Manufacturing companies must bring high-quality products to market faster than ever before. This tightened timeframe significantly impacts the manufacturing supply chain — a familiar problem to most computer-aided design (CAD) users. The need for interoperability is a natural con- sequence of MCAD system differentiation within the supply chain, coupled with growing trends toward outsourcing designs and components, and increased emphasis on design collaboration.

Figure 1: A Pro/ENGINEER model converted into CATIA using a Neutral File Format such as STEP or IGES. The feature history tree, which contains the intelligence of the model, has not been included in the conversion.
Figure 2: A Pro/ENGINEER model translated into CATIA using Feature-Based Translation Software. The feature history tree is intact.

Major original equipment manufacturer (OEM) companies rely upon an extended supply chain for more than just contract manufacturing — they actually are outsourcing the design of components and entire subsystems. The result is an environment where design collaboration and detailed communication is an absolute requirement, even during the earliest design stages. Complicating this issue is the fact that the CAD tool that suppliers use may not always be compatible with the tool that their customers use. The resulting set of potential communication problems can be expensive and time-consuming. Evaluating interoperability options becomes a must for CAD users.

Multiple solutions exist today for achieving CAD interoperability. Each approach provides a different outcome. Understanding the differences between various MCAD interoperability solutions is an important task, as results can vary widely based upon the solution selected.

  • Boundary representations. Most interoperability is achieved through the transfer of a geometric representation of a part or assembly, commonly referred to as a boundary representation, or B-rep. Breps provide a description of the overall geometric shape without including any of the underlying design intent used to develop that geometric shape. The most common way to create a geometric representation is through the use of neutral file format standards such as IGES and STEP, or through the use of direct system- to-system converters.

Whether using neutral file format standards or direct system-to-system converters, the advantage of B-rep translations is that they are fairly simple to use. The disadvantage is that B-reps can introduce serious complications into the overall communication process. These problems range from incomplete or inaccurate geometry and a lack of parametric features and design history, to unpredictable model behavior or unstable or unwieldy files caused by drastically increased file size. More companies are requiring their suppliers to deliver feature-based native design information.

  • Remastering. A common approach to achieving feature-based native design interoperability involves the recreation, or remastering, of the MCAD model. Today, the primary means of remastering is through manual redesign. While this method yields the desired outcome of interoperability, the process is error prone — the more complex the model, the higher the likelihood that human error will occur. Manual redesign in its purest sense represents duplication of effort, introducing added time and expense.
  • Feature-based native translations. True feature-based translations provide a direct database conversion of models with the feature history tree intact. Feature definitions, parametric relationships, and design history created in the original model are recreated in the specified target software application.

Feature-based native translations achieve the same outcome as a remastered model, with the advantage of an accelerated process. In addition, if the translation tool has a reliable built-in accuracy verification method, it overcomes the risk of human error associated with manual remastering.

A disadvantage of some feature-based translators is that not all solutions provide the full history tree in all instances. Some feature-based data exchange translators insert a B-rep when the software encounters a feature that it cannot translate. The inclusion of B-reps can create difficulties in translating models due to differences in how CAD systems apply modeling tolerances. In addition, parent-child relationships further down the history tree are impacted by the insertion of B-reps. With some feature-based data exchange products, the end result may very well be a translated file with only partial modifiability. The user must understand the differences between available solutions.

The issue of interoperability is complex. Because of the different approaches to modeling geometry employed by various CAD systems, as well as the variance in techniques that individual designers employ to construct models, there is no “one size fits all” solution. Understanding the differences between various MCAD interoperability solutions is an important task, because end results can vary widely based upon the solution selected. Companies must be cognizant of the need to define and comprehend the complexity of selecting an interoperability solution.

This work was done by Tom Kopinski, executive vice president of Translation Technologies, Inc. (TTI). For more information on TTI’s parametric feature-based native translations, contact TTI, 665 N. Riverpoint Blvd., Spokane, WA 99202; Tel: 877-358-2036; e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.; or visit the Web site at: