Importance

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Abstract

A control circuit (10) for an extrusion die (13) is operatively arranged to supply a command signal (e.sub.c) to an actuator (24,25) for controlling the movement of a mandrel (11) relative to a die head (12) as plasticized material is extruded through an orifice (14) to form a parison (15). The controller includes a memory (28) for receiving and storing a plurality of initial set points supplied from a keypad (29). A recalculation circuit (42) is operatively arranged to recalculate the magnitude of each set point according to the equation S.sub.n(r) =(S.sub.n(i) -G.sub.1)B+G.sub.2, where S.sub.n(r) is the recalculated value a particular set point, G.sub.1 is a first reference die gap, G.sub.2 is a second reference die gap, B is a scaling factor, and S.sub.n(i) is the corresponding initial set point stored in memory. The recalculation circuit is operatively arranged to supply each recalculated set point to the memory to replace the initial set point stored therein. The recalculated set points are supplied to the actuator, via an interpolator (30) for controlling movement of the mandrel during an extrusion cycle.

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First Claim