Know-How
Materials: Cycle Time—Science vs. Rules of Thumb, Part 6
This installment—on elastomers—completes a series, whose theme is to bring more science to the discipline of molding. The overall message: Ask a lot of questions whenever someone posits this or that ‘rule of thumb’ about processing.
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Tooling: Know the Basics of Sprue-Puller Design
Sprue-puller designs are quite varied, and there are no firm rules to follow. But here are some important cautions and caveats to keep in mind.
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Extrusion: The Challenges of Extruding Highly Filled Polymers
These materials require screw changes and modifications in upstream and downstream equipment and operating procedures.
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Injection Molding: No, Backpressure Does NOT Raise Melt Temperature
It’s a classic confusion between cause and effect. Melt temperature rises when screw speed is increased. Check out this data.
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Materials: Cycle Time: Science vs. Rules of Thumb—Part 5
Let’s examine the behavior of semi-crystalline materials that never reach their glass-transition temperature as they cool.
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Tooling: Dealing with Sprue Bushings On the Production Floor
Causes of and solutions to some problems you probably deal with every day.
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Extrusion: The Role of Polymer Density in Screw Design
Density affects the mass flow rate, and energy transfer is based on mass, not volume. As a result, polymer density enters into practically every calculation in a screw design.
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Injection Molding: DOEs Done Right
Doing DOEs for the sake of doing them wastes time and money. But they can provide vital information to determine which process variable is determining a critical part characteristic.
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Cycle Time: Science vs. Rules of Thumb—Part 4
While laboratory tests are helpful in determining how polymers behave, you must remember the fundamental differences between laboratory measurements and the real world of plastic processing. Let’s examine semi-crystalline polymers here.
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Extrusion: The Facts About Barrel-Temperature Override
Cooling the barrel more may extract heat from the barrel, but not necessarily from the process. Here’s why.
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