In blow moulding, a molten tube of plastic called a parison is extruded and then inflated to take the shape of a mould. The length of this parison must be carefully calculated to ensure enough material is available to fill the cavity without excessive waste.
The parison length depends on the final part dimensions, the material thickness, and the blow‑ratio – the ratio of the parison’s initial diameter to the final part’s diameter. By accounting for these variables, manufacturers can optimise cycle time and material usage.
The following relationship is commonly used for cylindrical containers: the parison length equals the half‑circumference of the final part, adjusted for the blow‑ratio, plus the material needed to close the ends.
D = bottle diameter (mm)
B = blow ratio (unitless)
t = material thickness (mm)
What is a parison in blow molding?
How does the blow-ratio affect parison length?
Why is calculating parison length important in blow molding?
What factors determine the parison length in blow molding?
Can you explain how to calculate the parison length?
Results are for informational purposes only and do not constitute professional advice.