A comprehensive experimental study and numerical modeling of parison formation in extrusion blow molding

Abstract

Parison dimensions in extrusion blow molding are affected by two phenomena, swell due to stress relaxation and sag drawdown due to gravity. It is well established that the parison swell and sag are strongly dependent on the die geometry and the operating conditions. The availability of a modeling technique ensures a more accurate prediction of the entire blow molding process, as the proper prediction of the parison formation is the input for the remaining process phases. This study considers both the simulated and the experimental effects of the die geometry, the operating conditions, and the resin properties on the parison dimensions using high density polyethylene. Parison programming with a moving mandrel and the flow rate evolution in intermittent extrusion are also considered. The parison dimensions are measured experimentally by using the pinchoff mold technique on two industrial scale machines.

A modeling approach to the effect of resin characteristics on parison formation in extrusion blow molding

“…The collected experimental data are compared with the numerical prediction of the parison formation, using the BlowParison 1 software developed at IMI. This software has been successfully used in the past to model the swell and sag, combined with the nonisothermal effects, for several industrial parts including fuel tanks [19][20][21][22][23][24]. It is also validated at high Weissenberg numbers (We [ 400) [25] and extremely high flow rates ([2000 g/s).…”

“…This software has been successfully used in the past to model the swell and sag, combined with the nonisothermal effects, for several industrial parts including fuel tanks [19][20][21][22][23][24]. It is also validated at high Weissenberg numbers (We [ 400) [25] and extremely high flow rates ([2000 g/s). The software couples a fluid mechanics approach to represent the die flow, with a solid mechanics approach to represent the parison behavior outside the die, and a mathematical swell model to account for the pronounced elongational and shear stresses at high Weissenberg numbers.…”

“…To our knowledge, this approach is the first that is able to yield stable predictions based on first principles, for high flow rates and small die gap annular systems. The fundamentals of this modeling tool can be found elsewhere [22,25].…”

Numerical simulation of suction blow molding process for producing curved ducts

“…To date, numerical modeling of the suction blow molding process is almost inexistent in the scientific literature. In a recent survey, we found no scientific publications in this area, most publications addressing the die swell simulation problem and the modeling of extrusion blow molding process , among others. During the annular extrusion, the parison swells and sags as it exits the die.…”

Lightweight Medium-Sized Parts Made of Foamed HDPE Processed via Extrusion Blow Moulding: Analysis of Parison Formation

“…Regardless, the parison must have sufficient melt strength to remain selfsuspended until the mould closes, clamping it [15]. There have been quite a lot of publications studying the theoretical models and simulating this annular flow process, introducing and varying all polymer properties, but to the best of the author's knowledge only a few studies have been focused to validate the experimental results with the results carried out real on-machine [16][17][18]. In fact, these scientific articles have not been much focused on the study of the shrinkage effect which is our main target in the characterisation of the parison section.…”