Using 3D AutoCAD Surfaces to Create Composite Solids

Transcription

1 Using 3D AutoCAD Surfaces to Create Composite Solids J.D. Mather Pennsylvania College of Technology GD211-2P This class explores the creation of 3D surfaces used in creating composite solids. Many solid shapes can only be created by editing with surfaces. AutoCAD now includes powerful tools for creating surfaces and using them in creating or editing solids. Examples appropriate for mechanical, architectural, and civil engineering will be demonstrated. About the Speaker: Dr. Mather is an assistant professor of CAD and Product Design at Pennsylvania College of Technology affiliate of Penn State University. He has taught AutoCAD courses for 13 years and has been an Autodesk Inventor Certified Expert since release 7. His advanced 3D Modeling tutorials are studied by users around the world. Previously he worked in industry for 15 years, including positions as Journeyman Machinist, Research & Development Technician and Industrial Engineering Technician

2 Using 3D AutoCAD Surfaces to Create Composite Solids Session Objectives Learn how to create and use planar surfaces for creating or editing solids. Learn how to create Extruded, Revolved, Swept and Lofted surfaces for use in creating or editing solids. Use surfaces with the Thicken Surface command to generate solids. Use the Slice command as a more efficient method of creating fairly simple geometry. Learn to use hybrid surface/solid modeling using the Slice command to create complex geometry. Target Audience Anyone who has used surfaces in earlier releases of AutoCAD and would like to learn the new AutoCAD surfaces techniques, or who has particularly complex geometry they need to create. Introduction AutoCAD now provides powerful surfacing tools to create complex composite solids. At one time we were limited to prismatic geometric shapes like boxes, or cylinders and spheres and whatever clever techniques we could devise to combine these primitive geometries to create more complex geometry. Often a solid geometry was not possible and we had to limit our design to surfaces. Surfaces were difficult to edit and did not return valuable information such as volumetric data. We can now use composite techniques using both surfaces and solids to generate complex algorithmic or rules-based solid geometry. There is no longer a need for a separate tool set for surfaces we use the same tools for surfaces or solids. The 3D virtual model is a source of validation of the information to build the real world. The Lesson The real world isn t flat. 2

3 Prior Knowledge Expectations For this class I will assume that you have attended the: GD105-1P 3D AutoCAD for All of Us GD111-3P 3D Visualization and Solid Primitive Design GD115-4P Using AutoCAD for Sophisticated Solid Model Design GD201-2P Editing 3D AutoCAD Solids classes or have some prior experience with the Dashboard in the 3D Modeling Workspace. Layers control panel 3D Make control panel Visual Style control panel Light control panel Materials control panel Render control panel 3D Navigate control panel 2D Draw control panel 3

4 Getting Started We may use other tools in the 3D Make control panel but I am going to concentrate on the following tools: We will look at the surface creation/editing functionality of these tools. Extrude Slice Revolve Thicken Sweep Convert to Solid Loft Convert to Surface Planar Surface 4

5 Solids vs Surfaces (Or maybe I should say Solids & Surfaces.) If we exploded a cube we would find that it is made up of 6 Surfaces. If we exploded it again we would find that the surfaces have a total of 24 edges. Whenever we have surfaces that meet in unambiguous watertight edges we can create our geometry such that the edges are combined and shared. The result is a solid that represents a volume and can easily be edited. We refer to the Faces of the solid rather than surfaces. In our cube example we have 6 faces with 12 edges. 5

6 Extrude If you run the List command on the entities you will see that the black entity is a polyline, the red entity is a line, the green entity is an arc and the cyan entity is a spline. Although the shape forms a closed area it is not a closed polyline, boundary or region. If we Extrude the entities we find that the result is 4 independent and infinitely thin surfaces The old Surfaces toolbar is no longer listed. We could type in the old commands, like rulesurf, but the surfaces created using the standard 3D Make tools with an open profile are much easier to create and more powerful as well. 6

7 Revolve Again, with an open profile the resulting feature when using the Revolve tool will be a surface. The Revolve surface can be any angle up to 360deg. 7

8 Sweep We have a variety of Sweep paths represented by lines, polylines, 2D splines and 3D splines. Tip: If the Sweep fails try changing the UCS. Although the command should re-align the profile I have had instances where changing the UCS will complete a swept feature that otherwise fails. Try with Twist 180 deg along the magenta line. Try with Scale Try with Alignment Yes/No. 8

9 Loft Like all of the surface features, Loft of surfaces works essentially the same as loft of solids. There is no longer a need for a separate set of surface tools. Create our open-profile crosssections and guides or a path as needed and we are ready to Loft surfaces. 9

10 Planar Surface For a Planar Surface all we need is a closed area. Notice that it isn t necessary to have a closed polyline, boundary or region. We can select Objects to define the Planar Surface edges or if it is rectangular surface simply click two points on the screen. 10

11 Slice This example is meant to be a simplified representation for calculating the volume of earth to be removed from a mountainous terrain to get to a volume of coal. Tip: I have had trouble in r2008 with the wrong side sometimes being retained. Simply undo and Slice again, this time electing to keep both sides. Then delete the side you don t want. 11

12 Thicken We can create a solid using any surface with the Thicken command. The surface can be thickened to either side by changing the +/- value. The only concern we have is the resulting solid cannot self-intersect. Consider for example offsetting an arc. We cannot offset the arc beyond its centerpoint. The self-intersection problem arises most often with Lofted surfaces and might not be readily apparent where the intersection would occur. 12

13 Using Surfaces Example 1 Here is an example utilizing Thicken, Taper Faces, Fillet, Shell and Presspull. Here s a tip on Shell worth the expense of attending AU Shell in 2D wireframe for faster results rather than while shaded. And have only one modelspace viewport rather than several tiled viewports. 13

14 Using Surfaces Example 2 The Slice command can be used in conjunction with surfaces to edit solids. We can very quickly create Planar Surfaces for Slice by allowing the DUCS to set our UCS on appropriate faces. Notice that each member is highlighted as you are prompted to select which side to retain or keep Both sides. 14

15 Using Surfaces Example 3 Using the new AutoCAD tools we ve learned let s simplify the design process of our hand tools. As you watch think about, How can these techniques be used in your work? 15

16 Using Surfaces Example 4 And for a little fun let s model a toy car body. All we need is a simple wireframe. 16

17 And a few surfaces. The real word is not flat. By using a combination of the AutoCAD solid modeling and surface tools we can generate composite designs. Have you recognized any ways you use these techniques in your work? 17

18 You might want to Rapid Prototype your parts. Use the STLOUT command to generate a stl file. With a physical rapid prototype model you can verify much of your design before sending the design to the manufacturing floor. Tip: Facetres variable controls the stl resolution. Tip: Your model must be in the positive xyz octant when using the stlout command you will get an error. If you run into a problem with your application of the techniques demonstrated in this class simply send me an jmather@pct.edu 18