Glycon Corp. is lowering prices for its DM2-brand feed screws based on the ET design, since the original patent now has expired.
Screw designer Robert Barr developed and patented the ET screw in 1982. The screw produces 15-20 percent more output that a typical barrier screw, with 25 percent less shear, Glycon said. Now Tecumseh, Mich.-based Glycon will provide all current ET configurations, as well as new designs for extrusion and blow molding.
“For the last 18 years, Glycon has held the exclusive license to produce these screws for injection molding applications,” said Glycon President Jeffrey Kuhman. “Now that patent protection has run out, we'll be able to deliver the exact same screws at prices that are 30-40 percent lower.”
Instead of using high shear, where the screw forces the resin against the barrel wall, the DM2 screw has a thermal crossover zone positioned along the screw at a point where 70-80 percent of the polymer is melted. The configuration of channels and undercut flights allows the melt, as well as unmelted pellets, to interact without excessive pressure buildup. As the plastic crosses over the undercut flights, it tumbles into the next channel. The crossover is repeated several times, providing a dynamic melting action similar to that of twin-screw extruders.
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