Method for producing a container from a blank, with retroaction on the basis of a real pressure of end of preblowing

A method of manufacturing a container (2) by stretch blow molding in a mold (8) from a blank (3) of plastics material which comprises the steps of: - introducing the preform (3), in the mold (8); - controlling the opening of a solenoid valve (17) pre-blowing at a flow rate (D) of predetermined pre-blowing; - measuring the pressure (P) prevailing in the interior of the blank (3); - detecting an instant (t) actual start of pre-blowing; - calculating an instant (t) of the end of pre-blowing as: t = t + Deltat - delta, where: At is a predefined opening time of the solenoid valve pre-blowing, delta is a predetermined constant, - derive a pressure (P) real end-blowing, - compare the pressure with a pressure (P) theory - if these pressures are not confused decreed, order a change in the speed (D) pre-blowing.