Introduction to AutoCAD

Introduction toAutoCAD

Video Lecture for ME119

Instructor: Amitabh Bhattacharya

Department of Mechanical Engineering,

I.I.T. Bombay

http://www.autodesk.com/education/free-software/autocad

Acknowledgement: Prof. Tanmay Bhandakkar, Prof. Salil K ulkarni

ComputerAided Drawing (CAD)

❑ Computer aided drafting (CAD) is a process of constructing drawing

computer screen with the help of specially developed software

❑ Advantages: Accurate, time saving, standardization, easily

shared, easy to edit

❑ Widely used commercial softwares:

• AutoCAD

• Pro/Engineer

• Catia

• SolidWorks

• NX Unigraphics

Snapshot of theAutoCAD screen

Ribbon panel

Command line

Status bar

Graphic cursor

Drawing space

Co-ordinate system (UCS)

Ribbon tab

Setting Units

• In this course, the units for drawing objects will

usually be in mm

– If nothing is mentioned then units are in mm

• AutoCAD does not use mm by default

– This may cause issues while printing/saving as pdf

– Becomes difficult to define other properties like line

thickness, etc

• We will first ensure that the units are in mm

– Also a good idea to set the precision to single decimal

place

Setting Units

Page Setup : Model

Printer name: D W G to PDF

Paper size: ISO full bleed A3 (420x297 mm)

Scale: 1:1

• Choose “dwg to pdf” for printer name

• Choose “ISO Full BleedA3 (420x297 mm)”

under paper size

• We won’t really worry about the page setup

for “Layout” tabs

Object Snap (OSNAPCommand)

• While hovering cursor, AutoCAD will

automatically select intersections, midpoints

etc.

• OSNAP command can be used to set which

points should be chosen

Utilities ‐>PointStyle

Make Nodes/Points Visible

• Sometimes we mark intersections/divisions

using nodes/points

• We have to make these intersections visible

using markers

Annotation –> Text Style ‐> Manage text styles

Annotation – Select Annotative

for text, dimensions and multi‐

leader style

Select annotativ e

Setting Up Text Style

• Text size should not be too large/small

compared to figures

– Always test your settings

Annotation –>

Dimension Style ‐>

Manage text styles

Command: DIMSTY

Dimensioning Style

Make sure that size of te xt and arrows are not too large/small

Again – test your settings

Layer manager

Add new layer

To activate a layer in the

drawing

To change the line type of a layer, click on the current line

type, then load, then select appropriate line type to load.

Now select the loaded line type.

New layers created using the layer manager

Using the layer manager you can add/delete layers, change

linetypes, colour and freeze and thaw layers

LAYER Command

You may use differen t colors for layers. Set all layers to white color

before exporting to pdf.

NEVERuse the ͞de fpoints͟ layer

Summary of Settings

• Units (to mm)

• Page setup (420x297 mm)

• Object snap settings (OSNAP)

• Make nodes visible

• Set text size

• Set dimensioning style

• Set Layer properties

COPY/MOVE

• Make a circle (CIRCLE command)

• Enter COPY command->select object (left-click)-

>right click (select base point)->drag object-

>right click (repeat if needed)

• Press Esc once you are finished copying

• MOVE command is very similar

(1,1)

(3,1)

(4,2)

(4,3)

(1,3)

PLINE: Different ways of creating polygons

Relative Cartesian coordinates

Command: PLINE

point: 1,1

point: 2,0

point: 1,1

point: 0,1

poin t: ‐2,0

poin t: c

Relative Polar coordinates

Command: PLINE

point: 1,1

poin t: 2<0

point: 1.414<45

point: 1<90

point: 3<180

poin t: c

Other important shapes: CIRCLE, SPLINE

ORTHO Mode

• ORTHO mode ON helps us draw lines that are

exactly parallel to axes

• Turn ORTHO OFF if line needs to be drawn at

an angle

❑ Paper, margins and name plate:

• Size of sheet is A3 (Width = 420 mm, Height = 297 mm)

• 10 mm margin on all sides

• Name plate (Size: 150 mm x 45 mm) should appear in the right bottom

corner as follows

Template to be used for all theAutoCAD sheets

Steps to generate the template

(1) Use "rectangle" command with corner co-ordinates (0,0) and (420,297) to generate

"A3" size drawing area.

(2) Use "rectangle" command with corner co-ordinates (10,10) and (410,287) to

generate border with a gap of 10 mm. Other option is "offset" command or relative

co-ordinates @.

(3) For name-plate, again "rectangle" command can be used with appropriate co-

ordinates.

