POLYMERSMOULDING OF PLASTICSTHEORY 1 Fabrication / Moulding of Plastics The fabrication is the process in which the prepared resins in the formofgranulesofpowderareconvertedintodesiredshapeby using various machines or moulds. Therearemanywaysbywhichthecompoundmaterialsat transformed into finished articles. Thebasicprincipleinvolvedinthisispartiallymeltingresigns massbytheapplicationofheatandthenfurthercompressedin dies / mould with the help of high pressure to get desired shape. The following methods for fabrication are in practice : (1) Compression moulding :GuidepinsPressureExtractionpinMouldingplasticingredientsincavityBottommouldingpart(femaledie)Topmouldingpart(maledie) Compression moulding of plastics Itisthemostcommonmethodformouldingtheresetting materials which can with stand high temp and press. Resinpowderispreheatedtoabout1200Candpressure from 2.000 to 10.000 psi are used. e.g.Ashtrays,electricswitchborestoradio,T.V.cabinets etc. POLYMERSMOULDING OF PLASTICSTHEORY 2 (2) Injection moulding :MouldingHingeArchimedainscrewNozzleBottommouldingpart(cold)Topmouldingpart(cold)HopperPlasticfeedFluidizedplasticHopperExtractionpin Injection moulding of plastics Itisoneofthemostwidelyusedprocessesformoulding thermoplastic materials. Resin powder is injected under pressure 1758 Kg. / cm.2 and temp is about 1000C. POLYMERSMOULDING OF PLASTICSTHEORY 3 (3) Transfer moulding :HingLowerpartofmouldLiquidplasticundergoingcurve UpperpartofmouldOrificePrc-heaterPlungerMouldingpowerinplasticstate Trasnfer moulding of plastics Itismethodusestheprincipleofinjectionmouldingandis used for thermo setting materials. Powderedresinsareplacedinaheatedchamber, maintainedataminimumtemp,atwhichitjustbeginto become plastic.This plastic material is then injected through anorificeintothemouldbyplungerworkingatahigh pressure. POLYMERSMOULDING OF PLASTICSTHEORY 4 (4) Extrusion moulding :PlasticHeaterScrewcoveyerMetallicwirePlasticfeedPlasticcoatedcableHopper Moulding of insulted electric cableby extrusion moulding vertical HopperDieExtrudedtubePlasticfeedConveyorbeltColdpartofdie Moulding of tube by horizontal extrusion moulding Itismainlyusedformanufacturingcontinuousmoulding articles of thermoplastic resins. e.g. tubes, rods, strips, pipes, insulated electric cable, etc.