Sponsored By

June 20, 1999

9 Min Read
Coping with the IGES blues

Editor's note: Moldmakers are fighting an uphill battle when it comes to electronic data transfer. Many customers send IGES files expecting to save time, when in fact, importing those files into your CAD/CAM system can add to the amount of work that must be done. International TechneGroup's Carl Izurieta (ITI-Milford, OH) broached the subject from a product designer's perspective (IMM, March 1998). This month, ITI's Robert Farrell shares insights on why the "fear of IGES" is reaching epidemic proportions among moldmakers as well. ITI specializes in software translation aids, so Farrell also recommends what can be done to reverse this trend.

ArticleImage1876.gif

A typical example of a 'bad' IGES file, which features a collection of trimmed surfaces with bad connectivity.

ArticleImage2876.gif

On closer inspection, a mold designer finds two edge curves sharing single endpoints with an unwanted gap.

ArticleImage3876.gif

Using CADfix, the gap was automatically removed and replaced with a common edge.

ArticleImage4876.gif

Here, a collection of trimmed surfaces have been repaired and sewn together into a solid using CADfix.

If importing IGES files into your CAD/CAM system is giving you the blues, you may be experiencing early symptoms of a serious affliction hitting industry today. "Igephobia" (fear of IGES files) is running rampant among moldmakers and others in the molding industry. Symptoms include breaking out in a cold sweat, irritability, and fatigue from spending countless hours fixing or recreating the files.

Today, mold shops and other downstream suppliers are the link in the product development chain where IGES meets the real world. Incompatibilities of IGES file translations between different CAD systems place mold shops in a no-win situation as they race to meet production schedules, maintain cost parameters, keep customers happy, and wage the "bad CAD" war. Depending upon the complexity of the design and the initial success of importing an IGES file, mold shops can spend anywhere from days to weeks doctoring up imported part design geometry to an acceptable level to begin their mold design.

During recent focus group meetings, ITI found that downstream users of CAD models were wasting anywhere from 20 to 70 percent of their time reworking or totally recreating bad CAD data. A growing number of manufacturers today are even incorporating model rework time into quotes.

When you consider that these downstream processes are generally concurrent and independent of one another, you can see the compounded magnitude of the problem. These findings are further backed up by studies from the automotive industry that identify "interoperability issues" (the inability to freely share product data across dissimilar software platforms) as the number one obstacle facing industry today.


Multiple CAD Systems
To help combat the problem, some mold shops have spent thousands of dollars on a variety of CAD systems to match those of customers. When IGES and other neutral file formats don't work, it forces mold shops to invest heavily in software systems and resources that they neither need nor can afford.

Scott Caley, president of Integrated Ideas (Elverson, PA), consults regularly with mold shops caught in the interoperability jam. "Within the past five years, the plastics industry has been radically redefined by the onslaught of designs being produced as solid and surface models. This is due in part to the recent advances in solid and surface modeling CAD packages," he says.

According to Caley, manufacturing considerations such as stepped draft and wild parting lines can now be designed right into the plastic part design with relative ease. In addition, sculpted ergonomic forms can also be defined in the accurate CAD model. Many of these smooth and flowing shapes simply cannot be completely defined in traditional 2-D drawings.

To accommodate this, most mold shops have embraced the new technology to enable them to build molds based directly on these 3-D solid and surface models. In addition to the acquisition of CNC machining centers, mold shops typically purchase a CAD package that caters to their needs as both mold designer and manufacturer.

Since their CAD package of choice may not readily accept IGES files from many of their customers' systems, they often invest in additional CAD packages to accommodate native CAD data transfers from some of their key customers.

These additional CAD packages are used by the mold designer to translate the incoming customer data into an acceptable IGES file that can be imported into their primary CAD package. Obviously, the best scenario is to find a way to make IGES files work, allowing mold shops to pick and choose the software system that meets their requirements-not those of their largest customer.

Translation Basics
IGES (Initial Graphics Exchange Specification) is the world's most popular and generally most successful data exchange standard. The idea behind IGES is a good one: to put data into a neutral format that can be easily read by other CAD/CAM systems. Sounds great. So what's the problem?

While it is true that IGES and other popular data exchange standards (STEP, VDAFS, STL, etc.) provide a neutral file format, the truth is that the translation process can still be riddled with problems.

