Analysis of common faults of plastic extruders

Plastic extruder is a common plastic machinery. During the daily operation of the extruder, various faults will inevitably occur, which will affect the normal production of the extruder. Below we will explain the faults of the extruder in detail. analyze.

Main motor cannot start

Cause:

● Driving procedure is wrong.
● There is something wrong with the main motor thread. Is the fuse burnt out.
● Interlocks related to the main motor function.

Approach:

● Check the procedure and drive again according to the correct driving sequence.
● Check main motor circuit.
● Check whether the lubricating oil pump is started and check the status of the interlock device related to the main motor. The oil pump does not turn on and the motor cannot turn on.
● Check if the emergency button is reset.
● The induction power of the frequency converter has not been discharged completely. Turn off the main power supply and wait for 5 minutes before starting again.

Host current is unstable

Cause:

● Uneven feeding.
● The main motor bearing is damaged or poorly lubricated.
● The heater in a certain section fails and does not heat.
● The screw adjustment pad is wrong, or the phase is wrong, or the components are interfering.

Approach:

● Check the feeder and troubleshoot.
● Inspect the main motor and replace the bearings if necessary.
● Check whether each heater is working properly and replace the heater if necessary.
● Check the adjustment pad and pull out the screw to check if there is any interference with the screw.

Main power starting current is too high

Cause:

● Insufficient heating time and high torque.
● A certain heater is not working.

Approach:

● When driving, turn the car by hand. If it is not easy, extend the heating time or check whether the heaters in each section are working properly.

The machine head is not discharging smoothly or is blocked

Cause:

● A certain section of the heater is not working and the material is poorly plasticized.
● The operating temperature is set too low, or the molecular weight distribution of the plastic is broad and unstable.
● There may be foreign matter that is not easily melted.

Approach:

● Check the heater and replace if necessary.
● Verify the set temperature of each section, and negotiate with the technician if necessary to increase the temperature set value.
● Clean and inspect the extrusion system and machine head.

The main motor makes an abnormal sound

Cause:
● Main motor bearing damage.
● One thyristor in the main motor thyristor rectifier circuit is damaged.

Approach:

● Replace main motor bearings.
● Check the silicon controlled rectifier circuit and replace the silicon controlled components if necessary.

Main motor bearing temperature rise is too high

Cause:

● Poor bearing lubrication.
● Bearing wear is serious.

Approach:

● Check and lubricate. Check the motor bearings and replace if necessary.

Machine head pressure is unstable

Cause：

● Main motor speed is uneven.
● The feeding motor speed is uneven and the feeding amount fluctuates.
Approach:

● Check the main motor control system and bearings.
● Check the feeding system motor and control system.

Lubricating oil pressure is low

Cause:

● The pressure setting value of the pressure regulating valve of the lubricating oil system is too low.
● Oil pump failure or oil suction pipe blocked.

Approach:

● Check and adjust the lubricating oil system pressure regulating valve.
● Check the oil pump and oil suction pipe.

The automatic screen changing device is slow or ineffective

Cause:

● The air pressure or oil pressure is low.
● Air leakage (or oil leakage) from the cylinder (or hydraulic station).

Approach:

● Check the power system of the screen changing device.
● Check the sealing condition of the cylinder or hydraulic cylinder.

Safety pin or safety key is cut off

Cause:

● The extrusion system torque is too large
● The connection between the main motor and the input bearing is not concentric

Approach:

● Check the extrusion system to see if any metal or other substances have entered and stuck the screw. When it first occurs, check whether the preheating heating time or heating value meets the requirements.
● Adjust the main motor.