Barrier flight melting screws

Barrier Flight Melting Screws 7.5.1 The Barrier Screw Concept... 

Campbell, G.A. and Spalding, M.A., Numerical Analysis of the Melting Process for Barrier-Flighted Single-Screw Extruders Using Screw Rotation Physics, SPE ANTEC Tech. Papers, 56, 418 (2010)... 

Maddock mixing screw Feed Primary flight v Barrier flight /Melt channel... 

Figure 6.25 Qualitative shapes of X and Tbed dimensions and melt film thicknesses for a barrier screw model with a transverse barrier flight (a) top view of the solids channel and the entry to the metering section, and (b) side view of the solids channel and the entry to the metering section. The cream color represents molten resin...

The restriction was mitigated by modifying the screw as outlined in the case study in Section 11.10.1. That is, the depth of the melt channel of the barrier section was increased to that of the solids channel at the entrance, and it was tapered into the depth of the melt channel over 2 diameters. The barrier flight was removed for the first 2 diameters and blended in with the melt channel, the shallower of the two channels in this region. The barrier flight for the next diameter was blended into the original undercut. With this modification the restriction still existed but it was spread over a three-diameter length of the screw instead of over half of a diameter. 

Figure 14.4 Channel depths for a 114.3 mm diameter screw with a barrier melting section. The lead length in the feed and meter sections is 114 mm the lead length of the main flight in the barrier section is 172 mm. The barrier flight starts at the pushing side of the channel and ends near the trailing side. The barrier flight clearance is 1.2 mm...

Figure 14.21 Schematic of a 114.3 mm diameter Fusion screw with a barrier melting section. The lead length of the screw was 131 mm for all sections of the screw except for the barrier melting section. The lead length in the barrier section was 159 mm. The undercut clearance on the barrier flight and the secondary flight in the Fusion sections was 1.3 and 2.5 mm, respectively...

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