The method for controlling a blowmolding machine during a process of making an object is disclosed. The machine includes a die head, a mandrel and an extruder that rotates and drives a plastic material between the mandrel and the die head to form a plurality of elongated parisons. The method comprises setting the distance between the die head and the mandrel and the rotation speed of the extruder to accomplish predetermined target values of the weight of the object and parison velocity. Plastic material is fed to the machine and the extruder is operated to form the parisons. A parameter related to the viscosity or melt index of the plastic material in the extruder is detected and the material distribution function and the speed of the extruder are adjusted in response to the parameter so that object weight and velocity of the parisons made are maintained substantially at target values.