Modeling

1.   Understand the terminology used in 3-D modeling. All sections.

2.   Define the most common types of 3-D modeling systems. p. 156

3.  Describe the similarities and differences between constraint-based modeling and direct modeling. p. 156

4.   Apply Boolean operations to 3-D objects. p. 153

5.  Understand the role that planning plays in building a constraint-based model. p. 157

6.  Understand how feature order affects feature editing and final model geometry. pp. 174-175

7.   Apply generalized sweeps to the creation of model features. pp. 161-163

8.   Apply construction geometry in the support of feature creation. pp. 163-164

9.   Apply constraints to a feature profile. p. 156

10. Apply feature duplication to model construction. p. 178

11. Identify the elements used to define a view of a 3-D model. p. 180

12. Understand how model data associativity supports engineering design and analysis. pp. 153-154

13. Generate 2-D documentation from a 3-D model. pp. 183-184

14. Construct assemblies from part and subassembly models. pp. 170-180

15.  Define the types of analyses that can be used with 3-D models. pp. 185-187

16.  Understand how CAM information is derived from 3-D models. pp. 185-187

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1.   What is a nonmanifold object? Sketch an example of one.

Manifold objects unambiguously divide a region into inside and outside. Nonmanifold objects don't do this. p134

2.   Describe the differences and similarities between B-rep models and CSG models; do the same for wireframe models and B-rep models.

CSG models use solid primitives and half spaces related by Boolean operations in a binary tree data structure.  B-rep models define a solid region by surfaces, edges, and vertices.  Wireframe models do not define a volume, but describe just the edges and vertices of a 3-D model. pp135-138

3.   Define the three types of Boolean operations, and sketch examples of each one. Can you derive the same final object using different Boolean operations and/or primitives?

p137

4.   What is "design intent"? Why does this play a role in planning the construction of a constraint-based model?

Changes in geometry of a feature should create model feedback or further changes in the model which reflect design performance or manufacturing constraints of the product. p139

5.   What is the difference between unidirectional and bidirectional associativity? What are the advantages and disadvantages of bidirectional associativity?

In a sweeping operation, a closed polygon, called a profile, is drawn on a plane and is moved or swept along a defined path for a defined length.  Linear, revolved, path-based, and blend. pp142-3

6.   What are the basic elements of a generalized sweep? Describe the major types of generalized sweeps used in feature creation.

Workplanes define the location and orientation of the profile sketch and construction geometry relative to the model and world coordinate system. Through, Offset/parallel, Angle, Point or edge and orientation, Tangent and orientation, Axes and points.  p143

7.   What are sketch planes used for? What are five ways a sketch plane can be defined?

These two types of constraints differ as to whether the modeling system infers the constraint based on the way the sketch was drawn, or whether the operator has to explicitly apply the constraint to the sketch. Closure (connected edges), Segment overlap, Endpoint/line overlap, Tangency, Parallelism, perpendicularity, Same size, Coincident.  pp147-8

8.   Give an example of a parent-child relationship. How is a feature tree used to identify parent-child relationships?

A child feature is defined relative to a parent feature through geometric definitions such as constraints, alignment, or workplanes.  Child features exist below their parent features on a feature tree.  pp159-160

9.   What are the two primary types of duplication methods? What input parameters are needed to define each one?

Linear and radial arrays.  Linear arrays need the number of copies to be made in each of two orthogonal dimensions and the offset in each of these dimensions.  Radial arrays need a rotation axis, radial distance from the axis, number of copies, and the angular offset.  p162

10. What are the elements used to define a view of a 3-D model? Which types of view commands don't change the projection of the model?

Model (object), viewer (camera), and projection (view) plane.  Panning and zooming don't change the projection in parallel projection.  pp163, 166

11. How is the base view used in generating multiviews from a 3-D model?

With unidirectional associativity, the supporting application’s data can be altered by changing the 3-D model, but not vice versa. With bi-directional associativity, changes in either the 3-D model or data in the supporting application will affect the other.  p163-164

12. Define the types of analyses that can be used with 3-D models. Will all of these always be used when designing a part?

13.  What advantages are there for using data from a 3-D model when analyzing the manufacture of a part?