Interaction of process and machine in multi-stage forging on a mechanical press

This paper presents a mathematical model which provides a basic description of the force and displacements arising in multi-stage forging on a mechanical press. Given the stiffness of tools and press structure, for a given operational sequence, the variations in shut-height caused by deJections of tools and press during forging, compared with that under no load conditions, can be determined. Also the efect of a change in process conditions at one forging station on forces and dimensions of workpieces produced at other stations can be calculated. The model has been validated by experiments undertaken on a crank press in which upsetting and extrusion have been performed as both single and simultaneous operations. NOTATION press crank radius current contact area between punch and workpiece for each stage deflection at a forging stage at bottom dead centre tool load press load height of workpiece at time t shut-height, press unload height of workpiece at time to workpiece reduction (working stroke) toolset stiffness press stiffness/die stiffness at each forging stage press stiffness press connecting rod length number of stage in a forging operation press stroking rate per minute relative average forming pressure ram displacement to start of a forging stage, press loaded ram displacement to start of forging stage, press unloaded press bed deflection press drive-train deflection press leg deflection relative deflection, press ram/press bed toolset deflection lower tool deflection upper tool deflection total deflection at a forging stage total deflection at a forging stage when it only is loaded working stroke, press unloaded press crank angle from top dead centre press crank rotational speed