Datasheet

UNDERSTANDING PARAMETRIC DESIGN 17
Making the virtual prototype allows the designer to explore the function of a mechanism before
lengthy design and engineering time is expended on a design that just won’t work. Developing
the virtual prototype eliminates the part procurement and creation process, slashing the design
time even further.
The virtual prototype can be proven with the use of stress analysis and dynamic motion sim-
ulation to find and correct weaknesses in the design, rather than just ensuring that everything is
overbuilt and calling it a good design. Interference between components is also easily discovered
while still in the design process.
The use of functional design in the prototyping process allows engineers to properly deter-
mine loads, power, stresses, inertia, and other properties before a machine is built. Weights,
center of gravity, and other physical characteristics are at your fingertips during any stage of
the design.
Too Busy Getting Drawings to the Shop to Build Virtual Prototypes?
You have deadlines to meet, and we are telling you to spend more time building models. Deciding
when to build a virtual prototype depends on your business and the complexity of the design. We
have all given sketches to the shop to get a part made, but no one wants to do that on a regular basis.
When designing food-processing equipment, the bulk of our work was custom conveyors. We had
basic designs that differed in length, width, and height. Items such as electrical panels were shown
in position, but we didn’t detail the mounting brackets because the fabricators could make them
more quickly than we could draw them. Core components, like the drive system, were fully detailed.
Building a virtual prototype for key subsystems would save time and money because you could
discover issues early when it is easier to resolve them.
When working for an international manufacturer, everything we did was made in volume in
several countries. Any error resulted in a lot of scrap and production delays. We built prototypes of
everything before releasing anything into the system. That company would s till build at least one
physical prototype, but doing virtual prototyping could trim weeks or months from the development
schedule.
Building virtual prototypes also pays off when you do a r evision or redesign. The better the model,
the easier it is to verify that a replacement component will fit properly. Doing a major redesign on a
product will go more smoothly if you have a solid base from which to work.
Understanding Parametric Design
In 2D design software such as AutoCAD or other legacy packages, including most surface model-
ers or 3D modelers capable of creating static models, the ability to modify the design is typically
limited. Modern 3D feature-based modelers provide the ability to easily change virtually any part
of the design within the model.
This ability to change or modify a design is based on constraints that control either the shape or
the size of a feature. The combination of geometric constraints and dimensional constraints allows
virtually any variation within the model.
Most of today’s 3D modeling systems utilize the same 2D constraint manager. As a result, the
2D constraints in use today are virtually identical from one software package to another. In like
fashion, the dimensional constraint systems are similar from one software package to another,
and these similarities allow you to more easily learn a second 3D modeling system the next time
around.