In the southern Meiyu season when the air humidity becomes larger, electricity should be applied every day. The heat generated by the electrical components themselves will be used to drive off the moisture in the CNC cabinet. To ensure the stability and reliability of circuit performance. Practice has proved that after a machine that has been parked for no use passes through Huang Meitian, it is prone to various types of failures. If the CNC machine tool is idle for more than half a year, the brush of the DC servo motor should be taken out so that the surface of the commutator may be corroded due to chemical action, the commutation performance may be deteriorated, and even the motor may be damaged.
9. For the parts that are frequently moved on the machine tool, whether it is from the machine or the control drive, it should be regularly checked as the focus. For example, in the CNC machine tool, in order to ensure the reliability of the machine tool, a lot of limit switches are used to limit the movement position. The reliability of these trip switches directly affects the reliability of the entire machine. In addition, the mechanical and electrical structures of the automatic tool changer on the machine tool are relatively complex and are prone to failure. Therefore, the electrical system that controls the selection and positioning of the tool magazine and the working status of the travel switch that detects the operation position of the robot should be checked frequently. To ensure the normal operation of the machine.
Any long-term operation of a CNC machine tool will inevitably lead to wear and failure, but it will prolong the working life of the components, prolong the wear cycle of the machine components, prevent accidental malignant accidents, and strive for long-term and reliable machine tool work. The purpose of preventive maintenance and maintenance of the machine tool. General machine tool manuals have specific requirements for maintenance inspections and should be operated strictly in accordance with the regulations.
