CAD data exchange
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CAD data exchange involves a number of software technologies and methods to translate data from one Computer-aided design system to another CAD file format. This PLM technology is required to facilitate collaborative work (CPD) between OEMs and their suppliers.
The main topic is with the translation of geometry (wireframe, surface and solid) but also of importance is other data such as attributes; metadata, assembly structure and feature data.
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[edit] Methods of translation
There are basically three methods of transferring data from one CAD system to another.
- Direct CAD system export/import
- Direct 3rd party translators.
- Intermediate data exchange formats
[edit] Direct internal
Some CAD systems can directly read and/or write other CAD formats, simply by using file open and file save as options. As most CAD file formats are not open, this option is limited to either systems owned by the same company or via hacking of competitor's file format.
[edit] Direct external
There are a number of companies that specialise in CAD data translation software, providing software that can read one system and write the information in another CAD system format. These systems have their own preparatory intermediate format some of which will allow reviewing the data during translation. Some of these translators work stand-alone while others require one or both of the CAD packages installed on the translation machine as they use code (APIs) from these systems to read/write the data.
[edit] Data translation formats
A common method of translation is via an intermediary format. The sending CAD system exports out to this format and the receiving CAD system reads in this format. Some formats are independent of the CAD vendors being defined by standards organisations while others, although owned by a company, are widely used and are regarded as quasi industry standards. Example formats
[edit] Level of information detail translated.
As each CAD system has its own method of describing geometry, both mathematically and structurally, there is always some loss of information when translating data from one CAD data format to another. The intermediate file formats are also limited in what they can describe, and they can be interpreted differently by both the sending and receiving systems.
It is therefore important when transferring data between systems to identify what needs to be translated.
If only the 3D model is required for the downstream process, then only the model description needs to be transferred. However, there are levels of detail. For example: is the data wireframe, surface, or solid; is the topology (BREP) information required; must the face and edge identifications be preserved on subsequent modification; must the feature information and history be preserved between systems; and is PMI annotation to be transferred.
With product models, retaining the assembly structure may be required.
If drawings need to be translated, the wireframe geometry is normally not an issue; however text, dimensions and other annotation can be an issue, particularly fonts and formats.
No matter what data is to be translated, there is also a need to preserve attributes (such as color and layer of graphical objects) and text information stored within the files.
Some translation methods are more successful than others at translating data between CAD systems.