(4) Other option is move the "ucs" to the right bottom corner of the inner rectangle.

Use "rectangle" command with corner co-ordinates (0,0) and (-150,45). Move the

"ucs" back to the left corner of the outer rectangle.

(5) For Name plate, the innermost smaller rectangle in the right corner is to be divided

into three equal parts. Switch on the ORTHO mode (F8). See the right corner of the

computer screen.

(6) Draw line to coincide with the horizontal edge of the smallest rectangle.

(7) "Move" the line along –y direction by 15 units w.r.t original location.

(8) "Copy" this line and move the new line relative to the 2

line further by 15 units in

the –y direction.

(9) In the bottommost rectangle of the name plate, use “Move" and "Copy"tofurther

divide the rectangle into three move parts. Keep both the ORTHOMODE and

Steps to generate the template

10) Add text using "text" command. The text should appear at the centre of the

rectangular boxes of the rectangles of the name plate. It’s a good idea to turn off

“Object Snap” (OSNAP), since the text placement can get constrained.

11) With TEXT command, you can always enter multiple text lines. Press CTRL-

ENTER to stop entering the text.

Snapshot of the template to be used for all theAutoCAD sheets

(0,0)

(420,297)

(410,287)

(10,10)

150

Example: Drawing a Hexagon

• Draw a hexagon with side 50 mm

Commands used: CIRCLE, LAYER, TRIM, TEXT, DIMALI

Example: Drawing a Spline

• Draw a polyline, connect the vertices with a

curve

Commands used: PLINE, POINT, LAYER, DIMALI, DIMANG

Example: Divide a Line

• Divide a line into 5 equal parts

Commands used: PLINE, DIVIDE, POINT, DIMALI,

• Use MEASURE command to verify distance

between divisions

Example: Final Sheet

• Use export‐>pdf to

• Always check print‐

>plot preview

Dimensioning for Scaled Objects

• Say actual square has dimensions 500mm, but I

want to show it with a square of 100 mm

– Scale is 1:5

• Use DIMLFAC statement

– Set DIMLFAC=5

LTSCALE: Adjusting Dashed/Dash-

Dot Lines

• Dashed/Dash-dot lines will have default

spacing between the dashes and dots

• LTSCALE can be used to set this spacing

• Usually LTSCALE value of between 0.1 and 1

is used

EXTEND: Extending Lines

• Construction lines may sometimes need to be

extended

• Areference line needs to be chosen, which

intersects the trace of the original line

• The original line is then extended by the

EXTEND statement

– Reference line can then be deleted

TRIM: Trimming Construction

Lines and Arcs

• Circles and long lines are sometimes used for

construction, and need trimming

• Areference curve (e.g. circle, line..) needs to

be chosen which intersects the construction

line/circle

• TRIM statement can then be used to trim the

construction line

Sectioning In AutoCAD

AutoCAD does not have a section line. We will

have to make our own section lines

Use QLEAD command for arrow

Set arrow size in properties

a,1

c,3

Two d ifferent layers are required for the dash-dot lines

Use HATCH command to hatch the section

ANSI 31 can be used, along with appropriate scaling

b,2

d,4

4' 3'

Isometric Drawing

• 1. To draw isometric views, use the ISODRAFT command

– https://knowledge.autodesk.com/support/autocad/learn-

explore/caas/CloudHelp/cloudhelp/2018/ENU/AutoCAD- Core/files/GUID-37463F74-

0B06-46E2-8791-6C5B852A069D-

htm.html

• 2. To draw isometric view of circle, use ELLIPSE command after using ISODRAFT

command

– https://knowledge.autodesk.com/support/autocad/learn-

explore/caas/CloudHelp/cloudhelp/2018/ENU/AutoCAD- Core/files/GUID-B46904E8-F4

43D8-AA74-E06B0D9E83FB-

htm.html

• 3. To dimension isometric drawings in AutoCAD, use the aligned dimensions, along w

the DIMEDIT and DIMTEDIT commands

– https://www.thesourcecad.com/how-to-make-isometric-dimension-and-

text-in-autocad/

ARC

AREA

ARRAY

BLOCK

CIRCLE

COPY

CYLINDER

DIM

DIMALINGNED

DIMANGULAR

DIMCENTER

DIMDIAMETER

DIMLFAC

DIMSTYLE

DIVIDE

ELLIPSE

ERASE

List of importantAutoCAD commands

(Details at knowledge.autodesk.com)

EXTEND

LAYER

LINE

MOVE

OFFSET

PLINE

POLYGON

QLEAD

RECTANG

REDRAW

ROTATE

SAVE

SCALE

TRIM

UCS

ZOOM