How to Measure an Extruder Screw
In plastic extrusion, proper maintenance, repair and replacement of extruder screws is essential to maintaining high productivity. A screw with excessive wear can cause a decrease in production quality or slow production. Because of this, it is a good practice to measure extruder screws regularly in order to document their wear and decide when a screw needs replacement or repair. Measuring a screw requires precision but no special training, so it can be done by any careful worker.
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Things You'll Need
- Wire brush or copper gauze
- Tape measure
- Flight micrometer or dial calipers
Instructions
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1
Clean the screw while it is still hot. To help remove any material coating the screw, use a wire brush or copper gauze. Using a purging compound will make it easier to remove the screw.
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2
Create a data sheet so that you can record your measurements and compare them to other measurements. Each section of a screw requires its own measurements and has a different method of measurement.
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3
Find the screw shank or drive. This is at the beginning of the screw and includes the feed pocket of the screw. The shank is measured from the pocket to the end of the shank, where it attaches to the feed section of the screw; you can use a measuring tape for this step. Also record the diameter of the shank and the bearing that it is attached to.
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4
Use the flight micrometer or dial calipers to measure the diameter at each turn of the screw.
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Measure the length of each section of the screw using a tape measure. There are three basic sections of an extruder screw: the feed section, the transition and the metering section.
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6
Measure each screw turn, both inside and outside the thread.
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References
Resources
- Photo Credit caliper measuring the egg image by JoLin from Fotolia.com
