HPDC Filling Tutorial Problem Description The geometry representing a HPDC will be built using existing STL files and F LOW-3D LOW-3D Cast primitives. Because there is s ymmetry only half of the simulation will be run to s ave on runtime. Properties will be defined for each component. This exercise can be setup in F LOW-3D LOW-3D Cast Extended and F LOW-3D LOW-3D Cast Advanced. To see a list of the Physical Models that can be u sed for each version go to the Manual, Theory, and then Auxiliary then Auxiliary Models. Models.
Problem Specification All STL files associated with this exercise are in centimeters.
Metal poured: A380 Tip material: Copper (CuCoBe) Initial Metal Temperature: 676 Initial Die Temperature: 176 Initial Tip Temperature: 121 Shot sleeve length minus biscuit: 19.5” Shot sleeve diameter: 2.75” Thinnest section of cast part (does not include gates and/or ingates to overflows): 1/16” Area of Runner 1 : 1.84e-4 m 2 Area of Runner 2 : 1.84e-4 m 2 Gate area for Runner 1 : 2.54e-5 m 2 Gate area for Runner 2 : 5.64e-5 m 2
The shot sleeve analysis will be done later in the exercise. The units in F LOW-3D Cast are in SI (kilograms-meters-seconds) and temperature default is . For this exercise we will use but the temperature units can be changed to Kelvin by selecting the Units ‣ Temperature ‣ Kelvin. This is important to know ahead of time, for material property definitions and imported geometry.
Exercise Objectives The objective of this exercise is to do a analysis of the filling. It will begin with two different designs; different gate types and different runner systems. Five simulations will be run to determine the best runner system, ensure shot sleeve parameters prevent or reduce air entrapment, and determine the location of overflows. The simulations will be as follows:
1. Run two simulations one for each runner system. The runner systems will be fed from runner through gates into part to analyze the flow pattern. One case has multiple gates so we will also check to see if the gates feed at same time. No shot sleeve for this analysis. 2. Determine which runner system is better. 3. Run two simulations with the full shot sleeve into casting to d etermine the location of overflows and best shot sleeve analysis. 4. Add overflows and run the entire filling process including heat transfer and early solidification.
Simulation Manager Creating a Workspace and Simulation File When F LOW-3D Cast is opened, the Simulation Manager tab is presented. This is where the user can create, save, copy, delete, and queue simulations to run. This tab also displays useful diagnostic information on simulations that are running or have been previously run. Simulations are grouped into Workspaces, which are like folders and may represent individual projects or users of the program. For example, simulations related to the same design project can be organized into one workspace for ease of their setup. All simulations in a workspace can be run sequentially at a click of the mouse.
If the F LOW-3D Cast interface is not open, open it by double-clicking on t he F LOW-3D Cast icon, 1. Create a new workspace.
on your desktop.
1. Select the Simulation Manager menu ‣ New Workspace. If this is your first time opening the Graphical User Interface (GUI) then a dialog will open asking where you would like your Workspace default location. Currently it is in your documents/FLOW-3D. To change this select the Browse button to specify new location. 2. Select the OK button to close dialog box. 3. A new dialog box, New Workspace will open, enter HPDC Filling Design Exercise for name of new workspace. 4. Ensure Create a subdirectory using workspace name is checked. Note The location of directory can be changed by selecting the Browse button. 5. Select the OK button to close the dialog box.
2. Create new simulation.
1. 2. 3. 4.
Right-click on the HPDC Filling Design Exercise workspace ‣ Add New Simulation. A dialog box New Simulation will open, enter the name of the simulation HPDC Filling Gate Location 1. Ensure the Create subdirectory using simulation name is checked. Select the OK button to close the dialog box. Notice the blue dot on the left of the simulation, this indicates that the simulation is loaded. You can have several simulations loaded (multiple dock-able windows) at the same time in case you want to do comparisons of setups. To see ho w many simulations are activated you can select the Window menu ‣ Activated projects. Simulations can be unloaded by selecting the simulation int he Simulation Manager and then select the File menu ‣ Unload Simulation.
Check For Geometry Errors and Fix if Needed 1. Open the geometry .stl files in netfabb Basic to visually see if there are any errors that were created during process of converting to stl.
1. netfabb Basic can be installed from the Internet. 2. Once installed, select the start menu ‣ click on netfabb Basic. 3. Register the software. 4. Select the Folder icon, to bring up Explorer. 5. Select the Browse button, browse to C:\Flow3d\CAST4\gui\stl_lib\HPDC Exercise and select the Left-Cover.stl. An error appears as soon as the part is displayed as seen in Figure 5.
2. Fix stl file(s). 1. To fix the part select the red plus icon,
located along the top.
2. Select the Automatic repair button in the Status tab. In the status tab you will see the errors found in netfabb Basic as seen in Figure 6. 3. Select the Execute button. 4. Select the Apply repair button in the Status tab. 5. A dialog box will open asking if you want to save the old part, select the Remove old part button. 6. Right-click on the Left-Cover(Repaired)(100%) and select Export part ‣ as STL. A dialog will open to prompting location to save stl file. The stl files will be renamed Left-Cover(Repaired). 7. Select Save button. A new dialog will open prompting about optimizing the tolerance. 8. Leave the tolerance default and select the Optimize button. 9. Select the Export button to finish saving the fixed stl file. Netfabb Basic found 2 invalid orientations, 5 holes, and 15 border edges.
3. Repeat steps 1-2 for Runner-1.stl, Runner-2.stl, Top-Overflow.stl, Bottom-Overflow.stl, and Lifter-Overflow.stl.
Model Setup For Runner System 1 The rest of the setup will take place in the Model Setup tab. The buttons on the left hand side represent a process flow which will be followed. The icons on the right are tools such as region pointers, baffles, and valves. Select Model Setup tab.
Change Display to White Background 1. 2. 3. 4. 5. 6. 7.
Select the Tools menu above the display ‣ and Options. A Color options display opens. Select the black color square next to Background . A Select color dialog opens with color palette to select from. Select the white square. Select the OK button to select color. Select the Apply button. Select the OK button to apply changes.
