Literally, "numerical control" and "machining center" are two keywords. "Numerical control" means "digital control", which is what we often call CNC. The control system can logically process programs with control codes or other symbolic instructions, and decode them through the computer, so that the machine tool can execute the specified action. .

In the actual production of CNC, it is inevitable that there will be some problems. JY Machinery,as a professional precision cnc machining factory has summarized some common CNC Machining problems and solutions for you, and hope to help the relevant personnel.

1. The size of the workpiece is accurate, and the surface finish is poor.

The cause of the fault: the tool tip is damaged and not sharp; the machine tool resonates and is not placed smoothly; the machine tool 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 tool; the machine has resonance or is not stable, adjust the level, lay the foundation, and fix it smoothly; the cause of mechanical crawling is drag The board guide rail is worn out, and the ball screw ball is worn or loose.

The machine tool should pay attention to maintenance, clean the iron wire after get off work, and add lubricating oil in time to reduce friction; choose a coolant suitable for workpiece processing, and if it can meet the processing requirements of other processes, try to choose a higher spindle speed.

2. The workpiece has a large and small head phenomenon.

The cause of the failure: the level of the machine is not adjusted properly, one high and one low, resulting in unstable placement; when turning the long axis, the contribution material is harder, the tool eats deeper, causing the tool to be used; the tailstock thimble is not concentric with the spindle.

Solution: Use a level to adjust the level of the machine tool, lay a solid foundation, and fix the machine tool to improve its toughness; choose a reasonable process and appropriate cutting feed to avoid the tool being forced to give it to the knife; adjust the tailstock.

3. The drive phase light is normal, and the size of the processed workpiece is sometimes large and sometimes small.

The cause of the failure: long-term high-speed operation of the machine tool carriage 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 processed workpiece still changes. 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.

Solution: Use a dial indicator to lean on the bottom of the tool post, and edit a canned 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, repair 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 over; the electronic gear ratio or step angle setting of the system is wrong.

Solution: If the rapid positioning speed is too fast, adjust the speed appropriately, and the cutting acceleration and deceleration and time will make the drive and motor work normally at the rated operating frequency; after the machine tool wears out, the carriage, screw and crane bearings will be too tight Stuck, you must readjust and repair;

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, the program must be modified. 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 whether the electronic gear and step angle are damaged. This phenomenon can be measured by using a dial indicator.

5. The machining arc effect is not ideal, and the size is not in place.

The cause of the failure: 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 looseness caused by the screw rod gap or the out of step caused by the screw rod is too tight; the timing belt Wear.

Solution: Find out the resonant component, change its frequency to avoid resonance; consider the processing technology of the workpiece material, and program it reasonably; for stepper motors, the processing rate F cannot be set too large; whether the machine is installed firmly, placed smoothly, and dragged Whether the plate is too tight after being worn, the gap is increased or the tool holder is loose, etc.; replace the timing belt.

6. In mass production, the workpiece is out of tolerance occasionally.

Cause of 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 to prevent the worker from making a misjudgment due to human negligence; the CNC system may When the external power source fluctuates or is disturbed, it will automatically generate interference pulses, which will be transmitted to the drive and cause the drive to receive the excess pulses and drive the motor to take away or drive the phenomenon.

Solution: Understand and master the law, try to use 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 are changes 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 block program are reasonable, whether they are in the predetermined track, 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 this function.

8. Each process of the workpiece has an increase or decrease phenomenon

Causes of failure: programming errors; unreasonable system parameter settings; improper configuration settings; mechanical transmission components change regularly and periodically.

Solution: Check whether the instructions used by 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 In order to observe the results and grasp the laws;

Check whether the system parameters are set reasonably or considered to be changed; whether the relevant machine tool configuration meets the requirements in the calculation of the coupling parameters and whether the pulse equivalent is accurate; check whether the transmission part of the machine tool is damaged, whether the gear coupling is uniform, and whether there is periodicity , Regular failure phenomena, if any, check the key parts and eliminate them.

9. Dimensional changes caused by the system are unstable

Reasons for failure: unreasonable system parameter settings; unstable operating voltage; system is affected by external interference, causing 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 parameter modification of the operator 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 absorbing capacitors; select the appropriate capacitor model; check whether the signal connection line between the system and the drive 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.

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