a method is disclosed for controlling an injection molding machine of the type having an injection screw drivable for axial movement within an extrusion cylinder by a drive - controlled servo motor through a mechanical transmission , to provide a filling phase , a dwell phase , and a plasticization phase , the servo motor having a velocity command signal input connection , and the molding machine having sensors for screw position and injection pressure . the method includes the steps of presetting desired values for at least one of the injection pressure and the screw position ; sensing the respective one of the corresponding actual injection pressure and actual screw position ; and transmitting non - zero velocity command signals to the drive - controlled servo motor during at least the plasticization phase , and preferably also the filling and dwell phases , to move the injection screw within the cylinder . the velocity command signals are calculated as a function of a deviation of the respective one of the actual injection pressure and the actual screw position from the respective preset desired value , preferably using a linear functional relation during small deviation values , and a non - linear functional relation for large deviation values , to improve stability .