Maintenance of CNC system
1. Strictly abide by the operating procedures and daily maintenance system
2. Prevent dust from entering the numerical control device: Floating dust and metal powder can easily cause the insulation resistance between components to decrease, leading to failure or even damage to the components.
3. Regularly clean the heat dissipation and ventilation system of the CNC cabinet
4. Frequently monitor the grid voltage of the numerical control system: the grid voltage range is 85% to 110% of the rated value.
5. Regularly replace the storage battery
6. Maintenance of the numerical control system when it is not in use for a long time: often power on the numerical control system or allow the numerical control machine tool to run a warm machine program.
7. Maintenance of spare circuit board Maintenance of mechanical parts
Maintenance of mechanical parts
1. Maintenance of tool magazine and tool change manipulator
1) When manually loading the tool into the tool magazine, ensure that it is installed in place and check whether the locking on the tool holder is reliable;
2) It is strictly forbidden to load overweight and overlong tools into the tool magazine to prevent the tool from being dropped when the manipulator changes the tool or the tool collides with the workpiece, fixture, etc.;
3) When using sequential tool selection, pay attention to whether the order of the tools placed on the magazine is correct. Other tool selection methods should also pay attention to whether the number of the tool to be changed is consistent with the required tool to prevent accidents caused by changing the wrong tool;
4) Pay attention to keep the knife handle and knife sleeve clean;
5) Frequently check whether the zero return position of the tool magazine is correct, check whether the position of the machine spindle return tool change point is in place, and adjust it in time, otherwise the tool change action cannot be completed;
6) When starting up, the tool magazine and manipulator should be run dry first to check whether each part works normally, especially whether each travel switch and solenoid valve can operate normally.
2. Maintenance of ball screw pair
1) Regularly check and adjust the axial clearance of the screw nut pair to ensure the accuracy of the reverse transmission and the axial rigidity;
2) Regularly check whether the connection between the screw support and the bed is loose and whether the support bearing is damaged. If there are any of the above problems, tighten the loose parts in time and replace the support bearings;
3) For ball screws with grease, clean the old grease on the screw every six months and replace with new grease. The ball screw lubricated with lubricating oil should be refueled once a day before the machine tool works;
4) Take care to prevent hard dust or chips from entering the lead screw guard and hitting the guard during work. If the guard is damaged, it should be replaced in time.
3. Maintenance of the main drive chain
1) Regularly adjust the tightness of the spindle drive belt;
2) Prevent all kinds of impurities from entering the fuel tank. Change the lubricating oil once a year;
3) Keep the connecting part of the spindle and the tool holder clean. It is necessary to adjust the displacement of hydraulic cylinder and piston in time;
4) Adjust the counterweight in time.
4. Hydraulic system maintenance
1) Regularly filter or replace the oil;
2) Control the temperature of the oil in the hydraulic system;
3) Prevent leakage of hydraulic system;
4) Regularly check and clean the fuel tank and pipeline;
5) Implement the daily point inspection system.
5. Maintenance of pneumatic system
1) Remove impurities and moisture from compressed air;
2) Check the oil supply of the lubricator in the system;
3) Maintain the tightness of the system;
4) Pay attention to adjusting the working pressure;
5) Clean or replace pneumatic components and filter elements;
Troubleshooting
In CNC machine tools, most of the faults are available for investigation, but there are also some faults. The alarm information provided is vague or even no alarm at all, or the period of occurrence is long, irregular, and irregular, which brings to the search and analysis Many difficulties. For such machine tool failures, it is necessary to analyze the specific conditions and perform patient search. In addition, comprehensive knowledge of machinery, electricity, hydraulics, etc. is particularly required during the inspection, otherwise it is difficult to quickly and correctly find the real cause of the failure.
Abnormal machining accuracy failures: system parameters change or change, mechanical failures, machine tool electrical parameters are not optimized, abnormal motor operation, abnormal machine tool position loops or incorrect control logic are common causes of abnormal machining accuracy failures of CNC machine tools in production. Find out the relevant If the fault point is dealt with, the machine tool can return to normal. In production, we often encounter faults with abnormal machining accuracy of CNC machine tools. Such faults are highly concealed and difficult to diagnose.
There are five main reasons for this type of failure:
1. The feed unit of the machine tool is changed or changed;
2. The zero offset (NULLOFFSET) of each axis of the machine tool is abnormal;
3. The axial backlash (BACKLASH) is abnormal;
4. The motor running status is abnormal, that is, the electrical and control parts are faulty;
5. Mechanical failure, such as screw rod, bearing, shaft coupling and other parts.
In addition, the preparation of the processing program, the selection of tools and human factors may also cause abnormal processing accuracy.
If the machining accuracy is abnormal due to mechanical failure, the following aspects should be checked one by one.
1. Check the machining program segment that is running when the accuracy of the machine tool is abnormal, especially the tool length compensation, the proofreading and calculation of the machining coordinate system (G54～G59).
2. In the jog mode, move the Z axis repeatedly, and diagnose the motion state by sight, touch, and listen. It is found that the sound of Z-direction movement is abnormal, especially when the jog is fast, the noise is more obvious. Judging from this, there may be hidden dangers in machinery [1].
Troubleshooting
1. Initialization reset method: Under normal circumstances, system alarms caused by instantaneous faults can be cleared by hardware reset or switch system power in turn. If the system working storage area is lost due to power failure, unplugging the circuit board or battery undervoltage, it will cause confusion , The system must be initialized and cleared. Before clearing, you should make a record of data copy. If the fault cannot be eliminated after initialization, perform hardware diagnosis.
2. Parameter modification and program correction method: System parameters are the basis for determining system functions, and parameter setting errors may cause system failures or invalid functions. Sometimes due to user program errors can also cause failures to stop, this can be checked by the system's block search function to correct all errors to ensure its normal operation.
3. Adjustment and optimization adjustment method: Adjustment is the simplest and most feasible method. Correct the system failure by adjusting the potentiometer. For example, during maintenance in a factory, the system display screen is chaotic, and it is normal after adjustment. For example, in a factory, belt slippage occurs when the main shaft starts and brakes. The reason is that the main shaft load torque is large, and the ramp-up time of the drive device is set too small, which is normal after adjustment.
Optimal adjustment is a comprehensive adjustment method to systematically achieve the best match between the servo drive system and the mechanical system being dragged. The method is very simple. Use a multi-line recorder or a dual-track oscilloscope with storage function, respectively Observe the response relationship between the command and the speed feedback or current feedback. By adjusting the proportional coefficient and integral time of the speed regulator, the servo system can achieve the best working condition with high dynamic response characteristics without oscillation. In the absence of an oscilloscope or recorder on site, based on experience, adjust to make the motor vibrate, and then slowly adjust in the reverse direction until the vibration is eliminated.
4. Spare parts replacement method: replace the faulty circuit board with a good spare part, and do the corresponding initial startup, so that the machine tool can be quickly put into normal operation, and then the broken board is repaired or repaired. This is the most commonly used troubleshooting method.
5. Method of improving power quality: Regulated power supply is generally used to improve power supply fluctuations. Capacitor filtering method can be used for high frequency interference, through these preventive measures to reduce the failure of the power board.
6. Maintenance information tracking method: Some large manufacturing companies constantly modify and improve system software or hardware based on accidental failures caused by design defects in actual work. These modifications are continuously provided to maintenance personnel in the form of maintenance information. Using this as a basis for troubleshooting, the fault can be eliminated correctly and thoroughly.
