The Barwell Gear Pump Preformer combines three key elements:

• The plasticising properties of a cold feed screw extruder
• The volumetric flow control properties of a gear pump
• The proven Barwell cutter system

This combination increases the process capabilities of difficult materials, including tight dimensional tolerances, and overcomes temperature to output restrictions.

The gear pump removes the effects of pulsing in the screw extruders. Inlet pressure monitoring will automatically adjust screw rpm to maintain inlet pressure stabilities, ensuring that the gear pump cavity is consistently full.

In turn, the outlet pressure is maintained and flow is constant in volume, allowing for either dimensionally stable profile extrusion or volumetrically precise preforms when the die face cutter is engaged.

The ability of the gear pump to compensate for pressure fluctuations greatly increases the versatility of the system. Constant and reproducible throughput ensures high quality extrusion or preforming uniformity.

As there is no die pressure to influence the screw extruder, the outputs for screw size are typically up to 20% higher than can normally be achieved if no gear pump is used.

Material flow through the gear pump is generally linear and, therefore, entirely dependent on the gear pump rotation speed. Increasing the gear pump rpm will automatically adjust the screw feed, maintaining the inlet pressure and cavity fill.

This linear effect is not influenced by varying material characteristics. As long as the screw is capable of achieving adequate plasticising, the throughput will remain linear.

Very little energy is put into the materials by the gear pump, enabling the system to run at lower temperature or to achieve higher output at normal process temperatures.

Barwell can offer complete Extruder-Gear Pump systems or Gear Pump retrofit packages to complement existing extruders.