E2004_Computer Aided Design 1_UNIT7

7/24/2019 E2004_Computer Aided Design 1_UNIT7

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DIMENSIONING

DIMENSIONING

OBJECTIVES

General Objective : To understand the concept of dimensioning and usage of

dimensioning tools.

Seci!ic Objective" : At the end of the unit you will be able to:

Create linear dimensions with DIMLINA!"

DIMC#NTIN$" DIM%A&LIN" DIMALI'ND.

Create radial dimensions with DIMDIAMT! and

DIM!ADI$&.

Create Angular dimensions with DIMAN'$LA!.

Create #rdinate dimensions with DIM#!DINAT.

Create and edit the dimensions.

#NIT 7


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7$0 INT%OD#CTION

As you (now" drawings created with CAD systems should be constructed with the same

dimensions and units as the real)world ob*ects they represent. The important of this practice ise+ident when you begin applying dimensions to the drawing geometry in AutoCAD. The features

of the ob*ect that you specify for dimensioning are automatically measured" and those +alues are

used for the dimensioning te,t. If the geometry has been drawn accurately" the dimensions will be

created correctly. The correct use of AutoCAD dimension tools is the (ey to producing clear and

concise measured drawings.

AutoCAD pro+ides a whole range of dimensioning tools which can be used to -uic(ly dimension

any drawing without the need for measurement. Dimensioning in AutoCAD is automatic lines"

arrows and te,t are all ta(en care of by the dimension commands. AutoCAD dimensions are

special bloc(s which can easily be edited or erased as necessary.

AutoCAD pro+ides lots of control o+er the way dimensions loo(. $sing a system similar to te,t

styles" dimension styles allow you to design dimensions so that they loo( *ust the way you want

them to.

INPUT 7aINPUT 7a


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/igure 0.1

/or e,ample"Figure 7.1abo+e shows two different dimension styles. The one on the left is the

default style (nown as &TANDA!D. If you do not create a style of your own or modify the

standard style" all dimensions will loo( li(e this. The dimension line has arrow heads and the

dimension te,t is positioned abo+e the line and is drawn using the current te,t style. The

dimension on the right has been drawn using a new style. The arrows ha+e been changed to

obliques" the +ertical alignment of the te,t has been centered and the current te,t style has been

changed.

AutoCAD di+ides dimensions into four main categories:Linear"Radial" OrdinateandAngular.

2hen you create dimensions" AutoCAD automatically creates a new layer called 3Defpoints3.

This is a special layer which cannot be deleted or renamed. AutoCAD uses this layer to store

dimension information and you can effecti+ely ignore it.

2hen wor(ing with dimensions it is +ery important that line origins are pic(ed accurately so that

the resulting measurement and te,t are correct. Always use an Osnap to pic( dimension line

origins.

7$1 SE'ECTING DIMENSION COMM(NDS


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&electing and wor(ing with the dimension commands in AutoCAD !14 is much easier than in

pre+ious +ersions. All commands can be accessed from the (eyboard and now most commands

are also a+ailable from the Dimension pull-down menu and the Dimension toolbar. The

Dimension toolbaris particularly useful because it places all the dimension commands a single

mouse clic( away. &ince the Dimension toolbar is not displayed by default you will need to

enable it from the Toolbars dialogue box.

To display the Toolbar dialogue bo," select

)*ll+,-.n en* Vie./T--lbar"

C-an, T--lbar

To display theDimension toolbar" clic( in the

chec(bo, against 3Dimension3 in the toolbar list.

/igure 0.5: Toolbars %o,

The main components of a dimension are

1. Dimension line

5. ,tension lines

6. Dimension te,t

7usually a numeric +alue 8

4. Arrowheads or tic( mar(s

/igure 0.6

Dimensioning an ob*ect correctly re-uires a number of difference dimensioning methods

based on the ob*ect you are dimensioning. This includes:)


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1. Linear methods for hori9ontal and +ertical.

5. Aligned.

6. Angular method for angles.

4. Diameter and !adius methods for circles and arcs.

. #rdinate method for datum)based.

7$2 TE 'INE(% DIMENSION COMM(ND

As the name suggests the Linear dimension commands are used to dimension along straight lines.

