Troubleshooting Common Problems with Polyurethane High-Pressure Foaming Injection Machines

Polyurethane high-pressure foaming injection machines are widely used in the automotive, construction, and home appliance industries to produce foam fillings, insulation materials, and more. During use, problems such as uneven mixing, abnormal pressure, blockage, and leakage may occur. The following are common troubleshooting tips and solutions.

1. Uneven Mixing (Improper A/B Ratio)
Possible Causes
Metering Pump Failure: Wear or blockage in the A or B material pump leads to an incorrect ratio.
Filter Clog: Impurities in the raw materials affect flow.
Temperature Unstable: Large temperature differences between the A and B materials lead to viscosity changes.
Mix Head Wear: Internal wear in the dynamic mixing head reduces mixing efficiency.
Solutions
Check the metering pump: Calibrate the flow rate and replace worn pump heads or seals.
Clean or Replace the Filter: Clean the filter regularly (recommended every 8 hours).
Adjust the Temperature: Ensure that the A and B materials are at the same temperature (usually between 20-25°C). Replace the mixing head: If the mixing head is severely worn internally, replace it with a new part.

2. Abnormal injection pressure (too high or too low)
Possible causes:
Raw material viscosity is too high: Low temperature or raw material deterioration results in poor fluidity.
Pipeline blockage: Accumulation of solidified material or obstruction by foreign matter.
Pressure sensor failure: Abnormal display, requiring calibration or replacement.
Hydraulic system problem: Unstable oil pressure or oil pump failure.
Solution: Adjust the raw material temperature: Increase the temperature (but do not exceed the material's tolerance).
Clean the injection line: Flush any blocked areas with a dedicated cleaning agent.
Check the sensor: Calibrate the pressure sensor and replace if necessary.
Maintain the hydraulic system: Check the oil pump and oil circuit to ensure stable oil pressure.

3. Clogged mixing head or nozzle
Possible causes: Failure to clean after shutdown: Residual material solidifies in the mixing head.
Raw material contamination: Impurities enter the mixing head.
Excessive injection interval: Partial reaction and solidification of the A/B material in the mixing head. Solution
Immediately shut down the machine for cleaning: Flush the mixing head with a dedicated cleaning agent (such as DOP or acetone).
Disassembly and cleaning: If severe blockage occurs, disassemble the mixing head to remove the solidified material.
Shorten downtime: If production is suspended for more than 5 minutes, it is recommended to circulate the cleaning agent.

4. Leakage (A/B material leakage)
Possible causes: Deterioration of the seal ring: Failure of the mixing head or piping seal.
Loose joints: Leakage at the threaded connection under high pressure.
Excessive injection pressure: Exceeding the seal's tolerance.
Solution: Replace the seal ring: Regularly inspect O-rings and oil seals (replacement every 3 months is recommended).
Tighten joints: Use a torque wrench to tighten to the standard.
Adjust the pressure: Ensure operation is within the rated pressure range of the equipment.

5. Poor foam quality (uneven density, shrinkage, bubbles)
Possible causes: Incorrect mixing ratio: Inaccurate A/B material ratio.
Unstable injection speed: Leading to uneven filling.
Uneven mold temperature: Local overheating or overcooling affects curing. Raw materials contain water or are contaminated: Moisture can cause bubbles or voids.
Solution
Recalibrate the metering system: Ensure the A/B material ratio is accurate.
Optimize injection parameters: Adjust the injection speed and pressure profile.
Control mold temperature: Maintain a uniform mold temperature (usually 40-60°C).
Check raw material storage: Ensure the raw materials are sealed to prevent moisture absorption.

6. Abnormal equipment noise (hydraulic system or motor noise)
Possible causes: Insufficient or contaminated hydraulic oil: Causes the oil pump to dry-run.
Bearing wear: Damaged motor or pump bearings.
Loose mechanical components: Loose screws or belts.
Solution: Check the hydraulic oil: Refill or replace with clean hydraulic oil.
Replace bearings: Stop the machine and inspect worn parts.
Tighten loose parts: Regularly check bolts and belt tension.

7. Daily Maintenance Recommendations (Preventative Measures)
Daily Inspection:
Clean the filter and check the seals.
Calibrate the A/B material ratio.
Weekly Maintenance:
Clean the mixing head and injection lines. Check the hydraulic oil level and quality.
Monthly Maintenance:
Replace worn seals.
Lubricate moving parts.