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RBaratt Member Posts: 1 |
posted October 28, 2004 09:16 AM
   
What kind of problems should I expect from an extrusion die with uneven flow characteristics? The die in question extrudes polyethylene zipper. The zipper grippers are the thicker areas with two thinner areas of film on each side of the grippers. IP: Logged |
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Tom C Moderator Posts: 395 |
posted October 28, 2004 01:11 PM
An unbalanced die will deliver flow based on the materials rheology. The rheology interacts with the width of the flow channels in a non-linear, exponential fashion. In other words a channel which is 1/2 as wide as another is likely to have 1/6 the flow. This sensitivity to width and the differences between material flow characteristics make die design difficult. Many techniques are used in an attempt to make a useable product. One method is to deliver the correct amount of material to each area of the die prior to the die exit. Then a quick transition is used from the balanced flow section of the die to the die exit shape. In this way there is little opportunity for the die exit shape to redistribute the flow. This concept of die design is called the "Cross Flow Minimalization Method". Presently I represent software products which support this method of die design. Please contact me if you are interested in more information. Tom Cunningham IP: Logged |
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