The reason why the machine generates crawling is that the carriage guide rail wears badly, and the screw ball wears or loosens. The machine tool should pay attention to maintenance. After work, the wire should be cleaned and the lubricating oil should be added in time to reduce the friction. The problem of unstable size of CNC machining can be It is very painful to say that Xiaobian has summarized ten common situations and corresponding solutions for you.
1, the workpiece size is accurate, the surface finish is poor
cause of issue:
1) The tool tip is damaged and not sharp.
2) The machine tool generates resonance and is not placed smoothly.
3) The machine has a crawling phenomenon.
4) The processing technology is not good.
Solution (with comparison):
1) 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.
2) The machine tool generates resonance or is not placed smoothly, adjusts the level, lays the foundation, and is fixed and stable.
3) The reason why the machine generates crawling is that the guide rail of the carriage is worn badly, and the screw of the screw is worn or loose. The machine should pay attention to maintenance, clean the wire after work, and add lubricating oil in time to reduce friction.
4) Select the coolant suitable for the machining of the workpiece; if it can meet the processing requirements of other processes, try to use a higher spindle speed.
2, the workpiece produces a taper size
cause of issue:
1) The level of machine tool placement is not adjusted well, one high and one low, resulting in uneven placement.
2) When turning the long axis, the workpiece material is relatively hard, and the tool is deeper, causing the knife phenomenon.
3) The tailstock thimble is not concentric with the spindle.
solution
1) Use the level to adjust the level of the machine, lay a solid foundation, and fix the machine to improve its toughness.
2) Choose a reasonable process and proper cutting feed to avoid the tool being forced to let the knife.
3) Adjust the tailstock.
3, the drive phase lamp is normal, but the workpiece size is different
cause of issue
1) The long-term high-speed operation of the machine tool carriage causes the screw and bearing to wear.
2) The repeat positioning accuracy of the tool holder is deviated in long-term use.
3) The carriage can accurately return to the machining starting point every time, but the size of the machined workpiece still changes. This phenomenon is generally caused by the spindle. The high-speed rotation of the spindle causes the bearing to wear seriously, resulting in a change in the machining size.
Solution (with comparison)
1) 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, and replace the bearing.
2) Check the repeatability of the tool holder with a dial indicator, adjust the machine or replace the tool holder.
3) Use a dial indicator to check whether the workpiece can be accurately returned to the starting point of the program after machining; if possible, repair the spindle and replace the bearing.
4, workpiece size change, or axial change
cause of issue
1) The speed of rapid positioning is too fast, and the drive and motor response are not generated.
2) After long-term friction and wear, the mechanical lead screw and bearing are too tight to be stuck.
3) The knife holder is too loose after the tool change.
4) The edited program error, the head, the end does not respond or does not cancel the knife to complete.
5) The electronic gear ratio or step angle of the system is set incorrectly.
Solution (with comparison)
1) If the fast positioning speed is too fast, the speed of G0 is adjusted appropriately. The cutting acceleration and deceleration and time make the drive and motor operate normally at the rated operating frequency.
2) After the machine wears out, the carriage is generated. If the screw and the bearing are too tight, the repair must be re-adjusted.
3) If the tool holder is too loose after the tool change, check whether the tool holder reversal time is satisfied. Check whether the turbine vortex inside the tool holder is worn, whether the clearance is too large, and whether the installation is too loose.
4) If it is caused by the program, the program must be modified, 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.
5) If the dimensional deviation is too large, check whether the system parameters are set properly, especially if the parameters such as electronic gear ratio and step angle are damaged. This phenomenon can be measured by playing a hundred tables.
5, the processing arc effect is not ideal, the size is not in place
cause of issue
1) The overlap of the vibration frequencies leads to resonance.
2) Processing technology.
3) The parameter setting is unreasonable, the feed rate is too large, and the arc machining is out of step.
4) Looseness caused by large screw clearance or out-of-step caused by excessive screw.
5) Synchronous belt wear.
solution
1) Find the part that produces resonance, change its frequency, and avoid resonance.
2) Consider the processing technology of the workpiece material and make a reasonable program.
3) For stepper motors, the processing rate F cannot be set too large.
4) Whether the machine tool is installed firmly, placed stably, the pallet is too tight after wear, the gap is increased or the tool holder is loose.
5) Replace the timing belt.
6, in the mass production, occasionally the workpiece is out of tolerance
1) Occasionally, there is a change in the size of the mass production, and then the processing is resumed without modifying any parameters, but it returns to normal.
2) Occasionally, a size is inaccurate in mass production, and then the processing size is still unsatisfactory, and the tool is accurate after re-setting.
solution
1) The fixture must be carefully inspected, taking into account the operator's method of operation, and the reliability of the clamping; due to the dimensional changes caused by the clamping, the tooling must be improved to minimize the misjudgment of the worker.
2) The numerical control system may be subject to fluctuations of external power supply or interference, and automatically generate interference pulses, which are transmitted to the drive to cause the drive to accept excess pulse to drive the motor to go more or less; to understand the rules, try to use some anti-interference measures. For example, the strong electric cable with strong electric field interference is isolated from the signal line of the weak electric signal, and the anti-interference absorption capacitor is added and isolated by the shielded wire. In addition, check whether the ground wire is firmly connected, the grounding contact is closest, and all anti-interference measures are taken to avoid the system. Disturbed.
