1、 Mechanical malfunction

1. Abnormal spindle vibration

• phenomenon：
  • The equipment shakes violently during the mixing process, accompanied by abnormal noise.
  • The temperature of the bearing rises sharply (exceeding 80 ℃).
• reason：
  • Spindle bendingLong term overload or material jamming leading to spindle deformation.
  • Bearing damageInsufficient lubrication, dust intrusion, or improper installation can cause bearing wear.
  • Poor alignment of the couplingThe gap between the motor and the spindle coupling is too large or eccentric.
  • Blade imbalanceUneven wear or loose installation of the blade leads to dynamic balance failure.
• process：
  1. Stop the machine and check the straightness of the spindle (measured with a dial gauge). If the curvature is greater than 0.1mm, replace the spindle.
  2. Disassemble the bearing, check the wear of the ball/raceway, and replace it with a bearing of the same model (such as SKF 6206-2RS).
  3. Readjust the coupling clearance (usually 0.1-0.3mm) and calibrate it using a laser alignment instrument.
  4. Repair or replace the blade and conduct a dynamic balance test (balance accuracy level G2.5).

2. Sealing leakage

• phenomenon：
  • Material or lubricating oil seeps out from the connection between the mixing chamber and the spindle.
  • Dust escapes from the sealed area, polluting the environment.
• reason：
  • Seal agingLong term high temperature or chemical corrosion can cause the sealing ring to harden and crack.
  • Installation deviationInsufficient compression or eccentric installation of the seal.
  • Main spindle surface damageScratches or corrosion can cause seal failure.
• process：
  1. Replace seals (such as fluororubber O-rings or mechanical seals) and choose materials that are temperature resistant and corrosion-resistant.
  2. Adjust the sealing compression amount according to the manufacturer's recommended value (usually 15% -25%).
  3. Repair the surface of the spindle (such as chrome plating or sprayed ceramic coating), with a roughness Ra ≤ 0.8 μ m.

3. Blade wear or breakage

• phenomenon：
  • Mixing efficiency decreases and material residue increases.
  • There is a gap or overall fracture at the edge of the blade.
• reason：
  • The material hardness is too highWear resistant blades were not used when mixing hard materials such as fiberglass and mineral powder.
  • Idle operationWhen there is no material, starting the equipment causes the blades to collide with the mixing chamber.
  • fatigue fractureLong term overload operation or blade design defects.
• process：
  1. Replace wear-resistant blades (such as high chromium cast iron or ceramic coated blades).
  2. Prohibit idling operation, ensure there is material in the mixing chamber before starting.
  3. Optimize blade design (such as adding stiffeners or changing blade angles).

2、 Electrical malfunction

1. Motor overheating or inability to start

• phenomenon：
  • The motor temperature exceeds the rated value (such as 120 ℃), or there is no response when the start button is pressed.
  • The frequency converter reports an "overload" or "overcurrent" fault.
• reason：
  • Power anomalyVoltage fluctuations (such as ± 10% rated voltage) or phase loss.
  • Motor overloadThe viscosity of the mixed material is too high or the blade is stuck.
  • poor heat dissipationFan damage or accumulation of dust on the heat sink.
  • Inverter parameter errorThe acceleration time is too short or the torque boost setting is too high.
• process：
  1. Measure the power supply voltage with a multimeter to ensure it is within the rated range (e.g. 380V ± 10%).
  2. Check the viscosity of the mixed material and reduce the blade speed or mix in batches if necessary.
  3. Clean the heat sink and replace damaged fans (such as axial fans).
  4. Reset the parameters of the frequency converter (such as extending the acceleration time to 10-15 seconds and increasing the torque to 5%).

2. Sensor malfunction

• phenomenon：
  • Abnormal temperature/pressure display (such as -999 ℃ or fixed value).
  • The automatic control system is unable to adjust its operating status based on parameters.
• reason：
  • Sensor damageInternal open circuit/short circuit of thermocouple or pressure transmitter.
  • signal interferenceThe sensor cable is not shielded or poorly grounded.
  • Installation location errorThe temperature sensor is not inserted into the material center or the pressure sensor is not installed vertically.
• process：
  1. Measure the sensor output signal (such as thermocouple millivolt value) with a multimeter and compare it with the standard value.
  2. Replace the shielded twisted pair cable for signal transmission and ground it at one end (grounding resistance ≤ 1 Ω).
  3. Reinstall the sensor to ensure full contact with the material.

3、 Process malfunction

1. Uneven mixing

• phenomenon：
  • Inconsistent color and particle size distribution of materials, or the presence of undissolved clumps.
  • The quality of products fluctuates greatly between batches.
• reason：
  • Insufficient blade speedNot reaching the critical shear rate (e.g. plastic mixing requires ≥ 1000rpm).
  • The mixing time is too shortNot reaching the required time for material dispersion (such as 5-8 minutes for glass fiber mixing).
  • Wrong feeding sequenceAdding powder first and then liquid causes clumping.
• process：
  1. Adjust the blade speed according to the material characteristics (such as 1200rpm for PVC mixing and 800rpm for rubber mixing).
  2. Extend the mixing time to the required process value and set a timer to automatically shut down.
  3. Optimize the feeding sequence (such as adding liquid material for pre wetting first, and then gradually adding powder material).

2. Material clumping or coking

• phenomenon：
  • The material adheres to the inner wall of the mixing chamber, forming a hard block.
  • The material color darkens or emits a burnt smell.
• reason：
  • Temperature too highThe heating system is out of control or the cooling is insufficient.
  • Long downtimeMixing interruption causes local overheating of the material.
  • Moisture absorption of materialsUntreated leads to moisture evaporation and clumping.
• process：
  1. Install a temperature controller (such as a PID controller) and set the upper temperature limit (such as plastic mixing ≤ 180 ℃).
  2. Shorten the single mixing time and avoid prolonged downtime.
  3. Pre drying treatment (such as drying at 80 ℃ for 4 hours) should be carried out on hygroscopic materials (such as nylon).

4、 Maintenance suggestions

1. Daily inspection

• mechanical part：
  • Check the spindle vibration, seal leakage, and blade wear.
  • Measure the bearing temperature (using an infrared thermometer), with a normal value of ≤ 70 ℃.
• Electrical part：
  • Check the motor current, frequency converter alarm records, and sensor display values.
  • Clean the dust in the electrical cabinet to ensure the normal operation of the cooling fan.

2. Regular maintenance

• Lubrication and maintenance：
  • Replace the lubricating grease (such as Mobil SHC 220) of the main shaft bearing every 3 months, and add the amount to 1/2-2/3 of the bearing chamber.
  • Replace the gear oil (such as Shell Omala S4 GX 320) of the gearbox every 6 months, with the oil level reaching the centerline of the oil gauge.
• Replacement of vulnerable parts：
  • Seals should be replaced every 1 year, and blades should be replaced every 2 years (to shorten the cycle under high wear conditions).
  • Check the tension of the belt every 6 months and adjust it to the specified value (if measured with a spring scale, the tension is 50-80N).

3. Operating standards

• Startup sequence：
  1. Check that there are no foreign objects inside the mixing chamber.
  2. Close the cover door and lock the safety interlock device.
  3. Start the cooling system (if any) first, then start the main motor.
• Shutdown sequence：
  1. Stop adding and continue mixing until the material is emptied.
  2. Turn off the main motor and open the cover door after the equipment stops.
  3. Clean up residual materials to avoid corrosion of equipment.