Needless to say, the blow molding of complex-shaped parts requires a parison programmer, and yet this control is only capable of making thickness adjustments in one axis.

The mechanized matrix, or core, is one of the techniques that enable to improve the distribution of material, but the profile only modifies a part of the longitudinal area of the blow-molded container.

Any molding that is asymmetrical requires another axis of wall thickness control, and therefore Techne in partnership with S.B.Enterprise has implemented the Parison Radial Adjustment (P.R.A.) system.

The conventional die is replaced with a flexible die made from a special alloy that is squeezed and stretched into ovality, during extrusion blow molding, by two or more electric or hydraulic actuators.

By varying the shape and concentricity of the die gap you will have a much greater degree of thickness control.



5 reasons to use Parison Radial Adjustment in extrusion blow molding process 

Why using the P.R.A (Parison Radial Adjustment) wall thickness device in the extrusion blow molding process? Here are 5 reasons why it is a great choice for your company:

  • Material Saving - remove material from areas where it is not needed. In some parts, this can reduce weight by more than 10%.
  • Faster Cycle Time - thick sections take much longer to cool. Eliminating them enables you to open the mold sooner.
  • Tighter Specifications - If you are setting the weight of the molding to achieve a minimum wall thickness in specific places then you’re probably wasting material in other places.
  • Reduced Distortion - thick sections shrink more than adjacent thin areas which cause distortion. The P.R.A. system gives you the control needed to eliminate the problem.
  • Increased Strength - Excessive wall thickness is one of the most common causes of drop test failure as thinner sections can absorb energy, like the crumple zones on an automobile.


Parison Radial Adjustment with two actuators 

The P.R.A. with 2 actuators is the standard solution for packaging starting from 20 liters and technical parts.

The flexible ring is pulled and squeezed by 2 actuators placed opposite, the parison programmer profile has typically the same shape but adjustments can be done in case of complex shapes.

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