Vol. 34 #2, Summer 2009
Screw Channel Depths
Understanding the depths of a screw channel is very important for understanding the performance
of a single-screw extrusion process. A sled device for measuring the depth of screw
channels, barrier flight undercuts, and mixer flight undercuts is shown in Figure 1. To use this
device, the sled is positioned on the top of the screw with the micrometer tip contacting the
top of the flight. The micrometer is zeroed at this position. Next the sled is then slid axial on
the screw and the micrometer is adjusted until the top of the micrometer probe contacts the
root of the screw. A similar procedure can be used to determine the undercut depths for barrier
flights or mixer flights.
- Mark A. Spalding, The Dow Chemical Company
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