Operating Procedures for Sheet Extruders

I. Scope of Application: This document applies to the operation, maintenance, and routine upkeep of sheet‑type extruders.

II. Operating Steps:

1. Power-on procedure

(1) Close the main power supply and the protective switch.

(2) Turn on the key switch; the power indicator light illuminates (green), and the temperature control instrument, ammeter, tachometer, pressure gauge, governor control panel, and other devices display their power‑on status.

(3) Heating: Heat the die head, screen plate heater, and screw; set the heating to the normal steady-state temperature.

(4) Heating times: The screen‑plate furnace shall be heated for at least 4 hours, the furnace body for at least 3 hours, and the three‑roller water‑mixing unit for 1 hour; (first heat the head section for 1 hour, then the body section, setting each temperature 20°C higher than the specified setpoint; once the equipment is running normally, adjust the temperatures back to their set values).

(5) Start-up and Production: Before starting up, adjust the gap between the three rollers so that the gap height matches the thickness specified in the production plan. However, the actual product thickness should be measured after normal production has commenced, with minor adjustments made as necessary. When adjusting the roller gap, ensure that no metal or hard objects—including feeler gauges—enter the gap to prevent damage to the rollers. The initial adjustment should ideally set the gap 0.05 mm thinner than the target thickness specified in the production schedule, with fine-tuning performed during the trial‑run phase.

(6) Before starting up, verify the material‑loading condition; do not operate the main unit without material. Upon startup, energize the motor, accelerate gradually, and feed material slowly. During start-up, keep the main‑unit speed below 10 rpm; only after confirming normal discharge and a stable ammeter reading should the speed be incrementally increased to its normal operating level.

(7) Since the main motor current reading increases as the feed rate accelerates, to prevent safety risks arising from excessive speed increases by operators, a maximum current limit—corresponding to the upper‑limit alarm threshold—is set in accordance with process requirements. The company specifies that the main motor current’s upper limit is 75 Hz.

(8) Start the circulating water pump and adjust the opening of each shut-off valve.

(9) Start the lubricating oil pump, and check the machine’s oil level and lubrication condition.

(1O) Start the prime mover and set the operating speed value of the main motor governor.

(11) Filler production: Set the filler feed rate according to the governor’s speed; once the product has been discharged and formed, set the cutting width, which shall conform to the width specified in the production plan.

(12) Adjust the winding unit’s speed according to process requirements, and wind up the qualified products.

(13) After the equipment has started up normally, periodically verify that the temperature, voltage, and rotational speed are consistent with the set values.

2. Shutdown Procedure

(1) When shutdown is required, first close the hopper gate and decelerate the machine gradually to a stop, ensuring that only a small amount of material remains in the screw. In the event of a sudden power outage, close the hopper gate, disconnect the power supply, and bring the main motor to a standstill.

(2) Stop the traction machine;

(3) Stop the winding machine and disconnect the air valve.

(4) Disconnect the main power switch.

3. Precautions

(1) If abnormal noise or vibration occurs in the main unit or the drive system, press the emergency stop button to shut down the machine.

(2) If the machine malfunctions, notify the maintenance personnel. Only after the fault has been rectified and the main motor and the filler speed‑control settings have been returned to the “0” position may the machine be restarted.

(3) As the feeder speed is gradually increased to boost the feed rate, closely monitor the main motor current and melt pressure to prevent overloading of the main motor or excessive die head pressure.

(4) For routine shutdowns, set the main motor and the feeder speed control to the zero position.

(5) When performing internal screw assembly and adjustment, do not remove the rear set to prevent improper meshing during reassembly.

(6) Start-up, shutdown, and emergency stop procedures must be carried out strictly in accordance with the prescribed operating steps.