There are fi+e linear dimension commands" namely: DIMLINEAR3 DIMCONTINUE3

DIMBASELINE3DIMALIGNEDandDIMROTATED. The DIMLINA! command is probably

the most common dimension command you will use.

7$2$1 Te 'inear Dien"i-n

Toolbar :

;ull)down :Dien"i-n/'inear


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/igure 0.4

C-an, Se6*ence

Command:DIMLINEAR

/irst e,tension line origin or press NT! to select: (pi!P1"

&econd e,tension line origin: 7pi!P28

Dimension line location 7Mte,t>Te,t>Angle>?ori9ontal>@ertical>!otated8: (pi! a point to position

t#e dimension line$ you will see t#e dimension rubber banding"

=ou may ha+e noticed that the first prompt as(s you to pic( the first e,tension line origin or to

press the NT! (ey. ;ressing the nter>!eturn (ey results in the following prompt:

&elect ob*ect to dimension:

AutoCAD allows you to dimension an ob*ect simply by pic(ing it. Try this out. Draw a line or a

circle and use this option rather than the two point option to see what happens.

/igure 0.

Dimensions will automatically ad*ust themsel+es to accommodate most situations. /or e,ample"

theFigure 7.%shows what happens to a dimension if the gap between the two e,tension lines is

too small for the dimension te,t.


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7$2$2 Te C-ntin*e Dien"i-n

Toolbar

;ull)down Dien"i-n/C-ntin*e

B&elect8: (pi!P3

&pecify a second e,tension line origin or 7$ndo>B&elect8: (pi! anot#er or to end"

There is no prompt for the first line origin" AutoCAD automatically selects the second line origin

of the pre+ious dimension to be the first of the new dimension.

There is also no prompt for the dimension line position" AutoCAD automatically matches up with

the pre+ious dimension.

/igure 0.

$sing the Continue command you can +ery -uic(ly generate a string of dimensions which align

perfectly. In the e,ample abo+e 7 Figure 7.& 8" the 364.413 dimension was drawn with the

DIMLINA! command all the other dimensions were drawn using the DIMC#NTIN$

command and simply pic(ing the four points" one after the other. =ou can only continue a

dimension in a single direction. To generate the 35mm3 dimension inFigure 7.&" you will need


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to use the DIMLINA! command and pic('and'4or)nterat the first prompt and pic( the

line.

7$2$& Te Ba"eline Dien"i-n

Toolbar

;ull)down Dien"i-n/Ba"eline


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In the /igure 0.0" the 36.03 dimension was created using the DIMLINA! command. The

others were created using DIM%A&LIN and pic(ing points 1 and 5.

7$2$4 Te (li9ne, Dien"i-n

Toolbar

;ull)down Dien"i-n/(li9ne,


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/igure 0.E

The DIMC#NTIN$ and DIM%A&LIN commands can both be used in con*unction with

DIMALI'ND dimensions.

7$& TE %(DI(' : CI%C'E / (%C ; DIMENSION COMM(ND

There are two main radial dimension commands" DIMDIAMT! and DIM!ADI$&. %oth

commands result in a similar loo(ing dimension so AutoCAD automatically inserts a ,, to

indicate a radius and the dimension symbol to indicate a dimension. =ou can get AutoCAD to

display the dimension symbol by including 3FFc3 in any te,t string. /or e,ample" in order to

draw the 4mm diameter te,t as it is shown in the illustrationFigure 7." you would need to type

3FFc4mm3. =ou can use this special character with any of the te,t commands.

/igure 0.G


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The Diameter and !adius commands are supplemented by the DIMCNT! command" which

can be used to add a center mar( to any circle or arc. The DIMDIAMT! and DIM!ADI$&

commands do not automatically draw a center mar(.

%y con+ention it is usual to dimension full circles using a diameter and arcs 7partial circles8 using

radius.

7$&$1 Te Diaeter Dien"i-n

Toolbar

;ull)down Dien"i-n/Diaeter


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Toolbar

;ull)down Dien"i-n/%a,i*"


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7$&$& Te Center Mar< C-an,

Toolbar

;ull)down Dien"i-n/Center Mar


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The Angular command is ama9ingly fle,ible and can be used to indicate an angle in almost any

situation. Hust li(e the other dimension commands" all parts of the process are rubber banded so

you can see the results of your actions before you ma(e the final pic(.

