Method for controlling a facility for producing containers

Abstract

The present invention relates to a method for manufacturing containers from thermoplastic materials by blow moulding or extrusion blow moulding a preform that has been pre-heated in a furnace then placed in a mould consisting of two half-moulds that define a moulding cavity, said preform being blown into the mould, optionally with a pre-blowing step. Said steps of heating the preforms, pre-blowing and blowing are controlled by a control unit on the basis of various control parameters such as the temperature in the furnace, the blowing pressure in the mould and/or the pre-blowing pressure and/or the pre-blowing flow rate and/or the speed of the stretching rod, for example. Said method is characterised in that it comprises at least the following steps: i) measuring the wall thickness of said containers at at least two different heights upon exiting the mould; ii) comparing the thickness measurements with setpoint values determined for each height of the containers; iii) if the difference between the thickness measurements and the determined setpoint values is greater than a determined threshold, modifying at least one of the control parameters, said modified control parameter(s) being selected at least by calculating the theoretical effects of the variation for each parameter on the thicknesses, then selecting the parameter or parameters that cause the smallest difference between the measured thickness values and the theoretical thickness values; iv) steps i) to iii) are repeated until the differences between the thickness measurements and the determined setpoint values are below said determined threshold.

Dependencies are inferred from the claim text.