Parametric & 3-D Solid ModelingParametric & 3-D Solid Modeling

Charles J. Kachmar

3-dimensional design software such as: AutoCAD 3-D AutoDesk Inventor PTC Pro/D or Pro Engineering Rhino Solid Works

Allows engineers to visualize proto-types before construction.

Allows engineers to perform simulated analysis mechanical analysis called Free Element Analysis.

Inspect the model before it is produced.

Detail important information like center of gravity and mass before it is constructed.

Check for tolerances and ergonometrics before any production money is spent.

Complete mechanical analysis in the design process saves money in the long run.

Provide presentation graphics of a proposed idea to future investors and engineering managers.

Provides designers working drawings that comply with all ISO and ANSI standards. These can be used oin the manufacture of the project.

Also converts designs to .iges or .stl for rapid prototyping and CNC operations.

Parametric Design - a system that constructs relations among the geometry of different elements. When one element is changed, the geometry of the rest of the elements are changed as well.

Parametric design changed the way products are designed and prototyped: design > prototype > manufacture … all on computer

Parametric Design Model: The nature of design problems: Many design problem can be informally

described as a problem in which a set of needs and desires is given and where the solution is a description of some structure that satisfies these needs and desires (Wielinga, Akkermans, and Schreiber, 1995).

Analysis process - designer transforms the needs and desires into a more formal and complete set of requirements and constraints.

synthesis process - a structure is developed —the design— that consists of a number of building blocks or elements with specified properties —such as dimensions, material etc.— and relations between them.

Needs &

Desires

Informal

Constraints

Analysis

Formal

Requirements

Formal

Constraints

synthesis DESIGN

Conceptual Engineering: resources that allow you to develop ideas at the earliest stages of the design process, without getting bogged down in specifications; systems that allow you to quickly explore design possibilities and rapidly capture ideas...

and allow you to go back and change almost any parameter of the design.

Reverse Engineering: producing 3-D images of manufactured parts when a blueprint is not available in order to remanufacture the part. Coordinate measuring machine (CMM) generates a wire frame model.

Output for CNC mills & routers

PTC- PTC- Design & Technology in Schools ProgramDesign & Technology in Schools Program

RapidProStacked paper slices

Wire Frame Modeling

• Stores positions of lines (in 2D or 3D)

• Helpful for drafting (easy multiple views and easy editing)

• Ambiguous surfaces limit the automation possibilities (e.g. no volume calculation, no CNC tool path generation)

Surface Modeling

• Stores equations of surfaces• Most 3D graphics librariesuse surface modeling• Good for visualizing complexsurfaces and automated NCpath generation of complexsurfaces• Material volume informationis ambiguous or hard todetermine (therefore can’tcalculate volume)

Solid ModelingVarious mathematical representations exist that each allow point-set classification: “Is a given point inside or outside the solid region?”

• Solid models can be used for:

– volume calculations

– Automatic FEA mesh generation

– Collision determination in robotics or CNC path generation

Different ways that a user can createsolid shapes:• Primitive creation• Boolean operations• Sweep operations• Surface operations• Engineering Feature-Based modeling• Parametric modeling

Solid Modeling Functions

• Primitives are simple solid

shapes with simplemathematical

surfaces• Can be controlled

by a smallnumber of

parameters andpositioned using atransformation matrix

Solid Modeling Functions

Solid Modeling Functions

Solid Modeling Functions

Solid Modeling Functions

References:Michigan Tech University

www.me.mtu.edu/~bettig/MEEM4403/lecture_05_11.pdf.

The College of New Jersey Engineering and Technology Department.