C-an, Se6*ence

Command:DIMANGULAR

&elect arc" circle" line" or press NT!: (pi! a line"

&econd line: (pi! anot#er line"

Dimension arc line location 7Mte,t>Te,t>Angle8: (pi! point"

Mo+e the cursor position until you are happy with the result. Notice that you can mo+e the cursor

to either side of the lines and the angular dimension will change accordingly.

/igure 0.14

=ou may ha+e noticed that at the first prompt you are gi+en the option to press )2T). If you use

this option you will be prompted to pic( the angle +erte, and then the two angle endpoints. This is

-uite useful if the angle you need to dimension is not defined by physical lines on the drawing.

The illustration onFigure 7.14shows the result of this option. The centre point of circle 1 was

pic(ed as the angle +erte, and the centre points of circles 5 and 6 were pic(ed for the two angle

endpoints.

The degree character is automatically inserted for you" howe+er" if you e+er need to type it" you

can do so by typing 3FFd3. This is another of AutoCADs special characters.


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7$ O%DIN(TE DIMENSIONS

#rdinate dimensions are not really dimensions at all in that they do not indicate a measurement.

!ather they annotate (nown co)ordinate points. The DIM#!DINAT command is used to

indicate the and = ordinate +alues at any point.

Te Or,inate Dien"i-n C-an,

Toolbar

;ull)down Dien"i-n/Or,inate


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The one on the right has a = ordinate" which has been forced to display in a +ertical position using

the =datum option. =ou could also use the Te,t or Mte,t options to clearly describe the point you

are annotating.

7$5 (NNOT(TION =IT 'E(DE%S

#rdinate dimensions are not really dimensions at all in that they do not indicate a measurement.

!ather they annotate (nown co)ordinate points. The DIM#!DINAT command is used to

indicate the and = ordinate +alues at any point.

Te 'ea,er C-an,

Toolbar

;ull)down Dien"i-n/'ea,er


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$nli(e other dimension commands the leader and annotation te,t are drawn as separate ob*ects.

&o" if you need to mo+e or edit the te,t" you can do so without affecting the leader line.

As you can see by the command line" there are a number of options with this command including

3/ormat3 options which include 3&pline3. ,periment with these options until you understand

them.


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(CTIVIT> 7a

(NS=E% ('' TE ?#ESTIONS$

0.1 'i+e /I@ 7 8 component of dimensionJ

0.5 &tate the techni-ue for dimensionJ

0.6 Draw the figure below with dimensioning. $se 3tart From 3rat# )nglis# setting.

;lease use all the dimensioning techni-ue that we ha+e learned.

/igure 0.10


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/igure 0.1E

/igure 0.1G

;LAT .5 mm


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@EEDB(CA TO (CTIVIT> 7a

(NS=E%S$

0.1 The components of a dimension are

Dimension line

,tension lines

Dimension te,t 7usually a numeric +alue 8

Arrowheads or tic( mar(s

0.5 Techni-ue for dimensioning

Linear methods for hori9ontal and +ertical

Aligned

Angular method for angles

Diameter and !adius methods for circles and arcs.

#rdinate method for datum)based

(n-ter 6*e"ti-n3 lea"e ,ra. care!*ll an, a!ter !ini"e,3 lea"e ,i"c*"" .it -*r -.nlect*re


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7$7 EDITING DIMENSIONS

The dimension edit commands" DIMDIT and DIMTDIT are used primarily to ad*ust the

position of the te,t part of a dimension. This is usually only necessary if the drawing is -uite

comple, and the dimension would read more clearly if it were in a different position.

7$7$1 Te Dien"i-n Tet E,it C-an,

Toolbar

;ull)down Dien"i-n/(li9n Tet! ( #oose youroptions "


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C-an, Se6*ence

Command:DIMTEDIT

&elect dimension: (pi! t#e dimension you want to edit"

nter te,t location 7Left>!ight>?ome>Angle8: (pi! a new position or use an option"

/igure 0.51

The results of the four a+ailable options are shown in theFigure 7.1.

The 'e!toption mo+es the te,t to a left *ustified position within the dimension.

