Closing the CAD/CAM Gap

At first glance, CAD and CAM seem to be more similar than they are different, but with over 25 years experience in mechanical product design, engineering, and manufacturing, I've found the opposite to be true. CAD and CAM technologies do share some similarities - you create something - one digital, one physical - however, CAD and CAM are different in more ways than they are similar. And, although major progress has been made to close the gap between CAD and CAM, a considerable gap still remains.

The major differences between CAD and CAM really come down to three basic things - workflow, features, and interoperability.
  • Workflow - By its nature, CAM is much more process oriented than CAD (which for obvious reasons, is product oriented), and the order or sequence in which different processes are performed can be critical in CAM. Simply, CAD defines a part, whereas CAM defines a part's manufacturing processes and how the part takes shape. Also, the concept of time is an important aspect of CAM that really isn't a factor at all in CAD. Time is especially important on the manufacturing side because a part continually changes with different processes over time.
  • Features - In CAD there are design features and in CAM there are manufacturing features. Design features define a part in a CAD system and can be additive or subtractive. Feature-based CAD packages display features and operations in history trees, and parts and assemblies can be directly manipulated and modified using these history trees. History trees also can provide beneficial overviews to manufacturing because they provide insight into how a design was created, as well as help understand design intent. Manufacturing features, on the other hand, group geometry that will have manufacturing processes, such as machining applied to them.
  • Interoperability - Even with all the advances that have been made, CAD/CAM interoperability is still a major problem issue today. Because of interoperability problems, design intent is often lost as design data moves from CAD to CAM. Data incompatibility is another huge problem, costing in the tens of billions of dollars annually. One of the most promising innovations to remedy CAD/CAM data incompatibility is the Super Model Project being driven by Step Tools Inc. The goal of the Standard for Product Data Exchange (STEP) is to provide a comprehensive, extensible standard for product data throughout a product's entire life cycle. The goal of the Super Model Project is to develop software and databases for an integrated design-to-manufacturing system that allows CNC machine tools to be controlled by product design data. So will STEP-NC signal the end of G-code for controlling machine tools? A number of CAM software vendors and manufacturing organizations are betting that it will.
While a few vendors of CAD products have managed to integrate CAM functions into their products, the more common approach is to have a suite of separate products for handling the CAD and CAM functions of design and manufacturing. There are, however, still major compromises if either approach is taken. On the one hand, CAD users don't want to be constrained by having to predict manufacturing processes. On the other hand, CAM users don't want to be forced to produce parts that are either too expensive to produce, or can't be realistically produced at all. So it's a tough dilemma getting CAD and CAM software products and their respective users to work together.

Even though they are so different, will CAD and CAM ever join as one? Ultimately, I think they will. For the time being, however, the differences between CAD and CAM will continue to impede their integration, largely because their workflows and final results are so different. Because of how they are used, most CAD and CAM software products look, feel, and behave differently, and probably will for the foreseeable future, but not forever.

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--Jeffrey Rowe is Editor and Publisher of MCADCafé and MCADWeekly Review. He can be reached at Email Contact.


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