Analysis of Common Faults in Plastic Extruders

Plastic extruder is a common plastic mechanical equipment. In the daily operation of the extruder, various faults are inevitable, which affect the normal production of the extruder. Below, we will analyze the faults of the extruder in detail.

 

1.The main motor cannot start

Cause of occurrence:

(1) There is an error in the driving program.

(2) There is an issue with the main motor thread, is the fuse burnt out.

(3) The interlocking device related to the main motor is activated.

Handling method:

(1) Check the program and restart in the correct driving sequence.

(2) Check the main motor circuit.

(3) Check if the lubricating oil pump is started and check the status of the interlocking device related to the main motor. The oil pump does not turn on, and the motor cannot be turned on.

(4) Check if the emergency button is reset.

(5) The induction power of the frequency converter is not fully discharged. Turn off the main power and wait for 5 minutes before starting again

2.The host current is unstable

Cause of occurrence:

(1) Uneven feeding.

(2) The main motor bearings are damaged or poorly lubricated.

(3) A certain section of the heater is malfunctioning and not heating.

(4) The screw adjustment pad is incorrect, or the phase is incorrect, resulting in component interference.

Handling method:

(1) Check the feeder and troubleshoot.

(2) Repair the main motor and replace the bearings if necessary.

(3) Check if each heater is working properly and replace it if necessary.

(4) Check the adjustment pad and pull out the screw to check for any interference.

3.Main power startup current too high

Cause of occurrence:

(1) Insufficient heating time and high torque.

(2) A certain section of the heater is not working.

Handling method:

When driving, use hand cranking. If it is not easy, extend the heating time or check if each section of the heater is working properly.

4.Poor or blocked discharge of the machine head

Cause of occurrence:

(1) A certain section of the heater is not working, and the material has poor plasticization.

(2) The operating temperature is set too low, or the molecular weight distribution of plastic is wide and unstable.

(3) There may be foreign objects that are not easily melted.

Handling method:

(1) Check the heater and replace it if necessary.

(2) Verify the set temperature for each section, and negotiate with the process engineer if necessary to increase the temperature setting value.

(3) Clean and inspect the extrusion system and machine head.

5.The main motor emits abnormal sound

Cause of occurrence:

(1) The main motor bearings are damaged.

(2) One of the thyristors in the main motor's thyristor rectifier circuit is damaged.

Handling method:

(1) Replace the main motor bearings.

(2) Check the thyristor rectifier circuit and replace the thyristor components if necessary.

6.The temperature rise of the main motor bearing is too high

Cause of occurrence:

(1) Poor lubrication of bearings.

(2) The bearings are severely worn.

Handling method:

Check and add lubricant. Check the motor bearings and replace them if necessary.

7.Unstable head pressure

Cause of occurrence:

(1) The main motor speed is uneven.

(2) The feeding motor speed is uneven, and the feeding amount fluctuates.

Handling method:

(1) Check the main motor control system and bearings.

(2) Check the feeding system motor and control system.

8.Low lubricating oil pressure

Cause of occurrence:

(1) The pressure setting of the pressure regulating valve in the lubricating oil system is too low.

(2) Oil pump malfunction or blocked suction pipe.

Handling method:

(1) Check and adjust the pressure regulating valve of the lubricating oil system.

(2) Check the oil pump and suction pipe.

9.The automatic screen changing device is slow or ineffective

Cause of occurrence:

(1) Low air pressure or oil pressure.

(2) Cylinder (or hydraulic station) leaks air (or oil)

Handling method:

(1) Check the power system of the screen changing device.

(2) Check the sealing condition of the cylinder or hydraulic cylinder.

10.The safety pin or safety key is cut off

Cause of occurrence:

(1) Excessive torque in the extrusion system

(2) The connection between the main motor and input bearing is not concentric

Handling method:

(1) Check if any metal or other substances enter the squeezing system and jam the screw. At the beginning, check if the preheating heating time or heating value meets the requirements.

(2) Adjust the main motor.

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