This month's focus on data exchange provides an excellent opportunity to share some of the 3D modeling information I've collected for my new Web site: http://www.3DCADTips.com/(figure 1). During my 25 years of experience, first as a 3D CAD designer and then as a writer, I've accumulated hundreds of technology tips. Some are useful regardless of what application you use. Others are specific to products such as Alias Studio Tools, Alibre Design, Pro/ENGINEER, Solid Edge, thinkdesign, and VX CAD/CAM.

Figure 1. 3DCADTips.com contains more than 270 tips on topics such as implementation, construction and editing techniques, performance issues, PDM, design collaboration, data exchange, and documentation.

I sponsor and help develop the site for the sole purpose of sharing this information with as many 3D CAD users as possible.

You can register and submit your own tips for the next update.

Figure 2. Each CAD system supports a subset of the IGES standard. The entity types supported by both systems are mapped from the sending system to the receiving system. Other entities within the subset may be ignored.

The site expands monthly, and I personally thank those of you who have contributed tips. So without further ado, let's get a little tip-sy.

Product-Specific Tips

How Data Loss OccursNeutral-format data exchange standards such as IGES and STEP are extensive in structure and scope. This is because they attempt to support a varied field of disciplines—mechanical design and AEC are only two among many. During the exchange process, a 3D model file is translated from one native CAD format (sending system) to an IGES or STEP file. This file is then translated into another native CAD format (receiving system).

Because of the size and scope of the standard, mechanical CAD systems support only a subset of the standard. While System A may support entities a, b, c, d, and e, System B may support only entities a, c, and e. So, you ask, what happens to entities b and d? System B ignores those entities because it doesn't support them. This is one way in which data can be lost (figure 2). See http://www.3DCADTips.com/for more about data loss during 3D CAD data exchange.

DATA EXCHANGE CHECKLISTS

Can Data Accuracy Change?Accuracy can change in many ways. Starting from the native sending system, what you see on the screen isn't necessarily what's in the 3D database. 3D modeling kernels can force geometry to connect or treat elements as though they connect even though they don't. Neutral-format data exchange can expose these inconsistencies.