Manufacturers share preventive measures for common mechanical failures of CNC machine tools.

Measures for CNC Machine Tool Manufacturers to Prevent Common Mechanical Failures of CNC Machine Tools

1. Tool clamping failure handling
   When the tool cannot be released after clamping, consider adjusting the pressure of the tool release hydraulic cylinder and the stroke switch device. At the same time, the nut on the disc spring can also be adjusted to reduce the spring compression amount to ensure that the tool can be released normally.
2. Spindle heating handling
   For spindle heating problems, first clean the spindle box to ensure its cleanliness. Then, check and adjust the amount of lubricating oil to ensure that the spindle can be fully lubricated during operation. If the heating problem still persists, the spindle bearing may need to be replaced to eliminate the heating phenomenon caused by bearing wear.
3. Spindle box noise handling
   When noise occurs in the spindle box, check the condition of the gears inside the spindle box. If the gears are severely worn or damaged, they should be repaired or replaced in time to reduce noise. At the same time, regularly perform maintenance on the spindle box, check the fastening condition of each part, and prevent noise caused by loosening.

1. Improving transmission accuracy
   (1) Adjust the preload of each motion pair to eliminate transmission clearance. By adjusting the preload of motion pairs such as screw nut pairs and guide sliders, the clearance can be reduced and the transmission accuracy can be improved.
   (2) Set up reduction gears in the transmission chain to shorten the transmission chain length. This can reduce the accumulation of errors and improve transmission accuracy.
   (3) Adjust loose links to ensure that all parts are firmly connected. Regularly check the connectors in the transmission chain, such as couplings and key connections, to prevent loosening from affecting transmission accuracy.
2. Improving transmission stiffness
   (1) Adjust the preload of screw nut pairs and supporting components. Reasonably adjusting the preload can increase the rigidity of the screw, reduce deformation, and improve transmission stiffness.
   (2) Reasonably select the size of the screw itself. According to the load and precision requirements of the machine tool, select a screw with an appropriate diameter and pitch to improve transmission stiffness.
3. Improving motion accuracy
   Under the premise of meeting the strength and stiffness of the components, reduce the mass of moving parts as much as possible. Reduce the diameter and mass of rotating parts to reduce the inertia of moving parts and improve motion accuracy. For example, use worktables and carriages with lightweight designs.
4. Guide maintenance
   (1) Rolling guides are relatively sensitive to dirt and must have a good protective device to prevent dust, chips and other impurities from entering the guide and affecting its performance.
   (2) The preload selection of rolling guides should be appropriate. Excessive preload will significantly increase the traction force, increase the motor load, and affect motion accuracy.
   (3) Hydrostatic guides should have a set of oil supply systems with good filtration effects to ensure the formation of a stable oil film on the guide surface and improve the bearing capacity and motion accuracy of the guide.

1. Tool magazine movement failure handling
   (1) If the tool magazine cannot rotate due to mechanical reasons such as loose couplings connecting the motor shaft and worm shaft or overly tight mechanical connections, the screws on the coupling must be tightened to ensure a firm connection.
   (2) If the tool magazine does not rotate到位, it may be caused by motor rotation failure or transmission error. Check the operating status of the motor, such as voltage, current, and speed, to see if they are normal. At the same time, check the wear condition of transmission components such as gears and chains, and replace severely worn components in a timely manner.
   (3) If the tool sleeve cannot clamp the tool, adjust the adjusting screw on the tool sleeve, compress the spring, and tighten the clamping pin. Ensure that the tool is firmly installed in the tool sleeve and will not fall during the tool change process.
   (4) When the tool sleeve is not in the correct up or down position, check the position of the fork or the installation and adjustment of the limit switch. Ensure that the fork can accurately push the tool sleeve to move up and down, and the limit switch can accurately detect the position of the tool sleeve.
2. Tool change manipulator failure handling
   (1) If the tool is not clamped tightly and falls, adjust the clamping claw spring to increase its pressure or replace the clamping pin of the manipulator. Ensure that the manipulator can firmly hold the tool and prevent it from falling during the tool change process.
   (2) If the tool cannot be released after being clamped, adjust the nut behind the release spring to ensure that the maximum load does not exceed the rated value. Avoid the tool being unable to be released due to excessive spring pressure.
   (3) If the tool falls during tool exchange, it may be caused by the spindle box not returning to the tool change point or the tool change point drifting. Operate the spindle box again to make it return to the tool change position and reset the tool change point to ensure the accuracy of the tool change process.

