High Pressure Die Casting (HPDC) is the manufacturing process of choice when it comes to realizing large series of cast aluminum components specifically for the automotive industry. Typical of the latter area of application are, among others, structural components of the body-in-white, often characterized by low wall thickness and complex shape, the latter e.g. expressed in a high surface area to volume ratio. The current “GigaCasting” trend in the automotive industry of producing ever larger structural parts in a single shot marks an apogee in this respect. The consequence is an increased susceptibility to residual stresses and distortion. Counteracting these tendencies is either costly (mechanical straightening) or risky for lack of flexibility (adapting die cavity geometry). The alternative is introducing a deliberately inhomogeneous cooling after casting or solution heat treatment (SHT) [1]. In order to reduce distortion in this way, local heat extraction must be adapted to the state of the part immediately before quenching. Assuming a HPDC process chain including SHT, our concept foresees a digital twin of the processing sequence up to the final stages of SHT providing the input data for definition of the required local cooling conditions. Experimental validation is done on the casting depicted in Fig. 1, which is produced using Bühler SC/N 66 HPDC equipment. Actual distortion of parts produced at different parameter settings is measured using optical 3D scanning. Both experimental and simulation data is utilized to train a data-driven model linking process parameters to part properties – namely distortion and residual stress -, as physics-based simulation techniques could not guarantee the necessary response times. Practical implementation of heterogeneous cooling is envisaged based on a spraying field composed of individually controlled spraying nozzles. Derivation of local heat transfer coefficients provided by these relies on parameterized models of their spraying characteristics previously determined experimentally. Finite Element Analysis (FEA) of position-dependent effects of individual nozzles on residual stress and distortion is used to establish combinations of nozzles at different positions capable of alleviating a specific deformation pattern.

[1] A. Ebrahimi; U. Fritsching; M. Heuser; D. Lehmhus; A. Struss; A. Tönjes; A. von Hehl Procedia Manufacturing 2020, 52, 144-149.