Confined parison inflation behavior of a high‐density polyethylene

An analysis of the confined parison inflation step associated with the extrusion blowmolding of a high‐density polyethylene is presented. Based upon simple geometrical considerations and material conservation principles, relationships describing the wall thickness variation have been obtained for various mold configurations. The experimentally measured part thickness distribution is found to be in good qualitative agreement and reasonable quantitative correspondence with the theoretical predictions. Furthermore, the expressions for the thickness variation have been utilized in order to estimate the confined inflation time for the case of a power‐law constitutive equation. In addition, a brief discussion of some practical mold design considerations is given based upon the theoretical analysis.