Data Exchange Between CAD/CAM Systems

• 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

Why do we need Data Exchange?

Number of Direct translators = 2 (N-1)

Alternative approaches

System A

System D System C

System B

Future System

Neutral

format

Alternative approaches

System A

System D System C

System B

Future System

• 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

Data Exchange Formats

3D - IGES • The Initial Graphic Exchange Specification

(IGES) format, is the most used neutral format to transfer data between heterogeneous CAD systems.

• Users can perform bi-directional data exchange between dissimilar systems with direct and automated access to IGES files.

IGES file structure

• Start section – Comment, filename, data name, etc

• Global section – System environment information

• Directory Entry section – Data index and data attribution

• Parameter Data Section – Real data value(coordinate, parameter value)

• Terminate Section

2D - DXF/DWG

• DXF/DWG : DXF formats were developed by AutoDesk.

• 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

• 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?

Questions to Ask about Data Exchange