Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 9 3D Modeling

3D Modeling Snapshot Since Mid 1980’s become common place in industry Software Types Wireframe (AutoCAD) Surface Modelers (CATIA)  Constructive Solid Geometry (CSG)  Boundary Representation Modeler (BMR or B-REP) Hybrid Modelers (CATIA/ Solid Works)

Wireframe Modeler Two types of elements defined  Points (Vertices)  Lines (Edges) Surfaces (Faces) Theoretically created

Pros & Cons of Wireframe Modelers Simple to adapt from 2D software Less Memory required Less Processing Power needed Cost less Ambiguity

Which of these is the correct representation of a solid from the wireframe model?

CSG- Constructive Solid Geometry Allows flexibility in both how primitives are defined and combined What are these operations called? Boolean 3 Types Union (U) Difference (-) Intersection (∩) What does Solid works call them? Join Cut Intersection Does it matter what order we do them in?

Primitives using CSG modeling

Boundary Representation (B-REP) Surfaces or faces define solid Contain both linear and curved edges Use faceted representation due to size of models

Surface Modeler Two types of elements used to define surfaces  Points (Vertices)  Lines (Edges)  Actual Surfaces are created

Hybrid Modeler Use combination of CSG and B-REP features (CATIA/ Solid Works) Solid Modeling Include Volume (weight) Apply materials and analyze

Most common techniques : Sweeping Revolving Lofting With a partner take out a piece of paper and sketch how you would model a boomerang.

Sweeping Need Profile (2DSketch or Directrix) Direction (Along 3D sketch (path) or Generatrix) What is our directrix in our boomerang? Genaratrix? Directrix-2D Genaratrix- used to generate 3D

Generalized Sweeps (Extrude) 2 things needed Closed profile & Direction What is needed for the oblique sweep? Closed profile & path Revolved Sweeps 2 things needed Closed profile & Axis

Revolving Need closed Profile (Sketch) Axis

Lofting Need 2 or more Profiles (Sketch or Directrix) Direction (Along Generatrix or Spine) What is our directrix in our dryer housing? Genaratrix?

Surface Patch Contains 4 connected Bezier Curves Controlled by 12 points

Quiz!!!! 1.What is needed to create a sketch? 2.What is needed to create a profile? 3.What is needed to create a solid part? 4.What is difference between open & closed loop profiles? 5.What is needed to create a generalized sweep (Extrude)? 6.What is needed to create a revolved sweep? 7.Which of the profiles below are closed loop? 8.Which of the profiles below are open loop? 9.What does CSG stand for? 10.What does B-REP stand for? 1.Work plane 2.Points and lines (Topology) 3.Closed profile/ Direction 4.Closed profile 5.Profile/ Direction 6.Profile/ Axis 7.A and C 8.B 9.Constructive Solid Geometry 10.Boundary Representation Modeling

Homework Model Figures (C & N)

Division of parts made up of more than one surface Trimmed Continuity Merging Continuity Merged

Divisions of Continuity A- Discontinuous- has holes or gaps B- Positional- Share boundary C- Tangent- Smooth Transition D- Continuous curvature- no noticeable transition

Options to define plane Through Offset/ Parallel Angle/ reference Point or Edge and Orientation Tangent and Orientation How would you create this?

Constraining Profiles 2 Types of Constraints Geometrical (Implicit) Dimensional (Explicit)

Duplicating Part Features Linear and Radial Arrays

What is the main reason for solid modeling software? Assemblies Hierarchical approach Network Approach- Toolbox in Solid Works Instances

The Goal in Assemblies is to control the degrees of freedom the product can move How many degrees of freedom does every object have? Constraint options: Surface Coincident Offset

Why Solid Modeling? Kinematics Movement Paths Clash Detection Design from Motion Mass Properties

Why Solid Modeling? Ergonomics

Why Solid Modeling? CAM- Computer Aided Manufacturing

CAM Rapid Prototyping Visual Inspection CNC Path Exported Virtual Reality Finite Element Analysis

DATA Exchange CAD to CAM Different File Types DXF- Drafting Exchange Format IGES- Initial Graphics Exchange Specification STEP- Standard for the exchange of product

Homework Ch 9 figure C dimensions

Homework Ch 9 figure N dimensions