Ramona Hölker

New Concepts for Cooling of Extrusion Dies Manufactured by Rapid Tooling

To prevent local overheating of the workpiece material in hot aluminum extrusion the influence of die cooling was investigated. Numerical simulations of extrusion revealed an advantage of the die bearing cooling, which can be accomplished by locating the cooling channels close to the die/bearing surface. Since the fabrication of especially geometric complex cooling channels located near the die surface is not possible by conventional manufacturing technologies, the technology of rapid tooling was introduced into hot aluminum extrusion and experimentally tested. Cooling channels near to the bearings show promising results allowing extensions of extrusion limits, especially the extrusion speed and therefore productivity.

Extrusion Benchmark 2013 - Experimental Analysis of Mandrel Deflection, Local Temperature and Pressure in Extrusion Dies

A bridge die was designed for the simultaneous extrusion of two rectangular profiles and used in a strictly monitored aluminum extrusion process. Experimental investigations aimed at the measurement of the mandrel deflection, the local die temperature, and the pressure inside the welding chamber by means of special measurement equipment. AA6082 alloy was used as extrusion material. The influence of the extrusion speed on the aforementioned objectives is reported. The experiments were repeated at least three times under the same conditions in order to achieve a statistical validation of the acquired data. These data are provided as reference for the 2013 edition of the Extrusion Benchmark.

Increased Productivity in Hot Aluminum Extrusion by Using Extrusion Dies with Inner Cooling Channels Manufactured by Rapid Tooling

The influence of local inner die cooling on the heat balance in hot aluminum extrusion was investigated. For the manufacturing of the die with cooling channels close to the forming zone, the layer-laminated manufacturing method was applied. The new tooling technology was applied in order to decrease the profiles exit temperature and to avoid thermally induced surface defects with the aim to raise the productivity in hot aluminum extrusion processes. Numerical and experimental investigations revealed that, while maintaining the exit temperature of the extrudate, a distinct increase of the production speed up to 300% can be realized, while the extrusion force increases only slightly. An effect on the profiles microstructure was also detected. By applying die cooling, grain coarsening can be significantly limited or even be avoided.