CAD data exchange
Encyclopedia
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 OEM
s 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.
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. It is becoming increasingly common for companies owning these quasi industry standards to further the use of their formats by openly publishing these data formats.
Example formats:
A number of CAD data exchange methods are described by recent academic studies. The neutral modeling command (NMC) method, proposed by Zhejiang University
, is an example of these methods.
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.
Sometimes, however, there is a problem caused by too much information being preserved. An example are the constraints placed on designers arising out of the design intent-history captured in parametric design systems. The receiving system must provide designers with the design freedom to modify geometry without having to understand the history of, or undo, the design tree.
Some translation methods are more successful than others at translating data between CAD systems.
The ability to visualize medium if not large scale assemblies was one of the early successes of these CAD translation formats. Hardware improvements and the development of lightweight formats supported larger scale assemblies.
Current advances now allow an “Active Mockup.” This technology allows design in context with simulations such as dynamic clearance analysis and automatic generation of motion envelopes. Active mockups allow the edit of components from directly within the multi-CAD assembly. Multiple level-of-detail displays support interactive performance even in huge assemblies.
In a true PLM environment, CAD to CAM data exchange must provide for more than the transfer of geometry. Product Manufacturing Information
, whether generated by the designer for use by manufacturing, or generated by the manufacturing organization for use by design, must be a part of the data exchange system. STEP-NC
was designed to carry GD&T and other PMI through CAD and CAM into a CNC.
Computer-aided design
Computer-aided design , also known as computer-aided design and drafting , is the use of computer technology for the process of design and design-documentation. Computer Aided Drafting describes the process of drafting with a computer...
system to another CAD file format. This PLM
Product lifecycle management
In industry, product lifecycle management is the process of managing the entire lifecycle of a product from its conception, through design and manufacture, to service and disposal...
technology is required to facilitate collaborative work (CPD
Collaborative Product Development
Collaborative product development is a business strategy, work process and collection of software applications that facilitates different organizations to work together on the development of a product...
) between OEM
Original Equipment Manufacturer
An original equipment manufacturer, or OEM, manufactures products or components that are purchased by a company and retailed under that purchasing company's brand name. OEM refers to the company that originally manufactured the product. When referring to automotive parts, OEM designates a...
s and their suppliers.
The main topic is with the translation of geometry (wireframe
Wire frame model
A wire frame model is a visual presentation of a three dimensional or physical object used in 3D computer graphics. It is created by specifying each edge of the physical object where two mathematically continuous smooth surfaces meet, or by connecting an object's constituent vertices using straight...
, surface
Freeform surface modelling
Freeform surface modelling is the art of engineering Freeform Surfaces with a CAD or CAID system.The technology has encompassed two main fields...
and solid) but also of importance is other data such as attributes; metadata
Metadata
The term metadata is an ambiguous term which is used for two fundamentally different concepts . Although the expression "data about data" is often used, it does not apply to both in the same way. Structural metadata, the design and specification of data structures, cannot be about data, because at...
, assembly structure
Assembly modelling
Assembly modelling is technology and methods used by computer-aided design and product visualization computer software systems to handle multiple files that represent components within a product. The components within an assembly are represented as solid or surface models.The designer generally has...
and feature data.
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
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.Direct external
There are a number of companies that specialize 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 proprietary 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.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. It is becoming increasingly common for companies owning these quasi industry standards to further the use of their formats by openly publishing these data formats.
Example formats:
- STEP – ISO 10303ISO 10303ISO 10303 is an ISO standard for the computer-interpretable representation and exchange of product manufacturing information. Its official title is: Automation systems and integration — Product data representation and exchange...
, a replacement for IGES and VDA-FS with the CAD specific parts:- STEP AP203 and AP214: Mechanical CAD systems
- STEP AP210: CAD systems for printed circuit boardPrinted circuit boardA printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board or etched wiring...
- STEP AP212: CAD systems for electrical installation and cable harnessCable HarnessA cable harness, also known as a wire harness, cable assembly, wiring assembly or wiring loom,is a string of cables and/or wires which transmit informational signals or operating currents...
- STEP-NC AP238: CAD, CAM, and CNC machining process informationSTEP-NCSTEP-NC is a machine tool control language that extends the ISO 10303 STEP standards with the machining model in ISO 14649, adding geometric dimension and tolerance data for inspection, and the STEP PDM model for integration into the wider enterprise...