The %i9toption mo+es the te,t to a right *ustified position within the dimension.

The -eoption returns the te,t to the home position after it has been modified.

The (n9leoption enables the te,t to be rotated about its center.

7$7$2 Te Dien"i-n E,it C-an,

Toolbar

;ull)down Dien"i-n/Obli6*e7other options are duplicated in DIMTDIT so donKt appear8


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C-an, Se6*ence

Command:DIMEDIT

Dimension dit 7?ome>New>!otate>#bli-ue8 B?ome: (#oose an option"

&elect ob*ects: (pi! one or more dimensions"

&elect ob*ects: (pi! more or end"

The command se-uence will +ary depending upon which option has been chosen but the results of

the +arious options are illustrated in /igure 0.55

/igure 0.55

The -eoption returns dimensions to their home position.

The Ne.option displays the Multiline Te,t ditor. The changes you ma(e to the te,t will be

applied to all selected dimensions so it is important not to delete the 33 mar(er from the te,t

string. Deleting this mar(er will remo+e the +alues from all selected dimensions.

The %-tateoption can be used to rotate dimension te,t about its center point. It wor(s in e,actly

the same way as the Angle option of the DIMTDIT command e,cept that you can rotate any

number of dimensions at once.

The Obli6*eoption is used to set the dimension lines at an angle. This option can be +ery useful

when you are dimensioning a drawing in isometri pro5etion7seeFigure 7.8. In this case the

drawing has been dimensioned using the Alignedcommand and then the obli-ue angle modified

to suit the dimension position. This usually means setting an angle of 6$ 6 or 6 degrees

depending upon the dimension orientation. If you are creating details in isometric pro*ection ma(e

sure you are using the isometric snap>grid option for greater efficiency.
http://www.cadtutor.net/acad/acadr14/dims/dims.html#alnhttp://www.cadtutor.net/acad/acadr14/dims/dims.html#aln


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/igure 0.56

7$ DIMENSION ST>'ES

Dimension styles are the main method used to control the way dimensions loo(. $sing styles you

can change the te,t font" the arrow head style" the relati+e position of the te,t" the scale of

dimensions and many other parameters. &tyles are created using the DIM&T=L command.

Dimension styling is a relati+ely comple, area of AutoCAD and the finer points are beyond the

scope of this unit. ?owe+er" the main points which will enable you to create clear" good loo(ing

styles are set out below.

7$$1 Te Dien"i-n Stle C-an,

Toolbar

;ull)down Dien"i-n/StleF


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&TANDA!D style as a default option. ?a+ing created a new style from &TANDA!D" then you

can apply any modifications you generally re-uire to the parent style and then more specific

modifications to the #ildstyles in order to create a style/amily.

/igure 0.54

Dimension styles are created using the Di#en$i%n St&le$dialogue bo,. The dialogue bo, is

shown onFigure 7.4. As you can see from the dialogue bo," a style is applied to a /amilyof

dimensions. %y default" any style changes are made to theparent. ach style parent has si, #ild

styles. The child styles" Linear" !adial" Angular" Diameter" #rdinate and Leader can be used to

modify the parent style when that particular type of dimension is used.

/or e,ample" you may li(e to use a tic( rather than an arrow head for your dimensions but

this isnKt really appropriate for a leader" so the Leader child style can be changed so that leaders

will always be drawn with an arrow head whilst all other dimensions of the same style family are

drawn using tic(s.

Name dit%o,


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7$$2 Creatin9 a Ne. Stle

To create a new dimension style" ma(e sure the &TANDA!D style is the current style" clic( in the

Name edit bo, and type the name of the new style you wish to create. Clic( the &a+e button. =ou

will see a message in the lower left corner of the dialogue bo, which says 3Created namefrom

&TANDA!D3 where name is the new style name which you typed. The new style is automatically

set as the current style. =ou may rename the new style if you wish" simply by typing a new name

in the Name edit bo, and clic(ing on the !ename button.

The new style which you ha+e created is identical to the &TANDA!D style" so you must now

modify your new style so that it can be used to create dimensions which conform to your own

re-uirements. &tyle changes are made in three categories" Ge%#etr&" '%r#at and Ann%tati%n

7 Figure 7.% 8. As you can see from the Dimension &tyles dialogue bo," each category is

represented by a button which leads to a dialogue bo, which is used to modify the settings in that

particular category.

