What is the difference between an extrusion pump and a gear pump for extrusion?

There is often confusion about the terms “extrusion pump” and “gear pump for extrusion”:

Extrusion pump

The extrusion pump is a kind of piston pump for the pumping/conveying of high viscous materials from drums (e.g. 55 gallon/200 litre) and pail cans. Such materials include Drum Extrusion Pumps

Drum Extrusion Pumps

fluids, such as silicone, sealant, adhesive, undercoating, PVC sol, epoxy and grease. Key figures for an extrusion pump are
maximum discharge pressure (e.g. 200-350 bar).
pressure ratio, refers to the ratio between air inlet pressure (usually 3-6 bar) and the maximum discharge pressure (up to 1:81 and higher)
conveying capacity

The extrusion pump is also referred to as “drum extrusion pump”, “sealant pump” and in the US as “ram pump” or “ram unit”. The company Graco calls them even “extruder”.

Gear pump (for extrusion)

Gear pumps, on the other hand, optimize the extrusion process of thermoplastics and polymer materials. They generate a constant pressure (up to 200 bar and more) and ensure a constant flow of material and therefore relieve the extruder of pressure build-up. Typical applications include recycling, due to the constant fluctuation of viscosity, and film production where smallest flow fluctuations could be seen immediately on the extruded products. Gear pumps are also employed for other materials such as paints, oils, additives, acids and casutic, and do not have to be necessarily of high viscosity. Here are further information about the working principle of a gear pump.

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