Extruder auxiliaries-melt pump Althoughtheextrusionprocessworkswithouttheuseofameltpump,addingapumpattheendoftheextruderoffersseveraladvantages. 1.Themainadvantageistheconsistencyandqualityoftheoutput. 2.Thegearpump,alsocalledameltpump,isapositivedisplacementdevicesotheoutputisaconsistentpredictablevolumeperrevolution. 3.Thegearpumpismadeforpumpingathighpressure;therefore,itismoreefficientthantheextruderatbuildingthepressurerequiredtoovercomethebackpressureofthesystem(dieandscreenchanger). 4.Thevolumetricefficiencyofthemeltpumpis98to99percent,whereastheextruder'sefficiencyisonlyabout45percent.Thismeansthataddingagearpumptotheextruderwillusuallyresultinlowertotalpowerconsumption. 5.Bytakingthepressurebuildingawayfromtheextruder,wearisalsoreducedonthecomponentsoftheveryexpensiveextruder. 6.Extrusionspumpsystems,includingdrivesandcontrols,usuallypayforthemselvesinafewmonthsbyreducedscrapandraisingthroughputs. 7.Pumpsformoltenpolymerarehighlyengineeredpositivedisplacementdevices.