Autocad 2d Module 34 PDF

8/14/2019 Autocad 2d Module 34 PDF

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Learning Outcomes:

AutoCAD Self-paced Learning Modules

AutoCAD 2DModule 34

Dimensioning - Part 1

When you have completed this module, you wil l be able to:

1. Describe the 11 basic dimensioning terms.

2. Describe the properties of associative, non-associative and exploded dimensions.3. Describe and apply the commands DIMASSOC, DIMASO and DIMSTYLE commands to

control and modify the appearance of dimensions.4. Describe and apply the commands BREAK and DIMCENTER commands to draw center

lines.

Drafting Lesson

Basic Dimensioning TermsFigure 34 -1 shows the 11 basic dimensioning terms that you will need to know when settingdimensioning styles.

Figure 34-1

Basic Dimensioning Terms

Dimensioning - Part 1 The CAD Guys Ltd. Copyright 1993 - 2007 Module 34
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34 - 2 AutoCAD Self-paced Learning Modules - AutoCAD 2D - Revised 2007-04-14

Dimensioning

Dimensioningis the process of adding size descriptions to the object you have drawn. The

drawing can then be plotted and used for construction or reference. Up to this point in themodules, you have only been adding shape description to the object you are drawing bydescribing the size and location. Since AutoCAD knows the exact size of the objects in the

drawing, you only have to enter the type and location of the dimension you want to insert andAutoCAD will do the rest. You never have to enter the size.

Dimensioning is a complex subject, not difficult, but there is a lot of data to learn. Therefore, in

the AutoCAD 2D Modules, you will be only learning to control the appearance, inserting andediting the basic dimension types. When you complete the AutoCAD 2D modules, you will beable to completely dimension an object for most applications. The advanced features ofdimensioning are taught in the AutoCAD Customization Modules.

Associative, Non-Associative and Exploded Dimensions

Associative and non-associative dimensions are dimensions that are intelligent, similar to an

associative hatch pattern and are tied to the object they are dimensioning. An exploded

dimension is simply a collection of AutoCAD objects indicating a measurement on the objectand has no relation to the object it is dimensioning. You cannot tell the difference betweenthem by simply looking at them, you will have to look at their properties. The differencesbetween them are as follows:

If you modify the object that is dimensioned with an associative dimension with most editingcommands, the dimension will change to reflect the changes to the object. If you modify theobject that is dimensioned with a non-associative dimension with the STRETCH command,the dimension will change to reflect the change to the object. If you modify the object that isdimensioned with an exploded dimension, there will be no effect to the dimension.

Associative and non-associative dimensions are harder to edit than exploded dimensions

because they are inserted as blocks. An exploded dimension is inserted with individualobjects. If the block that makes up an associative or non-associative dimension is exploded,the objects will become individual objects and the dimension becomes an explodeddimension.

If you edit the properties of the dimensioning style of an associative or non-associativedimension all dimensions on the drawing using that style will change. For example, if youwanted to change the dimension text size, change it once and all existing associative andnon-associative dimensions using that style will automatically display the new size. To dothe same thing for exploded dimensions, you would have to change each existing dimensiontext size individually.

Definition Points

Definition points are points that are automatically inserted on the drawing by dimensioning

commands. They are only inserted for associative and non-associative dimensions. Onedefinition point is inserted for each end of an extension line or on opposite sides of a circle orarc. The points are automatically placed on the Defpoints layer. If the Defpoints layer doesnot exist in the drawing, it will be created automatically when the first associative or non-associative dimension is inserted.



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AutoCAD Self-paced Learning Modules - AutoCAD 2D - Revised 2007-04-14 34 - 3

These inserted points are the intelligent part of the associative and non-associative dimension.

