subject: How Blowmoulding Works [print this page] How Blowmoulding Works How Blowmoulding Works
The blowmouldingmoulding processinvolves the processing of plasticgranules through a heated screw and barrel to heat the plastic to a molten state. The blowmoulding screw and barrel setupis similar to an auger arrangement where the material is pushed forward while the screw is rotating.
The melted material exits through the end of the screw and barrel via a diehead, which shapes the plastic into a cylindrical tube shape, which isreferred to as a parison
When the parison is of sufficient length, two halves of a mouldare moved into position and closed around the parison.The parison is then cut with a knife, and the tool is moved out of the way, to allow the parison to continue to extrudefor the next moulding cycle.
A cylindrical shaped blowpin isthen moved to theneck or opening in the mould, and blows the parison to the shape of the mould with compressed air, and the plastic is then allowed to cool. The tool then opens, and ejects the finished moulding.
While the plastic product is being formed and allowed to cool, the nextparison is beingprocessed through the screw and barrel, ready for the next cycle to begin.
The blowmoulding process produces productssuch as bottles, jerrycans, and drums.
Materials used in this process are called thermoplastics, and the most common ones used are polyethylene and polypropylene. These thermoplasticshave the ability to be reused directly back into the moulding process or combined with thew base raw material at varying percentages.
