15 Solutions for Common Machining Center Problems

I. Handwheel Malfunctions

Causes:

1. Poor contact of the handwheel axis selection switch.
2. Poor contact of the handwheel rate selection switch.
3. Damage to the handwheel pulse generator disc.
4. Breakage of the handwheel connection line.

Countermeasures:

1. Enter the system diagnosis to observe the contact condition of the axis selection switch (under the condition of intact connection lines). If damaged, replace the switch.
2. Enter the system diagnosis to observe the contact condition of the rate switch (under the condition of intact connection lines). If damaged, replace the switch.
3. Remove the pulse disc to measure whether the power supply is normal and whether the resistance between + and A, + and B is normal. If damaged, replace it.
4. Enter the system diagnosis to observe the contact condition of each switch. Also, measure whether the connection line between the axis selection switch, rate switch, and pulse disc has continuity with the corresponding points on the system terminal. If broken, replace it.

II. X, Y, Z Axis and Spindle Box Malfunctions

Causes:

1. Deformation and damage of the Y and Z axis guards.
2. Damage to the Y and Z axis drive bearings.
3. Servo parameters not matching the mechanical features.
4. Deformation of the servo motor and screw head connection, off center.
5. The counterweight chain inside the column is loose and displaced on the guide rail.
6. Wear and vibration of the column counterweight chain and guide wheel.
7. The pulley on the shaft and motor end are not parallel.
8. Spindle belt damage and deformation.

Countermeasures:

1. Carry out sheet metal restoration of the guard.
2. Inspect the main and fixed bearings of the axis. Determine which bearing is damaged and replace it.
3. Adjust the servo parameters to match the mechanics (servo gain, resonance suppression, load inertia).
4. Realign the coupler position or replace the connection.
5. Correct the guide rail and apply grease for lubrication.
6. Inspect wear conditions of chain and guide wheel, correct counterweight balance, and apply grease for lubrication.
7. Correct the parallelism between the two pulleys using a dynamic balancer.
8. Check for severe deformation or damage on the belt and replace if necessary. Clean the belt and adjust the belt tension.

III. Guide Rail Oil Pump and Cutting Oil Pump Malfunctions

Causes:

1. Insufficient oil level in the guide rail oil pump.
2. Damage to the guide rail oil pump pressure valve.
3. Damage to the machine tool oil circuit.
4. Blockage of the guide rail oil pump filter.
5. Customer purchased guide rail oil that is over the quality limit.
6. Incorrect timing setting for the guide rail oil pump.
7. Cutting oil pump overload causing the circuit breaker in the box to trip.
8. Air leakage at the cutting oil pump connector.
9. Damage to the cutting oil pump check valve.
10. Short circuit in the cutting oil pump motor coil.
11. Incorrect direction of the cutting oil pump motor.

Countermeasures:

1. Simply refill the guide rail oil.
2. Check whether the oil pressure valve is insufficient. If damaged, replace it.
3. Check whether the machine tool’s oil circuit for each axis is unobstructed, broken, or damaged. If damaged, replace it.
4. Clean the oil pump filter.
5. Replace with guide rail oil that meets the requirements of the oil pump.
6. Reset the correct oiling time.
7. Check whether the guide rail oil pump is intact, then reset the circuit breaker.
8. Locate the air leakage connector and reconnect it.
9. Check whether the check valve is blocked or damaged. If damaged, replace it.
10. Check the motor coil and replace the cutting oil pump motor if necessary.
11. Correct the direction of the cutting oil pump motor.

IV. Processing Faults

Causes:

1. Incorrect backlash compensation for X, Y, Z axes
2. Looseness in the main inserts for X, Y, Z directions
3. Damage in the X, Y, Z axis bearings
4. Deviation in machine body’s geometric accuracy
5. Axial and radial runout of the main spindle
6. Improper adjustment of system servo parameters and processing parameters
7. Errors in the client’s programming
8. Wear and tear in the X, Y, Z axis screws and nuts

Countermeasures:

