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CNC machining accuracy problem, what happened?

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

    Causes of failure: The tool tip is damaged and not sharp; the machine tool resonates and the placement is not stable; 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-sharpen the tool or choose a better tool to re-calibrate the tool; the machine tool resonates or the placement is not stable, adjust the level, lay the foundation, and fix it smoothly; the reason for the machine crawling is drag. The plate guides are severely worn, and the screw balls are worn or loose. The machine tool should be maintained. After get off work, the wire should be cleaned, and lubricating oil should be added in time to reduce friction; choose a coolant suitable for workpiece processing, and can meet the processing requirements of other processes. In this case, try to use a higher spindle speed.(Carpet Speaker Spikes)

    2. The workpiece produces the phenomenon of taper size head.

    Cause of the failure: the level of the machine tool is not adjusted properly, one is high and the other is low, resulting in unstable placement; when turning the long axis, the contribution material is relatively hard, and the tool eats the knife deeply, resulting in the phenomenon of letting the knife; the tailstock thimble is not concentric with the spindle.
    Solution: Use a spirit 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 force on the tool; adjust the tailstock.

    3. The phase light of the driver is normal, but the size of the processed workpiece is sometimes large or small.

    Causes of failure: The long-term high-speed operation of the machine tool carriage leads to wear of the screw and bearings; the repeated positioning accuracy of the tool holder deviates during long-term use; the carriage can accurately return to the starting point of processing every 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 bearing wear, resulting in changes in machining dimensions.
    Solution: use the dial indicator against the bottom of the tool holder, and at the same time edit a fixed cycle program through the system to check the repeatability of the carriage, adjust the screw clearance, and replace the bearing; use the dial indicator to check the repeatability of the tool holder, Adjust the machine or replace the tool holder; use the 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 workpiece size differs from the actual size by a few millimeters, or there is a great change in a certain axis.

    Causes of failure: The speed of rapid positioning is too fast, and the drive and motor cannot respond; after long-term friction loss, the mechanical carriage screw and bearing are too tight and stuck; the tool holder is too loose after changing the tool, and the locking is not tight; edited program Error, the head and tail do not respond or the tool compensation is not canceled; the electronic gear ratio or step angle of the system is set incorrectly.
    Solution: If the fast positioning speed is too fast, adjust the speed of the GO appropriately, and the cutting acceleration and deceleration speed and time make the drive and motor work normally under the rated operating frequency; after the machine tool wears, the carriage and screw crane bearings are too tight If it is stuck, it must be re-adjusted and repaired; if the tool holder is too loose after changing the tool, check whether the reversal time of the tool holder is satisfied, check whether the turbine worm inside the tool holder is worn, whether the gap is too large, whether the installation is too loose, etc.; if it is a program If it is caused by the reason, the program must be modified, improved 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 reasonably, especially the electronic gear and Whether parameters such as step angle are damaged can be measured by playing the dial indicator.(Cabinet Knob)

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

    Causes of failure: The overlapping of vibration frequencies leads to resonance; processing technology; unreasonable parameter settings, excessive feed speed, and out-of-step arc processing; looseness caused by large screw clearance or out-of-step caused by over-tight screw; synchronous belt wear.
    Solution: find out the parts that generate resonance, change their frequency to avoid resonance; consider the processing technology of the workpiece material, and make a reasonable program; for the stepping motor, the processing rate F cannot be set too large; Whether the plate is too tight after wear, the gap increases or the tool holder is loose, etc.; replace the timing belt.

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

    Cause of failure: The tooling fixture must be carefully checked, and considering the operator’s operation method and the reliability of the clamping, due to the dimensional changes caused by the clamping, the tooling must be improved so that workers try to avoid misjudgment due to human negligence; the numerical control system may After being fluctuated or disturbed by the external power supply, an interference pulse is automatically generated, which is transmitted to the driver, causing the driver to accept the excess pulse to drive the motor to take away or less.
    Solution: Understand and master its laws, try to take 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 capacitors and using shielded lines to isolate, in addition, check the ground wire Whether the connection is firm, the ground contact is the closest, and all anti-interference measures are taken to avoid system interference.

    7. There are changes in the processing of a certain process of the workpiece, and the dimensions of other processes are accurate.

    Cause of failure: Whether the parameters of the block program are reasonable, whether they are within the predetermined trajectory, and whether the programming format meets the requirements of the manual.
    Solution: If there are random teeth in the thread block and the thread pitch is wrong, then immediately think of the peripheral configuration (encoder) of the thread processing and the objective factors of this function.

    8. Each process of the workpiece has the phenomenon of increasing or decreasing.

    Causes of failure: programming errors; unreasonable system parameter settings; improper configuration settings; mechanical transmission components regularly and periodically change failures.
    Solution: Check whether the instructions used by the program are executed according to the required trajectory specified in the manual. You can judge by playing the dial indicator. Position the dial indicator at the starting point of the program and let the carriage return to the starting position after the program ends, and then repeat the execution. Even if you observe the results, master the rules; check whether the system parameters are set reasonably or are considered to be changed; whether the relevant machine tool configuration meets the requirements in the connection calculation coupling parameters, and whether the pulse equivalent is accurate; check whether the transmission part of the machine tool is damaged or not, gears Whether the coupling is uniform, check whether there are periodic and regular failures, and if so, check the key parts and eliminate them.

    9. The dimensional change caused by the system is unstable.

    Causes of failure: unreasonable setting of system parameters; unstable working 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 loss of useful signals; the signal between the system and the driver is lost Abnormal transmission; system corruption or internal failure.
    Solution: whether the speed and acceleration time are too large, whether the spindle speed and cutting speed are reasonable, whether the operator’s parameter modification causes the system performance to change; Add anti-interference absorbing capacitors; select the appropriate capacitor model; check whether the signal connection line between the system and the driver is shielded, whether the connection is reliable, check whether the system pulse signal is lost or increased; send it to the factory for repair or replace the motherboard.

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