A simulation study on the closed-loop control of screw press forgings using the impact energy as control input

Abstract

Screw presses are energy-restricted forming machines that use rotational energy stored in a flywheel for forming, which is converted into a linear movement by a threaded screw. Screw presses are widely used for forging steel, aluminum and brass. In a direct-driven electrical screw press, a reversible electric motor is mounted directly on the screw and on the press frame above the flywheel. With directly driven screw presses, the blow energy can be exactly dosed from one blow to the next. However, so far no prior work is known which uses the blow energy as a control input in a targeted manner to influence the properties of the forging. The purpose of the present work is to lay the foundations for property control through blow energy dosing during forging on screw presses. Process control becomes increasingly interesting due to ever increasing customer demands and needs for resource-efficient production. A major challenge is the variation of process parameters, e.g. temperature variations in the furnace, during transport or due to inherent uncertainty in the heat transfer to the dies and the environment. If the process conditions are changing the deviations from the planned process trajectory may lead to an insufficient die filling or undesired final properties. Forged parts require high precision considering the part geometry and material properties. During forming two mechanisms in terms of forming temperature take place: heat conduction due to contact with tools and heat dissipation due to plastic deformation. The heat transfer acts as disturbance, the impact energy can be used as control input. In this work, investigations into process control by impact energy dosing are put forward using FE (finite element) simulations.