Accurate workpiece size, poor Surface finish, failure causes: tool tip damaged, not sharp, machine tool resonance, placement instability, machine tool crawling phenomenon, poor processing technology. 

Solution: the tool is worn or damaged after not sharp, then re-sharpen the tool or choose a better tool re-tool; The reason of mechanical crawling is that drag plate and guide rail wear badly, lead screw ball wear or loose, the machine should pay attention to maintenance, after work should clean wire, and timely add lubricating oil to reduce friction; Select the coolant suitable for workpiece processing, in can meet the processing requirements of other processes, as far as possible to select a higher spindle speed.

 2. The workpiece produces the phenomenon of taper and small head, the fault reason is: the level of the machine tool is not adjusted well, one high and one low, resulting in unstable placement; when turning the long axis, the contribution material is relatively hard, the tool eats the knife relatively deep, causes the knife phenomenon; the tail seat thimble and the spindle are not the same center. 

Solution: use level meter to adjust the level of the machine tool, lay a solid foundation, the machine tool fixed to improve its toughness; select a reasonable process and the appropriate cutting feed to avoid force on the tool to let the tool; adjust the tailstock.

　　3. The driver phase light is normal, but the workpiece size is big and small when it is machined The repeated positioning accuracy of the tool holder causes deviation in the long-term use, and the drawing board can return to the machining starting point accurately every time, but the workpiece size still changes. This phenomenon is generally caused by the spindle, spindle high-speed rotation of the bearing wear serious, resulting in machining size changes. Metal processing wechat, the content is good, worthy of attention.

 Solution: with a dial indicator against the bottom of the tool carrier, while editing a fixed cycle through the system, check the drag plate repeat positioning accuracy, adjust screw clearance, replacement bearings; Use the dial indicator to check the repeated positioning accuracy of the tool holder, adjust the machine or replace the tool holder; use the dial indicator to check whether the workpiece is accurately back to the starting point of the program, if possible, repair the spindle and replace the bearing.

　　4, the size of the workpiece and the actual size of a few millimeters difference, or a large axial change, the fault reasons: fast positioning speed is too fast, drive and motor response; After a long-term friction loss mechanical drag plate screw and bearing too tight stuck; tool holder after changing too loose, lock is not tight; edit the program error, head, tail did not respond or did not cancel the knife repair on the end; The electronic gear ratio or step angle of the system is set incorrectly. 

Solution: fast positioning speed is too fast, then adjust the GO speed, cutting speed and time to drive and motor in the rated operating frequency under normal work; In the occurrence of machine tool wear, resulting in drag plate, screw crane bearing too tight stuck, then must be re-adjusted repair; Check whether the turbine worm inside the tool holder is worn, the clearance is too big, the installation is too loose, etc. , select reasonable processing technology, write correct program according to the instruction of instruction, if the size deviation is too big, check whether the system parameters are set reasonably, in particular, whether the parameters such as the electronic gear and the step angle are damaged or not can be measured by using a dial indicator.

　　5. Processing arc effect is not ideal, size is not in place, small and medium-sized CNC lathe, fault reasons: vibration frequency overlap leading to resonance; processing technology; parameters set unreasonable, feed speed is too large, out-of-step arc machining; out-of-step due to loosening or overtightening of screw rod caused by large screw clearance; synchronous belt wear. Solution: find out the resonant parts, change its frequency, avoid resonance; consider the workpiece material processing technology, reasonable programming; for the stepper motor, processing rate F can not be set too large; Whether the machine tool is installed firmly, placed smoothly, whether the drag plate is too tight after wear, gap increases or the tool rest is loose, and so on; replace the synchronous belt. Metal processing wechat, the content is good, worthy of attention.

 6, in the batch production, the occasional workpiece error, failure reasons: must carefully check the fixture, and take into account the operator's operating methods, and the reliability of the clamping, due to the size changes caused by clamping, tools must be improved so that workers are as far away from human error as possible; CNC systems may be subject to fluctuations in external power sources or generate interference pulses automatically when disturbed, the problem that the driver receives redundant pulse drive motor to take away or less walk, the solution: understand its rule, try to use some anti-interference measures, 

for example: strong cable with strong electric field interference and weak electric signal signal line isolation, add anti-interference absorption capacitance and use shielding line isolation, in addition, check whether the ground wire is firmly connected, the closest contact point, take all anti-jamming measures to avoid system interference.

　　7, the workpiece one process processing has the change, other processes size accuracy, the fault reason: the procedure section procedure parameter is reasonable, whether in the predetermined track, the programming format conforms to the specification requirements, the solution: Thread Program section appears when the teeth, pitch is not right, then immediately Lenovo to the processing thread peripheral configuration (encoder) and objective factors of the function.

 8. Each process of the workpiece has the phenomenon of increasing or decreasing. The reasons for failure are: wrong programming; unreasonable setting of system parameters; improper setting of configuration; periodic change of mechanical transmission parts; Solution: check that the instructions used by the program are executed according to the required trajectory specified in the specification, position the dial indicator at the starting point of the program to see if the board is back to the starting point after the program is finished. Repeat the operation even if observing the results and grasping the rules The relevant machine tool configuration in connection calculation coupling parameters single calculation whether it meets the requirements, whether the pulse equivalent is accurate; check the transmission part of the machine tool is not damaged, whether the gear coupling is uniform, check whether there is periodicity, regular failure phenomenon, if there is a check of its key parts and to eliminate.

　　9. The size change caused by the system is not stable. The reasons for the failure are: the system parameters are not set rationally; the working voltage is not stable; the system is subject to external interference, which causes the system to lose step; the system has been added a capacitor, however, the impedance mismatch between the system and the drive results in the loss of useful signal, abnormal signal transmission between the system and the drive, system damage or internal failure.

 Solution: speed, whether the acceleration time is too large, spindle speed, cutting speed is reasonable, whether the operator's parameter changes lead to system performance changes, install voltage regulator, ground wire and confirm the reliable connection, add an anti-interference absorption capacitor at the driver's pulse output contacts; select the appropriate capacitor model; check whether the signal connection between the system and the driver is shielded and reliable, check whether the system pulse signal is lost or increased; send to the factory to repair or replace the motherboard.