Setting Finish Conditions 1. Select the Time Controls button. This is where the Finish time and conditions will be set. Notice the button itself highlights in blue this indicates it is open and a tab appears below with the name of the button. 2. Enter 2 in the dialog box next to Finish time. 3. Select the Fill Fraction as finish condition. This finish condition will terminate the simulation, when all cells have at least 1% of fluid in them and are surrounded by cells with fluid or when the finish time is reached whichever comes first.
Defining Models and Numerics Defining Models
In this section we will add air entrainment, surface defects, cavitation potential, viscosity, turbulence, and gravity. 1. Activate the necessary General Physical Models. 1. Select the Models button. Two buttons are active, Finish Conditions and Models, and both can now be accessed via the tabs at the bottom. If you select the Models button again it will close the dialog box. 2. Select the General Models tab located on the left-hand side. 3. The default for gravity is defined as -9.81 in the box next to Z . Our parts will be imported such that the y-direction will be the direction of gravity. To change default, highlight -9.81 next to Z and set the value to 0.0. Next to the Y enter 9.81. 4. Select the radio button None under Thermal options. This will turn off heat transfer. 5. Constant density is being used because we do not have temperature dependent density nor are we looking at density variations due to temperature which requires the v olumetric thermal expansion coefficient or temperature dependent density data.
2. Activate the necessary Casting Models. 1. Select the Casting Models vertical tab. 2. Select the check box next to Cavitation potential . This will predict the likelihood of cavitation or die erosion. Leave the selected defaults already activated, air entrainment and surface defects.
3. Activate Viscosity and Turbulence Models. 1. The activated defaults are, Viscous flow, Constant viscosity, and RNG turbulent model with Dynamically computed max turbulent mixing length. We will leave these defaults because our flow is viscous, the viscosity will be defined as constant, the flow is turbulent and RNG model is the best choice, and having the solver determine the maximum turbulent length is the best option.
4. The following models will not be activated: solidification, lost foam, tilt/centrifugal, or granular flow models so these tabs can be skipped. Numeric Options
There are some numerics that need to be set in order to run an HPDC simulation. To address splashing and compressibility some limited compressibility will be added. This means that although the fluid is incompressible we will allow pressure waves to travel through the fluid so that it’s not so mathematically stiff . A realistic number will both improve the realism of the simulation and will improve convergence, reducing the simulation run time. To improve the numerics an initial time step will help. To speed up runtime
with minor losses, an implicit advection scheme will be used along with a velocity threshold that will use implicit methods for velocity higher than threshold. 1. If the Models button was closed, reselect to open it. 2. Select the Numerics tab on left-hand side. 3. Flow Calculation 1. Ensure the Solve momentum and continuity equations option is selected, this will allow for flow calculations.
4. Advection 1. Ensure the One fluid, free surface option is activated.
5. Pressure Solver 1. Ensure the GMRES method option is activated. 2. Select the Manual (compressibility) option under Limited compressibility. The default value is sufficient.
6. Time Step Controls 1. Set the initial time step to 1e-4.
7. Implicit/Explicit Options 1. Ensure Explicit option for Viscous Stress Evaluation is activated, this method gives a more accurate solution. 2. For Advection select the radio button for Implicit . 3. Select the Time step button next to Advection options and enter the gate velocity. According to the North American Die Casting Association (NADCA) the gate velocities should be between 17 m/s-40 m/s. This option will prevent the solver from using the time step for the droplets to control the time step throughout the filling. For this exercise the gate velocity to be used will be 35 m/s.
8. FSI/TSE Options 1. These models will not be used in this exercise so this window can be ignored.
Import, Apply Transformations, and Define Geometry Types for STL Stl files can be dragged and dropped into the display or can b e added via the Graphical User Interface (GUI). For this example we will use a combination of the two. All of the geometry for all of th e simulations will be loaded or created. The reason we will do this is because there are options available to disable and enable geometry for each simulation. This will save time because we can make a copy of a simulation and then deactivate/activate geometry without having to delete and add new geometry. 1. Add Mold from Remaining Space to create a mold automatically around the casting. 1. Select the Geometry button. 2. Select the Add geometry drop-down menu.
3. Select the Mold from Remaining Space. This will add solid volume the size of the mesh. Each time the mesh extents are changed so will the extents of the solid. 2. Drag and drop the Left-Cover(Repaired).stl and Runner-1.stl. 1. In Windows explorer, browse to C :\flow3d\Cast4\gui\stl_lib\HPDC Exercise. 2. Select Left-Cover(Repaired).stl and Runner-1.stl then drag and drop into F LOW-3D Cast Display window. 3. A dialog will open asking if you would like to copy the stl files to your simulation directory, select the Yes button.
3. Zoom in by rolling the mouse wheel away from you. 4. Add the rest of the stl files through the GUI. 1. Select the drop-down menu next to Add Geometry. A list of Geometry types are given. Geometry types are used to keep organization of parts and activate models associated with the geometry types. The following is a brief description of the types of geometry that will be used for this exercise. The rest of the geometry type definitions can be found in the manual in the Geometry Panel . Mold from Remaining Space-This will create a solid box the size of the mesh. If the mesh extents change so will the extents of the solid box. Casting Part -Is considered a hole that will be cut into a mold/die. This is the part that will be created from the casting process. These must be associated with a solid component specifically the mold/die. If the full die inserts were being defined as stl files (not using Remaining space), then this option would not be used but instead the stl files would be added to Mold. For this exercise the Default from Remaining Space was used. Moving -Is a solid geometry that will have motion and material properties added to it. More than 1 component can be assigned to this geometry type and have different properties as long as they are defined as separate components when imported or created. 2. Select the Casting Part . An Add Casting Part dialog opens. Several options are available in this dialog; assignment to components, definition of the geometry (stl or primitive), transformations. 3. Select the check box next to Component 1: Remaining Space Mold . This will cut the stl from the Remaining Space Mold . 4. Select the Add button and Window Explorer will open within the simulation directory. Browse to C:\flow3d\Cast4\gui\stl_lib\HPDC Exercise. 5. Select the Lifter-Overflow.stl, hold the ctrl key on the keyboard and then select Bottom-Overflow.stl, Top-Overflow, and Runner-2.stl. 6. Select the Open button. 7. Select check box next to Copy to simulation folder to copy the stl files.
