Single Screw Extruder knowledge-Part 1

Single Screw Extruder knowledge-Part 1

Screw Diameter

The diameter of screw usually means the outside diameter, it marked as the extruder's size or model. Such as SJ-35/25, SJ-65/36, SJ-90/38, etc.

In China, here has a standard(ZB G95 009.1-1988) definition of the screw diameter. It stipulates the diameter of screw in China is 20mm, 30mm, 45mm, 65mm, 90mm, 120mm, 150mm, 200mm. But today in China according to market requirements and the extrusion technogloy development, the screw diameter also includes 25mm, 35mm, 50mm, 75mm, 80mm, 100mm, etc is stipulated in the new standard-JB/T 8061-1996. It means the standards in China are in line with international standards. Thanks to WTO bring us advanced technolgoy.

Learned from the picture as above showing, you could find the screw position. It's position just like heart in human's body. This why we call the screw as extruder's heart part, it is such a imporatant part.

A process of plastic melt and calibration must equipped with an extruder. The melt materials extruded from the extruder by transmission, Compaction, melt and extrude. How to achive this process, let's check the below drawing.

L1, L2 and L3 is the three sections of one screw. L1 is section of transmission/feeding, L2 is section of compaction(pressure building), L3 is extrusion section.

D: Diameter, L: Screw length, so you will know the daily talking, we said one extruder is SJ-45/30, what the 45/30 means? It meas the L/D ratio. Such as a 65mm screw extruder, it's L/D=65/33, so we could calculate the screw length approx is 2145mm.

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