Screw and Barrel Service

Posi-Melt™ Multipurpose Screw

The perfect choice for processing a variety of materials in the same molding machine
Mike Durina has the experience, technical knowledge and software programs that can provide you with plasticating screws that are optimized for your exact situations.

When screw design is considered for a particular polymeric family, the rule of thumb has been: amorphous materials process better with low compression screw designs, while semi-crystalline materials prefer high compression designs. Since semi-crystalline polymers have a sharp melting point and transform quickly between solid and melted state, higher compression designs with shallower metering sections have been the standard preference. But these have a tendency to over-shear and over-heat amorphous polymers.

The Posi-Melt™ difference is a change to the core geometry of plasticating screws. We have separated the coordinate systems of the root and flight pitch to force the pellets through a channel that changes pressure and velocity while exposing 55-60% more pellets to the heated barrel wall for improved conductive heat transfer.

Mike’s advanced design exposes the polymer to changes in velocity and extensional strain. This enables molders to lower the volumetric compression for low shear heating while establishing a high “linear depth ratio” between the feed depth and metering depth. The lower volumetric compression works well with amorphous polymers by lowering the shear between the pellets in the transition zone, while the high “linear depth ratio” assures a shallow meter depth for efficient melting of semi-crystalline polymers.

The Posi-Melt™ General Purpose Screw has won acclaim from custom molders, resin suppliers and OEMs for its ability to broaden the process window when processing a variety of materials in the same molding machine. It offers significantly better melt preparation, enabling plastic processors the ablity to mold higher quality parts in a wide range of polymers. Improving your process is Mike’s goal.

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Posi-Melt™ XLA Mixing Screws

The ideal choice when precise color matching is needed or when residence time and swept volume dictate
In order to add a higher degree of homogenization to the melt pool, we developed an especially effective dispersive mixer that works by forcing the polymer to change direction numerous times over a short axial distance.

In order to add a higher degree of homogenization to the melt pool, we developed an especially effective dispersive mixer that works by forcing the polymer to change direction numerous times over a short axial distance. We also add extensional strain by forcing the material to cross over a shallower land multiple times for added shear. A positive pumping angle and major flight OD wiping action assures a low pressure drop for high throughput. It also pressurizes the channels, which promotes quick and effective melt purges during changeovers.

Posi-Melt™ MB Barrier Screws

The optimal solution for achieving maximum pressure and high throughput
Our proprietary MB barrier design forces the polymer between the barrier flight and the inside of the barrel.

Mike’s proprietary MB barrier design forces the polymer between the barrier flight and the inside of the barrel. This causes additional extensional strain to ensure complete melting. We can couple the XLA mixer to the MB barrier for processing a variety of polymer groups, including PP, HDPE, LDPE, PS, PET, ABS as well as many others. All Posi-Melt™ screws are precisely designed to promote the best possible solids conveying and pressurizing so the polymer is transferred properly through the transition and metering zones. Special care is taken to design-in the appropriate leading and trailing edge radii to avoid low-velocity sections in the channel and to maximize pressure. The benefits of Posi-Melt™ screw designs include:

  • Quicker color and material changeovers – Posi-Melt™ MB single channel design results in better and quicker purging.
  • Lower cost – Posi-Melt™ MB single channel design is less costly to manufacture.
  • Complete pressurization throughout for excellent conveying, melting, and pumping.

Plastic Injection Service and Training

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