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causes and solutions of accuracy failures of cnc stainless steel shears
release time:2020年9月7日    publisher: hangli heavy industry

accuracy has always been one of the important criteria for measuring the quality of a cnc shearing machine, and many friends' cnc shearing machines have lost precision after using them for a period of time. the following 9 tips will make your shears rejuvenate !
1. the size of the workpiece is accurate, and the surface finish is poor.
the cause of the failure: the tool tip is damaged and not sharp; the cnc shearing machine resonates and the placement is not stable; the cnc shearing machine has crawling phenomenon; the processing technology is not good.
solution: after the tool is worn or damaged, it is not sharp, then re-sharpening or selecting a better tool to re-calibrate the knife; the shearing machine generates resonance or is not stable, adjust the level, lay the foundation, and fix it smoothly; the cause of mechanical crawling in order for the carriage guide rail to be worn badly, the lead screw ball is worn or loose, the shearing machine should pay attention to maintenance. the iron wire should be cleaned after work, and lubricating oil should be added in time to reduce friction; choose the coolant suitable for workpiece processing, and it can reach other in the case of processing requirements, try to choose a higher spindle speed.
2. the phenomenon of taper and big head on the workpiece
the cause of the failure: the level of the cnc shearing machine is not adjusted properly, one high and one low, resulting in unstable placement; when turning the long axis, the contribution material is harder, and the tool eats the knife deeper, causing the knife phenomenon; tailstock thimble and spindle disagree.

solution: use a level to adjust the level of the shearing machine, lay a solid foundation, and fix the shearing machine to improve its toughness; choose a reasonable process and appropriate cutting feed to prevent the tool from being forced to yield; adjust the tailstock.
3. the drive phase light is normal, but the size of the processed workpiece is sometimes large and sometimes small
the cause of the failure: long-term high-speed operation of the carriage of the shearing machine causes the screw and bearing to wear; the repeated positioning accuracy of the tool holder produces deviations during long-term use; the carriage can accurately return to the starting point of processing each time, but the size of the workpiece is still changing . this phenomenon is generally caused by the main shaft. the high-speed rotation of the main shaft causes serious wear of the bearing, leading to changes in machining dimensions. metal processing wechat, the content is good, worthy of attention.
solution: use a dial indicator to lean on the bottom of the tool post, and at the same time edit a fixed cycle program through the system to check the repeat positioning accuracy of the carriage, adjust the screw gap, and replace the bearing; use the dial indicator to check the repeat positioning accuracy of the tool post, adjust the machine or replace the tool post; use a dial indicator to check whether the workpiece is accurately returned to the starting point of the program, if possible, check the spindle and replace the bearing.
4. the size of the workpiece is different from the actual size by a few millimeters, or there is a big change in a certain axis
the cause of the failure: the rapid positioning speed is too fast, the drive and the motor can't react; the mechanical carriage screw and the bearing are too tight after long-term friction loss; the tool post is too loose after the tool is changed, and the lock is not tight; the edited program wrong, the head and tail do not respond or the tool compensation is ended; the electronic gear ratio or step angle of the system is set incorrectly.
solution: if the rapid positioning speed is too fast, adjust the go speed appropriately, cutting acceleration and deceleration and time to make the drive and motor work normally at the rated operating frequency; after the shearing machine wears out, the carriage, screw crane bearing if it is too tight and stuck, it must be re-adjusted and repaired; if the tool post is too loose after tool change, check whether the reversal time of the tool post is satisfied, check whether the worm gear inside the tool post is worn, whether the gap is too large, whether the installation is too loose, etc.; if it is caused by the program, you must 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 the size deviation is found to be too large, check whether the system parameters are set properly, especially for electronics whether the parameters such as gear and step angle are damaged, this phenomenon can be measured by using a dial indicator.
5. the effect of machining arc is not ideal, and the size is not in place
the cause of the fault: the overlap of the vibration frequency leads to resonance; the processing technology; the parameter setting is unreasonable, the feed speed is too large, and the arc processing is out of step; the loosening caused by the screw rod gap or the out of step caused by the screw rod being too tight; the timing belt wear.
solution: find out the resonant parts, change their frequency to avoid resonance; consider the processing technology of the workpiece material, and program reasonably; for stepper motors, the processing rate f cannot be set too large; whether the shearing machine is installed firmly and placed stably , whether the carriage is too tight after being worn, the gap is increased or the tool holder is loose, etc.; replace the timing belt. metal processing wechat, the content is good, worthy of attention.
6. in mass production, occasionally the workpiece is out of tolerance
the cause of the failure: the tooling and fixture must be carefully checked, and the operator's operation method and the reliability of the clamping must be taken into account. due to the size change caused by the clamping, the tooling must be improved so that the worker may try to avoid misjudgment by human negligence; the cnc system may when the external power supply fluctuates or is disturbed, it will automatically generate interference pulses, which will be transmitted to the drive and cause the drive to receive excess pulses to drive the motor to take away or reduce the phenomenon,
solution: understand and master the law, try to adopt some anti-interference measures, such as: isolation of strong electric cables with strong electric field interference from signal lines of weak electric signals, adding anti-interference absorbing capacitance and shielding wire isolation, in addition, check the ground wire whether the connection is firm and the grounding contact is nearest, take all anti-interference measures to avoid system interference.
7. there is a change in the processing of a certain process of the workpiece, and the dimensions of the other processes are accurate.
cause of failure: whether the parameters of the program segment are reasonable, whether they are in the predetermined trajectory, whether the programming format meets the requirements of the manual
solution: if there are random teeth in the thread program segment, and the pitch is wrong, it immediately associates with the peripheral configuration (encoder) of the processing thread and the objective factors of the function.
8. each process of the workpiece has an increase or decrease phenomenon
reasons for failure: programming errors; unreasonable system parameter settings; improper configuration settings; mechanical transmission components change regularly and periodically.
solution: check whether the instructions used in the program are executed in accordance with the required track specified in the manual. you can judge by hitting the dial indicator. position the dial indicator at the beginning of the program and whether the carriage returns to the starting position after the end of the program, and then repeat the execution even if you observe the results and master the rules; check whether the system parameters are set reasonably or considered to be changed; whether the relevant shearing machine configuration meets the requirements on the connection calculation coupling parameters and whether the pulse equivalent is accurate; check whether the shearing machine transmission part has if there is no damage, whether the gear coupling is uniform, check whether there are periodic and regular failure phenomena, if there is, check the key parts and remove them.
9. unstable dimensional changes caused by the system
causes of failure: unreasonable system parameter settings; unstable operating voltage; external interference caused the system to lose synchronization; capacitors have been added, but the impedance between the system and the driver does not match, resulting in the loss of useful signals; signals between the system and the driver abnormal transmission; system damage or internal failure.
solution: whether the speed, acceleration time is too large, whether the spindle speed, cutting speed are reasonable, whether the modification of the operator's parameter causes the system performance to change; install a voltage stabilizing device; make sure that the ground wire is reliably connected, and the pulse output contact of the driver add anti-interference absorption capacitors; select the appropriate capacitor model; check whether the signal connection line between the system and the driver is shielded and whether the connection is reliable; check whether the system pulse signal is lost or increased; send it to the factory for repair or replacement of the motherboard.