Combating CAD File Translation

David Graves, Mid-South Design and Consulting, Inc. (Brandon, MS). It seems that everyone in the industry is going to 3-D solid designs. For my business, this is great because that's what we do. However, I still have many customers that rely on IGES files for universal distribution to their suppliers. In my opinion, the days of IGES are over, especially when dealing with solid models. This file format leaves too much margin for error and too many problems trying to stitch the surfaces back into a solid.

I have more success with STEP files. I have evaluated many different software packages for CAD and found that the translation package with SolidWorks performs pretty well. There also is a package out there called CADfix that is supposed to address this issue, but I have always had serious doubts about any package that claims to translate and automatically fix everything from virtually any CAD software. It is my belief that there will always be a margin for error in file translation until the industry can develop a standard for all of the CAD engines.

Ken Crow, The Society of Concurrent Engineering (Los Angeles, CA). There are several solutions, with the degree of compatibility and ease-of-use ranked in order of highest to lowest:

1. Use a common CAD system within the company and with suppliers.
2. Use CAD systems with a common kernel, e.g., ACIS, Parasolid, etc.
3. Use a commercially-available direct translator.
4. Use STEP.
5. Use IGES.

If the issue is CAD file translation to other CAE and CAM systems, a similar hierarchy of solutions exists.

Paul Finelt, Optimum Online. This is a complex problem that developed from a lack of clarity and understanding of the underlying math in both the user and vendor camps in the earliest years of the industry. IGES and STEP has continued to carry the cause of interoperability between vendors. Keep in mind that vendors have not always felt that it was in their best interest to provide 'perfect' translation. They outsourced the IGES translator segments of their code and really didn't QC the software. Vendors are in far better shape today than ever before in the quality of this end of their software. Most problems that I see today originate from a poor implementation of the pre-processor interface. Vendors leave out or fail to fully explain the effects of many parameters that they have placed at the user's control. Users do not understand the fire that they are playing with. If you aren't math oriented or trained, reading the IGES specifics for spline data and solids is difficult. They learn by playing around with the parameters and never 'converge on a solution.'

When users begin to understand what's going on at the pre-processor and post-processor ends, the user community will be able to make better decisions and use of the tools vendors have been able to provide. In most cases, this is not a task that they can afford or are inclined to accept as a challenge. In the end, there is quality software available that cleans up IGES data.

Terry Wohlers, Wohlers Associates, Inc. (Fort Collins, CO). Currently, it is impossible to overcome the problem entirely, unless the sender and receiver are using identical CAD software products. Assuming that this is not the case, users can take steps to minimize file translation headaches.

1. Consider the use of special software developed specifically to translate the sender's CAD file to the receiver's required file type. This software can be expensive, but worth it if you plan to move a lot of files from one system to another over a lengthy period of time. Some service providers will do it for you for a fee.

2. A few companies now offer file translation as an application service provider (ASP) on the Internet, so you may want to seek out one of them. Consider PlanetCAD's 3Dshare, Translation Technologies, Inc. or CADCAM-E.COM.

3. For years, countless companies have used IGES and more recently, STEP, with mixed results. IGES and STEP translators offer a number of settings that you must adjust. The happiest users are those who have discovered and documented what works and what doesn't between two CAD systems. When done correctly, it can dramatically reduce the number of surprises and the risk of expensive and time-consuming file repair by a skilled CAD user.

In all cases, it's wise to talk with others who have encountered similar problems. A surprising number of users have used a costly method of trial and error, so don't fall into that trap.

Peter Dicken, Delcam UK (Birmingham, UK). The role of the Internet in helping to overcome these problems consists of two aspects: (1) the availability of online translation software and (2), because communications over long distances are so much easier, any problems with the translation can be discussed and resolved more readily.

Another aspect to investigate is the efforts of the main CAD vendors to assist or prevent accurate data translation.

Dan Malone, CAD Repair (Erie, PA). There is a strata of activity promising to offer various solutions to this problem. For instance, there are technology solutions such as collaboration between kernel companies, model checking and model healing software and services; information handling solutions where responsibility for translations is centralized; training solutions and supervision solutions; and companies that are developing translators for translating native files with their associated parametric and feature tree data.

The most difficult and expensive CAD file translation problems are due to human error in the modeling - the modeling software leaving ambiguous geometry behind after the CAD operator has performed various operations. These details are not obvious and none of the CAD packages are very forgiving of imported geometry with ambiguous geometry. There also is the file size issue. Productivity is improved if the file size of a model is kept within the capabilities of the computer hardware to manipulate it. File size is kept down by loosening tolerances between surfaces and edges. The result is that anyone on the receiving end of those models will have substantial work to do to get their CAD program to recognize the model as a solid.

The easiest problem to deal with is translator issues. Companies will pay for basic training and maybe advanced training for a few, but will they train everyone who is translating files on the details of file translation? And the last category of translation problems has to do with differences in CAD systems that have roots in proprietary technology. The issue is compounded when the same file is translated into and out of several different CAD packages as it makes its way to Tier 4 suppliers.