What to look for:

- radially balanced melt pressure

- least areas of resin stagnation

- minimize heat history difference radially

- axial gum gap adjustment that does not cause die to tip concentricity change

- easy component assembly and disassembly

- easy cleaning

- lowest resin volume/inventory

- out put capacity matched to your product

- a large core handling capacity

- simplicity of design and manufacture

- small number of components

What to avoid:

- flow geometries that lead to weld lines, such as spider legs

- point heat sources; use circumferencial temperature control instead

- complex flow geometries; these usually have stagnation areas, are difficult to clean, and expensive to manufacture.

- large resin inventories / volume, this adds residence time / heat history

Mark Carter

Princepal Extrusion Engineer

Carter & Assoc., Contracting Extrusion Engineers