Parametric Modeling in 3D CAD

Parametric Modeling

• Parametric modeling uses parameters to define a design solution in 3D CAD programs.
• A parameter is a property of a system; its value dictates how the system behaves.

Types of Parameters

• 3D CAD programs typically have three user-defined parameters:
  • Geometric Constraints: These are relationships between elements such as parallel lines, concentric arcs, or horizontal lines. They're non-numeric, but measurements can be added. Examples include making two lines parallel, two arcs concentric, or a line horizontal. Common geometric constraint types include coincident, collinear, concentric, fix, perpendicular, parallel, horizontal, vertical, tangent, smooth, symmetric, and equal .
  • Parametric Constraints: These utilize formulas and ratios instead of precise measurements. An example is 3D printing at 50%.
  • Assembly Constraints: These are discussed later.

Parametric Equations

• Equations use variables, which can be substituted for numeric values.
• The resulting dimensions may change, but the formula remains constant.
• Symbols used are "+", "-", "*", and "/".
• In Onshape, each dimension is given a name, often starting with "d0," for "dimension 0".
• The "#" symbol is used for formulas in Onshape (e.g. #overallwidth). There should be no spaces after the '#' symbol
• d represents dimension
• Units like inches or degrees are given with the numeric values.

Parametric Equations in Onshape

• Dimensions are given variable names (e.g., d0).
• "d" stands for dimension.
• The "#" symbol is used before measurements in formulas (e.g., #overallwidth).
• Onshape uses variable tables (located on the right side, middle) to accommodate parametric equations.
• Alternatively, use the variable command (x).

Parametric Constraints in Onshape

• Used to govern geometry position and size.
• They can define limits.
• Are sometimes presented as simple numeric values (e.g., 2 inches).
• Can also represent abstract algebraic equations (e.g., (d2d0)/d5 or #length#depth/2).

Parametric Equations in Inventor

• Dimensions are named consecutively (starting with d0).
• The first dimension you create is labeled d0, the next d1, etc.
• Equations can replace numeric values in dimension dialog boxes.
• You can name any dimension with a parameter.
• Right-clicking a dimension allows changing its display mode.
• The "Name" option in dimension display shows parameter names, not numeric values.

Parametric Equations in Other CAD Software

• CAD programs (like Inventor and Onshape) use parameter tables for storing and displaying dimensional equations numerically.
• These tables document parameter names, units, equations, and numerical dimension values. Access the tables within the Manage tab.
• Users may modify parameter names, equations, or comments.
• Model dimensions automatically update when the user clicks "Done."

Parametric Modeling Projects

• Typical projects include designing prototypes, creating complex models, and solving real-world problems using parametric equations and dimensions.
• Students will be assigned roles within their modeling groups. Some examples are Researcher, Designer, Modeler, and Presenter roles.
• Students develop the projects by modeling three separate components, "Wedge", "Cylinder" and "Tall block" using parametric constraints and equations.
• Projects may assign a constant ratio between dimensions, such as Overall Plate Depth (d0) and Overall Plate Width (d1), ensuring consistent ratios when scaling.

Explore the fundamentals of parametric modeling in 3D CAD programs. This quiz covers types of parameters, including geometric constraints, parametric constraints, and their applications in design solutions. Test your knowledge and enhance your understanding of CAD modeling techniques.