Blow used to close it and the air

Blow MoldingBlow molding ( also called blow forming)  is a production method by which hollow plastic parts are produced like plastic bottles and pipes.Substances:Many blows molded pieces are made from several thermoplastic substances, following are:Polyvinyl Chloride (PVC)Polyethylene ( Both at low and high density)Polyethylene  terephthalate (PET)Polypropylene (PP)Method of blow molding Heat is provided to plastic until it melts down to make fluid which is viscous. Then blow molding die is used to make a tube shape called a Parison by extruding this plastic. Cavity including in mold is enclosed around a parison before The parison is grown against a cavity wall by blowing pressurized air. Then it is left for cooling and after some time it becomes hardened and then air is discharged. The part is taken out after mold opens.Types of Blow Molding There are three types of blow molding:Extrusion blow moldingInjection blow moldingStretch blow moldingExtrusion Blow MoldingThe vacant parison is used in extrusion blow molding in which plastic is extruded after melting.then it cold metal mold is used to close it and the air is injected into a Parison, through which hollow bottle, container, and many parts are obtained by forcing it against a cavity wall.Types of Extrusion Blow MoldingContinuous extrusion moldingIntermittent extrusion moldingContinuous extrusion molding Continuous extrusion uses an extruder for plastics in which continuously extrusion is done and a knife is used to separate out the parts.Intermittent extrusion moldingIntermittent extrusion in which extruder screw moves and then ceases for some time and pushes melt away. Then the mold is collected by the accumulator.Injection Blow Molding For the production of a large number of vacant substances, injection blow molding is used.The methods of injection molding areInjection Blowing EjectionInjectionThe plastic is melted which it is sent to a heated mold where neck forms. A final product is made up of this temporary shaped product.Blowing The preform is then moved to the vacant superhot mold. Then through the core gap, the air is inflated into preform material around a tight mold.Ejection The final product is chilled and separate out from the blow mold and the core rod.Stretch Blow MoldingThe preform is obtained by this process. Then machine used these preforms in which they are heated, passing the glass transition temperature by infrared heaters. Metal blow molds use high pressure to drive the air. Then the core rod is used to extend the preform. By using this method many different things can be produced such as bottles.Advantages of Blow MoldingIt is corelessRapid cooling is done by blow moldingComplex hollow shaped products can be manufacturedHigh production rateLow tooling and die costRecycling of flash can be doneDisadvantages of Blow MoldingIt is only used for hollow partsThick hollow parts cannot be formTrimming is neededLow Strength  


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