AutoCAD Lecture 01 - Introduction

8/13/2019 AutoCAD Lecture 01 - Introduction

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CAD Computer Aided Drafting Notes/Handout Introduction to AutoCAD

COMPUTER-AIDED DRAFTING AND DESIGN (CADD) the use of computer technology to aid in the design and especially the drafting (technical

drawing and engineering drawing) of a part or product, including entire buildings Computer Aided Design (CAD) is simply, design and draftingwith the aid of a computer.

o Design is creating a real product from an idea.

o Drafting is the production of the drawings that are used to document a design. CAD can be used

to create 2D or 3D computer models.o A CAD drawing is a file that consists of numeric data in binary form that will be saved onto a

dis.

Why should you use CAD?

!raditional drafting is repetitious and can be inaccurate. "t may be faster to create a

simple #rough$ setch by hand but larger more comple% drawings with repetitive

operations are drawn more efficiently using CAD.

a CAD (Computer Aided Design) software application for 2D and 3D design and drafting

developed and sold by Autodes, "nc.

"nitially released in late &'2, AutoCAD was one of the first CAD programs to run on personal

computers, and notably the "* +C.

AutoCAD 22 syste! "e#u$"e!e%tsperating system-

indows /! 0.1, *, 2111, + (indows '4 and ' can5t be used)

6A* and 7ard Dis 8pace

249 * of 6A* minimum

311* of hard dis space

90* of swap space

&11* free dis space in system folder

7ardware (re:uired)

+entium """ or later with 11 *7; processor or better

*ouse or other pointing device

&120 % 2 floppy, ?ip or CD) for saving files.

7ardware (optional)

+rinter or +lotter

8erial or +arallel port (for peripheral devices)

8ound card with speaers

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The AutoCAD S,"ee%

T$tle +"= !his will show you what program you are running and what the current filename is.

Pull-do.% !e%us= !hese are the standard pull=down menus through which you can access

almost all commands.

M+$% tool+"= !his has most of the standard indows icons, as well as the most common

AutoCAD commands.

P"o/e"ty tool+"= !his toolbar gives a way to :uicly modify an ob@ects properties, such as

layer and linetype.

Flo+t$%& tool+"= !his is a toolbar that can be moved around the screen, or doced as the

main toolbar is.

D"+.$%& s/+,e= !his is where you draw. Bou have an almost infinite area to draw and this is

@ust a section of the entire space.

S,"oll+"s= !hese wor lie in other windows programs. Bou can also use the +A/ command

to move around your drawing.

WCS I,o%= !his is here to show you which direction positive and positive B go. !he

means youre in the orld Co=ordinate 8ystem. ("t can be changed to a ser Co=ordinate8ystem.)

St+tus +" T"+y I,o%s= !hese icons give you updates on items lie reference files program

updates and print status. Command line = hen you type a command, you will see it here. AutoCAD uses this space to

prompt you for information. "t will give you a lot of information and tell you where you are inthe command.

St+tus +"= !his allows to see and change different modes of drawing such as rtho,

snaps, rid, trac, etc. Tool P+lette - Collection of tools in one area that can be organi;ed into common categories.

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The Coo"d$%+te Syste!

A good understanding of how co=ordinates wor in AutoCAD is absolutely crucial if you are to maethe best use of the program. "f you are not familiar with co=ordinates and co=ordinate systems, taesome time to familiari;e yourself with the basic concepts.

Co=ordinates fall into two types, namely Cartesian and +olar. A basic understanding of these co=ordinate types will help you to use AutoCAD to construct drawings more easily. "n addition, these twoco=ordinate types come in two distinct flavors. !hey can be either Absoluteor Relative. Enowing @ust

when and where to use the various types and flavors of co=ordinate is the ey to efficient drawing withAutoCAD.

C+"tes$+% Co-o"d$%+tes

!he Cartesian co=ordinate system is the standard co=ordinate system.

!he position of a point can be described by its distance from two a%es, and B. !his results ina simple point description using two numbers separated by a comma e.g. 01'34516'140.

