Dr.

Günther, Daniel

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  • Publication
    Hybrid Joining of Cast Aluminum and Sheet Steel Through Compound Sand Casting and Induction Heating To Enable Thin-Walled Lightweight Structures
    ( 2024)
    Locke, Christopher
    ;
    Guggemos, Martin
    ;
    Maier, Lorenz
    ;
    Hartmann, Christoph
    ;
    Volk, Wolfram
    ;
    Günther, Daniel
    Combining different joining processes to form a hybrid process offers new manufacturing possibilities. Adding induction heating to compound sand casting with additively manufactured lost sand moulds to preheat a metallic solid insert increases the degree of the metallic bond between sheet metal and casting metal. In this study, the manufacturability of thin-walled sheet steel/cast aluminum structures with reduced cast wall thickness in sand casting is characterized for the first time. Enabling lower wall thicknesses of sheet metal/cast metal structures in sand casting shifts the current limits and offers more significant lightweight construction potential. Shear tensile, compression shear, and pullout tests characterize the mechanical properties of the joints. Light microscopic imaging of metallographic samples quantifies the compound zone intermetallic (IMC) thickness. The shear tensile test specimens fail at wall thicknesses below 10 mm in the cast material, so metallurgical bond strength characterization does not occur. Therefore, the compression shear test is used to evaluate the metallurgical bond. Sound metallic bonding with smaller cast wall thicknesses of 8, 6 and 4 mm is achieved. Pullout specimens with 3 mm cast wall thickness further investigate the force-transmitting mechanisms of metallic bond, force-fit and form-locking. It is shown that metallic bonding is the predominant mechanism for force transmission when the compound sand casting process is enhanced by induction heating.
  • Patent
    Verfahren und Vorrichtung zum Formen einer aushärtbaren Formmasse
    ( 2023-11-22)
    Volk, Wolfram
    ;
    Günther, Daniel
    ;
    Klan, Steffen
    ;
    Erhard, Patricia
    ;
    Hartmann, Christoph
    ;
    Lechner, Philipp
    ;
    Steinlehner, Florian
    ;
    Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
    ;
    TU München
    Die Erfindung betriff eine Vorrichtung (10) und ein Verfahren zum Formen einer aushärtbaren Formmasse (202), mit:- Aufnehmen einer aushärtbaren Formmasse (202), die sich in einem flüssigen Zustand befindet, in einer Kavität (14), die von einem ersten Formteil (100) und wenigstens einem zweiten Formteil (101) eines Formwerkzeugs (12) begrenzt wird;- Erzeugen wenigstens einer ersten Relativbewegung zwischen dem ersten und dem zweiten Formteil (100, 101), so dass sich die Kavität (14) verkleinert;- Aushärtenlassen der Formmasse (202).
  • Publication
    Predicting and Evaluating Decoring Behavior of Inorganically Bound Sand Cores, Using XGBoost and Artificial Neural Networks
    ( 2023-07-06)
    Dobmeier, Fabian
    ;
    Li, Rui
    ;
    Ettemeyer, Florian
    ;
    Mariadass, Melvin
    ;
    Lechner, Philipp
    ;
    Volk, Wolfram
    ;
    Günther, Daniel
    Complex casting parts rely on sand cores that are both high-strength and can be easily decored after casting. Previous works have shown the need to understand the influences on the decoring behavior of inorganically bound sand cores. This work uses black box and explainable machine learning methods to determine the significant influences on the decoring behavior of inorganically bound sand cores based on experimental data. The methods comprise artificial neural networks (ANN), extreme gradient boosting (XGBoost), and SHapley Additive exPlanations (SHAP). The work formulates five hypotheses, for which the available data were split and preprocessed accordingly. The hypotheses were evaluated by comparing the model scores of the various subdatasets and the overall model performance. One sand-binder system was chosen as a validation system, which was not included in the training. Robust models were successfully trained to predict the decoring behavior for the given sand-binder systems of the test system but only partially for the validation system. Conclusions on which parameters are the main influences on the model behavior were drawn and compared to phenomenological-heuristical models of previous works.
