Data Exchange Between CAD/CAM Systems
Why do we need Data Exchange? • Design projects require data to be shared between suppliers • Different companies often used different CAD systems • All CAD systems have their own database formats • They are mostly proprietary and often confidential • Data is stored in different ways e.g. 1.0,2.0,3.0 or X1.0,Y2.0,Z3.0, etc. • Data conversion between systems becomes necessary
Alternative approaches System B
System A Future System System C
Number of Direct translators = 2 (N-1)
N e u t r a l f o r m a t
Data Exchange Formats • IGES (Initial Graphics Exchange Specification) •1980 US NIST, National Institute of Standards and Technology • DXF • VDA – German Automotive Industry • SET – Airbus • PDES – American fore-runner of STEP • STEP • STL • VRML
3D - IGES â€˘ The Initial Graphic Exchange Specification (IGES) format, is the most used neutral format to transfer data between heterogeneous CAD systems. â€˘ Users can perform bi-directional data exchange between dissimilar systems with direct and automated access to IGES files.
IGES file structure •
Start section –
Global section –
Data index and data attribution
Parameter Data Section –
System environment information
Directory Entry section –
Comment, filename, data name, etc
Real data value(coordinate, parameter value)
2D - DXF/DWG â€˘ DXF/DWG : DXF formats were developed by AutoDesk. â€˘ After creating drawings, designers can export data in DXF/DWG formatted files and import the 2D geometric data contained in a DXF/DWG file into other drawing tools.
DXF File Structure • • • •
Header Section Tables Section Block Section Entities Section
STL • STL format was developed by 3D Systems as a neutral format to input geometric data into their 3D printing systems • It represents the geometry as a series of triangular facets • It is now being used for other purposes besides 3D printing • It is simple to create but has little overall structure
VRML • VRML (Virtual Reality Modeling Language) format is also a facetted format • It can represents other aspects besides geometry, e.g. colour • It is widely used for graphics visualisation purposes
STEP • STEP AP203 / AP214 format (Standard for the Exchange of Product model data) • It supports geometry and assembly structures and handles topology (shells, solids) on export and import. • STEP files are human readable • Other STEP APs are available, e.g. electronics data
Questions to Ask about Data Exchange • Who is the data for? • What level of data is required (2D/3D, solids/surfaces)? • What will the data be used for? • How long will the data be kept?