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DATA EXCHANGE FORMAT IGES. A presentation by Mahesh Babu Gajula (206516) Data Management for Engineering Applications. 23-06-2014. Overview. Data Exchange in IGES History File structure IGES File Samples IGES Entities Structure Start Global Data Entry Parameter Data

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data exchange format iges


A presentation by

Mahesh Babu Gajula(206516) Data Management for Engineering Applications


  • Data Exchange in IGES
  • History
  • File structure
  • IGES File
    • Samples
  • IGES Entities
  • Structure
    • Start
    • Global
    • Data Entry
    • Parameter Data
    • Terminate
  • Advantages
  • Disadvantages
  • References
data exchange in iges
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
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 post-processor outputs the file into standard.
  • Number of two-way translators needed for n CAD systems to exchange data among them.


data exchange in iges contd1
Data Exchange in IGES(Contd.)




Pre Processor

Post Processor

Pre Processor

Post Processor

Figure 2. CAD data exchange

  • 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

All geometric entries are given here

2)Table 2 specifications of the IGES file

file structure contd

The file is divided into 5 sections:

  • 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).
output of above 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
Output of Above file(Contd.)
  • The above drawingcontains 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
IGES entities specification

Table1 : List of Entities

start section
Start section
  • Human readable introduction to the file.
  • Described as a “prologue” to the IGES file.
      • 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.
  • Global Section
directory entry section
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
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
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
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
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
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.