Features of CAD Packages;
Computer-aided design (CAD) is
the use of computer systems to assist in the creation, modification, analysis,
or optimization of a design. CAD software is used to increase the productivity
of the designer, improve the quality of design, improve communications through
documentation, and to create a database for manufacturing. CAD output is often
in the form of electronic files for print, machining, or other manufacturing
operations.
Computer-aided design is used in
many fields. Its use in designing electronic systems is known as Electronic
Design Automation, or EDA. In mechanical design it is known as Mechanical
Design Automation (MDA) or computer-aided drafting (CAD), which includes the
process of creating a technical drawing with the use of computer software.
CAD software for mechanical
design uses either vector-based graphics to depict the objects of traditional
drafting, or may also produce raster graphics showing the overall appearance of
designed objects. However, it involves more than just shapes. As in the manual
drafting of technical and engineering drawings, the output of CAD must convey
information, such as materials, processes, dimensions, and tolerances,
according to application-specific conventions. CAD may be used to design curves
and figures in two-dimensional (2D) space; or curves, surfaces, and solids in
three-dimensional (3D) space.
·
CAD may be used to design curves and figures in
two-dimensional (2D) space; or curves, surfaces, and solids in
three-dimensional (3D) space.
·
CAD is an important industrial art extensively
used in many applications, including automotive, shipbuilding, and aerospace
industries, industrial and architectural design, prosthetics, and many more.
CAD is also widely used to produce computer animation for special effects in
movies, advertising and technical manuals, often called DCC digital content
creation. The modern ubiquity and power of computers means that even perfume
bottles and shampoo dispensers are designed using techniques unheard of by
engineers of the 1960s. Because of its enormous economic importance, CAD has
been a major driving force for research in computational geometry, computer
graphics (both hardware and software), and discrete differential geometry.
·
The design of geometric models for object shapes,
in particular, is occasionally called computer-aided geometric design (CAGD).
·
Computer-assisted surgery (CAS)
·
Computer-aided surgical simulation (CASS)
·
Computational fluid dynamics (CFD)
·
Component information system (CIS)
·
Computer-integrated manufacturing (CIM)
·
Computer Numerical Controlled (CNC)
1. Drawing entities;
A drawing
is created using a no. of entities. A large no. of options are provided to draw
the entities depending upon the requirements. Common entities are
• Point, * Line, *
Arc, * Ellipse,
• Circle, *Polygon, *Spline, *Rectangle,
etc.,
2. Drawing Utilities;
Drawing utilities include several functions to
have the creation and storage of drawings. Common utilities are;
• *Screen
size, * Line type, * Scaling *
Layers,
• *Grid, *Snap,, *Units, , *file
utilities, etc.,
3.. Editing commands in CAD;
It is necessary to make the corrections and
alterations to the entities of a drawing. Editing commands are used for this
process.
A few
editing commands are listed below,
*Erase, *Move, *Array, *Fillet, * Chamfer
*Mirror *Rotate, *Trim, *Copy *Scale, etc.,
Various Edit and Inquiry commands in CAD;
Editing an entity or group of
entities in Autocad requires the entity or the group to be selected. There are
three ways of doing this :
1) Autocad
can be set to allow the user to select the objects first, and then accept
commands to process them. This is called noun/verb selection. This mode of
operation can be enabled/disabled using the DDSELECT command which opens up a
dialogue box.
2) The
commands can be given first, and the objects can be specified when the user is
prompted for them.
3) The
SELECT command can be used to select a specific selection set, which can be
referred to in subsequent editing operations.
Editing with grips :
Selected objects can be edited by
manipulating grips that appear on the selected entity. The Grips mode can be
enabled with the DDGRIPS command which opens up a dialogue box. The editing
operations possible using grips are :
Stretch,
Move, Rotate, Scale and Mirror
·
Erasing unwanted objects and retrieving
accidentally removed ones :
The ERASE command
permanently removes specified objects. To erase only the drawn object, enter
"L" at the 'select oblects' prompt.
2.