- STEP AP242, Managed Model-Based 3D Engineering – the merging of the two leading STEP application protocols, AP 203 and AP 214
- IGESIGESThe Initial Graphics Exchange Specification is a file format which defines a vendor neutral data format that allows the digital exchange of information among Computer-aided design systems....
- VDA-FSVDA-FSVDA-FS is a CAD data exchange format for the transfer of surface models from one CAD system to another.Its name stands for "Verband der Automobilindustrie - Flächenschnittstelle", which translates to the "organization of the automotive industry - surface translation format".Standard was specified...
- DXFAutoCAD DXFAutoCAD DXF is a CAD data file format developed by Autodesk for enabling data interoperability between AutoCAD and other programs....
- Parasolid XTParasolidParasolid is a geometric modeling kernel originally developed by ShapeData, now owned by Siemens PLM Software , that can be licensed by other companies for use in their 3D computer graphics software products....
- JT OpenJT (visualization format)JT is a 3D data format developed by and is used for product visualization, collaboration, and CAD data exchange. It can contain any combination of approximate data, exact boundary representation surfaces , Product and Manufacturing Information , and Metadata either exported from the native CAD...
- DRG
A number of CAD data exchange methods are described by recent academic studies. The neutral modeling command (NMC) method, proposed by Zhejiang University
Zhejiang University
Zhejiang University , sometimes referred to as Zheda, is a national university in China. Founded in 1897, Zhejiang University is one of China's oldest institutions of higher education...
, is an example of these methods.
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
Boundary representation
In solid modeling and computer-aided design, boundary representation—often abbreviated as B-rep or BREP—is a method for representing shapes using the limits...
) 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
PMI
-Computer science:* Portable Management Interface, a platform-dependent interface defined by Sun Microsystems used in network management* pmi , a command line utility for power management...
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.
Sometimes, however, there is a problem caused by too much information being preserved. An example are the constraints placed on designers arising out of the design intent-history captured in parametric design systems. The receiving system must provide designers with the design freedom to modify geometry without having to understand the history of, or undo, the design tree.
Some translation methods are more successful than others at translating data between CAD systems.
MultiCAD Digital Mockups
Two CAD/CAM/CAE PLM trends have been driving CAD Data Exchange technology. One is the need for close interaction throughout today’s extended multiCAD enterprises. The other is the increased reliance on digital mockups to permit visualization, design in context, simulation and analysis of large scale assemblies prior to the actual manufacture of the physical product. Ongoing advances in data exchange technology have enabled significant fulfillment of those needs.The ability to visualize medium if not large scale assemblies was one of the early successes of these CAD translation formats. Hardware improvements and the development of lightweight formats supported larger scale assemblies.
Current advances now allow an “Active Mockup.” This technology allows design in context with simulations such as dynamic clearance analysis and automatic generation of motion envelopes. Active mockups allow the edit of components from directly within the multi-CAD assembly. Multiple level-of-detail displays support interactive performance even in huge assemblies.
CAD to CAM Data Exchange
NC programming typically requires that the geometry received from a CAD system, whether in wireframe, surface, solid or combined formats, be free from any irregularities and inconsistencies that may have occurred in the CAD phase of geometry creation. Data exchange from CAD to CAM must therefore include tools for identifying and repairing those inconsistencies. These tools are typically included in the data exchange software of each CAM solution-set.In a true PLM environment, CAD to CAM data exchange must provide for more than the transfer of geometry. Product Manufacturing Information
Product Manufacturing Information
Product and manufacturing information, also abbreviated PMI, conveys non-geometric attributes in 3D computer-aided design and Collaborative Product Development systems necessary for manufacturing product components or subsystems. PMI may include geometric dimensions and tolerances, 3D...
, whether generated by the designer for use by manufacturing, or generated by the manufacturing organization for use by design, must be a part of the data exchange system. STEP-NC
STEP-NC
STEP-NC is a machine tool control language that extends the ISO 10303 STEP standards with the machining model in ISO 14649, adding geometric dimension and tolerance data for inspection, and the STEP PDM model for integration into the wider enterprise...
was designed to carry GD&T and other PMI through CAD and CAM into a CNC.