The document discusses the need for data exchange standards in CAD/CAM systems to facilitate effective communication of design and manufacturing data among various organizations. Traditionally, software incompatibilities hindered data sharing, prompting the development of neutral file formats like IGES and STEP to enable interoperability among different CAD/CAM systems. It emphasizes the importance of these standards in the evolving manufacturing landscape where multiple parties must collaborate on product design.

1. IPE-409 CAD/CAM
Dr. Nafis Ahmad
Professor
Department of IPE, BUET
Email:nafis@ipe.buet.ac.bd

2. Ch#7.
Data Exchange Standards
2

3. Reference books:
• CADCAM Principles, practice and manufacturing
management-
• Chris McMohan and Jimmie Browne
• CAD/CAM Theory and Practice
• Ibrahim Zeid

4. Introduction
• A critical concern of CAD and CAM is the
communication of design and manufacturing data
within an engineering organization and indeed
between those organizations involved in the
manufacturing of a product.
• Earlier software and hardware were incompatible
with each other.
• Each system vendor used a unique data structure
• Divergence in data formats had the effect of tying
companies to particular CAD/CAM systems, other
vendors found themselves constrained.
• The wish to improve the accessibility of computer
languages led early on to the establishment of
standards for these

5. Introduction

6. Introduction

7. Data Exchange standards
• Application of CAD has been accompanied both by growth
in product variety and a broadening of the range of
companies involved in the design of a particular product.
• Traditionally car companies designed almost all parts.
Now the trend is to delegate design authority to the
suppliers.
• As a result thousands of parties need to share their design
information with others.
• To support this process, a great deal of design data has
to be exchanged between various companies.
• In order to accomplish this transfer quickly and accurately,
CAD systems employed by various manufacturers should
be capable of exchanging data with each other.

8. Data Exchange standards
• The easiest way is to use the same
CADCAM software operating at the
same level.
• Large manufacturers put pressure on
their suppliers to adopt the same
system as themselves.
• But a more equitable solution is for
the various CADCAM systems in the
market to be able to exchange data
with each other.
• Earlier converters were used. As the
number of CADCAM system
increases, this approach became
impractical.
• The solution is to effect the data
exchange by first into a neutral
format and then from the neutral
format to another target system data
structure.

9. Data Exchange standards
• The neutral file solution is easier said than done.
• International manufacturing environment.
• Wide variety of CAD: 2D, 3D-wireframe, surface and solid; order
of polynomial
• Still there are some effort since 1970s
• Initial Graphics Exchange Specification (IGES)-US
originated
• Due to vagueness and lack of willingness for full
implementation prompted French company to use
SET(Standard Exchange Transfer)
• To accommodate solid modelling data Experimental
Boundary File (XBF) and eventually merged with IGES
as Experimental Solid Proposal (ESP)
• Around 1989 ISO introduced STEP ( Standard for the
Exchange of Product Model Data) which uses a formal
model for the data exchange called EXPRESS

10. Data Exchange standards
• EXPRESS language is human readable and computer
processable.

11. Neutral Format Examples
IGES
Sections:
1. Start section-manually entered by creator to assist end user.
2. Global Section -parameters necessary to translate the file
3. Directory Section -entry for each entity and it’s associated with
the code representing the entity
4. Parameter Data Section -Entity specific data like coordinates
etc.
5. Termination Section -Marks the end of the data

13. Neutral Format Examples
DXF
Sections:
• HEADER section-AudoCAD system variables
• TABLES Section-Line styles, user coordinate system etc.
• BLOCKS Section- Definitions of block instances in the model
• ENTITIES Data Section-Entity specific data like coordinates etc.

14. Neutral Format Examples
DXF

15. Neutral Format Examples
DXF

16. 16
Thanks!
Any questions?
You can find me at: https//ahmadn.info
Twitter@ahmadn
Email:nafis@ipe.buet.ac.bd