1. Correct backlash compensation with a micrometer
2. Adjust the looseness of the main inserts for each axis, observe the system load and adjust to the optimal state
3. Inspect the bearings, replace if damaged
4. Use marble squares and gauge rods to inspect geometric accuracy, correct if there are deviations
5. Repair the precision of the spindle bore, the spindle bearing runout gap, replace if not repairable
6. Adjust servo position loop, speed loop gain, load inertia ratio, machining accuracy coefficient, acceleration/deceleration time constant
7. Optimize and adjust programming techniques
8. Compensate for screw clearance using a laser interferometer

V. Tool Release Faults

Fault Causes:

1. Damage to the tool release solenoid valve
2. Damage to the spindle’s tool knocking cylinder
3. Damage to the spindle’s spring plate
4. Damage to the spindle’s drawbar
5. Insufficient air supply from the client
6. Poor contact of the tool release button
7. Wire breakage
8. Lack of oil in the tool knocking cylinder’s oil cup
9. Client’s tool handle collet does not meet required specifications

Countermeasures:

1. Inspect the action of the solenoid valve, replace if damaged
2. Inspect the action of the tool knocking cylinder, replace if damaged
3. Check the damage level of the spring plate, replace the spring plate
4. Inspect the condition of the spindle’s drawbar, replace if damaged or worn
5. Check the damage level of the button, replace if damaged
6. Check for wire breakage
7. Refill oil for the tool knocking cylinder’s oil cup
8. Install a standard collet

VI. Machine Tool Unable to Return to Zero Point

Causes:

1. The original switch contact is stuck and can’t operate
2. The original block can’t press the original switch to the switch operation position
3. Water intrusion in the original switch causing poor contact
4. Original switch circuit disconnected or input signal source failure
5. Burnout of the PLC input point

Countermeasures:

1. Clean the stuck parts, ensure the movable parts operate smoothly, or replace the travel switch
2. Adjust the installation position of the travel switch, so that the zero-point switch contact can be smoothly pressed by the block to the switch operation position
3. Replace the travel switch and take appropriate waterproof measures
4. Check the switch circuit for open circuit or short circuit, and check for signal source (+24V DC power supply)
5. Replace the input point on the I/O board, set up parameters properly, and modify the PLC program

VII. Alarm for Over/Under Hard Limit of Machine Tool

Under normal circumstances, this alarm should not trigger. It might occur if the machine tool is operated before returning to zero, as the system does not set a fixed mechanical coordinate system before zeroing, and the soft limit is ineffective. Therefore, it is essential to return to zero before operating the machine tool.

Reasons:

1. The travel switch contact is pressed or stuck (over-travel).
2. The travel switch is damaged.
3. There is an open circuit, short circuit, or absence of signal source in the travel switch circuit.
4. The limit block can’t press the switch contact to the action position.
5. The PLC input point is burned out.

Countermeasures:

1. Manually or handwheel away from the safe position, or clean the switch contact.
2. Replace the travel switch.
3. Check for short circuits in the travel switch circuit and reprocess if any. Check the signal source (+24V DC power supply).
4. Adjust the installation position of the travel switch, so it can press the switch contact to the action position properly.
5. Replace the input point on the I/O board and set the parameters well, modify the PLC program.

VIII. Tool Change Failure

Causes:

1. Insufficient air pressure.
2. Poor contact or circuit breakage of the tool-release button.
3. Burnout of the PLC input address of the tool-release button or no signal source (+24V).
4. Inactivity of the tool-release relay.
5. Damage to the tool-release solenoid valve.
6. Insufficient tool striking.
7. Lack of oil in the tool striking cylinder’s oil cup.
8. Failure of the tool striking cylinder.

Countermeasures:

1. Check the air pressure until it reaches 6 kg ±1 kg.
2. Replace the switch or check the circuit.
3. Replace the PLC input port on the I/O board or check the PLC input signal source, modify the PLC program.
4. Check whether the PLC output signal exists or not, whether the PLC output port is burned out, modify the PLC program.
5. Replace the solenoid valve coil if burned out. If the solenoid valve body leaks air or the piston does not operate, replace the valve body.
6. Adjust the tool striking amount until the tool-release is smooth.
7. Add hydraulic oil to the oil cup of the tool striking cylinder.
8. If the screws inside the tool striking cylinder are loose or air leaks, tighten the screws again, replace the sealing rings in the cylinder. If the cylinder cannot be repaired, replace the tool striking cylinder.

