Extrusion Technical Services

Bad wire coating design 2D Simulation

These graphics show the flow inside a wire coating die which had problems with burning. The material is PVC. Flow is from left to right. The top image shows flow velocity, blue being low and red high. The bottom image shows flow lines. While a basic visual inspection of the die geometry looks streamlined, the analysis shows that it is anything but streamlined. The pumping ability of the wire being pulled through the die (the bottom boundary moving left to right) counters the flow of the resin in the die creating an eddy current in the die transition area. The eddy is indicated by the circulating flow lines. Further analysis shows low velocity and very high residence time of the material in this area. Basically the PVC in this area gets trapped and eventually burns. A very counterintuitive design was required to resolve the problem.

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