Analyze the four precision fault causes and solutions of CNC machine tools
Accuracy has always been one of the important criteria for measuring the quality of a CNC machine. Many of our friends' machines have lost their accuracy after a period of use. The following 9 strokes will rejuvenate your machine!
1, the workpiece size is accurate, the surface finish is poor
The cause of the failure: the tool tip is damaged, not sharp; the machine tool generates resonance, the placement is not stable; the machine tool has crawling phenomenon; the processing technology is not good.
Solution: If the tool is not sharp after being worn or damaged, re-grind the knife or choose a better tool to re-align the tool; the machine will generate resonance or place it is not stable, adjust the level, lay the foundation, and fix it smoothly; the reason for the mechanical creep is drag The plate guide rail is very worn, the lead screw ball is worn or loose, the machine tool should pay attention to maintenance, the wire should be cleaned after work, and the lubricating oil should be added in time to reduce the friction; the coolant suitable for the workpiece processing can be selected to meet the processing requirements of other processes. In the case, try to use a higher spindle speed.
2, the workpiece produces a taper size head phenomenon
The cause of the failure: the level of the machine tool is not adjusted well, one high and one low, the placement is not stable; when turning the long axis, the contribution material is relatively hard, the tool is deeper, causing the knife phenomenon; the tailstock thimble is not concentric with the main shaft.
Solution: Use the level to adjust the level of the machine, lay a solid foundation, fix the machine to improve its toughness; choose a reasonable process and appropriate cutting feed to avoid the tool force to make the knife; adjust the tailstock.
3. The driver phase lamp is normal, and the processed workpiece size is large and small.
The cause of the failure: the long-term high-speed operation of the machine tool carriage causes the lead screw and the bearing to wear out; the repeated positioning accuracy of the tool holder is deviated in the long-term use; the carriage can accurately return to the machining starting point every time, but the size of the processed workpiece still changes. This phenomenon is generally caused by the main shaft, and the high-speed rotation of the main shaft causes the bearing to wear seriously, resulting in a change in the machining size. Metal processing WeChat, the content is good, it is worthy of attention.
Solution: Use the dial gauge to lean against the bottom of the tool holder, and edit a fixed cycle program through the system, check the repeat positioning accuracy of the carriage, adjust the screw clearance, replace the bearing; check the repeat positioning accuracy of the tool holder with the dial indicator. Adjust the machine or replace the tool holder; use a dial indicator to check whether the workpiece is accurately returned to the starting point of the program. If possible, repair the spindle and replace the bearing.
4. The workpiece size differs from the actual size by a few millimeters, or a certain axial direction changes greatly.
The cause of the fault: the speed of rapid positioning is too fast, the drive and the motor do not react; after long-term friction loss, the mechanical lead screw and the bearing are too tightly stuck; the tool post is too loose after the tool change, the lock is not tight; the editing procedure Error, the head and tail did not respond or did not cancel the tool to complete; the system's electronic gear ratio or step angle setting is wrong.
Solution: If the rapid positioning speed is too fast, the speed of the GO will be adjusted appropriately. The cutting acceleration and deceleration and time will make the drive and the motor work normally at the rated operating frequency. After the machine wear occurs, the carriage and the screw crane bearing are too tight. If the card is dead, it must be re-adjusted. If the tool holder is too loose after the tool change, check whether the tool holder reversal time is satisfied, check whether the worm gear inside the tool holder is worn, whether the clearance is too large, whether the installation is too loose, etc.; If the cause is caused, it is necessary to modify the program, improve according to the requirements of the workpiece drawing, select a reasonable processing technology, and write the correct program according to the instructions of the manual; if it is found that the dimensional deviation is too large, check whether the system parameters are set properly, especially the electronic gear and Whether the parameters such as the step angle are destroyed, this phenomenon can be measured by dialing a dial indicator.
