What is this "Design Intent" I keep hearing about?

Design Intent is not a buzz phrase like "ideation funnel" or "value streaming." It is a real term, with a real purpose. Ok, so those other buzz phrases are real too, but I'm just not talking about them at the moment.

Design intent could be better understood simply by reversing the order of the words. Does "intended design" make any more sense to you? Design intent comes into play when using parametric solid modeling programs, such as SolidWorks, ProENGINEER or Catia. As a refresher, "parametric" refers to a model that has features with a meaningful relationship to other model features or data. It is these meaningful relationships in the CAD world, these parametric relations, that make 3D modeling so powerful to us in the engineering realm.

Back in the days of 2D CAD (way back to the early 1990s), programs could not incorporate design intent into a model. It could display geometry of a design, but the model itself did not contain any information beyond the start and end points of a line, or the diameter of a circle to construct the model. In the mid and late 1990s 3D CAD powered onto the scene, allowing the model to become a virtual representation of a design. Associated data became contained within the confines of the model file, not simply the geometry required to construct the model. These other data covered information such as density, material, and the locations and sizes of features. This data could then be retrieved and modified at any time. When these modifications were changed, due to parametric relationships, the entire model would update itself. Of course as some of us have discovered, the extent and scope of these "automatically updating" features were highly dependent on design intent.

To build a robust parametric model (that is also easily editable), some design intent in the form of forethought on how the model is to be constructed must be given. After all, designs are conceived to fulfill a purpose. Take for example a strip of metal requiring a hole in the center of its width, much like a lawnmower blade. The design mandates a hole to be drilled in the center of the part's width and length. If you model the design by dimensioning a hole half the width from the edge, it is indeed "in the middle" of metal strip, but you have ignored the design intent of the hole. If the width changes in the future your hole would still be a half the original width away from the edge, and no longer in the middle of the part. Had you placed your hole in the mid-plane of the metal strip, no matter how the width changed the hole would remain in the middle of the strip. The design intent of the hole was maintained, and all it took was a little forethought during the modeling process.

This forethought does not stop at the part level however, as parametric relations are not confined internally to part models alone. Parametric relations can span between several models, along with their associated drawings, or be driven by the top level assembly itself. For this reason, design intent is very important and should be considered early on in the design phase of every project.