"n the e%ample on the above the point described lies 01'34drawing units to the right of the B a%isand 16'140drawing units above the a%is. !he first value (01'34) is nown as the co=ordinatebecause its value is measured along the a%is. !he second value is nown as the B co=ordinatebecause its value is measured along the B a%is. !he and B a%es are two lines of infinite length

which intersect at the origin point. !he co=ordinate value of the origin point is always 5. henviewed in plan the and B a%es are always perpendicular to one another with the a%is in ahori;ontal position and the B a%is in a vertical position (8ee illustration). co=ordinate values becomenegative to the left of the B a%is and B co=ordinate values become negative below the a%is. All co=

ordinate values (both and B) are negative in the lower left hand :uadrant and positive in the upperright hand :uadrant. /ormally we try to wor in the positive :uadrant. Although this is not essential forAutoCAD to operate, it does tend to mae life easier because we dont need to worry about negativenumbers.

AutoCAD allows you to use co=ordinates to draw ob@ects rather than using pic points. For e%ampleyou could draw a line lie this-



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Co!!+%d Se#ue%,e

Command: LINE

From point: 34.897,45.473

To point:54.896,65.395

To point: (to end)

!his se:uence draws a line between the two co=ordinate points specified. /ote that if you enter a co=ordinate that is off the screen the line will still be drawn to the re:uired point. Bou will then need to

;oom out in order to see the whole line. Bou can also start the Gine command by clicing on the

Draw toolbar or from the pull=down menu (Draw Gine).

Pol+" Co-o"d$%+tes

+olar co=ordinates achieve the same result i.e. the

description of the position of a point.

!he main difference is that polar co=ordinates use one

distance and one angle to describe the position of a

point rather than the two distances in the Cartesiansystem.

!he distance and angle measurements are made

relative to an origin. !his results in a point descriptionwhich loos lie this 01'3470where the first figure isthe distance (in drawing units) and the second is theangle.

/otice that the separator in the case of polar co=ordinates is the Hless thanH mathematical

symbol. "f you loo at your eyboard you will see that this symbol is typed by using 8hift andcomma.

AutoCAD angles start at 3 ocloc (i.e. along the positive portion of the a%is) and increase in

an anti=clocwise direction.

Bou can specify negative angles if you need to define an angle in a clocwise direction

although this is not really necessary because angles are circular, hence an angular value of=31 degrees will give the same result as an angular value of 331 degrees (there are 391degrees in a full circle).

The UCS I,o%

"n the bottom left hand corner of the AutoCAD drawing window you

will see a symbol lie the one shown on the right.

!his is called the C8 (ser Co=ordinate 8ystem) icon and it is there

to remind you which is the a%is and which is the B a%is.

!he empty bo% at the intersection of the and B a%es is there to

remind you that you are using HorldH co=ordinates and that the C8



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icon is not positioned over the true origin of the current co=ordinate system, probably becauseit is off screen.

Asolute 8 Rel+t$9e Co-o"d$%+tes

Bou can enter points directly on the command line using three different systems.

A8G! C=6D"/A!8 = sing this method, you enter the points as they relate to the

origin of the C8. !o enter a point @ust enter in the e%act point as :5;.

6GA!"I C=6D"/A!8 = !his allows you to enter points in relation to the first point you

have entered. After youve entered one point, the ne%t would be entered as?



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8ay, for e%ample, you wanted to draw a hori;ontal line with a length of 31 drawing units. 8tart the

Gine command, Draw Gine from the pull=down menu or from the Draw toolbar. hen prompted,to specify the first point for the line, pic a point somewhere on the left side of the drawing area.

Bou now need to constrain the line to the hori;ontal. Bou can do this using +olar !racing . se the+GA6 button on the status bar to turn on +olar !racing. sually, +olar !racing is on by default, soyou may not need to do this.

/ow, move your cursor to the right of the first pic point. "fyou are within a few degrees of the hori;ontal, you shouldsee something similar to the illustration on the right. 7oldyour cursor in this position and simply enter 31 at theeyboard. hen you hit the 6eturn ey, a line segment isdrawn, 31 units long and in the direction you were pointing.

bviously, you could vary this se:uence to get different effects. "f you only want to draw hori;ontal orvertical lines, you could use rtho rather than +olar !racing. r, you could configure polar tracingto snap to other angles lie 04L or 31L. Bou might even want to turn both rtho and +olar !racing off

and use free angles.