8. Add 0.01 under Global scaling to scale from centimeters to meters. The stl files were given in centimeters from Problem Specification and needed to be converted to meters.
5. Expand the trees under Geometry type for Unused , Casting Part , and Mold . 6. Assign Unused stl files to Casting Part . 1. Select Runner-1 under Unused and hold left mouse down, drag, and drop under Casting Part . 2. A Reassign Casting Part dialog will open. Select the check box next to Component 1: Remaining Space Mold . 3. Select the OK button. 4. Right-click on Left-Cover under Unused ‣ Assign to another type ‣ Casting Part . 5. Repeat 5b-5c.
7. Rescale Left-Cover(Repaired).stl and Runner-1.stl. 1. Select the Left-Cover(Repaired) from the tree. 2. Select the Details tab. 3. Expand Transformations
4. Enter 0.01 next to Global Scaling . 5. Repeat 6a-c for Runner-1
Note When performing transformations keep in mind they need to follow this order: Scaling, Rotation, and Translation.
Create Shot Sleeve and Piston Geometry Using Primitives and Assign Geometry Type 1. Create shot sleeve using F LOW-3D Cast primitives and translate. 1. Select Geometry tab. 2. Select drop-down menu Add geometry and then select the Casting Part . Casting part means it will make a hole from assigned component. 3. Select check box next to Component 1: Remaining Space Mold . 4. Next to Type select from drop-down menu Cylinder . 5. Enter Shot Sleeve next to Subcomponent name. 6. Enter an outer radius of 0.03493. 7. Define low z as 0 and high z as 0.4826. 8. Select the OK button to create the shot sleeve cylinder. 9. Select Shot Sleeve under Casting part then select the Details tab. 10. Under Translations and next to Y enter -0.26074 . 11. Under Translations and next to Z enter 0.0127 .
2. Create piston. 1. Repeat steps 1 a-i but with the following changes: 2. Add geometry as Moving type. 3. Enter Piston next to Name and next to Subcomponent name. 4. Enter an outer radius of 0.041716. The diameter of the piston needs to be at least 20% larger than the shot sleeve to prevent fluid leakage. 5. Under Translation next to Z enter 0.4953.
Disable Geometry Not Used In For This Simulation The first simulation will only have the Runner-1.stl and the Left- Cover.stl . So all the other geometry, except Mold type can be disabled. The Mold type will be defined once the meshing has been created. Disabled means the stl files will not be used for this simulation. 1. Under Moving unselect the check box next to Piston and Piston. 2. Under Casting Part unselect Shot Sleeve, Top-Overflow, Bottom-Overflow, Runner-2, and Lifter-Overflow.
Defining Solid Geometry Properties For this simulation since heat transfer will not be activated, the die properties are not important. Remember what we are trying to get out of the simulation and that is which runner/gate system is better. The properties will be added later once the runner s ystem has been selected, piston velocity parameters are good, and the overflows have been placed.
Meshing For this part of the exercise only one mesh block will be used to save on computational time. The placement of the mesh will encompass a portion of the thickest section of the runner where there won’t be high gradients across it around the rest of the part. Meshing is iterative so we will mesh, FAVORize, and repeat until the geometry and flow regions are well resolved. A mesh fit to enabled/visible geometry will be adjusted and fixed points will be added if necessary to resolve geometry. The geometry will be FAVORized to see if the resolution is enough to capture the geometry and if not the cell size will be adjusted to ensure aspect ratio among the x-y-z-directions of the mesh blocks is < 3. Rule of Thumb
Minimize the size of the computational domain to avoid unnecessary computations. Do not minimize the size of the computational domain to the p oint where the boundary conditions are too close to regions of high flow gradients as this can affect the results. Use minimum number of mesh blocks. If thermal penetration is activated then ensure mesh around casting is larger than the thermal penetration depth by at least 2 cell sizes.
1. Add a mesh block. 1. Select the Meshing button. 2. Select the New button to add a mesh. 3. A Create Mesh Block Options dialog box will appear. Select the radio button next to Fit to enabled/visible geometry. 4. Select the OK button. 5. A Fit Mesh Block 1: Block 1 to Geometry dialog box opens to define cell size or total number in any or all directions.
6. Select the radio button next to Size of cells. 7. The thinnest section of the casting from the Problem Specification is 0.0016 m we want at least 2 cells across that so we shall start with a cell size of 0.0008. Enter 0.0008 next to Size of cells.
Note Since heat transfer is not on, we can move the mesh extents closer to the part. 2. Adjust the mesh block. 1. Select the Details tab.
2. Select a 2-D image in the display window either , and zoom in using the roller mouse scrolling away to bring the geometry closer. The right mouse click is for translation. 3. The top gridline is already selected so enter the value of -0.1 under Change Location.
4. Select bottom Gridline and enter the value of 0 under Change Location. Only half of the geometry will be modeled because the part is symmetric. 5. Select the y radio button under Direction and repeat above steps to set the extents in y direction to -0.16 and 0.06. 6. Select the z radio button under Direction and repeat above steps to set the extents in z direction to -0.016 and 0.006.
Note The x radio button for Direction is selected so we will adjust the x extents of mesh first. We can use the slider to adjust the mesh extents and then adjust values to get rounded num bers or we can just add values instead.These values can be adjusted within the text box by adding or subtracting. The gridlines are always in ascending order. 3. Adjust cell size until aspect ratio of each mesh block 1. This means the ratio between , , and are equal to 1. Whenever the mesh extents are adjusted so is the cell size, so this will have to be adjusted as well. 1. Select the Mesh blocks tab. 2. Select the radio button next to Size of cells. The value of 0.0008 that we entered earlier is still valid. 3. Select the Automesh button. 4. Select the left-mouse button in display and move to rotate part. 5. Select the Mesh menu above the display ‣ Flow Mesh ‣ View Mode ‣ Grid Lines.
