Assessment of the Optimization Strategy for Nitrogen Cooling Channel Design in Extrusion Dies

Abstract

Aluminum extrusion is an efficient industrial process. However, one of the main problems is related to the temperatures developed during the process that can detrimentally affect the achievable productivity, profile quality and/or die life. Cooling of the die with liquid nitrogen represents an efficient solution to overcome this limit but a further issue arises lying in the number of process and design variables that need to be managed in order to set-up of an efficient system. In this context, a 3D FE model of the extrusion process, coupled with a 1D model of the cooling channel, previously proposed by the authors, has been integrated in an optimization platform in order to iteratively and automatically adjusts the channel geometry and the process variables gaining to a final optimal solution in terms of thermal balance, cooling efficiency and nitrogen consumption. The original channel design used during the extrusion of industrial hollow AA6060 profile guaranteed an efficient but unbalanced cooling with a maximum temperature deviation of 60 °C registered by the thermocouple positioned around the bearings. The optimized designs showed temperature deviations below the 16 °C as well as the reduction of 50% in terms of nitrogen consuming.

Investigation on the topological optimization of cooling channels for extrusion dies

“…4b). The numerical approach based on the 1D modelling of the nitrogen cooling was tested and validated in different previous works of the authors [8][9][10][11], proving the good accuracy of the achieved results at very reduced computational time if compared to the approach based on a full 3D model of the nitrogen flow. In this work, the accuracy of the numerical model was demonstrated by analyzing, in terms of temperature prediction, the experimental-numerical differences in both uncooled and cooled conditions.…”

“…If many works have been reported on aluminum extrusion FE (Finite Element) modelling [6,7], stating the robustness and reliability of the approach, only recently Reggiani and Donati [8], and Pelaccia et al [9,10] proposed a comprehensive numerical model for the prediction of the thermal gradient during the extrusion process with nitrogen cooling. In addition, very promising results have already been achieved, by the same authors, by integrating the comprehensive FE model in an optimization platform able to change the channel sections iteratively and automatically along the path [11]. However, the main limitation of the procedure lies in leaving the optimizer free to vary only the cross-sections point by point, but not the path.…”