Flow lines in blown film
What was the problem?
Flow lines appearing in blown film!
The customer saw flow lines appearing in their film. They did not know what was causing it, and how to fix it. They were under pressure to fix it and it was delaying production.
What was the root cause?
Leakage from adjacent spiral and low shear stress
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The channels and the gaps in the spiral mandrel and body were not designed correctly. Some material from the adjacent spiral was leaking out and flowing backwards. furthermore, the shear stress near the wall of the the first spiral channel was too low, which lead to stagnationg and degradation. The flow lines were a result of back-flow and degradation.
How it was solved?
Improve the design of the spiral distribution system!
Using the VEL Spiral Die module, we redisgned the spiral distribution system. Using particle path tracing, we were able to check for back flow. We also ensured that there was adequate shear stress at the walls.
The optimized die was built and the lines did not appear again.
Bottom Line
This was the kind of problem that could days to simply determine the root cause of the problem. Using simulation and our experience, we were able to identify where the problem was coming from and find a solution quickly.