4. FAVORize geometry. FAVORize is used to determine if the mesh has adequately resolved the geometry or the open regions of flow. If the details are not resolved accurately then fixed points and/or smaller mesh cell size might be necessary. 1. Before we render, we want to be able to see the geometry, not the mesh. Hide the mesh b y selecting Mesh menu above display ‣ Flow Mesh ‣ View Mode ‣ Outline. 2. Above the display select the Eye icon, . A dialog box will open. 3. Select Open volume from drop-down next to Geometry surface to view open volume. 4. Select the Render button. The results can be seen in the display window. Rotate the part around and if you want a point of rotation you can select the Ctrl button on the keyboard then left-click where you would like the pivot. A gray flat oval shape will appear in that location.Now when holding left mouse key down and movin g the mouse the rotation will occur at that pivot point. To turn off or hide the pivot point select you can look at the options available in theView menu ‣ Pivot Point Options. 5. The geometry looks well resolved and the FAVOR checker found no errors during FAVORization. For more information on FAVOR checking refer to Manual section, FAVOR Checking . 6. Select Close button to close FAVORize dialog.
Rule of Thumb In meshing it is necessary to refine the mesh until the geometry (solid/open) is adequately resolved.
Boundary Conditions The Filling will begin at the larger Runner section which aligns with the mesh. A velocity boundary condition will be applied at the lower y mesh plane. Symmetry boundaries will be used for the rest of the boun dary conditions since there is no heat transfer or friction along the mesh planes. The default is symmetry so only the minimum y boundary needs to be defined. Since cavitation will occur at about 40 m/s we will use 35 m/s as our gate velocity for fast shot. We will use this v alue to obtain the velocity at runner by using the continuity equation.
V 1 is the gate velocity V 2 is the runner velocity A 1 of the gates are A 2 of runner Rearrange equation to get velocity at the runner
Plugging in values of area given in the Problem Specification we get a value of 4.83. 1. Define boundaries. 1. Select the Boundary Conditions button. 2. Select the Y Min from drop-down next to Boundary. 3. Select the radio button next to Metal . This simulation is 1 fluid simulation so metal is what we want entering the domain. 4. Select Specified Velocity from drop-down that shows Symmetry. 5. Next to Y Velocity under Velocity enter the velocity value 4.83.
Metal properties 1. Add A380 Aluminum to the Material Database. 1. Select the Metal Properties button. 2. Select the Edit properties button. 3. Select the Load from materials database button. 4. Expand the Aluminum and Aluminum Alloys tree. 5. Select the Aluminum Alloy A380 (LM24, ADC10/AC4B). 6. Select the Load button. 7. A Loading Materials dialog box will open. Leave defaults and select the OK button to accept and close it. 8. Another dialog box will open informing the user that the Aluminum has been loaded as fluid 1. Select the OK button to accept. 9. Close the Select material dialog box by selecting the Close button and DO NOT CLOSE the Metals Properties dialog box yet.
2. Add air entrainment and cavitation parameters to l oaded material properties. 1. Add 0.914 next to Surface tension coefficient this is on the Liquid tab in Metal Properties dialog. This is for the air entrainment model. If you closed the Metal properties dialog box, select the Edit properties button. 2. Add 0.05 next to Air entrainment rate coefficient in the Liquid tab in Metal Properties dialog. This is also for the air entrainment model.
3. The cavitation pressure can be estimated using the formula from: for liquid aluminum. log(P)=10.917-16211/(T) Where: P is the pressure in Pascals T is the temperature of metal in Kelvin Rearranging the equation we get: P=10 (10.917-16211/T) If we use the pouring temperature we get a small pressure of the order 1e-7. This is close to zero, add 0 next to Cavitation pressure in the Liquid tab in Metal Properties dialog. 4. Select the OK to close the Material Properties dialog box.
Tracers Tracers are used to visualize the flow. If fluid passes through the flux plane, the fluid is colored. The colors are automatically selected and when two streams come together it is easy to see the mixture. Since there are two gates we will add two of them. When adding tracers make sure you add them sequentially along a path. You don’t want to have Tracer 7 next to Tracer 1 because a color gr adient between the two will be large and confusing mixing with the other Tracers. 1. Create a baffle. 1. To hide the die, select it by double clicking on it in the display window it should turn green. Right-click and select Hide.
2. Select the option for xy plane by selecting the z icon, ( or ) above display. 3. Zoom in on gate location. 4. Place cursor in display window and then select and hold the shift key on the keyboard. You will see cross-hairs. Keep holding the shift key and move mouse to gate, where you want to place the tracer, right-click with mouse. A dialog opens with icons and numbers. The numbers indicate the location the point passes perpendicular to solid surfaces. To see what the icons are you can move the cursor over the icons it will tell you what they are. We want the orange baffle icon,
along the x.
5. Select the first baffle orange icon, to adjust it.
. A baffle has been placed in this location with the extents of the mesh. We need
2. Define baffle as a tracer and limit the extents to upper gate. 1. Select the baffle orange icon, located on the right-hand side of the GUI. A Baffles dialog will open on the righthand side of the GUI. All of these dialog boxes are detachable including the ones on the right. 2. We have created a baffle but we need to make it a flux plane and a tracer. Select the check box next to Flux surface. 3. Select the check box next to Enable Tracers. 4. We need to limit the extents of the tracer so we can add another in the s ame location but only across the top gate. To do this select the Shape tab. 5. Enter 0 next to Y Low.
3. Create tracer at lower gate at same location. 1. Select New button in Baffles dialog. 2. Name it Upper Gate. 3. Select the check box next to Flux Surface. 4. Select the check box next to Enabled tracer . 5. Select the Lower Gate in the list. 6. Select the Location tab. 7. Select the value in box next to the selected radio button for X Coordinate. 8. Right-click on the value and select Copy. 9. Select Upper Gate in the list. 10. Select the box next to selected radio button for X Coordinate. 11. Right-click and select Paste. 12. Select the Shape tab. 13. Enter 0 next to Y High to limit the tracer to upper gate.
