CAD/CAE Modeling

1
CAD/CAE Modeling

• Parametric vs. Variational
• Adaptive Modeling
• Feature Based Modeling
• Dynamic Modeling
• Modelers use variable driven modeling vs.
  explicit modeling

2
Dynamic Vs. Static modeling

• PTC introduced commercial version of variable
  modeling
• Uses dimensions and constraints
• Feature Based design
• Uses primitives and parameters rather than
  coordinates and orientation
• Features are directly placed in models

3
Modeling Modes

• Issue How to capture/define parameters
• Issue How to capture design intent and translate
  to variables
• Issue After capture, how to maintain
  parameters/variables
• Explicit modelers use geometry. Changes are
  expensive (time and effor)
• Combines wires, sheets, solids

4
Variable Driven

• Design intent is captured
• Allows users to explore various design
  alternatives
• Two popular sub-methods in use are parametric and
  variational modeling methodologies

5
Parametric Modelers

• Transaction history is captured
• Order dependent and hierarchical model creation (
  ordered steps to follow)
• Solution speed is a great advantage to this
  method
• Must FULLY constrain before next element is
  defined (every step)
• DAG (Directed Acyclic Graph) modeling

6
Variational Modelers

• Solves set of simultaneous equations
• Driving dimensions can be based on complex
  equations Eg Dimensions based on material
  properties
• No specific order dependency.
• Constraints dimensional, geometric, algebraic
• Eg Parallel lines A and B can both move

7
Adaptive Modelers

• CSG tree based
• Boolean operators
• Parameters alter the CSG primitives
• Euclid (MDV) used this method
• Changes are still expensive due to boolean
  operator costs

8
Dynamic Modelers

• Use Feature Recognition Technology
• No prerequisite knowledge of models assumed
• HP PE solid designer uses this method
• No inter-relations available between features.
  This could be a limitation

9
Feature Based Modelers

• Features are named entities which follow rules
• Engineer friendly terms ( fillets, boss, slots
  etc.,) used in modeling/design workbench
• Topological integrity must be maintained (
  through holes remain after higher thickness)
• Follow rules. Process information is captured for
  manufacturing and applications

10
Sketches in Modeling

• Contributes to how easy to edit and recreate
  designs
• 2D-gt 3D can be done using extrude, revolve, sweep
  operations
• Automatic parameterisation is more common in 2D.
  3D problem domain is much more complex

11
Geometric Modeling Features

• Rules and Data for Features
• Solid 3D models and features use DATUM feature in
  Pro/E
• Changes and Edits are critical to evaluate for
  ease of use and speed
• Variable Driven modeling is a must for all future
  systems

12
Advanced Modeling

• Assembly models are collection of parts with
  position and orientation
• Positional variables are used to relate parts
• Stresses, Volumes, Geometric contraints are
  placed in assembly context
• Tolerance Analysis application uses variables to
  help simulation/manufacturing