A complete pipe extrusion line involves a chain from material storage and mixing to packaging and storage. Key components include extruders, dies, and downstream equipment. Optimizing these components and their interaction is essential for high output, low reject rates, and low cost per pipe length.
The extruder plasticizes and transports the polymer. Double screw extruders are common for PVC dry blend, offering positive displacement transport and self-wiping flights. Single screw extruders are used for PO granules, relying on friction. Modern designs, particularly for PO, incorporate grooved intakes for forced transport. Extruder design influences melt homogeneity, specific energy consumption, and output capacity.
Die heads shape the polymer melt into a hollow pipe. Spider dies are common for PVC, while spiral mandrel and basket dies are used for PO. Die design is critical for pipe quality aspects like wall distribution, spider line weld quality, and reducing die drool. Features like double compression tooling in spider dies optimize melt flow and weld quality. Multi-layer dies enable production of pipes with different core materials (e.g., foam core).
Downstream equipment includes calibration, cooling tanks, haul-offs, cutters, and belling machines [Mentioned as part of the line but not detailed]. Optimization of downstream equipment, such as quick tool change (QTC) capabilities, improves line utilization. Gravimetrics and scanners integrated into the line help control material usage and wall thickness, reducing overweight and reject. Automated Temperature Centring (ATC) also aids in maintaining wall distribution.
Enhancement programs like Total Production Management (TPM) or Six Sigma focus on overall production improvement. Key metrics include output rates, reject rates, overweight, and idle time. Continuously improving performance is supported by modern electronic controls providing data for analysis and visualization. Effectivity (mastering the process) should precede efficiency (speeding up).