7, each step of the workpiece has an increasing or decreasing phenomenon
cause of issue
1) Program writing error.
2) The system parameter setting is unreasonable.
3) Improper configuration settings.
4) The mechanical transmission components have regular periodic changes.
solution
1) Check whether the instructions used by the program are executed according to the required trajectory specified in the manual. You can judge by dialing the hundred tables. Position the dial indicator at the starting point of the program to let the board return to the starting position after the program ends, and then repeat the execution. Observe the results and master the rules.
2) Check if the system parameters are set properly or artificially changed.
3) Whether the calculation of the relevant machine tool configuration on the connection calculation coupling parameters meets the requirements, and whether the pulse equivalent is accurate.
4) Check whether the transmission part of the machine tool is damaged, whether the gear coupling is uniform, check whether there is periodicity or regular failure phenomenon. If yes, check the key parts and give them exclusion.
8, the workpiece size and actual size are only a few differences
cause of issue
1) The machine tool rubs and wears in long-term use. As the gap of the screw increases, the backlash of the machine tool is too large, so the size of the machining process floats, so the error of the workpiece always changes within the gap.
2) The tool used for machining the workpiece is incorrectly selected, vulnerable, and the tool is not clamped or not tight.
3) According to the workpiece material, select the reasonable spindle speed, cutting feed rate and cutting amount.
4) It is related to the balance and stability of the machine tool placement.
5) When the CNC system generates out-of-step or drive selection, the power is insufficient, the torque is small, etc.
6) Whether the lock is locked after the tool change.
7) Whether there is a phenomenon that the main shaft has a beating motion and a poor coaxiality of the tailstock.
8) In some special processing occasions, the backlash cannot be replenished, resulting in always deviation in processing.
Solution (with comparison)
1) After the machine tool wear screw gap becomes larger, reduce the gap by adjusting the screw nut and tightening the middle carriage line, or obtain the gap value by using a hundred parts (the general clearance is within 0.15 mm), which can be replenished into the computer. The gap compensation function of the computer is used to replace the gap, so that the workpiece size meets the requirements.
2) Since the tool material changes the size of the machined workpiece, the tool is selected reasonably according to the requirements, and the tool angle and tooling fixture are reasonably selected according to the process requirements of the workpiece due to improper tool clamping.
3) When it is suspected that it is a process problem in processing, according to the nature of the material, the machining process is reasonably programmed to select the appropriate spindle speed, cutting feed rate and cutting amount.
4) Due to the resonance of the machine tool, the machine tool is placed stably, the level is adjusted, the foundation is laid down if necessary, and the installation is stable.
5) The dimensional change produced by the CNC system, first determine whether the program is compiled according to the size requirements of the paper, and then check whether the set parameters are reasonable according to the selected configuration (such as: G0 fast positioning speed and acceleration/deceleration time constant during cutting, etc.). Whether someone deliberately changes, the second is to consider whether the selected driver power is reasonable, by judging the phase lamp to observe whether the pulse sent by the computer is out of step.
6) Check that the tool holder has a reversal time after the tool change. Is there enough time for the tool holder to lock? Check the positioning of the tool holder and whether the locking screw is loose.
7) Check if the coaxiality of the main shaft and the tailstock are bouncing or striking.
8) Use programming skills to eliminate gaps.
9, the system caused dimensional instability is unstable
cause of issue
1) The system parameter setting is unreasonable.
2) The working voltage is unstable.
3) The system is subject to external interference, causing the system to lose synchronization.
4) The capacitor has been added, but the impedance between the system and the driver does not match, resulting in loss of useful signal.
5) The signal transmission between the system and the drive is incorrect.
6) System damage or internal failure.
Solution (with comparison)
1) Fast speed, whether the acceleration time is too large, the spindle speed, the cutting speed is reasonable, whether the system performance changes due to the operator's parameter modification.
2) Install voltage regulator equipment.
3) Ground wire and make sure it is connected reliably. Add anti-interference absorption capacitor at the pulse output contact of the driver. Under normal circumstances, the interference of the inverter is large. Please judge with load, because the larger the load will be The larger the load current of the inverter, the greater the interference.
4) Select the appropriate capacitor model.
5) Check whether the signal cable between the system and the driver is shielded, whether the connection is reliable, and check whether the signal of the system pulse is lost or increased.
6) Send the factory for repair or replace the motherboard.
10, mechanical processing instability caused by dimensional instability
cause of issue
1) Is the stepper motor damping plate too tight or too loose?
2) The insulation of the motor plug is reduced, and the motor is damaged.
3) The size of the machined workpiece is not properly clamped.
4) The workpiece appears elliptical.
5) The screw backlash is too large.
6) The mechanical screw is installed too tightly.
Solution (with comparison)
1) Adjust the damping disc to make the motor non-resonant.
2) Replace the motor plug, protect it, or replace the motor.
3) Check if the feed amount is too large or too fast, and check the workpiece clamping. The chuck should not extend too long to avoid the knife.
4) Check the spindle's runout, overhaul the spindle, and replace the bearing.
5) Check the backlash of the screw by dialing the dial indicator, whether the gap has been filled in from the system, and whether the gap is too large after the filling.
6) Check if there is crawling on the screw, and there is a slow response.