HPDC

Salt core high pressure die casting

Courtesy of Buhler

Of the many different metal casting techniques, high pressure die casting presents some of the biggest challenges for any casting simulation software. The parts being filled often have very thin walls, so that the number of computational cells must be large in order to suitably resolve the geometry with a mesh. What’s more, the metal enters the die cavity under high pressure and at great speeds. The resulting jetting and splashing of the metal throughout the die cavity can lead to defects such as porosity (caused by entrained air) or folds and inclusions (caused when metal reaches an area of the part and begins to cool before the part fills completely). FLOW-3D Cast has several features that substantially improve the accuracy of a die filling simulation, and enable the user to better understand the filling process, including its highly-accurate TruVOF algorithm for tracking moving metal fronts and the FAVOR™ method to accurately represent the complex geometries typically involved in high pressure die casting. Plus, FLOW-3D Cast has numerous models for detecting areas of defects like entrained air, thermal stress, microporosity and fold and inclusions.

Thermal Die Cycling

Thermal die cycling metal casting simulationDie cycling simulations are essential for high pressure die casting since the same die is used repeatedly to produce many thousands of castings. It is important to maintain die temperatures for each and every casting because the temperature cycles can cause warping in the die pieces themselves which will lead to dimensional instabilities in the casted parts. With FLOW-3D Cast, the temperature distributions resulted from the combined effects of die heating (during filling and solidification), spraying and air blow-off (during the opening), and the location of cooling channels and inserts can be accurately and efficiently predicted.

Shot Sleeve Optimization

Shot sleeve metal casting simulationIn HPDC, a shot cylinder is used to rapidly push liquid metal into a die. Typically the sleeve profile is oriented horizontally and metal is poured into it through a fill hole on the top surface. A piston pushes the metal down the cylinder to an outlet at the opposite end. The goal of a properly designed shot sleeve profile is to push the metal into the die as fast as possible to avoid early solidification that could cause incomplete filling or internal defects.However, if the piston moves too fast, the liquid metal will fold over, trapping air that may appear as internal defects in the final cast part.

Filling Simulations

Die casting filling simulationWhen modeling high pressure die casting, the most difficult challenge is to accurately track the metal as it enters the die cavity under high pressure and at great speeds. The resulting jetting and splashing of the metal throughout the cavity presents the greatest obstacle to prediction of defects for any software. With our TruVOF method we can help the design engineer determine the location of gates to ensure they have the best flow pattern, the location of overflows to ensure the defects flow to them, and if there will be early solidification.

Modeling Solidification

FLOW-3D Cast helps engineers investigate the formation of internal porosity that can affect the quality of the final part. Also, FLOW-3D Cast enables the investigation of segregation in binary alloys. Finally, a detailed temperature history helps determine whether chills or cooling lines need to be added or modified, and whether the initial metal temperature should be changed. FLOW-3D Cast enables engineers to investigate the formation of internal porosities, thermally induced stresses, and segregation in binary alloys. Also, a detailed temperature history helps determine whether chills or cooling lines need to be added or modified, and whether the initial metal temperature should be changed.

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