Operation specification for twin screw extruder

1.The correct way to switch colors and materials

The stable and efficient production of twin-screw extruder is a long-term pursuit of the industry. The continuous startup time is an important indicator that can reflect the equipment quality and production process. However, in reality, due to the material process or production batch, it is often necessary to constantly switch the process formula or adjust the screw combination, for example, to produce one batch of product A and then another batch of product B.

01.The batch size of the product should correspond to the size of the machine. It seems self-evident. However, many processors do not have a good scheduling. When a twin-screw extruder is used to produce 500 kg of material, 100 kg of waste has already been produced

02.Write out the operating procedures for cleaning or withdrawing the screw of the twin-screw extruder producing each product, which will help operators plan time and eliminate their arguments about how much die material will be produced.

03.Help the operators to place the clean operating tools around the twin-screw extruder. If the materials are changed frequently, set up a workbench around the extruder to prepare everything needed.

04.Study the sequence of raw materials and finished products flowing in and out of the operation site. Arrange so that the operators spend less energy on moving the transportation tools.

05.Find out the requirements of the next product on the cleanliness of the twin-screw extruder. If you know that the next product requires thorough manual cleaning, do not waste time and materials to clear the machine.

06.If possible, the production shall be arranged in the order of reducing the cleaning of twin-screw extruder. This means going from light to dark. On the contrary, you have to adjust the combination by pulling the screw several times.

2.The correct way to start and stop the twin-screw extruder

Common error operation modes:
Operators are used to turning on the twin-screw extruder to preheat it when they arrive at the factory in the morning, and then go to work on other things. This allows the twin-screw extruder to stand idle for several hours after being heated to the design temperature. This will enable the polymer to adhere to the screw and barrel, and then these polymer materials will continue to degrade and carbonize. It is difficult to completely remove these materials when cleaning the machine. What’s worse, once the twin-screw extruder starts to produce products, black spots will periodically exist in the materials extruded from the screw and barrel, contaminating the products and leading to substandard product quality.

Correct startup method:
Plan when you will actually start processing the product, and then figure out the time period required for the set temperature to reach the predetermined value. Make other preparations. After reaching the preheating temperature, immediately feed the machine barrel for filling and start production.

Correct shutdown method:
Before shutdown, inert polymer (such as HDPE) shall be filled in the twin-screw extruder to the maximum extent to seal the gap of the machine. HDPE drives away the oxygen and is coated on the metal surface, greatly reducing the formation of carbon oxides. After the twin-screw extruder is “sealed”, it is better to quench the extruder instead of cooling it in the air for 18 hours. Quenching is to set all temperatures to zero and open all cooling water valves. Turn on the cooling water pump to make the cooling water pass through all cylinders for rapid cooling. Rapid cooling will avoid polymer degradation and carbonization.