"ts also worth pointing out that when +olar !racing has snapped to an angle, as in the illustrationabove, a !ool !ip is displayed. !his !ool !ip displays a relative polar co=ordinate from the first picpoint to the current cursor position. !he first number is the distance between the two points and it canbe :uite useful as a drawing guide since the value updates dynamically.

A Wo">ed E+!/le

"n this e%ercise, we will use direct distance entry to draw the closed shape shown below using theassociated dimensions.

&. Chec that you have either +olar !racing or rtho modeturned on.

2. 8tart the +olyline command, D"+. Polyl$%efrom the pull=

down menu or from the Draw toolbar.

3. hen prompted to specify the first point, pic a pointsomewhere in the lower left :uadrant of the drawing area.!his will be the point mared HstartH in the illustration.

0. /ow, follow the command se:uence below. "n each case,

point the cursor in the direction you want the line drawn andenter the distance for that particular line segment at the eyboard.

oint #p-pe$i/ net point or 12r$a"idt+Lent+ndoidt+: 40

oint ri+t-pe$i/ net point or 12r$C"o!ea"idt+Lent+ndoidt+: '5

oint don-pe$i/ net point or 12r$C"o!ea"idt+Lent+ndoidt+: 5



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oint ri+t-pe$i/ net point or 12r$C"o!ea"idt+Lent+ndoidt+: 0

oint #p-pe$i/ net point or 12r$C"o!ea"idt+Lent+ndoidt+: 5

oint ri+t-pe$i/ net point or 12r$C"o!ea"idt+Lent+ndoidt+: '5

oint don-pe$i/ net point or 12r$C"o!ea"idt+Lent+ndoidt+: 40

Bou should now be at the point mared HendH on the illustration. All you need to do now is enter HCH toclose the polyline and end the command.

-pe$i/ net point or 12r$C"o!ea"idt+Lent+ndoidt+: C

!he closed polyline shape you have drawn is located arbitrarily because you @ust piced a start pointsomewhere in the drawing area. "f you had wanted to start at a particular location, you could haveentered a co=ordinate value for the start point instead of @ust picing.

bviously, the e%ercise above is a very simple e%ample but there are many circumstances wheredirect distance entry can be used. "ts a very useful tool to add to your AutoCAD sills toolbo% and canhelp you towards greater drawing efficiency.

U%$ts +%d S,+les

Among the most important concepts that newcomers to AutoCAD need to get to grips with are

those of drawing scale and drawing units.

Bou cannot start creating sensible drawings with AutoCAD until you are familiar with scale,

units and the commands you use to control them.

At .h+t s,+le should I d"+.?

As a general rule, everything you draw with AutoCAD will be drawn full si;e.

hen you start drawing with AutoCAD you do not have to decide upon a drawing scale as you

do when using a drawing board. hen drawing on paper you must decide do draw at say, &-21or &-211 depending upon the si;e of the ob@ect that you are drawing so that your scaleddrawing will fit on the drawing sheet, be that A3 or A&.

"n AutoCAD you do not need to decide upon a drawing scale until you come to print the

drawing and because the scaling of your drawing taes place at the printing stage, you cancreate drawings at a scale of &-&.

A! I d"+.$%& $% !et"es o" !$ll$!et"es?*ost people who use AutoCAD, draw using decimal drawing units. hat these drawing unitsrepresent is entirely up to the individual. 7owever, you must decide what units you will use before youstart drawing. ne drawing unit could represent one millimetre, one centimetre, one metre, ilometre,mile, furlong or fathom. "t is entirely up to you. 7owever, in most parts of the world it is commonpractice to wor in either millimetres or metres. hich of these two units you use will largely dependupon the type of drawing you are creating. For e%ample, if you were creating a detail drawing of aflight of steps, you would most liely use millimetres (Architects will almost always use millimetres). "f,on the other hand you are drawing a landscape masterplan, you would probably want to wor inmetres (Gandscape Architects and Civil ngineers usually use metres).

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y way of e%ample, consider a drawing where you need to draw a footpath in plan. !he footpath istwo metres wide. "f you are woring in millimetres, the footpath would be drawn 2,111 drawing units

wide but if you are woring in metres, the footpath would be drawn @ust 2 drawing units wide. !otranslate this into practical terms, if you had drawn one edge of the path and you intended to draw theother edge using the ffsetcommand, you would enter either H2,111H or H2H for the offset valuedepending upon whether you were using millimetres or metres respectively.Although decimal drawing units are the most commonly used, you can configure AutoCAD to wor

with other types of drawing units. !o change the unit type, you must use the Drawing nits dialoguebo%.

