Importance

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Abstract

In a blow-molding system in which a parison programmer is coupled to orifice tooling in an extrusion die head for controlling wall thickness of an extruded parison fed to a blow-molding apparatus, a method of synchronizing operation of the parison programmer contemplates placement of observable indicia on the parison after the parison exits the die head. This indicia placement preferably is carried out under control of the parison programmer to place the indicia at a predetermined position along the parison profile, such that mis-positioning of the indicia indicates absence of phase synchronization of the parison programmer. The indicia is then observed on a molded article to determine phasing of the parison programmer relative to the molding apparatus, and operation of the parison programmer is adjusted to correct any mis-positioning. In the preferred implementation of the invention, the readable indicia comprises an optically readable spot or dot, and position of this spot or dot on the molded article is determined by an optical sensor that provides an electrical signal for automatic closed-loop correction of parison programmer phasing without operator intervention.

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First Claim