DATA EXCHANGE FORMAT IGES

DATA EXCHANGE FORMATIGES 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 • 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 post-processor 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.) IGES CAD CAD Pre Processor Post Processor Pre Processor 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 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).

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 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 Table1 : List of Entities

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 • 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 http://link.springer.com/chapter/10.1007/978-3-642-45114-0_13. http://link.springer.com/chapter/10.1007/978-0-387-23324-6_6. https://filemonger.com/specs/igs/devdept.com/version6.pdf. http://en.wikipedia.org/wiki/IGES. http://www.researchgate.net/publication/. http://download.autodesk.com/us/algor/userguides/mergedProjects/Opening_Models/IGES_Entities_Supported.htm.

Thank you

DATA EXCHANGE FORMAT IGES