Data Output To reduce the results file, selected data will be selected and an output basis of fill fraction will be used as the interval of the spatial output data. By selecting fill fraction and leaving the default the output frequency will be every 1% filled. 1. Select the Output button. 2. Select the radio button next to Fill fraction under Basis for output . 3. Select the Select Data button and check boxes as seen below.
Reminder Selected data saves on computational time and size of file because it is outputting only selected data at that frequency as op posed to restart data which sends all available data to output.t
Model Setup For Runner System 2 We will now copy the newly created simulation so we can activate the second runner system and d eactivate the first runner system. Once this is done we can simulate the workspace and the simulations will be run in batch mode. Then we will compare and decide which runner system is better and move on to the next simulation of shot sleeve parameters.
Copy Simulation 1. Select the Simulation Manager tab. tab. 2. Right-click on simulation HPDC Filling Filling Gate Location 1 ‣ Add Simulation Copy. Copy. 3. A New Simulation dialog Simulation dialog box will open. Change the name and check options as seen below.
Modify New Simulation The copied simulation may need to be modified to allow us to run with runner system 2. The geometry needs to be changed, tracers need to be removed since there is only 1 gate, and velocity needs to be recalculated since the gate area is different than the first one. 1. Enable runner 2 and disable runner 1. 1. Select the Model Setup tab. 2. Select the Geometry tab or button if it is not already open. 3. Disable Runner-1 and enable Runner-2.
2. Remove tracers.
1. Select the baffle orange icon, on the right-hand side of GUI. 2. Select Lower Gate from list. 3. Select the Delete button. 4. Select the Yes when prompted if it is okay to delete. 5. Repeat for Upper Gate. 6. Close the Baffles dialog by selecting the X in the right-hand corner of the dialog b ox. 3. Change inflow at boundary. 1. Select the Boundary Conditions button. 2. Select the Y Min from drop-down next to Boundary. 3. Using the calculation from previous section with the new gate size the velocity now becomes 10.7 m/s. Enter this value next to Y Velocity.
Run the Simulations in Batch Mode 1. Select the Simulation Manager tab. 2. Right-click on the HPDC Filling Design workspace ‣ Simulate Workspace.
Post-Process Results and Compare Runner Systems Now it is time to look at our results. First we must know what is important to view and what is not.
Air Entrainment or gas porosity: flow porosity or air packets due to turbulence, jetting of flow, and/or improper venting. Surface defects: laminations that form when cooler flows collide, usually at the end of the fill near the ends of ribs or bosses. Oxide formation: defects formed during air exposure. Cavitation or washout: this occurs when cavitation pressure drops and the flow circulation causes erosion.
1. Open the HPDC Filling Gate Location 1 results file. 1. Select the Results button to open the FlowSight to post-process. 2. Select the File in top menu bar.
3. Select the Show portfolio icon, Manager . 4. Select the HPDC_Filling_Gate_Location_1 the HPDC_Filling_Gate_Location_1.. 5. Select the OK button. button.
this will show simulations in your Simulation
2. Open the HPDC the HPDC Filling Gate Location 2 results 2 results file. 1. Select the File the File ‣ Open in Open in top menu bar. 2. A New Case dialog Case dialog box will open. Select the radio button next to Keep to Keep currently loaded data. data. 3. Select OK button. button.
4. Select the Show portfolio icon, Manager . 5. Select the HPDC_Filling_Gate_Location_2 the HPDC_Filling_Gate_Location_2 in in the portfolio. 6. Select the OK button. button.
this will show simulations in your Simulation
3. Turn off mesh. 1. Select the Mesh list tab. 2. Uncheck the boxes next to Block 1 for Case 1 and Case 2. 4. Change data from restart to selected data. 1. In the Time section, select from drop-down under Timeline Selected for all cases. Whichever case is selected it will use that timeline for all the cases. Since Case 1 took twice as long we will use it. The isosurface will disappear in the window until we define an isosurface from selected data. 5. Create isosurfaces and viewports. 1. Select the Isosurface list tab. 2. Select Case 1. 3. Create a new iso-surface by selecting the Create button. 4. A Create Isosurface dialog opens. Expand all trees. 5. Select check box under Case 1 and next to Block 1. 6. Select check box under Case 2 and next to Block 1. 7. Select the drop-down menu next to Surface under Creation and select Fluid_selected . 8. Select the drop-down menu under Color next to Color by and select volume_fraction_of_entrained_air_Selected . 9. Select the Create button. 10. Repeat steps 3e-i to create second iso-surface for Case 1 and Case 2. 11. The isosurfaces for Case 2 may not show up in the list but they have been created.
6. Modify background and viewports. 1. Right-click in display ‣ select Viewports layout ‣ 4 Equal .
2. Right-click in display ‣ select Default print colors. 3. Select the first iso-surface Isosurface - 2 under Case 1, you should see a blue dot indicating it has been selected. 4. Select the eye icon with boxes below it, . This will allow us to determine locations of surface areas. 5. A dialog box will open showing all the viewports. The green boxes indicate the visibility of the colored iso-surface. For this isosurface we want it to be in the upper left-hand corner. To unselect boxes, select until on ly upper left hand box is green. 6. Repeat for the next iso-surface Isosurface - 3 for Case 1 and ensure it is in the lower left-hand corner. 7. Repeat for Case 2 iso-surfaces placing them in upper right-hand corner and lower right-hand corner. All iso-surfaces will be colored by air entrainment.
7. Modify views and color bar. 1. Select the colors on the color bar, you should see green arrows for movement or stretching, hold left mo use down and move it up. 2. To modify the color scale select the color scale until green arrows are seen on it, then right-click and select Modify. Here you can change the name of the color bar, the extents, the format to floating point, and v arious other options are available. 3. To link the images, right-click in a viewport ‣ Linkall . 4. Zoom in on the part, zoom away from you usin g the roller on the mouse. 5. Unlink the images, right-click in a viewport ‣ Unlink all . 6. For the bottom two images rotate to the side by right-clicking in the bo ttom left viewport and select View ‣ Z-.
