Association between extrusion process stability and dimensional accuracy of aluminum profiles

Abstract Dimensional deviations in aluminum extrusion are strongly influenced by the non-stationary conditions occurring during individual production cycles. This study investigates the association between extrusion-speed and main-cylinder-pressure stability and the cross-sectional accuracy of ring-shaped EN AW-6082 aluminum profiles produced on a 3000-ton direct extrusion press. The industrial campaign included one initial cycle using a 393 mm billet and five subsequent cycles using 600 mm billets. Extrusion speed and pressure were continuously monitored, while outer and inner diameters were measured in two perpendicular directions at the front and rear regions of the extrudate, before and after mechanical straightening. Process variability was quantified using the coefficient of variation, and ovality changes were evaluated by statistical testing and effect-size analysis. Relatively stable intervals exhibited extrusion-speed CV values of approximately 4–5% and pressure CV values near 6%, whereas transient intervals showed substantially greater variability, with extrusion-speed CV values above 35% and pressure CV values reaching 38.32%. Higher ovality was generally observed in the rear regions. Mechanical straightening significantly reduced outer-diameter ovality in both evaluated series ( p < 0.01), although local deviations were not fully eliminated. The findings confirm the practical value of pressure–speed monitoring for identifying production intervals associated with increased dimensional-quality risk.