Eliminate degradation in PVC flat dies
What was the problem?
Material degradation in a PVC Flat die!
The customer observed degradation nnear the end of the the manifold section of their PVC die. Materials would collect in that region and degrade over time. When PVC degrades, it releases corrosive by-products, which break through the chrome layer and attack the metal underneath.
What was the root cause?
Low Shear Stress at the wall!
Adequate shear stress at the walls is required to keep the system “self-cleaning”. After analysing the geometry, we found that shear stress near the walls of the end of the manifold section region was too low, which led to build up of material, which eventually degraded.
How it was solved?
Increase the shear stress near the walls!
We analysed the die using the VEL Flat Die module and calculated the shear stress. We then modified the geometry until the shear stress at the walls went above the minimum required value.
After the new die was built, the customer could run the line for weeks. There was no longer any degradation in this manifold section region.
Bottom Line
Stopping and starting the line to remove degraded material is prohibitively expensive. Furthermore, degradation of PVC releases harmful and poisonous gases which can be hazardous to the health of the emploeeys in the plant.
By using simulation, we were able to find the root cause of the problem and find the optimized geometry in less than 2 hours. The solution saved the customer thousands of dollars every year.
