Selection of the Injection Unit

To select the correct configuration of injection unit for a particular material or material range, consideration must be given to the following factors  

The screw should be of a suitable corrosion resistance, (e.g., nitrided, Arbid (boronising heat treated), bimetallic) 

The design of the screw is very important for plastieation. Some typical screw configurations will be shown in the next section. 

The compression ratio can be defined as the ratio of the flight depth in the feed section to that in the metering section. As an example, a screw for a polyamide material may have a compression ratio of 3 1 on a 20L/D screw with a 30 mm diameter. 

1 Mixing Screws for Additives and Fast Cyciing Machines 

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