Injection Molding Machine Hydraulic System Common Failure Phenomena And Solutions

An injection machine is a kind of general-purpose equipment, which can produce many types of plastic products by using it with different special injection molds. The injection machine mainly consists of a frame, moving and static templates, closing and pressure maintaining parts, pre-molding parts, injection parts, a hydraulic system, an electrical control system, etc.

The moving and static templates of the injection machine are used to install different types of special injection molds in pairs. The moving and static templates of the injection machine are used to install different types of special injection molds in pairs. There are two structural forms of clamping parts: one is to use hydraulic cylinders to push the moving template directly, and the other is to use hydraulic cylinders to push the mechanical mechanism, and then drive the moving template to work through the mechanical mechanism.

No Pressure in the Hydraulic System

*Cause of Hydraulic System Failure

1. Hydraulic pump steering reversed.
2. Insufficient pressure in the oil tank, clogged oil filter does not supply oil.
3. The pressure relief valve is open.
4. Improper adjustment of the pressure valve or clogged valve spool.
5. Solenoid valve coil burned out or slid badly.
6. Serious wear of spool element, or sealing element is damaged, serious leakage.

*Solutions

1. Re-wire.
2. Refill the oil tank: clean the oil filter.
3. Adjust the pressure relief valve to normal.
4. Re-adjust or check the pressure valve spool.
5. Check and adjust or replace the solenoid valve.
6. Replace or check seals.

Unstable Hydraulic System Pressure

*Cause of Hydraulic System Failure

1. Improper setting or adjustment of the pressure valve.
2. Damage to hydraulic pump vanes.
3. The hydraulic pump stator is badly worn.
4. Damaged hydraulic pump bearings, large axial runout.
5. Severe wear of the oil distribution disk.
6. Pump internal leakage generates flow.
7. Serious leakage in the oil circuit and insufficient supply of oil.
8. The valve spool is stuck by foreign objects or spring failure.
9. Poor or clogged cold water piping.
10. Poor or clogged oil filter.
11. Insufficient system supply due to leaky accumulator.

*Solutions

1. Reset the pressure valve or adjust the pressure.
2. Repair hydraulic pump vanes.
3. Repair or replace the hydraulic pump stator.
4. Replace hydraulic pump bearings.
5. Repair or grind the oil distribution plate.
6. Plug leaks or replace the hydraulic pump.
7. Check seals and repair leaking lines.
8. Clean and replace spool valves.
9. Clean and unclog cold water lines.
10. Clean and unclog oil lines and filters.
11. Check accumulator performance and recondition.

Hydraulic System Fluid Overheating

*Cause Hydraulic System of Failure

1. Improperly regulated system pressure, working under high pressure for a long time.
2. Cooling system is clogged or the cooling capacity is small.
3. Low level of oil tank causes lower heat dissipation performance.
4. Improper design or laying of the oil circuit, such as long, thin, curved oil pipe causing pressure loss.
5. Power loss due to mechanical wear and leakage in the system.

*Solutions

1. Adjust the system pressure setting.
2. Clean the cooling system to eliminate clogging.
3. Add hydraulic oil.
4. Improve the oil circuit.
5. Check the lubrication, improve the sealing, and improve the assembly precision.

Hydraulic System Vibration and Noise

*Cause Hydraulic System of Failure

1. Loose ground bolts between the hydraulic pump and motor, resulting in excessive coaxiality.
2. The hydraulic pump stator inner surface is severely worn.
3. Damaged hydraulic pump bearings.
4. Damaged hydraulic pump vanes that are unable to slide.
5. Hydraulic pump motor foundation vibration.
6. Clogged oil filter creating swirling vacuum foot screws.
7. Oil temperature too high or too low.
8. Oil level too low or viscosity too high.
9. Improperly positioned return line.
10. Vibration of the tank wall or loose connections.
11. Air mixed in the oil pipe and oil circuit.
12. Serious wear between the spool and seat of the control valve.
13. Deformed or damaged spring in the control valve.
14. Poor contact or control of the solenoid valve.
15. The control valve blocked foreign objects, improper pressure, and flow regulation, resulting in hydraulic shock.
16. Control valves and other valves resonance.

*Solutions

1. Test the coaxiality of the hydraulic pump motor and hydraulic pump, and tighten the foot screws.
2. Check, and replace the pump stator.
3. Replace the hydraulic pump bearings.
4. Replace hydraulic pump vanes.
5. Tighten the foot screws.
6. Clean the oil filter.
7. Reduce oil temperature.
8. Add enough hydraulic oil.
9. Place the oil return pipe in a suitable position to avoid air mixing in the oil.
10. Install anti-vibration measures on the tank wall.
11. Check the air venting valve for air venting.
12. Repair the spool of the control valve, the valve seat clearance or replacement.
13. Replace the control valve.
14. Check and repair solenoid valves.
15. Clean damping holes, etc., and reasonably adjust system pressure and flow parameters.
16. Disassemble, check, or improve each valve.

Oil Leakage Or Seepage

*Cause Hydraulic System of Failure

1. The 0-ring at the valve base closure is worn and aged.
2. The O-ring at the hydraulic cylinder end cap is worn out.
3. The hydraulic cylinder piston oil seal is worn out, resulting in internal leakage.
4. Loose oil pipe joint or oil leakage from oil pipe.

*Solutions

1. Replace the closed 0-ring at the valve base.
2. Replace the seal at the cylinder end cap.
3. Replace the seal.
4. Tighten the oil pipe fitting, or replace it if there is serious oil seepage.

Hydraulic System Not Working Properly

*Cause Hydraulic System of Failure

1. Failure of the pressure element causes the main spool to be blocked by foreign matter.
2. Deformation of spool and seat.
3. Solenoid valve actuator stuck.
4. Damaged main valve spring.
5. Solenoid coil burned out or poor insulation.
6. Solenoid coil stuck with movable iron core.
7. Damage to coil caused by oil leakage from the sleeve.
8. High voltage variation.
9. Solenoid valve commutation frequency is too large.
10. High reversing pressure or flow rate exceeds the standard.
11. Loose screws inside and outside the coil.
12. Poor welding of coil leads.
13. Solenoid valve electrical control failure or hydraulic control failure of the board.

*Solutions

1. Clean the main valve spool.
2. Check for wear and tear.
3. Replace damaged parts.
4. Inspect and repair the solenoid valve actuator.
5. Replace the solenoid valve coil.
6. Handling.
7. Troubleshooting valve sleeve oil leakage.
8. Stabilize drive voltage.
9. Reasonable selection of solenoid valve commutation frequency.
10. Use high-capacity valves.
11. Lock the screws and check them regularly.
12. Re-solder coil leads.
13. Check the measurement and process.

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