New advances in die design improve extrusions, save time and compound.

This results in a stable and accurate finished product that will remain concentric regardless of extruder speed.

For years the rubber industry has extruded tubing using two standard die designs - inline and crosshead cross·head  
n.
Inline designs have typically been used to form simple rubber tubing or profiles and crosshead designs have typically been used for applying a rubber jacket over a substrate - a wire or another tube.

Inline designs have used a spider die design, which has an inherent flaw: It generates weld or knit lines. These are lines of longitudinal weakness caused by the separation and rejoining of the compound at the die's legs, or supports. These are unavoidable because the spider is around flow passage - a tube - with three or four legs that hold a tip(also known as a mandrel )in place in the center. It is around this tip (or mandrel) that a molten compound flows to form the i.d. of a tube. A spider die design simply must have legs, and there is no way the compound's flow cannot be interrupted.

Like the inline design, the crosshead design has an inherent flaw. Typically, the compound flows into a helicoid a cylinder that deflects and distributes the flow of compound around a core tube, which slides into the helicoid and holds the mandrel. The helicoid, like the spider, must create a longitudinal weakness.

In the case of the crosshead, however, the substrate - the wire or already existing tubing - travels through the helicoid, which is typically tubulartthe compound enters the crosshead at 90 [degrees] to the production line and is channeled around the substrate by the helicoid. The problem is that the compound is deposited on the extruder side of the helicoid and must flow around it before adhering to the substrate. By the time the compound travels 180 [degrees] to the far side of the substrate, it is either thinner or thicker than it was on the extruder side. This unbalanced flow results in an uneven jacket and the use of excessive compound or extensive operator adjustment to achieve your minimum acceptable walls.

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Tube Notching Specialties

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