Computer-Aided Design & Drafting 007.00 Explain and demonstrate basic CAD commands and techniques

Computer-Aided Design & Drafting 007.01 Explain CAD terms and concepts

CAD Computer-Aided Design – Generally reflects design utilizing a 3D modeling database. Computer-Aided Drafting – Appropriate if one is producing mainly 2D documents. Computer Aided Design/Drafting – A combination of the two.

Reasons for Using CAD Can reduce drawing time and improves productivity Prevents having to make repeated drawings of often-used symbols Improves overall appearance and readability of drawing Allows for easy revision of drawings Can be transmitted electronically

Reasons for Using CAD 3D models, as the 3D database can be used to: generate multiview drawings construct prototypes generate code for CAM increase visualization analyze mass properties of objects (volume, center of gravity, moments of inertia, etc.)

Computer-Aided Design & Drafting 007.03 Explain 3D modeling commands and concepts

Types of 3D Modeling Systems Wireframe Model Surface Model Solid Model

Wireframe Modeling Wireframe modeling is the simplest of all modeling techniques Based on edges, vertices, and faces Wireframe modeling is the simplest form of 3D modeling. It is also a direct extension of 2D geometry. Its main elements are edges and vertices. The model is “anchored” in space by the X,Y,Z coordinates of the vertices. The edges connect between these locations. Wireframes are also comprised of faces, which basically amount to the area between the edges and vertices. Specific information in a wireframe model is tabulated in an Edge List. This list does not contain coordinate information. The location, orientation, and length of an edge must be derived from the calculations of the vertices.

Wireframe Modeling Wireframe modeling suffers from uniqueness and ambiguity issues Wireframe models generally suffer from issues of lack of uniqueness and ambiguity. Since they contain no surface information, it is difficult to determine which side or face you are viewing. Some more advanced wireframe modelers have the ability to remove portions of edges that are hidden from a given viewpoint.

Surface Modeling Surfaces define the shape of a hollow model. Surface modeling gives designers a great amount of control and flexibility. Surface modeling gives the designer a great deal of control over tangency and continuity conditions on a model, as well as shape flexibility. By using higher-order mathematical surfaces, designers have many more options when it comes to the look and feel of their product. However, true surface modelers lack the ability to compute feature intersections due to the void that exists between surfaces on the boundary.

Solid Modeling Objects are defined as a solid mass. May contain information about the density, mass, moment of inertia, volume and center of gravity of the object. Surface modeling gives the designer a great deal of control over tangency and continuity conditions on a model, as well as shape flexibility. By using higher-order mathematical surfaces, designers have many more options when it comes to the look and feel of their product. However, true surface modelers lack the ability to compute feature intersections due to the void that exists between surfaces on the boundary.

Solid Modeling Primitives Rectangular Prism Triangular Prism Cylinder What are the minimum number of parameters needed to define each one: a cylinder a sphere a cone a torus a rectangular prism a wedge Torus Sphere Cone

Solid Modeling B Primitives can be used to build solid geometry with Boolean Operations A A  B A  B A - B Boolean Operations SUBTRACT UNION DIFFERENCE INTERSECTION INTERSECTION