CNC lathes are mainly used to process a variety of precision parts, but sometimes we will find that the precision of CNC lathes is not stable, what is the reason for this? Summarize 9 reasons and corresponding solutions, hope to be helpful to you.
1. Accurate workpiece size, poor surface finish
Fault cause: the cutter tip is damaged and not sharp; CNC lathe resonance, the placement is not stable; The machine tool has crawling phenomenon; The processing is not good.
Solution: after the tool wear or damage is not sharp, then re-sharpen the knife or choose a better tool on the knife; The machine produces resonance or the position is not stable, adjusts the level, lays the foundation, the fixed is stable; The reason for mechanical crawling is that the guide rail of the towing plate is badly worn and the ball of the lead screw is worn or loose. The machine tool should be maintained carefully. The iron wire should be cleaned after work and lubricating oil should be added in time to reduce friction. Select the coolant suitable for workpiece processing, in the case of meeting the requirements of other processing procedures, try to choose a higher spindle speed.
2, the workpiece taper size head phenomenon
Failure reason: the machine tool placement level is not adjusted well, one high one low, resulting in unstable placement; When turning the long shaft, the contribution material is hard and the cutter is deep, which causes the phenomenon of letting the cutter. The tail thimble is not centered on the spindle.
Solution: Use the level to adjust the levelness of the machine tool, lay a solid foundation, and fix the CNC lathe to improve its toughness; Choose reasonable process and appropriate cutting feed to avoid the tool under force; Adjust the tailstock.
3, the driver phase lamp is normal, and the workpiece size is large or small
Failure causes: The screw rod and bearing wear due to the long-term high-speed operation of the machine tool towing plate; The repeated positioning accuracy of the tool holder has deviation in long-term use. The pallet can be returned to the machining starting point accurately every time, but the size of the workpiece still changes. This phenomenon is generally caused by the spindle, spindle high-speed rotation makes the bearing wear seriously, resulting in machining dimension change.
Solution: use the dial indicator to rest on the bottom of the tool holder. At the same time, edit a fixed cycle program through the system to check the repeated positioning accuracy of the towing plate, adjust the screw clearance, and replace the bearing; Check the repeated positioning accuracy of the tool holder with a dial indicator, adjust the machine or replace the tool holder; The dial indicator is used to check whether the processed workpiece is returned to the starting point of the program accurately. If possible, the spindle is repaired and the bearing replaced.
4, the size of the workpiece and the actual size of a few millimeters, or a great change in the axial
Fault cause: The fast positioning speed is too fast, and the drive and motor can't respond; After long-term friction loss, mechanical towing plate screw and bearing become too tight and stuck; The tool holder is too loose after changing the tool, and the lock is not tight; Edit the program error, the head, tail did not echo or did not cancel the knife to fill 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 make the driver and motor in the rated operating frequency under the normal work; If the towing plate and the screw crane bearing are too tightly stuck after the machine tool wear occurs, it must be adjusted and repaired again. If the tool holder is too loose after tool change, check whether the reversal time of the tool holder is satisfied, check whether the turbine worm inside the tool holder is worn, whether the clearance is too large, whether the installation is too loose, etc.; If it is caused by the program, it must modify the program, improve according to the requirements of the workpiece drawing, select a reasonable processing technology, and prepare the correct program according to the instructions in the manual. If it is found that the size deviation is too large, check whether the system parameters are set reasonably, especially whether the parameters such as electronic gear and step Angle are damaged. This phenomenon can be measured by the dial indicator.
5, processing arc effect is not ideal, size is not in place in small and medium-sized CNC lathe
Fault causes: vibration frequency overlap leads to resonance; Processing technology; The parameter setting is unreasonable, the feed speed is too large, the arc machining step is out of step; Loose lead screw caused by large gap or out of step caused by too tight lead screw; Synchronous belt wear.
Solution: Find the part that produces resonance and change its frequency to avoid resonance; Consider the processing technology of the workpiece material, and make a reasonable program; For stepper motor, the processing rate F should not be set too high; Whether the machine is firmly installed and placed smoothly, whether the drag plate is too tight after wear, whether the clearance increases or the tool holder becomes loose, etc.; Replace the sync tape.
6. In batch production, the workpiece is out of tolerance occasionally
Fault reasons: must carefully check the CNC lathe fixture, and considering the operator's operation method, and the reliability of clamping, due to clamping caused by the size change, must improve the tooling so that workers as far as possible to avoid human negligence misjudgment phenomenon; The NUMERICAL control system may automatically generate interference pulse when it is subject to the fluctuation of external power supply or interference, and transmit to the driver, which causes the driver to accept the phenomenon that the redundant pulse-driven motor is taken away or less removed.
Solution: grasp the rule, try to use some anti-jamming measures, such as: strong electric field disturbance of high voltage cables and weak current signal of the signal isolation, join the absorption capacity of anti-interference and a shielding wire isolation, in addition, check whether the ground wire connection is firm, grounding contact recently, all anti-interference measures should be taken to prevent the system disturbance.
7, the workpiece has a process of change, the size of other processes accurate
Cause of failure: Whether the parameters of the program segment are reasonable, whether they are in the predetermined trajectory, and whether the programming format meets the requirements of the specification
Solution: When the thread program segment appears disorderly teeth, the pitch is wrong, immediately associated with the processing of thread peripheral configuration (encoder) and the objective factors of the function.
8, each process of the workpiece has the phenomenon of increasing or decreasing
Cause of failure: programming error; The system parameter setting is unreasonable; Improper configuration setting; Mechanical transmission components have regular periodic changes in failure
Solution: Check whether the instructions used by the program are executed in accordance with the required track specified in the manual. It can be judged by the dial indicator. Position the dial indicator at the starting point of the program and let the drag plate return to the starting point after the program is finished. Check whether the system parameters are set reasonably or considered changed; Whether the single calculation on the coupling parameters of the related machine tool configuration meets the requirements and whether the pulse equivalent is accurate; Check whether the transmission part of the machine tool is damaged, whether the gear coupling is uniform, check whether there is periodic and regular failure phenomenon, if there is, check the key part and give elimination.
9. The size change caused by the system is unstable
Failure reason: the system parameter setting is unreasonable; Unstable working voltage; The system is out of step due to external interference; Capacitance has been added, but the impedance between the system and the driver does not match, resulting in the loss of useful signals; Abnormal signal transmission between the system and the driver; System damage or internal failure.
Solution: Whether the speed, acceleration time is too large, spindle speed, cutting speed is reasonable, whether the operator's parameter modification results in system performance changes; Installing voltage stabilizing equipment; Grounding wire and make sure that the connection is reliable, add anti-interference absorption capacitance at the driver pulse output contact; Select the appropriate capacitance model; Check whether the signal connection line between the system and the driver is shielded and whether the connection is reliable, and check whether the system pulse signal is lost or increased; Send to factory for repair or replacement of main board.
On 2018-08-08 11:45:46
