Swirl-like pattern

One of the benefits of static mixers like those mentioned above are the secondary flow patterns set up by the swirling helical flow. 

Structural-web molding is a low pressure foam molding method. It is the phrase usually used to identify the gap between structural foam (SF) molding and injection molding. Its surface does not have the usual SF characteristic swirl pattern. It can produce very large, lightweight parts with smooth surfaces like conventional injection molded parts. 

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