Plastic Blow Molding machine’s processes represent the most popular way of producing hollow products
such as bottles, drums, and other vessels out of thermoplastic materials.
This modern industrial technology has evolved from the ancient art of glass
blowing. Among the many types of resins used are:
• various densities of polyethylene
• polyethylene terephthalate polypropylene
• polyvinyl chloride
• thermoplastic elastomers
• polystyrene
• fluoropolymers, and many others
The principle process is “extrusion blow molding.” Others include injection blow molding, biaxial stretch blow molding, and co-extrusion blow molding.
All of which utilize elements of either extrusion or injection, or both. All of the processes share distinct production stages:
• plasticizing or the melting of resin
• parison production which refers to most blow molding operations; or preform
production when referring to biaxial stretch blow molding
• inflation and cooling phases in the mold
• ejection from the mold
A fifth stage required in extrusion blow molding involves trimming the final product.
*Process Operation
The same blowing technique is common to all the process variations and is accomplished through either a blow pin, needle, stuffer, or a core rod.
The process begins with applications of heat and pressure to create the “melt.” The melt is then processed through a reciprocating screw and ram assembly that pushes the material through a die to produce the “parison.”This production of the parison may be continuous or intermittent and is similar to the injection molding process. The reciprocal screw, which heats and moves the resin, has feed, compression, and metering zones. Once the proper amount of melt is available, a ramming action delivers the material to
the die and forms the parison. In the case where very large parisons need to be formed, an accumulator type of machine is used.

Edited by: Zhang Jia Gang Great Machinery Co.,Ltd.
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