IX. Abnormal Sound During Three-Axis Operation

Causes:

1. Bearing failure.
2. Imbalance between the screw mother line and the guide rail.
3. Severe wear of the wear-resistant piece leading to serious scratches on the guide rail.
4. Mismatch of the servo motor gain.

Countermeasures:

1. Replace the bearing.
2. Correct the screw mother line.
3. Replace the wear-resistant piece. If the scratches on the guide rail are too serious, reprocess it.
4. Adjust the servo gain parameters to match the machine.

X. Lubrication Failure

Causes:

1. Lack of oil in the lubrication pump oil tank.
2. Lubrication pump oiling time is too short.
3. The unloading mechanism of the lubrication pump unloads too quickly.
4. Oil leakage in the oil pipe and oil route.
5. Inaction of the one-way valve in the oil route.
6. Damage to the oil pump motor.
7. Damage to the lubrication pump control circuit board.

Countermeasures:

1. Add lubricating oil to the upper limit line position.
2. Adjust the oiling time to 32 minutes and oil for 16 seconds.
3. If adjustable, adjust the unloading speed, if not, replace it.
4. Check and fix the oil pipe and oil route interfaces.
5. Replace the one-way valve.
6. Replace the lubrication pump.
7. Replace the control circuit board.
8. In case of emergency, forcibly set M64S to 1A and E60 to 32 in the I/F diagnosis, the machine tool can temporarily work.

XI. Program transmission failure, alarms P460, P461, P462 are triggered.

Countermeasures:

1. Inspect the transmission line for open circuits or cold solder joints, and ensure plugs are correctly inserted.
2. The parameters of the computer transmission software should match those on the machine tool side.
3. Attempt transmission with a different computer.
4. Verify the stability of the grounding.

XII. Tool Magazine Issues

Causes:

1. The tool changing process suddenly stops and cannot continue.
2. The turret style tool magazine cannot be extended.
3. The tool cannot be released during the tool changing process.
4. The tool disk cannot rotate.
5. The tool disk suddenly rotates in the opposite direction, off by half a tool position.
6. During tool changing, there are error alarms for releasing or tightening the tool.
7. Loud noise from the main spindle side when returning the tool during the tool changing process.
8. After changing, the main spindle cannot load the tool (tool release anomaly).

Countermeasures:

1. Ensure sufficient air pressure (6 kg).
2. Check if the tool magazine’s retraction signal is in place, and whether the tool magazine’s in/out solenoid valve circuit and PLC have any output.
3. Adjust the tool strike amount, and check for water accumulation in the tool strike cylinder body.
4. When the tool disc rotates after extension, check for disconnection in the tool magazine motor power line, and any damage in contacts or relays.
5. The tool magazine motor brake mechanism is loose and cannot brake properly.
6. Check air pressure, ensure full actuation of the cylinder (check for water accumulation), ensure the tool release position switch is pressed in place, but not overly so (just enough to have signal input).
7. Adjust tool strike amount;
8. Modify tool change program (macro program O9999).

XIII. Machine Tool Cannot Be Powered On

Causes:

1. Poor three-phase contact or damage to the main power switch.
2. The operation panel cannot be powered on.

Countermeasures:

1. Replace the main power switch.
2. Inspect:
   A. Whether the switch power supply has voltage output (+24V).
   B. Poor contact of the system power-on switch, power-off switch circuit is open.
   C. Poor contact of the system power-on relay, unable to self-lock.
   D. Circuit is open.
   E. Poor contact of the driver power-on AC, fault in the system power-on relay.
   F. Check if the circuit breaker has tripped.
   G. Whether the system has completed normal preparation or if there is damage to the Z-axis driver, causing no automatic power-on signal output.

XIV. Cooling Water Pump Malfunction

1. Inspect for any burnout in the water pump
2. Verify if the power supply phase sequence is reversed
3. Check for any burnout in the AC contact and relay
4. Ensure there is an input signal at the panel button switch

XV. Air Blowing Failure

1. Inspect whether the solenoid valve is functioning
2. Verify if the air blowing relay is working
3. Ensure there is a signal at the panel button and PLC output interface