The effect of pocket shape in extrusion dies

A multi-hole die with four L-shaped openings was produced with four different pocket shapes and two different profile thickness (2 and 3mm respectively) in order to determine different material flows inside the die. A classical pocket shape was used as a reference on 2 mm thickness profile while the other adopted pockets were: a conical pocket on a 3mm thickness, a step pocket on 3mm thickness and a uncentred pocket on 2mm thickness. AA6082-O aluminium alloys was utilized. The extrusion experiments were performed at two ram speeds (0.5 and 5 mm/sec), and each condition was replicated three times. Process load, die and profile temperatures were recorded as well as profiles lengths (for each hole) in order to analyze the material flow inside the die. The experiments showed that, at low production rates, the conical pocket determines a slower exit speed with respect to the stepped one, while the classical centred pocket flows much faster than the not centred one. Finally, at high production rates the material flow differences strongly decrease.