Know-How
Telltale Temperatures
Here's how to get a 'feel' for a screw design without actually seeing it. And how to use this information.
Read MoreHow to Establish an Acceptable Range for Pressure at Transfer
Pressure at transfer tells you the viscosity of the resin, providing the fill time is the same. Monitoring pressure at transfer—or better yet, the integral under the pressure vs. time curve—provides insight into the process.
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Melt Flow Rate Testing—Part 6
Once degradation has been established, the discussion inevitably turns to how it happened. It might be expected that the answer to this question is widely known. Not so. The good news is that the influences that cause polymer degradation during processing are few.
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Minimizing Black Specks
Black specks in molded parts are one of the most infuriating problems to resolve on the shop floor. Here's how to fix them.
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Don’t Overlook the Feed Section
Most extrusion screw designers often do not design the feed section with the same rigor as other sections. This is odd since nothing goes through the screw that doesn鈥檛 first go through the feed section.
Read MoreMelt Flow Rate Testing—Part 5
There are two points in the manufacturing supply chain where a determination of average molecular weight (MW) is important. The first is when the material is first received by the molder. The second is after molding.
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Regrind and Melt Pumps
Changing levels of regrind can result in unstable output. If not set up properly, a melt pump can add to this instability鈥攖he opposite of the intended effect.
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Melt Flow Rate Testing—Part 4
Few molders perform the test in-house. Of those that do, most don't understand why they are doing it or what they are measuring.
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Don’t Forget the Cold Slug Well
Its primary function鈥攁s the name suggests鈥攊s to act as a trap, or 鈥渨ell,鈥 for the cold slug.
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