Often, errors occur when a system's translator is interfaced with the IGES format. As it is written, the IGES specification is open to much individual interpretation. Vendors developing their own IGES translators are often left to make judgment calls as to the meaning and definition of IGES rules. As a result, IGES translators from vendor to vendor, although based on a common technology, can vary greatly in terms of how they define IGES rules.

Some common causes stem from these factors:

  • How the model was built.

  • Different interpretations of the neutral file specification among developers.

  • Level of entity support in IGES translators.

  • The quality of today's translation software.

  • Functional differences between software systems and neutral files.

  • Functional differences between source and destination systems.

  • User's knowledge and comfort level relative to the IGES specification.

Another contributing factor to the poor interoperability between systems can be traced to a general lack of interest from the CAD/CAM vendor community itself. Understandably, vendors place the highest priority on continuing to develop core applications. This is their reason for being in business and why users chose that particular system in the first place. Still, many vendors tend to give data exchange capabilities a very low priority. As a result, it is the user trying to operate in an integrated CAD/ CAM/CAE environment with unintegrated tools who suffers the most.

For many years, the mere thought of making their system interface with that of a competitor was unthinkable for many vendors. They preferred to believe that some day the world would wake up and start using their system exclusively. But today's users have shown that they want the freedom to pick and choose the system or system module that fits their applications, needs, and budget. As a result, vendors are beginning to adopt a more realistic and somewhat humbling view-a realization that success depends on providing open systems allowing users to work with the tools of their choice. Where system interoperability was once a luxury, it is today an absolute necessity.

Curing the Problem
There are methods that moldmakers can use to directly impact data exchange effectiveness. A basic way to influence the process is by becoming better informed and prepared. Other remedies include the following strategies:

  • Validate data before sending it on to customers/suppliers.

  • Learn the proper settings for configuration switches on translators.

  • Adopt guidelines for creating CAD/CAM/CAE files.

  • Increase functionality of IGES processors.

  • Discuss IGES capabilities with vendors.

  • Increase your knowledge of IGES.

  • Employ a CAD fix-up tool.

By adopting a proactive approach to data exchange and taking the time to learn about the standards, the process, the systems, and the data exchange tools, you can make the process much more effective and painless. CAD/CAM users who share data with others should learn a few things about their systems and customers in order to make the exchange process more reliable. Take the time to learn what does and doesn't work with your particular system and document what parameters work best with key suppliers and customers.

It sounds simple, but it's surprising how often the same problems are repeated unnecessarily. Take the time to perform interoperability testing between systems and read the translator manuals that came with your system to learn the recommended settings for those translators; again, you may be surprised at how many times the answer is as simple as adjusting these settings.

Correct settings should be covered in your user's manual, but be warned-documentation from vendors can run the full range in terms of completeness. Some devote a good deal of detail to the function of each setting on the translator, while others barely mention it at all. So in order to get those settings, you may have to make a phone call to your vendor.

Healing Files
There are several software tools designed to fix faulty CAD models for downstream users. ITI's offering, called CADfix, analyzes the data and highlights problem areas. These problems may be corrected automatically or fixed manually. The software also allows users to import one type of file, IGES for example, repair the model, then output a Parasolid, ACIS, ANSYS, STL, STEP, or other type of file.

This feature is valuable for downstream organizations working with a variety of customers, suppliers, and software packages. CADfix offers these users the ability to "heal" and repair these models to the extent that they can use them in their own internal systems-whether it means getting rid of duplicate points and edges or tightening up a series of surfaces so that they can be stitched into a solid.

Caley, who uses this package in helping his customers, believes the level of automation is the key. "The CADfix Wizard seeks out problem areas, then applies intelligent fixes automatically, all within safe tolerances that the user can control," he explains. "It also provides interactive tools to evaluate and repair IGES files at a part modeling level. The user works with points, edges, faces, surfaces, and solid bodies, not lines of ASCII code from IGES files."

Contact Information
International TechneGroupMilford, OH
Robert Farrell
Phone: (513) 576-3845,
Fax: (513) 576-3994
Web: www.cadfix.com

Sign up for the PlasticsToday NewsFeed newsletter.

You May Also Like