How should the forming process of HDPE double-wall corrugated pipe be controlled?

The main process controls are as follows:  
① Currently, most systems use two single-screw co-extruders to separately plasticize and extrude two different materials to form the inner and outer pipe walls. Alternatively, a single-screw extruder can be used to plasticize and extrude the same material to form both inner and outer layers. The screw length-to-diameter ratio of the extruder is typically selected as 33:1;  
② The barrel temperature of the extruder is generally controlled between 170°C and 210°C, while the die temperature is usually maintained between 200°C and 210°C;  
③ For HDPE double-wall corrugated pipes, corrugation formation is mostly achieved by external vacuum forming combined with internal air blowing for sizing—known as "external suction, internal blow." The vacuum level and compressed air pressure during forming are adjusted according to the pipe diameter and wall thickness. Typically, the vacuum level is controlled at -0.08 to -0.07 MPa, and the compressed air pressure ranges from 0.03 to 0.06 MPa.
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