Extruder postforming

There is off-line (for small quantity of products) or in-line postforming. The in-line refers to forming/shaping the extrudate (tube sheet, etc.) just after it emerges from the extruder die but before the plastic has a chance to cool. It provides specialty products with performance and cost advantages. Upon leaving the extruder s die and... 

Postforming identifies plastic sheet, rods, tubes, and other profile shapes that are formed into different shapes (coils, corrugated tubings, tubular nets, etc. Its major use is inline with an extruder processing... 

Acetal resins may also be fabricated into rod, slab, and other shapes by profile extrusion. Extruded shapes are frequently further machined. Parts fabricated by molding or extrusion are ammenable to all typical postforming processes. 

A popular forming technique that has provided both performance and cost advantages, principally for long production runs, is applied as the plastic sheet, film, or profile exits an extruder. Upon leaving the die, and retaining heat, the plastic is continuously postformed. 

Fig. 5-16. In-line postforming with extruder embossing one or both sides with shallow or deep patterns.

Information on the technique of forming is covered later in this chapter under Forming. In-line postforming, or postextrusion processing, refers to the special processing that may be done to the extrudate, usually just after it emerges from the die but before the material has a chance to cool. 

Various methods can be used for postforming products after the hot plastic melt leaves the extruder die. Examples are netting products that are flat to round shapes, rotated mandrel die makes perforated tubing, spiral spacer web around a coated wire or tube, varying tube or pipe wall thickness, and different perforated tubing or pipe pattern. 

Postforming (1) The heating and reshaping of a fuUy or partially cured laminate, on cooling, the formed laminate retains the contours and shape to which it has been postfomed. (2) Operations applied to still warm extrudates, particularly some types of profile extrusions, in which limbs of the extrudate pass through fixtures that bend or curl them into their final shapes. 

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