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Many extruders are run without vents. If you can get away without a vent life can be much easier.
I'm a vent fan myself. But given the constraint of having to live with the current design, if a plugged vent will work why not.
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NEVER Plug a Vent! I've witnessed a catastrope once and I'm not sure if the law suite is yet settled. It's downright dangerous. Verify this with your Extruder Manufacturer too.
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I am running 100% regrind although it is pelletised. I thought it was because it was wet so i dried it for several hours at 90c. However, it still comes out! It is not just a trickle either, it is a flood. I have checked screw design, vent design, pressure and changed the temp profile. I can only deduce that it is material related as if i double pass the material it seems to run ok. Any ideas would be much appreciated.
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I have had this problem with one of our HIPS extrusion lines. You can run for weeks then out of the blue material will start to leak from the vent.
Does it happen when the machine has stopped?
If so, and you are using a high percentage of regrind? it may contain moisture.
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Has the vent always leaked or is this a recent development. How restrictive is the screen pack you're running, I'd try increasing Adaptor Zone(s) and the Screen Changer to 230C. The second stage of your screw isn't keeping pace with the first, so maybe increase the feed zone temp a little (to retard the amount of material being conveyed into the first stage of the screw)
Have you seen this article by Chris Rauwendaal? http://www.plasticstechnology.com/articles/200201ts1.html
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I am running HIPS on a 30:1 4.5" My temp profile is as follows:
190,205,205,160,220, screen/coex/die at 235 all in Celsius.
Pressure 1000-1500 psi.Speed about 60 revs. I have leakage through vent.
Any ideas??
I have tried reducing conveying in first stage by incresing temp in 2&3 to 220 but no joy.
The vent may be badly designed but i have to live with it for now.
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