1、Accurate size of work piece, but poor surface fineness
Reason: the tool tips are damaged and blunt; the machine tool created the resonances, and placed unsteadily; there is crawling phenomenon for the machine tool; the poor processing technology.
Solution: if the tool tips were damaged and blunt, it should be sharpen or choose a better cutter; if the machine tool created the resonances, and placed unsteadily, the workers should adjust the level, lay a foundation and keep it steady; the reason why there was crawling phenomenon is that the carriage guide way was worn seriously, the guide screw and ball was worn or loosen. In this case, the machine tool should be maintained frequently, before and after the using, the guide screw should be cleaned and added lubricating oil, thereby reduce the friction force; choose suitable coolant and higher speed of spindle.
2、The size of the first error of the taper work piece
Reason：the level of the machine tool were not adjusted well , so it placed unsteadily; when turning the long axis, the contributed materials are hard, which caused deep penetration of tool and cutter relieving; the thimble in tailstock and the main spindle are not concentric.
Solution：Using level meter to adjust the level of the machine tool, laying a stable foundation and keeping it steady, which is beneficial to improve their toughness; choosing suitable technology and the cutting feed which can avoid cutter relieving; adjusting the tailstock.
3、The phase modulation of the driver is working, but the size of the processed work pieces are various.
Reason：the carriage of the machine tool works in high speed for long time, which led to the abrasion of screw and bearing; some errors the repetitive position precision occurred; the carriage can back to the processed starting point precisely, but the size of the processed work pieces still change. The main reason of it is that the main spindle works in high-speed which wear the bearing seriously and change the size of the processed work pieces.
Solution：put the dial indicator in the bottom of the tool rest, edit a stable loop program by using system, check the repetitive position precision of the carriage, adjust the clearance of the screw and change bearings; using the dial indicator to check the repetitive position precision of the tool rest and adjust or change the tool rest; using the dial indicator to check whether the processed work pieces can go back to starting point accurately. If they can, check the function of the main spindle and change the bearing.
4、there are errors of the size of the work pieces, or some changes along an axe
Reason：for the driver and motor, the speed of the quick positioning is too fast to response; after wearing for long time, the carriage screw and bearing are too tight; after changing the cutters, the tool rest is loose; the program is wrong, so it is over without the cancelling the cutter compensation or there is not coherent; the electronic gear ratio or the step angle was set incorrect.
Solution：if the speed of the quick positioning is too fast, the speed of the GO should be adjusted, the driver and motor can work successfully due to the time, the acceleration and deceleration of the cutting under rated operating frequency; if the carriage screw and bearing were too tight, they should be adjusted again; if the tool rest was loose, workers should check whether the inversion time of the tool rest is satisfied or not, check whether the worm turbine is worn and the clearance is too big or not; if the program is the reason of this errors, the program should be edited according to the image of the work piece, and workers should choose the suitable processed technology; Using level meter to check whether the parameters of the system are suitable or not, especially for the electronic gear and the step angle.
5、the results of the manufacture of the arc are not ideal, and the size is not accurate enough
Reason： creating the resonance due to overlapping vibrational frequency; the processed technology; the parameters are set unreasonably, the feed speed is too fast, caused the errors when process the arc; the screw is too loose or tight because of the clearance of the screw, which lead to loss of synchronism; the synchronous belt was worn.
Solution： finding the part which create the resonance, changing its frequency, which is helpful to avoid resonance; consider the processed technology according to the materials of the work pieces, and program in suitable way; for the stepping motor, the value of the processed speed F cannot be set too large; check the whether the machine tool was put steadily, the carriage was too tight, the clearance was too big and the tool rest is loose or not; change the synchronous belt.
6、In production, there are some extremely unsatisfying work piece randomly
Reason：Workers should check the tooling and fixtures and consider the operational approaches, and the reliability of the fixtures. When the size changes due to the fixtures, the fixtures should be improved which is beneficial for workers to avoid the human errors; the numerical control system would be affected due to the external power supply variations and interference pulse.
Solution：Understanding the rules and using some anti-interference measures, for example: isolate the power cable from signal wire. On the other hand, checking the ground wire connects firmly and the contact is lowest or not. Use various methods to avoid influence of the interference.
7、some changes happened in a single process, but the size of work piece is accurate in others processes
Reason：Check whether the parameters of program are suitable or not, whether in the expected track or not, whether the format of the program meets the requirements of the specification or not.
Solution：When errors happened in the section of the arc program and the thread pitch is different, the workers should consider the peripheral equipment (encoder) of the processed arc and others objective factors.
8、the size of the work piece is increasing or decreasing with every processes
Reason：there are bugs in the program; the parameters of system are not suitable; configuration is undeserved; there are some errors for the mechanical transmission components periodically
Solution： Using the dial indicator to check whether the commands of the program execute following the requirements of the specifications or not. Put the dial indicator in the starting point of the program and check the carriage can be go back to the starting point at the end of the program. After observing the results, the rules can be understood; check whether the parameters of the program are suitable or are changed, or not; the related machine tool whether meets the requirement when calculated the coupling parameters and the pulse equivalent is accurate or not; check whether the drive part of the machine tool is damaged or not, whether the gear coupling is uniform or not, and check whether there exists a periodic errors. If there were, workers should check these important parts.
9、the unstable changes of size caused by system
Reason：the parameters of system are not suitable; the working voltage is not stable; the system is influenced by external elements, which causes the loss of system synchronism; after adding capacitance, the impedance between the system and drive mismatch, leading to the loss the existed signal; the signal which transferred between the system and driver is not normal; the system is damaged.
Solution：judge whether the speed is too fast and the acceleration time is too long or not, whether the Spindle speed and cutting speed are suitable or not, whether the operators make mistakes when they edit the parameters which influence the system performance or not; adding the pressure equipment; ensure the connection of the ground wire, and add the anti-interference absorption capacitance on the point of the pulse output contact of the driver; choose suitable capacitance; check whether the interconnects has shield version and the connection is stable or not, whether the signal of system pulse add or lost or no; change the mainboard or send it to the company for maintenance.