7. Repeat for bottom right hand view. 8. Zoom in on both images. 9. To view the other defects, select the Isosurface tab and change the Color by for each case. 10. To create a snapshot, select File ‣ Export ‣ Image. 11. A Save image dialog box will open allowing for selecting of format, the Prefix is to define the path and name of the image and the Advanced allows for quality. 12. Animations can be created the same way. 8. Creating a flip book will allow us the ability to rotate the parts and get a look the filling. 1. Select the Create/edit flipbook icon, located in lower right-hand corner. 2. Select the Load button. 3. Once the flipbook has been created, notice next play the controls the drop-down now shows flipbook instead of original . The flipbook allows the animation to play and gives the user control to rotate.
Comparison From the images it appears that Case 2 has less defects. Looking at the flip boo k by selecting the play button in the time window: Case 1 shows jetting of two streams from the gates that hit the opposite end of the part and then around the top and bottom going across both the front and back of the part. Typically for bosses you want the flow to go across the back and then flow back aroun d. The jetting streams cause turbulence increasing air entrainment and even though Case 1 ran slower than Case 2, the turbulence and multiple stream fronts causes higher concentration and locations of defects.
The user can create an animation of this by selecting the camera icon,
and follow directions.
Further improvements on the runner system would also help reduce the initial non-filled runner system. Other runner designs will not be looked at for exercise.
Shot Sleeve Analysis Case 2 was selected for the shot sleeve analysis because it had less defects. The erosion for both cases was small enough that the selection for case 2 is still warranted. The following simulations will look at at Case 2 with two different shot sleeve profiles and determine where overflows should be located. There are several methods available for shot sleeve analysis especially critical shot. We will compare Marilyn Thome’s method and a cycloid method. Marilyn Thome’s method looks at the differential equation and the cycloid uses the idea that the time of descent of an object falling under gravity along a cycloidal path is the same no matter where on the cycloid the object begins its fall. Since there is less than 20% of metal in the shot sleeve the critical shot will have to last longer to reduce wave formation. Marilyn Thome’s calculation does not guarantee smooth wave profile for less than 20%. We will not try to improve the shot profiles but instead just chose one or the other. Spreadsheets of the shot profiles for both Marilyn Thome’s and the cycloid will be provided and imported. Typically you never want to only mo del just half the shot sleeve. The reason for this is that it is not symmetric because the flow will rise along the outer surface of the wall earlier than if it was a full shot sleeve. The partial shot sleeve will cause early wave rollover. The user should run shot sleeve simulations to see the effects of half and full shot sleeve modeling. For this exercise only half will be modeled but because we are applying the same method to both the end results will determine which method is better.
Copy Simulation 1. 2. 3. 4. 5.
Select the Simulation Manager tab. Right-click on simulation HPDC Filling Gate Location 2 ‣ Add Simulation Copy. A New Simulation dialog box will open. Change the name to Shot Sleeve Analysis Thomes. Select the check box next to Check all . Select the OK button.
Enable/Disable Geometry 1. 2. 3. 4.
Select the Model Setup tab. Select the Geometry button. Select the check box next to Shot Sleeve under Casting part tree. Select the check boxes next to Piston under Moving and Piston under Piston.
Define Shot Sleeve Motion 1. 2. 3. 4. 5. 6. 7.
Select the top (BLUE) Piston. Select the Details tab. Select the Moving tab. Under Moving Object select the /Time button next to z Direction under Velocity. Select the Import Values button. Select the Browse button, browse to C:\flow3d\Cast4.0\gui\stl_lib\HPDC Exercise\Thomes.cvs. Select the second row and then select the OK button to add to simulation.
Modifying Mesh and Add an Additional Mesh Block 1. Modify mesh block 1 . 1. Select the Meshing button. 2. Mesh Block 1 ‣ Details tab. 3. Select the radio button next to Y . 4. Select the top gridline. 5. Change the value to -0.2 under the Change Location box. 2. Ensure the cell size is still 0.0008. 1. Select the Mesh blocks tab. 2. Select the radio button for Cell Size under Automesh. 3. Select the Automesh button.
3. Add a new mesh block and adjust for shot sleeve. 1. Select the Add button. 2. Select the OK button to copy mesh block. 3. Select the Details tab. 4. Select the first Gridline ‣ enter -0.04 under Change Location. 5. Select the radio button next to Y . 6. Select the first Gridline ‣ enter -0.3 under Change Location. 7. Select the second Gridline ‣ enter -0.2 under Change Location. 8. Select the radio button next to Z . 9. Select the second Gridline ‣ enter 0.506 under Change Location. 4. Ensure cell size is 0.0008 in all directions. 1. Select the Mesh blocks tab. 2. Select the radio button for Cell Size under Automesh ‣ enter 0.0008 next to it . 3. Select the Automesh button.
Changing Boundary Conditions 1. Select the Boundary Conditions button. 2. Select the Mesh Block 1 from the drop-down menu next to Mesh Block .
3. Select Y Min from drop-down menu next to Boundary. 4. Select Specified Velocity from drop-down and select Symmetry.
Add Metal in the Shot Sleeve 1. 2. 3. 4. 5. 6. 7.
Select the Metal Properties button. Select the New button. Select the Browse button, browse to C:\flow3d\Cast4.0\gui\stl_lib\HPDC Exercise\Metal 2.stl. Enter Initial Metal next to Metal region name. Apply scaling in all directions of 0.01. The geometry was given in centimeters and needs to be in meters. Select the OK button to create metal region. The metal needs to be translated almost the same amount as the shot sleeve. The best way to see this would be to add the metal as a solid to visually see and adjust it. Then the geometry could be disabled and added as a metal and all the transformations would be known. Since the values are already known we will enter them. Select the Details tab. 8. Enter -0.26074 next to Y under Translation. 9. Enter 0.4952 next to Z under Translation.
Copy Simulation 1. 2. 3. 4. 5. 6.
