Extrusion Dies with Local Internal Cooling Channels Manufactured by Additive Manufacturing Technologies for Extending the Process Limits in Hot Extrusion

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Within the scope of this funding period the fundamentals for the use of additively manufactured extrusion dies with conformal internal cooling was investigated, aiming at extending the process window of hot aluminum extrusion. For this purpose, dies with cooling channels close to the die bearings on the basis of the layer-laminated manufacturing method and selective laser melting were developed. Besides design suggestions for the construction and set-up of the dies, measuring methods for the detection of the local die temperature in the difficult to access area of the die bearings were developed. The interactions between billet, die, and process parameters were investigated fundamentally by experimental and numerical investigations. While limiting the profile's exit temperature, a significant increase of production speed is possible by applying a local die cooling in hot extrusion. By localizing the cooling to the area close to the forming zone, the extrusion force increase only disproportionately in comparison to the reference trials without die cooling as well as in the case of lower preheated billets. Even though the use of the cooling close to the die bearings leads to significant reductions in the local die and profile temperatures, differences in the sensitivities of the influencing parameters could be detected. A variation of the billet temperature and of the extrusion speed has a higher impact on the profile's exit speed than the parameters influencing the cooling, like the dimension and position of the cooling channel as well as the coolant temperature. The potential of an increased productivity in hot extrusion might be accompanied by higher manufacturing costs for the die. To overcome the economic disadvantages, first concepts for hybrid die components for hot extrusion were developed. For exploiting the full potential of this novel die technology, an analytical model for the description of the heat balance using die cooling has to be developed. This will support the design of the cooling and the estimation of the workpiece temperature with given parameters. Furthermore, the transferability of the developed technology to complex die shapes has to be investigated.