In this project from Doug McIntosh, volunteer instructor at Hancock Central School, Hancock MI, a plaque of the HCS Bulldog is first machined in wood and then in aluminum from stock measuring 8” x 8” x 5/8”. This aluminum core is then used to press a hollow cavity into sand that has been treated with a strength bonding agent. Click here to learn more about the sand casting process.
In Part 1 of this tutorial we will show you how the 2D drawing of the HCS Bulldog is turned into a 3D mesh using the VisualART Create Puffed Volume command.
The CAD Geometry
To produce a raised 3-dimensional mesh of the HCS Bulldog for machining, a 2D vector drawing is first created from the mascot image file. This can be done in VisualCAD by loading the picture file as a background image and then drawing border and detail curves over it like a template. Here is the HCS Bulldog image loaded as a background into VisualCAD.
2D lettering and various diameter curves are also added to facilitate the machining process in the MILL module. The resulting 2D drawing is shown below on the left. The 3D geometry including the resulting bulldog mesh, cylindrical extruded base and raised letters are shown on the right.
|(Left) The HCH Bulldog logo starts out as a 2D vector drawing in VisualCAD.||(Right) The 3D plaque geometry consists of a raised HCH Bulldog mesh & extruded base and letters.|
Create the VisualART Project
VisualCAD/CAM-ART (also called VisualART), a free module that is included in MecSoft’s VisualCAD/CAM and RhinoCAM products. Once the 2D drawing of the HCS Bulldog is created in VisualCAD the ART module is loaded from the VisualCAM main menu on the Home ribbon bar.
The first step is to define the Project. This is done by selecting the Project icon from the VisualART toolbar. This will display the Project dialog shown below. You can define the Origin, Extents, Colors, Max Z Height, Resolution and Material. Pay special attention to the Resolution and Base Height settings. The higher the resolution, the more triangular facets in the resulting 3D mesh. The Base Z Height should not exceed the size of your stock material you plan to cut the project from.
When you pick Generate, the Project is created, added to the Projects tree and displayed on the screen as shown below.
Create the Puffed Volume
For this project we only need to use one VisualART command. It is called Create Puffed Volume. As the name suggests, the command will raise the 2D vector drawing into a 3-dimensional mesh! The command icon and dialog is shown below.
The dialog has two tabs named Parameters and Relief Curves. From the Parameters tab we have the puffing option set to Parabola we give the operation a name, set the Type to Add, set the Max Puffing Height to 0.4 and the Smoothing to 2. The graph in the center of the dialog allows you to adjust the general shape of the puffed areas. You can select and drag the curve to change its shape.
Next from the Relief Curves tab you see that it has two sub tabs named Border Curves and Detail Curves. From the Border Curves tab we pick the Select Border Curves button and then select the border curve from the drawing and then right-click or press enter to add it to the dialog. For our 2D drawing we have all closed curves merged into one curve, the Merge Curves command is located on the Curve Modeling tab.
Now we select the Detail Curves tab and again pick the Select Detail Curves button. For this selection we want all of the interior curves selected but not the border curve. The dialog and curve selections are shown below.
The easiest way to do this is to first hide the unrelated curves. Just select them and pick Hide from the Modeling Aids tab. Now with only the curves in question displayed, window select all of the curves or just press Ctrl+A to select all geometry. Then with the Ctrl key pressed, pick the border curve to remove it from the selection and then right-click or press enter to add the selected curves to the Relief Curves tab of the dialog.
Now we’re ready to pick Generate to calculate and display the puffed up Bulldog! The display below shows the results of the Create Puffed Volume operation in VisualART.
The image below shows a close-up of the puffed Bulldog with the Border Curve, Detail Curves and a few Z Heights illustrated. Each area between detail curves is raised between Z0 and Z0.4 to create 3D volume depending on the amount of area. Our detail curves are all closed curves but you also use open curves to give your puffed volume the exact amount of detail needed.
Export as Meshes to CAD
Once we are satisfied with the Create Puffed Volume operation, the geometry can be converted to a 3-dimensional mesh in VisualCAD. From the Relief Operations tab in VisualART, we select the Export Meshes to CAD icon.
Two 3D mesh objects are created. For our project, the planar base project mesh can be deleted. We are left with the raised HCS Bulldog mesh. This is the mesh that we will machine in the MILL module.
Let’s take a closer look at the raised HCS Bulldog mesh that was created. We see that its border lies on the XY plane and that it is raised upward a total of 0.341”.
Modeling Additional CAD Geometry
To prepare our VisualCAD file for milling in the MILL module we have created a few additional objects. An 8” diameter by ¼” deep cylinder mesh was added. It begins at Z0 on the XY plane, at the base of the HCS Bulldog mesh and extrudes downward. We have also extruded each letter as a mesh and then Uadded them
Stay tuned for part 2 of this tutorial where we show you the toolpath strategies used to machine this part.
More about the Hancock Central High Bulldogs
Hancock is a city in Houghton County in the U.S. state of Michigan. It is located across the Keweenaw Waterway from the city of Houghton on the Keweenaw Peninsula. The city has been consistently ranked as the third-snowiest city in the United States. The Hancock Public Schools was created to serve the descendants of the hardworking immigrants who worked the mines in the area. The Bulldog pride in the Hancock community stems from the values of this diverse community. To learn more about Hancock Central High School we invite you to visit them online here.