1. Failure manifestations
   Variable pumps should be used for hydraulic pumps to reduce the heating of the hydraulic system. The filter installed in the fuel tank should be cleaned regularly with gasoline or ultrasonic vibration. Common failures are mainly pump body wear, cracks, and mechanical damage.
2. Preventive measures
   (1) Clean the filter regularly to ensure the cleanliness of hydraulic oil. Prevent impurities from entering the hydraulic system and damaging hydraulic components.
   (2) For failures such as pump body wear, cracks, and mechanical damage, generally, major repairs or replacement of parts are necessary. In daily use, pay attention to the maintenance of the hydraulic system and avoid overload operation and impact loads to extend the service life of the hydraulic pump.
   (B) Pneumatic system
3. Failure manifestations
   In the pneumatic system used for tool or workpiece clamping, safety door switch, and chip blowing in the spindle taper hole, the water separator and air filter should be drained regularly and cleaned regularly to ensure the sensitivity of moving parts in pneumatic components. Valve core malfunction, air leakage, pneumatic component damage, and action failure are all caused by poor lubrication. Therefore, the oil mist separator should be cleaned regularly. In addition, the tightness of the pneumatic system should be checked regularly.
4. Preventive measures
   (1) Drain water and clean the water separator and air filter regularly to ensure that the air entering the pneumatic system is dry and clean. Prevent moisture and impurities from entering pneumatic components and affecting their performance.
   (2) Clean the oil mist separator regularly to ensure good lubrication of pneumatic components. Select appropriate lubricating oil and perform oiling and cleaning at regular intervals.
   (3) Regularly check the tightness of the pneumatic system and detect and handle air leakage problems in a timely manner. Check pipeline connections, seals, valves and other parts to ensure good tightness of the pneumatic system.
   (C) Lubrication system
5. Failure manifestations
   It includes lubrication of machine tool guides, transmission gears, ball screws, spindle boxes, etc. The filter inside the lubrication pump needs to be cleaned and replaced regularly, generally once a year.
6. Preventive measures
   (1) Clean and replace the filter inside the lubrication pump regularly to ensure the cleanliness of lubricating oil. Prevent impurities from entering the lubrication system and damaging lubrication components.
   (2) According to the machine tool’s operation manual, regularly perform oiling and maintenance on each lubrication part. Select appropriate lubricating oil and adjust the oiling amount and oiling time according to the requirements of different parts.
   (D) Cooling system
7. Failure manifestations
   It plays a role in cooling tools and workpieces and flushing chips. The coolant nozzle should be cleaned regularly.
8. Preventive measures
   (1) Clean the coolant nozzle regularly to ensure that the coolant can be sprayed evenly on tools and workpieces, playing a good role in cooling and chip flushing.
   (2) Check the concentration and flow rate of the coolant and adjust it according to processing requirements. Ensure that the performance of the coolant meets processing needs.
   (E) Chip removal device
9. Failure manifestations
   The chip removal device is an accessory with independent functions, mainly to ensure the smooth progress of automatic cutting and reduce the heat generation of CNC machine tools. Therefore, the chip removal device should be able to remove chips automatically in a timely manner, and its installation position should generally be as close as possible to the tool cutting area.
10. Preventive measures
    (1) Regularly check the working status of the chip removal device to ensure that it can remove chips automatically in a timely manner. Clean the chips inside the chip removal device to prevent blockage.
    (2) Reasonably adjust the installation position of the chip removal device to make it as close as possible to the tool cutting area to improve chip removal efficiency. At the same time, ensure that the chip removal device is firmly installed and will not shake or shift during the processing process.