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CAD: Back to Engineering's Bedrock, Iteration

Brian Sather

Product design

Computer-aided design has come a long way since its early days when it primarily served as a way to document drawings. Even so, you still may not be using CAD to its full capabilities when it comes to exploring and changing your designs. Many engineers, for instance, simply document their finished designs within the CAD system.

But if you’re not using CAD from your initial design stage, you may not realize you’re missing out on a hugely helpful, even vital feature of the tool: its capability to explore design iterations until the model exactly suits your needs.

In its early inception, CAD was used to create engineering documents such as 2D drawings. But with the advent of 3D models came part geometries that—via parametric and direct modeling—could be easily changed and experimented upon: Meaning you could iterate upon their CAD model until it matched both your client specifications and your own vision.

When you explore deeper into their own designs, when you experiment with many possibilities, you’re expanding on previous engineering work; you’re leveraging engineering knowledge that builds over time, engineer by engineer.

CAD as an Exploration Aid

So 3D CAD allows you to get back to engineering’s very foundation: exploration and iteration. At its base, engineering is about trying one approach, seeing it fail, trying a different approach and getting feasible, but not optimal results, then trying yet another approach and finally, maybe after even more exploration and iteration, coming up with the best possible design.

CAD expands engineering. Even with the tool’s limited, older capabilities, CAD helped engineers iterate much quicker than they could with pen and paper or with early graphical computer programs. And of course CAD’s limits and capabilities have only grown since the tool’s inception.

Let’s look at a few of the features found, whether separately or together, in modern CAD systems, with an eye toward how they aid design exploration.

Parametric modeling allows users to build intelligent and reactive sequences of geometries in which engineers gradually capture their design intent. In this case, intelligent and reactive means the capability to create geometric objects that react to each other and behave as they would in the real world, rather than just on a computer.

So as you iterate and change your model, the software’s parametric modeling capability maintains consistent relationships between elements. So if you lengthen an I-beam within a model, all other model geometries change automatically in accordance with that new length.

CAD packages that offer direct modeling capabilities allow you incredible flexibility in changing design geometry, letting you explore design possibilities you potentially hadn’t envisioned when building the original model.

With direct modeling, you manipulate a model’s geometry by pushing, pulling or twisting it. This allows you to focus initially on creating geometry rather than thinking about building features, constraints and design intent into models. You add features and constraints when editing the model, so you don’t have to edit the interim model stages.

And CAD systems that are integrated with product data management systems allow for design branching. This is when alternative designs are kept, as it were, in their own, separate sandboxes with boundaries between alternative designs. When similar designs don’t overlap, influence, or touch each other, you can explore different alternatives and merge—from the various sandboxes—desirable aspects of each design into one final design.

Because today’s CAD software includes those capabilities—again, whether separately or within the same software package—CAD is now more capable than ever of supporting design iteration.

So Why Not Use CAD?

All this sounds appealing, yet not every engineer or engineering company uses CAD for part and assembly design.

Some engineers still sketch things out by hand on graph paper. Others say that by the time CAD is brought into the process all the real engineering decisions have already been made. These engineers are likely waiting until the design is complete and then documenting it with their company’s CAD software.

Some engineers might argue that design exploration is easier on graph paper than with CAD because different options could be created relatively quickly. The question is, are you able to truly evaluate different design options with pencil drawn sketches? Can you get a real sense for what it will look like and evaluate how it will perform? Can you identify potential interferences? The answer is likely no.

So why haven’t all engineers turned to CAD? Is that they aren’t used to designing digitally? That they aren’t used to designing with a 3D model? Maybe they feel that 2D design allows them to design more conceptually, that a design with a third dimension takes them out of the design process.

Or are the holdouts simply a little older than their counterparts? In other words, of a generation that used pen and paper to balance the checkbook, to write reports before typing them, and to design at work.

Likely, engineers’ reasons for not calling upon CAD are as varied as the engineers themselves.

But CAD systems allow for greater design exploration than at any point in the history of engineering. They help engineers explore at much quicker speeds than by hand or by the 2D drafting process.

So do you use CAD for design? What’s been your experience with it? Do you find it helpful and, if so, how and why?

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