Is it likely that a unified CAD format will emerge?

Published by - Admin On September 10, 2014

Most well-known CAD and CAE design software have their own proprietary formats, and they also support the most popular CAD formats. Furthermore, many of the well-known CAD design software provide built-in translators for converting less well-known CAD formats into their proprietary formats.

Obviously, the purpose of proprietary formats is to hide CAD design details from competitors. Therefore, many less well-known CAD design software have difficulty in CAD file exchange, and must rely on third party translators for file conversion.

The purpose of this article is to determine whether the evolution of one universally adopted CAD format could emerge, or whether one universally recognized translator could emerge.

What are the main reasons why CAD formats differ?

Modern CAD software is complex because it provides many design features. Because of the complexity, the corresponding file system is proportionally complex. The complexity cannot be avoided if all different details in a design should be stored in a form which can be recalled. For example, boundaries or geometrical shapes and colors of an object should be stored, and should be easy to retrieve.

Because CAD formats evolve as the software is developed or created, many software developers find it necessary to create a proprietary CAD format which is compatible with the design features provided by the software. Major CAD systems enable data exchange by either writing to other CAD formats or by providing translators for different CAD formats. Many other CAD systems rely on third-party translators.

In spite of the necessity to have proprietary CAD formats, there are known neutral CAD formats which try to store and extract all essential geometry, color and design information from a file.

Because it is impractical to list all CAD file formats in this article, we shall list 3 well-known neutral formats, 3 proprietary formats, and 3 translators.

Well-known neutral file formats include:

IGES, proposed by ANSI/ASME (American National Standards Institute, American Society of Mechanical Engineers),
STEP, proposed by ISO (International Organization for Standardization),
VRML, proposed by Web3D, ISO.

These formats can capture geometry, part(s), bill of materials, and colors into a design file.

Well-known proprietary file formats include:

Inventor, owned by Autodesk®,
CATIA, owned by Dassault Systems®,
Solidworks, owned by DS Solidworks®.

These formats can capture geometry, multiple parts, bill of materials, and colors into a design file.

Some translators operate as standalone translators. They can read information from one CAD file system and write the information into another CAD file system. Such translators have their own intermediate file system for reviewing, filtering and analyzing the information, before writing it to another file system. Other translators work as intermediaries between two CAD systems. The translators utilize APIs (Application Programming Interface) provided by the two CAD systems for information acquisition, processing, and transmission.

Well-known CAD translators include

CADverter, provided by Theorem Solutions®,
capvidia, provided by Capvidia®,
DXF-DWG, provided by Graphisoft®.

Translators have limitations.

Each CAD system has its own method for describing geometry. Because the method could be mathematical or structural, there could be loss of information when translating data from one CAD format to another.
Intermediate file formats are limited in what they can describe. Therefore, the information exchanged between two CAD systems may not be 100% correct.
Levels of detail may be difficult to preserve. Examples are (a) wireframe, surface, or solid data, (b) topology such as face or edge identifications which may change between modifications, (c) preservation of feature and information history, and (d) PMI (Product and Manufacturing Information) annotation.

What will be the challenges in creating a unified CAD format?

It has been explained that it is necessary for many CAD systems to utilize proprietary CAD formats which are compatible with the design features provided by the software. Therefore, a universally adopted CAD format must overcome several challenges in order to integrate myriads of CAD formats into one format. It will be necessary to create a consortium or committee to supervise the creation of a unified CAD format. Such a unified CAD format should satisfy certain conditions:

Distinguish between vector and bitmap formats. Because bitmaps have their own file systems, it is not necessary for a unified CAD format to recreate bitmaps.
Distinguish between 2D and 3D formats.
A unified CAD format should distinguish between grayscale and color coded drawings.
Cater to different methods for representing geometric shapes. For example, one CAD system may represent a circle in 2D by exercising a mathematical formula which requires that coordinates of the center of the circle and its radius should be provided. Another CAD system may require that a circle in 2D should be represented by connected arc segments. Likewise, a sphere may be represented mathematically, or by connected surface segments.
Should be able to incorporate manufacturing information, when the input file format provides the information.
Should be able to filter the input information, perform necessary analysis and calculations, and write the information to a specified output format. Because there are so many different file formats, a committee should set guidelines for supporting output file formats.

This list of conditions specified for a unified CAD format is not exhaustive. However, it provides a flavor for the requirements and conditions that a committee should develop.

Furthermore, dedicated software development and support teams will be required to maintain the unified CAD format and to keep it current or up to date.