Matters Needing Attention in Production and Operation of Twin Screw Plastic Extruder


Compared with common single screw extruder, twin screw extruder has the same operation procedure. However, the control system of twin-screw extruder is much more complex than that of single screw extruder, because there are two screws meshing in the barrel of twin-screw extruder, and the forced feeding equipment is needed to provide stable production materials for the extruder. I hope I can help you with some information. The details are as follows:

I. The structure of twin-screw extruder is different from that of single screw extruder, since the parameters of assembly clearance between two screws are added. This parameter must be adjusted to ensure stable and normal production of extruder. The assembly clearance between twin screw and barrel is as follows:

Assembly clearance between twin screw and barrel   /Unitmm

Screw diameter








Counter rotating twin screw








Conical twin screw








        Note: the diameter of conical twin screw refers to the diameter of small end screw. The data in the assembly clearance table are for reference only.

II. Before production, it is necessary to check and verify in advance that the screw direction of twin screw and forced feeding equipment should meet the production requirements.

III. When the plastic extruder is turned on, it is necessary to control the heating and preheating of the barrel. The gap between the screw and barrel of the twin-screw extruder is large, and the material is sufficient. Generally, the time is not recommended to be less than 2 hours.

VI. When the device is started, we do not recommend to start it directly. After the barrel is heated, you should first use the hand or spanner to shift the coupling to make the screw rotate for several circles, and observe whether the pulling is flexible during the trial run, and there is no blocking phenomenon.

V. Before starting the twin screw motor, the lubricating oil pump motor should be activated first, and the oil pressure of the lubrication system should be adjusted to 1.5 times of the working pressure. It is necessary to check whether there is any leakage in each oil delivery system. After all normal, the relief valve is adjusted, so that the working oil pressure of the lubricating oil system meets the requirements of the equipment manual.

VI. There is no raw material for production in the barrel, and the shorter the screw hole running test time is, the better. In order to prevent the friction between screws and barrel and scratch the barrel or screw, the screw low-speed idling time should not exceed 2-3min.

VII. The material for twin-screw barrel is provided by screw feeder. Pay attention to the initial production of forced screw feeding, the amount of material shall be less and uniform. Pay attention to the current change of screw drive motor, and reduce the amount of material when overload current occurs; If the current pointer swings smoothly, the feeding amount of barrel can be increased gradually; In case of long-time current overload, stop feeding immediately, stop to check the cause of fault, and then continue to start production after troubleshooting.

VIII. The rotation of plasticizing screw of twin-screw extruder, the forced feeding screw and the oil pump motor of lubrication system are controlled by interlocking. If the oil pump of the lubrication system doesn't work, the plasticizing twin screw motor can't start; If the double screw motor doesn't work, the feeding screw motor can't start; If the double screw motor does not work, the feeding screw motor cannot be started. In case of emergency stop, press the emergency stop button, and the three transmission motors will stop working at the same time. At this time, pay attention to the feed motor, plasticizing twin-screw motor and lubricating oil pump drive motor speed control knob back to zero. Shut down other auxiliary machines to make them all stop working.


Ningbo Fangli Technology Co., Ltd. is a mechanical equipment manufacturer with nearly 30 years’ experiences of plastic extrusion equipment, new environmental protection and new materials equipment. If you have more needs, welcome to contact us, we will provide you with professional technical guidance and equipment procurement suggestions.

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