Screw VBET

Figure 14.15 Cross-sectional views for a Maddock solidification experiment for a 63.5 mm diameter VBET screw running ABS resin at a screw speed of 60 rpm [30]. The A and B channels are labeled along with the axial positions in diameters...

As shown In EIgs. 14.10 and 14.15, the cross-sectional views at axial distances less than 10 diameters were similar for both ET and VBET screws. Eor example, the views at 6 diameters were composed of a compacted bed of discrete pellets. The views at 8.4 diameters were In the transition section, where the pellets compacted, softened, and began to melt. For the ET screw, the compaction process had just... 

Figure 14.16 Extrudate sampies as a function of screw speed for a 100 1 ietdown ratio of white ABS (Ti02) to biack ABS resin using a VBET screw [30]...

Some of the more widely used high-performance screws include the Energy Transfer (ET) screw [19], the Variable Barrier Energy Transfer (VBET) screw [20], the Double Wave screw [21], Stratablend [22] and Stratablend II [23] screws, and the Unimix [24] screw. Other devices can, however, act as a trap for solid materials from the melting section. These devices include Maddock-style mixers [25], spiral dams, and blisters. They will be briefly discussed in this section as many of them have been the subject of many articles on secondary mixing processes. 

Figure 5.39 Schematic of a VBET screw showing two sub-channel designs.

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