DATA EXCHANGE FORMAT
IGES
A presentation by
Mahesh Babu Gajula
(206516)
Data Management for Engineering Applications
23-06-2014
Overview
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Data Exchange in IGES
History
File structure
IGES File
– Samples
• IGES Entities
• Structure
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Start
Global
Data Entry
Parameter Data
Terminate
• Advantages
• Disadvantages
• References
Data Exchange in IGES
• IGES stands for International (originally ‘Initial’)
Graphics Exchange Standards and a neutral data
format that allows the digital exchange of information
among CAD systems.
Figure 1. Data exchange using neutral file
Data Exchange in IGES(Contd.)
• When this neutral file is used, each CAD system
needs only one pre-processor and one
postprocessor which form one set of translators .
• Figure 2 illustrates the way the pre-processor
imports the data into the system and the postprocessor outputs the file into standard.
• Number of two-way translators needed for n
CAD systems to exchange data among them.
N=c(n/2)=n!/2!(n-2)!
Data Exchange in IGES(Contd.)
Post Processor
CAD
Pre Processor
Pre Processor
IGES
CAD
Post Processor
Figure 2. CAD data exchange
History
• The Initial Graphics Exchange Specification
(IGES) (pronounced eye-jess) is a file format which
defines a vendor neutral data format that allows
the digital exchange of information among computer
aided design (CAD) systems.
• First developed by National Institute of Standards
and Technology (NIST) in 1980.
History(Contd.)
• IGES version 1.0 was developed in January
1980 mean for two dimensional and three
dimensional mechanical drawings.
• Then adopted by the American National
Standards Institute (ANSI) in 1981 year,which
it is used for communicating product
definition data.
IGES MODEL DRAWINGS
Skull model
IGES model of a car
FILE STRUCTURE
Start section
Global section
Directory entry section (DE)
Parameter data section(PD)
Terminate section
2)Table 2 specifications of the IGES file
All geometric entries
are given here
FILE STRUCTURE(Contd.)
The file is divided into 5 sections:
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Start
S
Global
G
Directory Entry
D
Parameter Data
P
Terminate
T
The above characters are listed in Column 73.
Characteristics and geometric information for an entity is
split between two sections;
– Two record, fixed-length format (the Directory Entry, or DE
Section).
– Multiple record, comma delimited format (the Parameter Data, or
PD Section).
IGES FILE
Output of Above file
When displayed, the user should see:
• 2 Yellow points.
– (Hard to see on a white background, but most CAD systems use a
black background).
• 2 Red circular arcs
• 2 Green lines.
Output of Above file(Contd.)
•The above drawing contains only two POINTS (Type 116), two CIRCULAR ARC (Type
100), and two LINE (Type 110) entities. It represents a slot, with the points at the
centres of the two half-circles that form the ends of the slot, and the two lines that
form the sides.
IGES entities specification
Table1 : List of Entities
Start section
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Human readable introduction to the file.
Described as a “prologue” to the IGES file.
Global Section
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Characters used as delimiters between individual entries and between records (usually
commas and semicolons respectively),
The name of the IGES file itself,
Vendor and software version of sending (source) system,
Number of significant digits in the representation of integers and
single and double precision floating point numbers on the sending
systems,
Date and time of file generation,
Model space scale,
Model units,
Minimum resolution and maximum coordinate values,
Name of the author of IGES file.
Directory Entry Section
• List of all entities in IGES file with certain attributes with
them.
• The entry for each entity occupies two 80-character records.
– Divided into a total of twenty 8-character fields .
• The first and eleventh(beginning of the second record of any
given entity) fields contains the entity type number
– Such as 100 for circle ,110 for line etc.
• The second field contains a pointer to the parameter data
entry for the entity in the PD section.
Parameter data section
• Contains the actual data defining each entity listed in
the DE section.
• Each entity has always two records in the DE section.
• The number of records required for each entity
varies from one entity to another
– (the minimum is one record) and depends on the amount
of data.
• Parameter data are placed in free format in columns
1 through 64.
Parameter data section(Contd.)
• The parameter delimiter (usually a comma).
– To separate parameters
• The record delimiter (usually a semicolon).
– To terminate the list of parameters.
• Both delimiters are specified in the Global section
of the IGES file. Column 65 is left blank.
• Columns 66 through 72 on all PD records contain the
entity pointer specified in the first record of the
entity in the DE section.
Terminate Section
• The Terminate section contains a single record that
specifies the number of records in each of the four
preceding sections for checking purposes.
Advantages of IGES
• Product data exchange among different CAD/CAM
systems are even animation and documentation
software are of great importance to computer –
integrated manufacturing(CIM) .
• The sharing of data is also key successful
development to he concurrent engineering.
• IGES also educes lead time of product development.
• Due to the large variety of CAD systems in the market
,design data exchange among different CAD systems
is indispensable.
Disadvantages of IGES
• IGES file does not have a formal information model.
• Problems occur during file exchanges and
manipulations .
• Hard to understand file formats.
• IGES does not support life cycle information which
may be relevant for engineering applications other
than design.
References
1) http://link.springer.com/chapter/10.1007/97
8-3-642-45114-0_13.
2) http://link.springer.com/chapter/10.1007/97
8-0-387-23324-6_6.
3) https://filemonger.com/specs/igs/devdept.co
m/version6.pdf.
4) http://en.wikipedia.org/wiki/IGES.
5) http://www.researchgate.net/publication/.
6) http://download.autodesk.com/us/algor/user
guides/mergedProjects/Opening_Models/IGE
S_Entities_Supported.htm.
Thank you