Daily maintenance of CNC machines

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To fully utilize CNC machines, reduce the occurrence of failures, and extend their average time between failures. Programmers, operators, and maintenance personnel of CNC machines must receive specialized technical training and possess knowledge in areas such as machining processes, hydraulics, measurement, and automatic control. Only in this way can they fully understand and master CNC machines, and carry out proper maintenance and upkeep of them. I. Contents and requirements for the daily maintenance of CNC machines. Operators of CNC machines must strictly adhere to the operating procedures as well as the systems for daily maintenance. They should operate the machines in a correct and proper manner, in accordance with the instructions provided in the machine and system manuals, in order to avoid any issues resulting from improper operation. 1. Check the oil level gauge and oil quantity in the guide rail lubrication tank daily, and add lubricant as needed; the lubrication pump should be able to start and stop promptly to supply lubricant. 2. Remove chips and dirt from the guide rail surfaces in the X and Z directions daily, check whether the lubricant is sufficient, and inspect the guide rail surfaces for any scratches or damage. 3. Check the pressure of the pneumatic control system using the compressed air source daily; it should be within the normal range. 4. The automatic water separator and filter for the air supply, along with the automatic air dryer, are used to remove the water accumulated in the separator on a daily basis, ensuring the proper operation of the automatic air dryer. 5. Check the level of oil in the dynamo converter and turbocharger daily; top up the oil promptly if it is at an insufficient level. 6. Ensure that the lubrication oil tank for the main shaft functions properly daily, with sufficient oil volume and an appropriate operating range. 7. Verify that the balance pressure indicator of the hydraulic balancing system is normal daily, and that the balance valve operates properly during rapid movements. 8. Daily, there are no abnormal noises from the hydraulic system’s oil tank and oil pump; the pressure gauge shows normal readings, there are no leaks in the pipelines or connections, and the level of the working oil is within the normal range. 9. Daily, the cooling and ventilation devices in each electrical cabinet, as well as the cooling fans of each electrical cabinet, operate properly, and the air duct filters are not clogged. 10. Daily, check the CNC input/output devices to ensure that the I/O devices are clean and that the mechanical components are properly lubricated. 11. Daily, various protective devices such as guide rails and machine tool guards should show no signs of looseness or leakage. 12. Clean the filters in each electrical cabinet on a weekly basis. 13. Cool the oil tank and water tank periodically; check the liquid level at any time, add oil or water as needed, and replace and clean the oil tank, water tank, and filters when they become too dirty. 14. Regularly remove the accumulated used oil from the waste oil tank to prevent overflow. 15. The periodic chip remover should regularly clean the chips and check for any blockages, etc. 16. Regularly check the spindle drive belt; adjust its tension as required by the instructions, and replace it promptly if it is damaged. 17. Periodically check the shims and compression rollers on the guide rails of each axis, and adjust their tightness according to the machine tool’s manual. 18. Every six months, clean the old lubricant from the ball screw and apply new lubricant. 19. Every six months, clean the relief valves, pressure regulators, oil filters, and oil tank in the hydraulic system, and replace or filter the hydraulic oil. 20. Every year, clean the filters in the main shaft lubrication oil tank and replace the lubricating oil. 21. Every year, inspect and replace the brushes of the DC servo motor, check the surface of the commutator, blow away carbon dust, remove burrs, and replace brushes that are too short. 22. Every year, clean the bottom of the lubricant tank in the lubricant pump and filter, and replace the oil filter. II. Daily Maintenance of the Mechanical Structure: CNC machines are automated tools that integrate mechanical, electrical, and hydraulic components. Through the functional actions of these various components, tasks such as movement, rotation, clamping, releasing, speed adjustment, and tool changing are carried out by the mechanical actuation mechanisms. It is evident that proper daily maintenance of these mechanical actuation mechanisms has a direct impact on the performance of the CNC machine. The daily maintenance of the mechanical structure of CNC machine tools mainly includes the maintenance of the machine tool body, spindle components, ball screw nut assemblies, guide rail assemblies, etc. 1. Exterior maintenance · Clean the machine tool daily, remove iron shavings, and wipe away the coolant from the guide rail areas. At the end of work, apply machine oil to all machined surfaces to prevent rust and stop the guides from rusting. · Check daily to ensure that the guide rails and machine tool guards are complete and in good condition. · Check daily for any dents, scratches, or strains inside and outside the machine tool. · Regularly remove chips and oil residue from all components, ensuring no dead corners remain, and keep them clean both inside and outside to prevent rust. 2. Spindle maintenance: In CNC machines, the spindle is the most critical component, as it plays a decisive role in the machining accuracy of the machine. Its rotational accuracy affects the machining precision of the workpiece, while power level and rotational speed influence the machining efficiency. The maintenance of the mechanical structure of the spindle assembly mainly includes spindle support, transmission, lubrication, etc. · Regularly inspect the spindle support bearings: Insufficient bearing preload, loose preload screws, or excessive play can cause axial movement of the spindle, which should be adjusted promptly ； Bears that are abraded or damaged should be replaced promptly. · Regularly inspect the spindle’s lubrication oil tank, clean the filter in a timely manner, and replace the lubricating oil to ensure proper lubrication of the spindle. · Regularly inspect the gear sets; if there is severe damage or the gear mesh clearance is too large, the gears should be replaced and the mesh clearance adjusted promptly. · Regularly check the spindle drive belt; adjust its tension as needed or replace it when necessary. 3. Maintenance of ball screw nuts: Ball screw drives are widely used in CNC machines due to their advantages such as high transmission efficiency, high precision, smooth motion, long service life, and the ability to pre-tighten them in order to eliminate play. Its routine maintenance includes the following aspects: · Regularly check the axial clearance of the ball screw nut; under normal circumstances, this clearance can be eliminated through automatic compensation by the control system ； When the gap is too large, it can be adjusted by modifying the ball screw nut assembly. Most ball screw nut assemblies in CNC machines use a dual-nut design, and the gap can be eliminated through pre-tightening of these two nuts. · Regularly inspect the screw guard to prevent dust and abrasive particles from adhering to the surface of the screw, which could affect its service life and accuracy; any damage to the screw guard should be repaired or replaced promptly. · Regularly check the lubrication of the ball screw nut: The lubricants for ball screw nut assemblies can be divided into grease and oil. Replace the grease every six months: clean the old grease from the screw and apply new grease ； Using a lubricated roller screw nut, oil can be applied once before each machine operation. · Regularly inspect the support bearings: It is necessary to regularly check whether there is any looseness in the connection between the screw support bearings and the machine tool, as well as whether the support bearings are damaged. If such issues are found, the loose parts should be tightened promptly and the support bearings replaced. · Regularly check the connection between the servo motor and the ball screw: the connection between them must be gap-free. 4. Maintenance of guide rails: Guide rails are important functional components in CNC machines, with sliding guide rails and rolling guide rails being the most common types. The maintenance of guide rails is generally carried out irregularly, and the main tasks include: · Checking the shims and compression rollers on the guide rails of each axis to ensure that there is a proper gap between the guide rail surfaces. Adjust the tightness level according to the machine tool’s instructions. The methods for adjusting the clearance include adjusting the clearance using pressure plates, adjusting it with inserts, and adjusting it by using both pressure plates and inserts. · Pay attention to the lubrication of the guide rails: Lubricating the surface of the guide rails can reduce friction and wear, as well as prevent them from rusting. Adjust the amount of lubricant for the guides in a timely manner based on their lubrication condition, maintain the appropriate lubricant pressure, and ensure proper lubrication of the guides.