  • Publication
    Compound Casting of Aluminum with Sheet Steel in 3D Sand Casting Using an Inductive Heating System
    ( 2023)
    Locke, Christopher
    ;
    Guggemos, Martin
    ;
    Gruber, Maximilian
    ;
    Maier, Lorenz
    ;
    Mayr, Lukas
    ;
    Weiß, Tony
    ;
    Volk, Wolfram
    ;
    Günther, Daniel
    Compound casting is a process in which a single component is made from two metallic materials, such as aluminum and steel. Solid-liquid bimetallic compounds can be produced by suitable process control. This technology can reduce the number of joining processes, and the specific properties of the respective metal component can be used for specifically designed product properties, for example, where lightweight and high strength are needed. This paper presents an experimental methodology for producing a purely material-bonded bimetallic joint from cast aluminum and zinc-coated sheet steel in 3D sand casting using an inductive heating system. The process-related temperature characterisation in the compound zone is described using a heating test rig and temperature measurements. It shows that inductive preheating can only produce a material bond between the aluminum casting and the coated steel sheet. Shear tensile tests showed strengths between 15 MPa and 22 MPa. Laser surface pre-treatment using laser ablation cutting on the coated steel sheet was carried out to investigate the benefit of possible microform-locking. The results show a strength-reducing influence on the tensile shear tests. Micrographs showed the formation of Al4.5FeSi and Al7Fe2Si, as well as the formation of other undefined intermetallic phases. The thickness of the compound zone is 10 µm.
  • Publication
    Advanced Procedures for Series Production with 3D-Printed Core Packages
    ( 2023)
    Erhard, Patricia
    ;
    Hartmann, Christoph
    ;
    Li, Rui
    ;
    Volk, Wolfram
    ;
    Günther, Daniel
    The application of additive-manufactured cores and molds is of great interest for complex cast components. Nevertheless, several challenges still exist in utilizing binder jetting in the multi-step additive manufacturing process for foundry applications to its fullest extent. This contribution shows methods that facilitate the use of 3D-printed sand molds and cores in casting series applications. The binder jetting process itself is assessed from an overall process chain perspective to highlight the benefits of its application in series production. The challenges associated with automating mold cleaning for highly complex casting contours are depicted. In particular, employing the method of cleanable mold partitioning is shown to enhance the automation level of the overall process. Mold design tailored to 3D printing is demonstrated to contribute to overall cost and time savings in enhanced core packages. Topology-optimized, lightweight part designs involving complex freeform surfaces may require mold partitioning associated with laborious burr removal processes. A new approach in answer to the shortage of skilled workers in the harsh and hazardous foundry environment is shown. Implementing motion tracking technology is demonstrated to enable economical automated burr removal for minor quantities or high variant diversity in the future foundry. All the methods shown are of great importance for introducing printed core packages into series production.
  • Publication
    Characterization of Slurry-Cast Layer Compounds for 3D Printing of High Strength Casting Cores
    ( 2021)
    Erhard, Patricia
    ;
    Angenoorth, Jan
    ;
    Vogt, Joachim
    ;
    Spiegel, Johannes
    ;
    Ettemeyer, Florian
    ;
    Volk, Wolfram
    ;
    Günther, Daniel
    Additive manufacturing of casting cores and molds is state of the art in industrial application today. However, improving the properties of chemically bonded casting cores regarding temperature stability, bending strength, and surface quality is still a major challenge. The process of slurry-based 3D printing allows the fabrication of dense structures and therefore sinterable casting cores. This paper presents a study of the slurry-based fabrication of ceramic layer compounds focusing on the drying process and the achievable properties in slurry-based 3D printing of casting cores. This study aims at contributing to a better understanding of the interrelations between the drying conditions in the 3D printing process and the properties of sintered specimens relating thereto. The drying intensity influenced by an IR heater as well as the drying periods are varied for layer thicknesses of 50, 75, and 100 µm. Within this study, a process window applicable for 3D printing of sinterable casting cores is identified and further indications are given for optimization potentials. At layer heights of 75 µm, bending strengths between ~8 and 11 MPa as well as densities of around 50% of the theoretical density were achieved. Since the mean roughness depth Rz is determined to be <30 µm in plane, an application of slurry-based 3D printing in investment casting is conceivable.