Select the Simulation Manager tab. Right-click on simulation Shot Sleeve Thomes ‣ Add Simulation Copy. A New Simulation dialog box will open. Change the name to Shot Sleeve Analysis Cycloid. Select the check box next to Check all . Select the OK button.
Define Shot Sleeve Motion 1. Select the top (BLUE) Piston. 2. Select the Details tab.
3. 4. 5. 6. 7.
Select the Moving tab. Under Moving Object select the /Time button next to z Direction under Velocity. Select the Import Values button. Select the Browse button, browse to and select C:\flow3d\Cast4.0\gui\stl_lib\HPDC Exercise\Cycloid.cvs. Select the second row and then select the OK button to add to simulation.
Run the Simulations in Batch Mode 1. Select the Simulation Manager tab. 2. Right-click on Shot Sleeve Analysis Thomes ‣ Run Simulation ‣ Local .
Post-Process the Results The post-processing will compare the different shot sleeve profiles to determine which profile is the better one. The sim ulation will then be run with overflows and activation of heat transfer, solidification. 1. Open the Shot Sleeve Analysis Thomes results file. 1. Select Results button to open the FlowSight to post-process. 2. Select File in top menu bar. 3. Select the Show portfolio icon, this will show simulations in your Simulation Manager . 4. Select the Shot_Sleeve_Analysis_Thomes. 5. Select the OK button. 2. Turn off mesh. 1. Select the Mesh list tab. 2. Uncheck the boxes next to Block 1 and Block 2 for Case 1. 3. Change data from restart to selected data. 1. In the Time section, select from the drop-down under Timeline Selected . The isosurface will disappear in the window until we define an isosurface created from selected data. 4. Create isosurface. 1. Create a new iso-surface by selecting the Isosurface List ‣ Create button. 2. A Create Isosurface dialog opens. Expand all trees. 3. Select the check box next to Block 1 and Block 2. 4. Select the drop-down menu under Color next to Color by and select volume_fraction_of_entrained_air_Selected . 5. Select the Create button. 5. Modify color scale, add viewport, and adjust views.
1. Select the colors on the color bar, you should see green arrows for movement or stretching, hold left mouse down and move it up. 2. To modify the color scale select the color scale until green arrows are seen on it, then right-click and select Modify. Here you can change the name of the color bar, the extents, the format to floating point, and v arious other options are available. 3. Right-click in viewport ‣ select View ‣ change to Orthographic. 4. Right-click in viewport ‣ select View ‣ select +X . 5. Select Edit menu ‣ select Transformation editor ‣ select Z radio button. 6. Slide the slider completely to the right. 7. Select the X in upper right-hand corner to close the dialog box. 6. Show open volume. 1. Select the Geometry List tab. 2. Select the check box next to Open Volume. 3. Right-click on it, select Transparency and adjust to 84. 7. Add velocity versus time of shot sleeve plot for each of the cases. 1. 2. 3. 4. 5. 6. 7. 8.
Select the red history plot icon, above display. Select Case 1: flsgrf.Shot_S leeve_Analysis_Thomes. Select Component 2 GMO reference point z-coordinate. Select the check box next to Advanced . Select from drop-down Differentiate. Enter the name Shot Sleeve Profile Thomes. Select the New plot button. Select the Close button once plot is seen.
8. Modify display. 1. To modify the plot select the axis intersection until green arrows appear, right-click and select Modify. 2. Right-click in display ‣ select Default print colors. This may have to be done twice. 3. Select the hide/show key icon, . 4. Select the Time text in viewport until green arrows appear, then left-click, and move. 5. Zoom in on the shot sleeve and change current time to 1.397 next to Cur .
9. Open the Cycloid shot sleeve simulation and apply context. 1. Select File menu ‣ Open. 2. A New case dialog box will open. Select radio button next to Replace case.
3. Select the Show portfolio icon, Manager . 4. Select the Shot_Sleeve_Analysis_Cycloid . 5. Repeat steps 2-8 from Thomes until it matches image below.
this will show simulations in your Simulation
10. Below are the comparisons at the end of fill of air entrainment, surface defect concentration, and cavitation potential.
As can be seen the Cycloid’s shot sleeve analysis provides less defects. However, when looking at the wave fronts entering the runner system both cases have rolling waves but the cycloid is much greater. Running the simulations with the full shot sleeve would have eliminated the extreme wavefront seen. Since the exercise is already long we will not spend the time to run the full sho t sleeve. The part’s requirement is that it needs to be flat so the less defects the better. For this case we will chose the C ycloid case. Overflows at top and bottom along with across from gate will be added to capture the air entrainment and surface defects.
Run the Filling Simulation with Heat Transfer and Overflows This case will run with the cycloid shot sleeve profile including the overflows and activating heat transfer and solidification. 1. Copy Simulation and Rename. 2. Activate heat transfer and solidification. 1. Select the Models button. 2. Select the General Models tab. 3. Select the radio button next to Conduction in Solids. 4. Select the Solidification tab. 5. Select the check box next to Solidification to activate it. 6. Define the Solidification Drag Coefficient as 600. This value can be experimentally determined or estimated as 180/SDAS 2 where SDAS is the secondary dendritic arm spacing. 3. Add properties to the Die. The die is Stainless steel H-13. 1. Select the Geometry tab. 2. Select the Mold then select the Details tab. 3. Select the Edit Properties button. 4. Select the Load from material database button. 5. Select Steel-H-13. 6. Select the Load button. A dialog will prompt asking about temperature unit options and loading options. 7. Select the OK button to close this dialog. 8. Another dialog will open stating the material has been added. Select the OK button to close this dialog.
