This document discusses CAD/CAM data exchange standards and interfaces. It describes four key types of product data that must be exchanged - shape, non-shape, design, and manufacturing data. It outlines requirements for a standard interface, including handling all data types, avoiding information loss, and being adaptable. Common neutral file formats are described - IGES, DXF, STL, and STEP. STEP sections like header, data, and terminate are summarized. The IGES process and DXF sections are outlined briefly. Clipping in CAD is also discussed, along with point, line, area, curve, and text clipping. Common clipping algorithms like Cohen-Sutherland and Sutherland-Hodgeman are mentioned.

1. CAD/CAM
DATA EXCHANGE

3. Interface
An interface can be regarded as an collective
of conditions, rules and conventions which
describes the information exchange, between
two communicating objects.

4. The complete product description of product
consists of 4 types of data.
1. Shape data : geometry & topology info.
2. Non-shape data : shaded images, measuring units.
3. Design data : volume , area, mass etc..;
4. Manufacturing data : tolerances, process planning

6. Requirements for Standard Interface
• The interface must be capable of handling all kinds of
manufacturing data.
• There should be no information loss when data is transferred
between heterogeneous systems.
• The system must be capable of handling the real time
requirements of a manufacturing system efficiently and
effectively.
• The system should be open-ended to permit extensions or
contractions.
• The system should be adaptable to other standards.
• The system must be independent of the computer and
communication architecture used.
• The systems should be capable of handling maximum number
of data entities. Ideally, there should not be any limitation

7. • It must be possible to form application-
oriented subsets of the standard to reduce cost
and overheads.
• The system should be capable of achieving
production data.
• The interface must be upward and downward-
compatible in a hierarchical control structure.
• Test procedure must be provided to verify the
efficiency and accuracy of data transmission.

8. To exchange data, there are two approaches:
1. Direct
2. Indirect

12. STANDARD NEUTRAL FILE FORMATS
1. IGES (Initial Graphics Exchange Specification)
2. DXF (Drawing Exchange Format)
3. STL (Standard Triangular Language)
4. STEP (Standard For Exchange of Product Data)

14. STEP

21. STEP (Standard For Exchange of Product Data)
 HEADER:
 Mandatory, non-repeatable section. Must contain one
instance of each of the following entities:
1. file description,
2. filename,
3. file schema, and they shall appear in that order.
4. Optional entities include schema population, file
population, section language, and section context

22.  ANCHOR; Optional, non-repeatable section. Introduced in
2016 version. The anchor section defines external names for
instances in the exchange structure so that they can be
referenced. Anchors can be associated with entities, values,
and other items in the exchange structure.

23. 3. REFERENCE; Optional, non-repeatable section.
Introduced in 2016 version. Each entry in the
reference section shall associate an entity instance
name (e.g., #10) or value instance name (e.g., @70)
with an entity or a value.

24. 4. DATA; mandatory, repeatable section. The DATA sections
contain the core content of the model instance. If an exchange
structure contains more than one DATA section, each
"DATA" keyword shall be followed by a parenthesized list
containing a name for this DATA section and a single schema
name that governs the content of this section. Following these
parameters come a sequence of entity instances, with each
entity having a unique name in the form of "#" followed by a
sequence of digits.

25. 4. SIGNATURE; Optional, repeatable section. Introduced in
2016 version. Holds a digital signature to permit verification
that the file content before the SIGNATURE section has not
been corrupted and to validate the credentials of the signer.
Follows the "END-ISO-10303-21;" terminator.

26. IGES PROCESS

31. • Flag section: The Flag section is used only
with the compressed ASCII and binary
formats. The ASCII format comprises two
types: a fixed 80-character record length and a
compressed form. The compressed form is
simply an ASCII file compressed by
eliminating spaces from the records.
• Start section: The Start section provides a
human-readable description of the file, such as
the system that generated the original data,
comments, and annotations.

32. • Global section: The Global section includes
information describing the pre-processor and
information needed by the post-processor to
interpret the file. Some of the items specified
in this section are

33. • Directory Entry Section: It includes the number of
entities, type of entities and their attributes,
which are used to create the model. The
attributes are color ,style etc.
• Parameter Data Section: It includes the data
required to describe each entity such as point
coordinates, coefficient of curves and surface
equation text types and characteristics.
• Terminate section: It is a single record of ten 8-
character fields. These characters contain
information of the end of the previous sections.
This is used at the end of the file.

34. Drawing interchange format (DXF)
• Drawing interchange format (DXF) files were
originally developed to give users flexibility in
managing data and translating AutoCAD'
drawings into file formats that could be read and
used by other CAD/CAM/CAE systems.
• Because of the popularity of AutoCAD, DXF
became the standard of interchanging CAD
drawing files for almost all CAD/CAM/CAE
systems. In fact, almost every newly introduced
CAD/CAM/CAE system tends to provide
translators to and from the DXF file.

35. • Header Section -Includes general information about the
drawing.
• Classes section- Class section contains the information for
application-defined classes whose instances appear in the
BLOCKS, ENTITIES, and OBJECTS sections of the database.
• Table section- Includes definitions of various items such as
line type ,layers ,tables, coordinate system view port
parameters , text style etc.
• Block section -Includes definitions of the block and its
comprising entities were included in this section.
• Entities section- Includes drawing entities along with its
related properties
• End section- Includes information about the end of the file.

36. Clipping

39. Need of Clipping
1. Drawing and painting operations that allow parts
of a picture to be selected for copying, moving,
erasing, or duplicating.
2. Extracting part of a defined scene for viewing
3. Analyzing line segments or object boundaries

40. Types of clipping
1. Point Clipping
2. Line Clipping
3. Area Clipping (polygons)
4. Curve Clipping
5. Text Clipping

41. 1. Cohen Sutherland Line Clipping Algorithm
2. Sutherland Hodgeman Polygon Clipping

42. Region code (ABRL)

44. THE END

45. THE END