For plastic extruders, operators must be thoroughly familiar with the machine’s structural features in order to properly control processing parameters and operate the equipment safely. Below, Shuangda Machinery outlines the safety operating procedures for plastic extruders.

I. Pre-Startup Preparations

1. Materials intended for extrusion must meet the required drying specifications and may require additional drying.

2. Based on the product’s type and dimensions, select the appropriate die specifications for the plastic extruder, then assemble the machine in the prescribed sequence, installing the die flange, die body, die land, perforated plate, and filter screen.

3. Connect the compressed air line, install the core‑mandrel electric heating rod and the nozzle heating coil, and inspect the water‑cooling system.

4. Adjust the clearances at all locations of the die to ensure uniformity, and verify that the centerlines of the extruder’s main unit and auxiliary equipment are aligned.

5. Start up all operating equipment of the plastic extruder, verify that it is functioning properly, and promptly address any malfunctions detected.

6. Turn on the electric heater to evenly heat and raise the temperature of the machine head, the machine body, and the auxiliary equipment. Once the temperature of each component is approximately 10°C higher than the normal operating temperature, maintain this temperature for 30–60 minutes to ensure uniformity between the internal and external temperatures of the machine.

II. Power-On Procedure

Starting up a plastic extruder is a critical step in the production process; improper control can damage the screw and die, while excessively high temperatures may cause the plastic to decompose, and temperatures that are too low can harm the screw, barrel, and die. The startup procedure is as follows:

1. Start the machine at low speed, run it idling, and check for any abnormalities in the screw, as well as ensure that the motor and ammeter readings show no signs of overload, and that the pressure gauge is functioning normally. Do not allow the machine to idle for an extended period, as this may cause excessive wear between the screw and the barrel.

2. Gradually add material in small quantities; only resume normal feeding once the material begins to extrude from the die. Before the plastic is extruded, no personnel shall be positioned directly in front of the die to prevent injuries or fatalities.

3. Immediately after plastic extrusion, the extrudate must be slowly conveyed to the cooling and shaping section using traction equipment, which should be started in advance. Subsequently, based on the readings of the control instruments and the requirements for the extruded product, appropriate adjustments should be made at each stage until the extrusion process reaches a stable, normal operating condition.

4. Cut samples, inspect their appearance to ensure compliance with specifications, verify that dimensions meet standard tolerances, and perform rapid performance testing. Then, adjust the extrusion process according to quality requirements to ensure the final product meets the specified standards.

III. Shutdown Procedure

1. Stop feeding material, extrude all the plastic from the extruder, and turn off the barrel and die power supplies to prepare for the next operation.

2. While turning off the host power, also turn off the power to each auxiliary device.

3. Open the die head connection flange and clean the porous plate and all components of the die head. During cleaning, use copper rods and copper sheets; after cleaning, apply a thin layer of machine oil. For cleaning the screw and barrel, if necessary, the screw can be pushed out from the rear of the machine, cleaned, and then reinstalled. In most cases, transitional material changeover can be used for cleaning.

4. For extruding polyolefin plastics, the extruder is typically shut down when fully loaded (with material remaining in the barrel). During such shutdowns, care should be taken to prevent air from entering the barrel to avoid oxidation of the material, which could compromise product quality during subsequent production. For polyvinyl chloride plastics, a similar approach—shutting down with material remaining—is also acceptable; first close the feed port, then reduce the temperature at the die‑head connection (flange) by 10–20°C, and stop the machine once all material has been extruded from the barrel.

5. Turn off the main power supply and the cooling water valve.

IV. Maintenance and Care of Plastic Extruders

1. The cooling water used in the system is typically softened water, with a carbonate hardness of less than 2 DH and a pH of 7.5–8.

2. When starting up, ensure safe startup procedures are followed; first start the feeding device, and when shutting down, stop the feeding device first. Empty operation with material is strictly prohibited.

3. After shutdown, promptly clean the barrel, screw, and the feed ports of both the main and auxiliary machines, and inspect for any agglomerates. It is strictly prohibited to start up at low temperatures or to reverse the machine while material remains in the system.

4. During routine operation, ensure proper lubrication of all lubrication points and the two tandem thrust bearings, and check for leaks at the screw‑seal joints. If any issues are detected, promptly shut down the equipment for maintenance.

5. Regularly inspect the wear of the brushes in the plastic extruder motor and perform timely maintenance or replacement.