SNS COLLEGE OF ENGINEERING (An Autonomous Institution)

Department of Mechanical Engineering

ME8691 AIDED DESIGN AND MANUFACTURING

ME8691/CADM/BALAMURALI.B/AP/MECH 1 UNIT - 3 CAD STANDARD Topics Covered

• Standards For Computer Graphics • (GKS) • Standards For Exchange Images • Open Graphics Library (Opengl) • Data Exchange Standards • IGES, STEP, CALS

ME8691/CADM/BALAMURALI.B/AP/MECH 2 Standards For Computer Graphics

• A set of guidelines for the way Computer-aided design (CAD) drawings should appear, to improve productivity and interchange of CAD documents between different offices and CAD programs, especially in architecture and engineering.

• Need for graphic standards Need for portability of the geometric model among different hardware platforms.  Exchange drawing database among software packages.  Need for exchanging graphic data between different computer system.  Need for the requirement of graphic data exchange formats and their details such as IGES ,DXF,STEP

ME8691/CADM/BALAMURALI.B/AP/MECH 3 Graphics Standards

ME8691/CADM/BALAMURALI.B/AP/MECH 4 Graphical Kernel System (GKS)

• GKS is basically a set of procedure which can be called by user programs to carry out certain generalized functions such as arc,circle,ellipse etc. • It is a standardized system of graphical functions for processing graphical data to create and process 2D images. • GSK implementations have been made by many hardware manufactures in many languages.

ME8691/CADM/BALAMURALI.B/AP/MECH 5 Features of GKS

• It is an independent device ,it can work with all types of input and output devices. • All text and annotation can be prepared and stored in natural languages. • Graphic functions are defined for both 2D and 3D • GKS defines an international coordinate system called normalized device coordinate system .

ME8691/CADM/BALAMURALI.B/AP/MECH 6 Standards For Exchange Images

ME8691/CADM/BALAMURALI.B/AP/MECH 7 Open Graphics Library (Opengl)

ME8691/CADM/BALAMURALI.B/AP/MECH 8 Data Exchange Standards

• The goal was to define a standard to cover all aspects of a product (i.e. geometry, topology, tolerances, materials, etc.), during its lifetime. • Fundamental difference in IGES and STEP. • The central unit of data exchange in the IGES model is the entity. • The central unit of data exchange in the STEP model is the application, which contains various types of entities. • Data is exchanged between systems it is done in terms of application units.

ME8691/CADM/BALAMURALI.B/AP/MECH 9 IGES, STEP, CALS

• Codes a superset of common entities of all CAD/CAM systems to facilitate the translation between various systems.

ME8691/CADM/BALAMURALI.B/AP/MECH 10 IGES File structure Flag section • Used only with the compressed ASCII and binary format • IGES data in a file can be represented in two formats ASCII and binary • ASCII - American Standard Code for Information Interchange. • ASCII format comprises two types : fixed 80- character record length and compressed format . • Compressed format contains compressed file by eliminating spaces from the records.

Start section • Provides a human –readable description of the file, such as the sending system that generated the original data, the pre-processor ,and the product being described.

11 ME8691/CADM/BALAMURALI.B/AP/MECH Directory Entry section • Is a list of all the entities together with Global section certain of their attributes. • Included information telling the pre- • All product definition data are expressed processor and as a list of predefined entities (geometry information needed by the post –processor and annotation entitles ) . to interpret the • Entry each entity occupies two 80 – files. character records that are divide into a total • Some item specified example : the data of twenty 8-character fields . and time of the file generation . • First and the eleventh field contains entity type number . • Second field contains pointer to the Parameter data entry for the entity in the parameter data section. • Remain entity will contain (line fonts ,layer number, transformation matrix )

ME8691/CADM/BALAMURALI.B/AP/MECH 12 Parameter data section • Section contains the actual data defining each entity listed in the Terminate data section directory entry section . • Section contains a single record which • Example: straight line entity is defined specifies the number of records in each by the 6 coordinates its two end points . of the four preceding sections for • Each entity always has two records in checking purpose the directory entry section and number of records need for each entity in the parameter data section. • Parameter data is placed in free format of columns 1 through 64. • Column 65 left blank. • Columns 66 to 72 on all parameter data records contain the entity pointer specified in the first record of the entity in the data entry section

ME8691/CADM/BALAMURALI.B/AP/MECH 13 Continuous acquisition and life –cycle support (CALS). • It was developed by US department of defense. • It prescribes the formats for storage and exchange of technical data. • Focuses mainly technical publications

Important CALS standards

1.Standard generalized markup language (SGML) is an important standard developed ibn 1960s IBM . It has the document description language.

2.Computer graphics metafile (CGM) is next important standard .developed in 1986 it is used for the vector file format for illustrations and drawings.

ME8691/CADM/BALAMURALI.B/AP/MECH 14 STEP • STEP (Standard for the Exchange of Product model data) is a new International Standard (ISO 10303) for representing and exchanging product model information. • Support any industrial application such as mechanical, , plant design, and architecture and engineering construction. • To include all four types of data which is relevant to the entire life- cycle of a product: design, analysis, manufacturing, quality assurance, testing, support, etc.

Three layers of STEP • Application layer –consist of information of various application areas. • Logical layer-provide a consistent , computer-independent description of the data constructs that contain information to be exchanged. • Physical layer –deals with the data structures and data format for exchange file itself. • EXPRESS is a formal data specification language used to specify the representation of product information.

ME8691/CADM/BALAMURALI.B/AP/MECH 15 Thank you

ME8691/CADM/BALAMURALI.B/AP/MECH 16