It is these points that cause the dimension to automatically update since they are moved in theobject editing commands and the dimension follows them. In an associative dimension, thepoints are attached to the object. Therefore, almost all editing commands move the points withthe object. For non-associative dimensions, the definition points will only move with the

STRETCH command since they are not connected in any way to the object.The definition points will not plot and are not affected by the point type and size appearance. If

you explode an associative or non-associative dimension, the points attached to it willautomatically be erased. The Defpoints layer cannot be deleted or purged.

AutoCAD System Variable: DIMASSOCThe DIMASSOC system variable is used to enable either associative, non-associative or explodeddimensions being inserted by dimensioning commands.

Command: DIMASSOC

Enter new value for DIMASSOC : 0Command: DIMASSOC

Enter new value for DIMASSOC : 1Command: DIMASSOCEnter new value for DIMASSOC : 2Command:

0 - Dimensions will be inserted as exploded dimensions.1 - Dimensions will be inserted as non-associative dimensions.2 - Dimensions will be inserted as associative dimensions.

Note: This system variable is available in 2002-2008 only. For 2000-2000i, use the

system variable DIMASO.

AutoCAD System Variable: DIMASOThe DIMASO system variable is used to enable either non-associative or exploded dimensionsbeing inserted dimensioning commands..

Command: DIMASO

Enter new value for DIMASO : OFFCommand: DIMASOEnter new value for DIMASO : ONCommand:

OFF or 0 - Dimensions will be inserted as exploded dimensions.ON or 1 - Dimensions will be inserted as non-associative dimensions.

Note: This system variable should only be used in 2000-2000i. For 2002-2008, use

the system variable DIMASSOC.

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Dimensioning Styles

A dimensioning style is similar to a text style. A dimensioning style controls the way your

dimensions appear in your drawing. There are many different settings in a dimensioning styleso it will take you a while to get used to setting them. Be patient and practice setting andinserting dimensions as often as possible.

You can create new styles or edit existing dimensioning styles with the DIMSTYLE command.

AutoCAD uses the current dimensioning style properties when inserting dimensions with anydimensioning command. By modifying a dimension style, you can update all existingassociative and non-associative dimensions on the drawing inserted with that style.

The dimensioning style Standard exists in each drawing and cannot be deleted. Even though

the Standard style can be used, it is not a good practice to use it. Create and name your ownstyles.

AutoCAD Command: DIMSTYLEThe DIMSTYLE command is used to create or modify

dimensioning styles.Shortcut: DDIM

2004-2008

2000-2002

Use the Styles toolbar to pulldown a list and select a name tochange the current dimensioningstyle for the active drawing.

When the list is not in its pull-down state, itdisplays the current dimension style.

The Styles toolbar is only available in AutoCAD2004 to 2008



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AutoCAD Self-paced Learning Modules - AutoCAD 2D - Revised 2007-04-14

Creating and Editing Dimension Styles

Step 1 Start a new drawing using the template Module Template B .

Step 2 Save and name the drawing AutoCAD 2D Workalong 34-1.

Step 3 Enter theDIMSTYLE command. Itwill open the DimensionStyle Manager dialoguebox as shown in FigureStep 3.

Authors Comments:

Note that the only stylethat is defined in a newdrawing is Standard. Thisis the default

dimensioning style andmust be included in everydrawing. It cannot bedeleted and must bepresent so that additionalstyles can be created. Figure Step 3You should never use theStandard dimensioning style to dimension with. It is best to create your own styles givingthem suitable names. Although the Standard style could be used, there is a very goodreason not to. It is a common practice in industry to combinetwo or more drawings to form one drawing. In most cases,they are drawings created by different operators and a lot ofthe time, working at different companies. If the drawings tobe combined all used the Standard dimensioning style toplace the dimensions on their drawings, all dimensions on thedrawing being added would take the style properties of thedrawing that it is added to. This can produce very unwantedresults.

Step 4 Notice the graphic in the Preview of: window. It

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gives you a pictorial view of how the dimensions using thedimensioning style being previewed would appear on a

Figure Step 4

drawing. As you make changes to the style, the preview window will change to reflect thosechanges. See Figure Step 4.

