Highest precision for the best quality

Gear pumps for extrusion

The extrusion process is very diverse. In the extrusion of plastics a wide variety of profiles and tubes can be produced. It is also possible to produce monolayer or multilayer films by means of extruders. In coextrusion, various materials are made into a film using multiple extruders. Besides the classical polymers, e.g. Polypropylene or polycarbonate are also used in extruding filled polymers. In Wood Plastics Composites (WPC) wood parts are bound in a polymer matrix.
In the food industry extrusion technology is also used. For extrusion of foodstuffs very high demands on the purity. The production of licorice should be mentioned here as an example.

Steady pressure

Due to the design, extruders do not ensure a very constant pressure at the outlet. Also, the efficiency of increasing the pressure in an extruder is not very good. Therefore, a gear pump is used after the extruder. On the one hand, the pump takes over the pressure build-up and thus relieves the extruder. On the other hand, the gear pump ensures even pressure and reduces the pulsations. The extrusion tools are optimally supplied with the melt.

Survey on advantages

  • Pulsation-free transport of the melt
  • Constant pressure circumstances
  • Low heat input
  • Increase of product quality
  • Pressure Relief of the extruder

Use of melt pumps

Classic applications where melt pumps are used:

  • Processes where transportation must be without pulsation
  • Processes where screen changers are used
  • In the granulation
  • In connection with filters
  • For compounding processes
  • With the processing of thermoplasts, elastomers and highly-filled plastics
  • During rubber extrusion

To the melt pump program

Structure of a melt pump of the EXTRU series

Extrusion is a versatile field of application for melt pumps. In many processes, it is a matter of creating constant pressure conditions and reducing the heat input into the medium. This is essential to ensure consistent product quality and to avoid excessive scrap.

The WITTE melt pump is usually operated downstream of the extruder in order to build up sufficient pressure for the subsequent process steps, for example. Common combinations include gear pumps and single-screw extruders. The pump takes over the pressure build-up in order to overcome the resistance caused by screen changers or profile tools.

When using a gear pump in the extrusion process, the product flow is constant and pressure-stable.