ISSUE 3/2014

/// 03
Müller, S.; Pries, H.; Dilger, K.
Enhancing the design process of cooling systems for die-casting dies
A significant contribution to quality and lifetime


High-pressure die-casting dies are subjected to high cyclic temperatures and mechanical loads. Heating and cooling cycles cause thermal expansion and contraction of the material, generating strain fields which lead to a significant plastic deformation. An accumulation of plastic deformations often leads to unexpected failures at the surface of the die-casting die. The selection, quality and the processing (e. g. heat treatment) of hot work tool steels are parameters that are often discussed in scientific literature. However, the temperature control of the die-casting die is another important parameter for the achievement of reasonable lifetimes. The article illustrates, how characteristic properties of conventional internal cooling systems (e. g. the wall heat transfer coefficient and the pressure drop) can be calculated by CFD simulation (Ansys Cfx) and verified by experimental investigations. The calculated specific values for the pressure drop and the wall heat transfer coefficient were processed and transformed into engineering specifications. Using this knowledge, the design process of the cooling system is more accurate than an estimated guess based on gained practical experience. However, due to restrictions in the performance of conventional cooling systems, an alternative method to establish conformal cooling channels is discussed: the segmentation of the die-casting tool. In order to demonstrate the potential, advantages and restrictions of this method, an existing die-casting tool insert is used. The article finishes with a brief summary and an outlook on further improvements to the approaches.




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