High Pressure Die Casting

Salt core high pressure die casting buhler
Courtesy of Buhler

High Pressure Die Casting (HPDC) presents some of the biggest challenges for casting simulation software. FLOW-3D CAST has several features that substantially improve the accuracy of a die filling simulation, enabling the user to critically analyze 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. FLOW-3D CAST also offers models for detecting areas of defects due to entrained air, thermal stress, microporosity, and fold and inclusions.

Thermal Die Cycling

Thermal die cycling simulations are essential for high pressure die casting, since the same die is used repeatedly to produce thousands of castings. Maintaining consistent die temperature becomes more challenging over time due to warping in the die pieces leading to dimensional instabilities. With FLOW-3D CAST, the temperature distributions resulting from the combined effects of die heating, spraying and air blow-off, as well as the location of cooling channels and inserts can be accurately and efficiently predicted.

Thermal die cycling metal casting simulation
Shot cylinder metal casting simulation

Shot Sleeve Optimization

In high pressure die casting, a shot cylinder rapidly pushes liquid metal into a die. Oriented horizontally, the metal is poured into the sleeve through a fill hole on the top, then a piston pushes the liquid metal down the cylinder. The goal of a properly designed shot sleeve profile is to push the metal into the die quickly enough to avoid premature solidification, which can cause incomplete or defective filling. 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.

FLOW-3D CAST can be used to analyze different shot profiles with simulations that take just a few minutes of computational time. This simulation compares two shot profiles: a constant velocity two-stage process (top) and a gradually accelerating velocity (bottom).  The resulting data show significantly different outcomes. Courtesy of Simulated Engineering, Inc.

Filling Simulations

The most complex challenge in HPDC simulation is accurately tracking metal as it enters the die cavity under high pressure and at speed. The resulting splashing of the metal throughout the cavity presents a significant challenge to prediction of defects for any software. Using our TruVOF method, we can determine the location of gates to ensure the best flow pattern, the location of overflows to ensure the defects flow to them, and the presence of early solidification.

Die casting filling simulation
Early solidification simulation by Littler Diecast
Courtesy Littler Diecast

Modeling Solidification

FLOW-3D CAST helps engineers investigate the formation of internal porosity that can affect the quality of the final part. FLOW-3D CAST also 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.