of the advancing screw an injection pressure or a production cycle time in to fig3 actual and setpoint value graphs of the aforementioned situation are shown in this figure a horizontal broken line d 1 denotes a setpoint pressure curve and a solid line denotes a measured pressure curve d 2 in a p x diagram the vertical broken lines which run over further diagrams confine an x range between x 1 and x 2 in this range the pressure curve d 2 runs above the pressure curve d 1 the area defined by this is shown by broken lines in the p x diagram a v nom x diagram shows a speed setpoint curve g 1 which is shown by a broken line a v act x diagram shows a measured speed curve g 2 this defines a hatched area with a horizontal line shown as a broken line in the x range identified by the vertical broken lines the injection pressure exceeds the predetermined maximum pressure curve d 1 the speed setpoint profile g 1 is constant in this range on account of the injection pressure being exceeded the speed setpoint profile g 1 is corrected in the substitutional control branch described with reference to fig2.