/igure 0.5


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7$$& Settin9 te (rr-. ea, Te

The style of arrow heads is set using the 'eometry dialogue bo," illustrated in /igure 0.5. As

you can see" the &TANDA!D style has Closed /illed arrow heads as a default. To change the

arrow head style for a new dimension style" ma(e sure the style is current and that the 3;arent3

radio button is selected 7this assumes you are not modifying a child style8" clic( on the

3'eometry3 button and select a new arrow head type from the 31st3 drop)down list. #nce

selected the new arrow type is illustrated in the dialogue bo,. If you re-uire different arrow heads

at each end of your dimensions you can set the other type using the 35nd3 drop)down list. Clic(

on 3#


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the scale factor and chec( the results. The scaling applies to indi+idual styles" so you could create

different styles with different dimension scales to be used for different plotting scales.

Note that changing the scale of dimensions does not affect the dimension +alue" this is always

calculated in drawing units.

7$$ Settin9 te Tet '-cati-n

To change the te,t location clic( on the ('%r#at3 button in theDimension 3tylesdialogue bo,.

The /ormat dialogue bo, is shown in Figure 7.7. %y default the #oriontal 5usti/iationis set to

3Centered3 and the 0ertial 5usti/iationto 3Abo+e3. This means that the dimension te,t will

appear centered abo+e a hori9ontal dimension line and centered left of a +ertical dimension line.To ha+e the te,t cantered within the dimension line" clic( on the down arrow of the 3@ertical

Hustification3 pull)down list to re+eal the options and clic( on 3Centered3. The illustration

changes to reflect your choice. Clic( on 3#


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/igure 0.50

=ou can also use Te,t the option in this dialogue bo, to change the te,t orientation in aligned

dimensions. %y default all dimension te,t is aligned with the dimension. This option allows you

to force te,t to appear hori9ontal" irrespecti+e of the orientation of the dimension. =ou ha+e

independent control o+er dimension te,t which appears inside and outside of the dimension lines.

The illustration on the /igure 0.5E shows a dimension with +ertical *ustification set to 3Abo+e3

7 left8 and to 3Centered3 7right8.

/igure 0.5E

7$$5 Settin9 Tet Stle an, #nit"

Te,t style and units are both set using the Annotation dialogue bo," illustrated in /igure0.5G To set a te,t style to a dimension you must first ha+e created the style using the Te,t &tyle

command 7@-rat/Tet StleF from the pull-down menu8. To assign the te,t style to a

dimension style" clic( on the 3Annotation8,button in theDimension 3tylesdialogue bo," clic(

on the drop)down list in the 3Te,t3 area of the Annotation dialogue and select the re-uired te,t

style from the list. Clic( on 3#


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/igure 0.5G

In such a case it is a good idea to include units to a+oid confusion. !emember that the main idea

behind dimensioning is to gi+e the ma,imum amount of information in the clearest and most

concise way. To add units to a dimension style" clic( on the 3Annotation3 button in the

Dimension &tyles dialogue bo, and enter the re-uired unit character7s8 in the 3're/ix3 and>or

33u//ix3 edit bo,es of the 3;rimary $nits3 area of the dialogue bo,. /or e,ample" if you wanted to

display meters" you would type 3m3 in the 3&uffi,3 edit bo,.


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7$8 TE DIMENSION #)D(TE COMM(ND

Toolbar;ull)down Dien"i-n/#,ate


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(CTIVIT> 7b

(NS=E% ('' TE ?#ESTIONS$

0.4 Draw the following figure using the dimension gi+en.

/igure 0.6


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/igure 0.61


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@EEDB(CA TO (CTIVIT> 7b

Cec< te c-lete, ,ra.in9 .it -*r lect*rer$


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EE%CISES$

?*e"ti-n 7+1:

a8 Draw the figure below with dimension gi+en.

i8


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/igure 0.65

ii8

/igure 0.66


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@EEDB(CA TO SE'@+(SSESSMENT

Cec< -*r ,ra.in9 .it -*r lect*rer$

E2004_Computer Aided Design 1_UNIT7

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