The OOPS command restores only the most recently
erased objects.
3.
Copying and Moving :
The commands available are :
MOVE, COPY, ROTATE, SCALE, MIRROR, STRETCH and ARRAY
The MOVE
and COPY commands are for recreating the object at another place.
The COPY command retains a copy
in the original place while the MOVE command does not.
4. The SCALE
command allows the size of objects to be changed. It scales the object about a
reference point, by expanding/shrinking it equally in all directions. SCALE can
be used to rescale an entire drawing in one go.
5. The ARRAY
command creates multiple copies of entities in a rectangular or polar pattern.
To change the orientation of the array, use SNAP Rotate command or SNAPANG
system variable.
6.
Changes,
Cuts and Constructions
: These commands
allow you to
change
properties
of objects |
(like |
color,
layer,etc.) and modify
objects by trimming |
/extending their ends, |
and |
cutting sections out of them. They can also be used to |
draw
fillet arcs, chamfer lines, parallel lines, offset curves, and construction
markers.
The available commands are :
CHANGE, DDEDIT, BREAK, TRIM,
EXTEND, FILLET, CHAMFER, OFFSET, DIVIDE, and MEASURE
The CHANGE command is used to change the following
: color, elevation, layer, linetype, thickness
Characteristics other than the
above can also be changed by specifying a point instead of choosing one of the
above properties. Then this "change point" is used to modify the
object depending on whether the object is a line or a circle, etc. The
"change point" method works for multiple entities also.
Variations of the CHANGE command are : DDCHPROP and CHPROP
·
The DDEDIT command allows editing of both
text and attribute definitions. The command can be used either in paper space
or in model space, whichever is active when the command is issued. It cannot be
used on text attributes that are part of a block.
·
The BREAK command erases part of a line,
trace, circle, arc or 2D polyline The end points of the part are specified by
the user.
·
The TRIM command is used to trim objects
such that they end exactly at cutting edges defined by other intersecting
objects.
·
The EXTEND command is the complement of the
TRIM command because it lets you extend an object till it meets another object.
·
The FILLET command connects two lines, arcs
or circles by means of a smoothly fitted arc of specified radius.
·
The CHAMFER command is similar : it trims
two intersecting lines a specified distance from the intersection and connects
the trimmed ends with a new line segment.
·
The OFFSET command constructs an entity
parallel to the specified one, either through a given point or at a given
distance.
·
The DIVIDE command lets you divide an
entity into several equal-length parts, placing markers along the object at the
dividing points.
·
The MEASURE command is similar to the DIVIDE
command : it measures an entity and places markers at specified intervals.
Polyline, Mesh, and Block Editing :
There are two basic commands for
this : PEDIT and EXPLODE. PEDIT is used to edit 2D and 3D polylines, and 3D
polygon meshes.
The EXPLODE command breaks up a complex entity as follows :
A Block or associative Dimension
is replaced with copies of simple entities comprising the Block or Dimension.
Polylines are replaced with simple and arcs; 3D polygon meshes with 3D faces
and polyface meshes with 3D faces, lines and points.
Undoing commands :
·
U command : causes the most recent command to be
undone.
·
REDO command : reverses the effect of the most
recent U command.
·
UNDO command : can undo several commands
simultaneously.
·
Inquiry commands are commands which allow the user
to inquire into locations and relationships into entities.
·
Inquiry commands available in Autocad are :
·
LIST : lists data for an entity.
·
DBLIST : lists data for every entity in the
drawing.
·
ID : gives co-ordinates of a point specified in
the graphics window.
DIST : measures angle and distance between
4. 2D transformations in CAD;
In computer graphics drawing are created by
serious primitives which are represented by the coordinates of their end
points.
Certain changes in these drawings can be made by
performing some mathematical operations on these coordinates. The basic
transformations are Scaling, Rotation, translation, etc..,
Related Topics
Privacy Policy, Terms and Conditions, DMCA Policy and Compliant
Copyright © 2018-2023 BrainKart.com; All Rights Reserved. Developed by Therithal info, Chennai.