IGES (Initial Graphics Exchange Specification)

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Introduction

**IGES (Initial Graphics Exchange Specification) **is an intermediate file format for exchanging geometric data such as drawings and 3D models between CAD (Computer-Aided Design) systems. It was established by the American National Standards Institute (ANSI) in 1980 with the aim of ensuring compatibility between different CAD software. It has been widely used as a standard format for sharing and reusing design data of parts and structures between vendors, especially in the manufacturing and mechanical design industries.

Data Format Overview

IGES files are basically ASCII text files and consist of the following five sections:

Start Section

Comments including information about the file creator and CAD system

Global Section

Unit system (mm, inch, etc.), date, format version, etc.

Directory Entry Section

Overview information about the entity (type, attributes, hierarchy information, etc.)

Parameter Data Section

Details of the actual shape, dimensions, and geometry data

Terminate Section

Section indicating the end of the file

Pros

High compatibility: Can be read and written by many CAD software
**Open specifications: **Specifications are publicly available, allowing developers to implement them
**Long track record: **Widely used since the 1980s, highly reliable
**Supports a variety of data formats: **Supports a variety of entities including 2D, 3D, and annotations

Cons

Not suitable for solid modeling: As an intermediate file, it only covers surfaces, and volume information is incomplete.
Old format: Outdated compared to STEP and other new XML-based formats.
**Interoperability issues: **Complete conversion between CAD models may not be guaranteed (shape distortion and missing attributes).
File sizes tend to be large: Data tends to become redundant.

Application Scenario

IGES has been used extensively in the manufacturing industry and in the fields of mechanical and automotive design. For example, IGES has served as a “common language” for the exchange of product design data between companies using different CAD systems due to its high compatibility. The IGES format is also used to share design data with external parties in the early stages of 3D printing and when migrating design assets from legacy CAD systems to new environments. It has also been used as a bridge to CAE (numerical analysis) and CAM (manufacturing and processing), and has played an important role as an intermediate medium to facilitate a series of data exchanges from design to analysis and processing.