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Hints and Tips - An Overview of FLOW-3D Cast
FLOW-3D Cast is a specialized version of FLOW-3D designed specifically for simulating casting engineers' applications. The article below outlines some helpful hints and tips about how to use the software that will help FLOW-3D Cast users run efficient and accurate simulations.
Understanding “Priority” in Geometry Interpretation
Geometry Interpretation is used to determine what volume an STL file will comprise at the start of a simulation. If a given volume in the mesh is occupied by more than one STL (overlapping of geometries), then the STL geometry having a higher order or “Priority” will be considered to be the dominant one in the overlapping volume.
There can be several materials representing the various components in a casting. Each material with different properties has to be defined using different CAD geometry STL files, e.g., Casting, Core, Chill, Filters, Insulating Materials (Sleeves & Refractory), etc.
Setting priorities to the CAD files is important because the Heat Transfer Coefficient (HTC) between different materials will affect the casting solidification pattern. For instance, if a chill is placed lower in priority than a gas region, then in an overlapping volume of the chill and gas, the effects of the chill will not be considered in the heat transfer calculation.
- “Remaining Space,” which is generally ‘Mold,’ is the lowest priority.
- Next are the cavity geometries that are defined as ‘Gas’ for a filling simulation or ‘Metal’ for a direct solidification (without filling simulation).
- Gas/Metal will be followed in priority by Filters, Sand Core, Insulating Materials (Sleeves & Refractory), etc. This sequence is followed since the molten metal in the cavity is in constant contact with chills, sand cores and insulating material. These solid objects will have their own HTC that will affect the solidification of the metal near its location. For example, chills absorb heat from the casting from thick mass zones while Insulating risers maintain heat for a longer time at small wall thickness.
Drag-and-Drop STL Files to Import Geometry
Importing geometries one-by-one can be time consuming, especially if they are in large numbers. To reduce the geometry importing time, select all the STL files that are required for the simulation from a folder, and drag-and-drop all those selected CAD files to the new *.SPF file created. Now all the CAD models (STL) files are ready for “Geometry Interpretation.” If any of the geometries need to be repositioned, select Flow/Geometry/Reposition Objects. Importing geometries this way does not affect the priority in the geometry.
Open *.SPF Files using Drag-and-Drop
Drag and drop option for *.SPF file works the same way as it does for importing STL files. Select the *.SPF to be viewed and drag it onto the FLOW-3D Cast GUI to open the file.
Adding Valves, Pointers and Metal Inputs Graphically
An easy way to add Valves, Pointers or Metal input is by using the “Pick a point” button. Select the point on the geometry and then select either “Go to Pointers” or ‘Go to Valves” or “Go to Inputs.”
- Go to Valves: this can be used to define the air vents at selected location and define a Valve ‘Loss Coefficient.’
- Go to Pointers: this can be used to define a void/fluid region. Void pointers can be used for defining air pressure or can also be used to define the cooling channels used in high pressure die casting or low pressure die casting.
- Go to Inputs: this option picks the point where metal mass source can be given as a input. A metal source can be based on Flow Rate with Volume/time (m3/s) or Mass/time (Kg/s) or Filling time(s).
Generating Valves and Pointers Inside the Geometry
When a point is selected on a geometry using “Pick a point” button, the point is generated on the surface of the geometry. To place the pointers inside the geometry, the user must shift the coordinate value of the point along the corresponding axis. Another way to place pointers inside the geometry is by using the “Clipping” option and then selecting the point of interest to generate the pointers.
Scan Along an Axis to View Defects Inside the Geometry
To locate defects inside the casting, look at the cut sections along each axis. The FLOW-3D Cast Postprocessing window makes it easy to scan through a given axis (X,Y,Z). The casting geometry is placed in a convenient orientation and the user can select the desired axis for sectioning the casting. The surface color variable of interest can be Microporosity, Surface Defect, Air Entrainment, Solid Fraction, etc.
FAVORizing Geometry
The FAVORize option resolves only Open Volume (gas regions). To check if a solid object like a Chill or Core is well resolved by the mesh:
- Change the geometry interpretation of the solid obstacle to Gas (under Geometry Interpretation tab), that is, change from Chill or Core to Gas. Select OK.
- Select Meshing and then select FAVORize to see the open volume.
- If required, change the mesh to obtain the desired geometry resolution.
- After completing the meshing, change the geometry interpretation of the solid obstacle from Gas to its original interpretation.
FLOW-3D Custom Variables
While entering values for custom variable parameters, one has to ensure that units are in the CGS system. This is because when FLOW-3D Cast passes these values to the solver, there is a conversion.
Load and Clear Calculation Results from the *.SPF File
The *.SPF is a document file that stores all information about the simulation such as geometry, meshing, materials selected, calculation results, etc. At the end of a simulation, the calculation results are compressed and stored in the*.SPF file.
Results can be cleared from the *.SPF file, e.g., so that you can transfer the file over email. Select Flow/Result data/Clear calculation results.
Results can be loaded into the *.SPF again from ‘flsgrf’ file in *.cal folder. Select Flow/Result data/Load calculation results from the solver.
Merging Simulation Results
Results from two different simulations (two *.SPF files) can be merged. This is very useful while merging restart simulations for viewing filling and solidification continuously.
Saving and Loading View Angles
The user can save the orientation of the casting at which it was placed and view the same orientation the next time.
Generate Custom Sand Material using the “Sand Tool”
The Sand tool can be used to create custom sand materials used for cores or sand molds. The user can enter the percentage of Silica, moisture, clay, etc. and add it as a material in the material database.