9. Select the OK button to close the Solids Database. 4. Add initial temperature to the Die. 1. The initial temperature of the Die is 176°C as per the Problem Specification. This is added in the Details tab next to Initial temperature. Make sure you still have the Remaining Space Mold selected from the geometry tab. 5. Add thermal penetration depth to die to reduce run time. The thermal boundary layer is calculated using a one-dimensional semi-infinite boundary layer approximation and is determined from the following equation: (1) Where: is the solid thermal diffusion defined as:
,
is the solid thermal conductivity is the solid density times the solid sp ecific heat at constant pressure is the time of exposure (filling time) is the boundary layer thickness or thermal depth penetration The derivation is left to the user. For this exercise a calculator from GUI will be used. 1. Select the Utilities menu‣Calculators‣Thermal penetration depth. 2. Properties are pre-loaded with H-13 properties. Since we are modeling entire process we will use the estimated finish time. The thermal penetration depth should always be larger so round up. If it estimated and the distance is to o short then the die will be hotter than expected and solidification time will be longer. Enter 2 seconds for the f inish time.
3. Select the Calculate button. 4. Copy this value and paste in Details tab of the Default Mold next to Maximum thermal penetration depth.
6. Add properties to Material Database for Piston. 1. Select the Geometry tab. 2. Select the Piston then select the Details tab.
3. Select the Edit Properties button. 4. Select the Load from material database button. 5. Select CoCuBe. 6. Select the Load button. A dialog will prompt asking about temperature unit options and loading options. 7. Select the OK to close the dialog. 8. Another dialog will open stating the material has been added. Select the OK button to close the dialog. 9. Select the OK button to close the Solids Database. 7. Add initial temperature to the Piston. 1. The initial temperature of the piston is 121°C as per the Problem Specification. This is added in the Details tab next to Initial temperature. Make sure you still have the Piston (higher level or with Blue text) is selected from the geometry tab. 8. Activate overflows. 1. Select the Geometry button. 2. Select the check boxes next to Bottom-Overflow, Lifter-Overflow, and Top-Overflow. 9. Adjust mesh block 1 to account for heat transfer. 1. Select the Meshing button. 2. Select Block 1 in the Mesh blocks tab. 3. Select the Details tab. 4. Adjust the mesh so the extents go beyond the overflows and are at least 2 cells larger than the thermal penetration depth. 5. Select the Mesh blocks tab. 6. Select the radio button next to Size of cells. 7. Ensure 0.0008 is the defined cell size. 8. Select the Automesh button.
10. Adjust Mesh block 2 to account for heat transfer.
1. Select Block 2 in the Mesh blocks tab. 2. Select the Details tab. 3. Adjust the mesh so the extents.
11. Add initial temperature of the metal.
1. Select the Metal Properties button. 2. Select the Details tab next to Region tab. 3. Add 676 next to Fluid temperature. 12. Define the heat transfer coefficient between the metal and die, and piston and metal. 1. 2. 3. 4.
Select Heat transfer coefficient button. Select Metal under Between and Component 1: Mold under and . Enter 20,000 for heat transfer coefficient. We will let the solver calculate the heat transfer between the piston and the metal. Note Heat transfer coefficients are estimates. The user will have to fine tune these values and compare with what they are seeing in the simulation to thermal imaging.
13. Define output variables. 1. Select the Output button. 2. Select the Select data button. 3. In addition to previous selected data, select Internal energy and Solid fraction. 14. Save the simulation and run it. 1. Select the File menu ‣ Save Simulation. 2. Select the Simulate button ‣ Run Simulation ‣ Local .
Post-Process the Results The following results show that the overflows are doing their job.
The user should also look at early solidification and cavitation potential. An animation showing the flow patterns will also determine if the runner system needs to be improved.
Optional: Modeling Vents as Valves To look at back pressure the adiabatic bubble model need to be activated and valves (simulate the flow exiting the vent) need to be defined. The vents are usually located at end the of the overflows so ensure you have these activated. The valve model uses continuity and the Bernoulli equation. (2)
(3) Eliminating
and solving for mass flow rate we get the following:
(4) The equation just derived assumes incompressible and frictionless flow, so we need to add some compressibility.
(5) Where: is the discharge coefficient,
is the area, is the compressibility factor, and is the density. For the valve model, the coefficients are lumped together and a total loss coefficient is defined as: Valve loss coefficient:
(6) (7) Where: is the external pressure outside of the domain (typically atmospheric pressure). The discharge coefficient is a number between 0 and 1. Remember the larger the discharge coefficient, the less the losses. For an orifice a typical value is 0.6. We will use 0.5 as a discharge coefficient Cd. The compressibility factor Y for air at standard pressure and temperature is roughly 1. The compressibility factor can be found from a compressibility chart. The density of air should be calculated using the ideal gas law with temperature of die and atmosphere pressure. The valve model needs a point location which will be determined in the following steps. The vents for this problem are located in the top-overflow and the bottom-overflow along the center. The cross-sectional area of the vents are 4.84 -6 . 1. Activate the adiabatic bubble model. 1. Select the Models button. 2. Select the General Models tab. 3. Select the radio button next to Adiabatic gas regions. 4. Enter 1.41 as the Adiabatic constant for air.
5. Select the OK button to leave the dialog box. 2. Define location of valves.
1. Select one of the x, y, or z icons ( , , )above display for a 2-D view. This is important because the interactive valve toolbar will select the first surface and last surface and any surfaces in between that it encounters. The user will then have the option to chose where inbetweeen/on the surfaces they would like to place the valves/vents. 2. Hold shift-key on keyboard and right-click at valve location. 3. There are two points showing the first and last surfaces which belong to the die. Select the left hand drop-down and select the second from the list point. This is the first surface after the die surface which is what we want. The valve needs to be located within the overflow. 4. Select the second point, right of the slider, and select the third point from the top this will be the surface before the end of the die surface. 5. Select the valve green icon,
. This will create a green probe showing the location of the valve.
3. Define vent loss coefficient and external pressure. 1. Select the green icon, on the right-hand side of the GUI. 2. Rename Top Vent . 3. Calculate the loss coefficient: Estimate the density of the air using ideal gas law:
(8) Where: is the gas constant 287 J/kg-K is estimated as the temperature of the die (449 is the estimated initial pressure of 101325 loss coefficient = 0.5 * 4.85 -6 * 1 * sqrt (2/0.786) 4. Enter loss coefficient of 3.87 -6. 5. Enter external pressure of 101325.
)