U%$ts Co%t"ol

!oolbar none

+ull=down

Format nitsM

Eeyboard/"!8

hen you start the nits command, the

first thing you see is the Drawing nits

dialogue bo%, shown on the right. !he dialogue bo% is divided into four main

sections.o !he upper two are HGengthH, which

refers to linear units and HAnglesH,referring to angular units.

o 8ettings for linear units and angular

units can be made independentlyand in each case, you can controlboth the type and precision.

o "n addition, the Angles section also

allows you to specify the direction in which angles are measured. 8ee below for moredetails.

o A third section, entitled Drawing units for Design Center blocs allows you to assign a

specific unit to the drawing so that when blocs are inserted via the AutoCAD DesignCentre, they will automatically be scaled.

o !he final section, 8ample utput, gives you a preview of the drawing units as they will

be displayed using the current settings.

@$%e+" U%$tsBou can see from the dialogue bo% that there are five different linear unit types for you to choosefrom, one of which is HDecimalH, the default. !he table below shows the effect of the different unit

settings on two drawing unit values to give you an idea how the various settings might be used alongwith a brief description.

U%$t Ty/e'6 D"+.$%&U%$ts

6 D"+.$%&U%$ts

Des,"$/t$o%

Decimal &.4111 &411.1111 *etric or 8" units

8cientific &.4111N11 &.4111N13Decimal value raised to apower

ngineering 1=&.4111H &24=1.1111H Feet and decimal inches

Architectural

1=& &>2H &24=1H Feet and fractional inches

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Fractional & &>2 &411 hole numbers and fractions

o /otice that when you change the unit type, the co=ordinate display on the status bar changes

to show co=ordinates using the current unit type.o Changing the unit type also affects the way distances, areas and volumes are reported when

using the appropriate in:uiry command.o For the most part you should not need to change the unit type. nits such as HArchitecturalH

and HngineeringH are there mainly for AutoCAD users in the 8A where Feet and "nches arestill in common use.

A%&ul+" U%$tsGooing at the Drawing nits dialogue bo% again, you will notice that there are also five angular unittypes. !he default is decimal degrees, but there are other options. !he table below shows the effectof the different unit types on two angular unit values. As with the linear units, there are not manycircumstances under which you would want to use anything other than the default.

U%$t Ty/e2'6 A%&ul+"U%$ts

A%&ul+"U%$ts

Des,"$/t$o%

Decimal

Degrees&2.411 &1.111 *etric units

Deg>*in>8ec &2d311H &1d11HDegrees, *inutes and8econds

rads &3.'g 211.111g 011 grads O 391 degrees

6adians 1.2&r 3.&02r 2 +i radians O 391 degrees

8urveyor /


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/orth. !o change the direction of angular measurement, simply clic on the appropriate radiobutton.

U%$t P"e,$s$o%o !he Drawing nits dialogue bo% can also be used to set the precision of linear and angular

units.o y default, AutoCAD sets the linear unit precision to four places of decimal, so distances

appear in the form 1.1111. Angular unit precision is set to whole degrees only.

o !o change the precision with which linear

and angular values are displayed, simplyclic the down arrow against theappropriate drop=down list (see illustrationon the left) and select the number ofdecimal places re:uired.

o !he default setting of four decimal places

is usually ade:uate for linear units.o "t is, however, often necessary to change

the precision for angular units.o oring in whole degrees does not usually

give an ade:uate level of detail for manydrawing functions.

o 7owever, you do not needto change the

precision of either linear or angular unitsunless you have a specific reason fordoing so.

o Changing the unit precision does not mae

your drawing more accurate, it @ust means that the co=ordinate display on the status bar andthe results from the various in:uiry commands will be displayed with a higher degree of

precision.o !he accuracyof your drawing will be determined by the values you enter for the si;e of ob@ects

when you draw and edit them and by the correct use of the various ob@ect snaps and drawingaids.

+ d b E G$l t R * + &1

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AutoCAD Lecture 01 - Introduction