Step 5 Click the New button. It will open theCreate New Dimension Style dialogue box asshown in Figure Step 5. In the New StyleName: box, enter the name Module Englishand then click the Continue button.

...continued on page 34-6 Figure Step 5



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Creating and Editing Dimension Styles 2006- 2008 - Continued

For AutoCAD 2006-2008 users only. If you are using AutoCAD 2000-2005, skip to page

34-11)

Authors Comments:

The AutoCAD 2D Modules will only cover the first five tabs in the Dimensioning Styles

dialogue box. When you can set the variables in these five tabs, you will be able todimension any drawing using standards dimensioning techniques. Advanced dimensioningwill be covered in the AutoCAD Customization Modules.

Step 6 In the

Modify DimensionStyle dialogue box,enable the Linestab as shown inFigure Step 6.

Figure Step 6

Step 7 In the Extension lines area, change the Extend beyond dim lines: box to 0.1750

and the Offset from origin: box to 0.075 as shown in Figure Step 7A. Figure Step 7B showswhat dimension style variables you are setting.

Figure Step 7A

Figure Step 7B

...continued on page 34-7



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Creating and Editing Dimension Styles 2006-2008 - Continued

Step 8 Enable the Symbols and Arrows tab as shown in Figure Step 8.

Figure Step 8

Step 9 In the Arrowheads area, set the Arrow size: to 0.175. See

Figure Step 9A and 9B.

Figure Step 9A

Figure Step 9B

Step 10 In the Center marks

area, enable Line and set theSize: to 0.1000. See Figure Step10A and 10B.

Figure Step 10A

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Dimensioning - Part 1 The CAD Guys Ltd. Copyright 1993 - 2007

Figure Step 10B

Module 34


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Step 11 Enable the Text tab as shown in Figure Step 11.

Figure Step 11

Step 12 In the Text appearance area, select the ...

box as shown in Figure Step 12. Clicking it opens the

Text Style dialogue box to create a new text style.

Step 13 Step 12 will open the Text Style dialogue

Figure Step 12

box. This is the same dialogue box that you open when you use the STYLE command.Create a new text style, named Module English, with the font romans.shx as shown inFigure Step 13.

Figure Step 13




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Step 14 In the Text appearance area, pull down the

list of available text styles in the Text style box andselect Module English as shown in Figure Step 14A.

Set the text height to 0.1500 in the Text height box asshown in Figure Step 14B.

Figure Step 14A

Figure Step 14B

Figure Step 15A

Step 15 In the Text placement area, set the

Offset from dim line to 0.1000 as shown inFigure Step 15A and 15B.

Figure Step 15B

Step 16 Enable the Fit tab as shown in Figure Step 16. It should be left as default for

now. Ensure yours matches the figure.

Figure Step 16


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Step 17 Enable

the Primary Unitstab as shown inFigure Step 17.

Figure Step 17

Step 18 In the Linear dimensions area, set the

Precision to two decimal places as shown in

Figure Step 18.

Figure Step 18

Figure Step 19

Step 20 Click OK

and you will return tothe Dimension StyleManager dialogue box.Select the Style

Module English andthen click the SetCurrent box. Ensurethat Module English isthe current style by

Step 19 In the Angular dimensions area, set the

Units format to Degrees Minutes Seconds and setthe Precision to 0d00'00" as shown in Figure Step

19.

Figure Step 20

checking the top left corner of the dialogue box. See Figure Step 20.

Step 21 Save and close the drawing and skip to page 34-15.



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Creating and Editing Dimension Styles 2000 - 2005 - Continued

34 - 11

For AutoCAD 2000-2005 users only. If you are using AutoCAD 2006-2008 skip to page 34-

15)

Authors Comments:

The AutoCAD 2D Modules will only cover the first four tabs in the Dimensioning Styles

dialogue box. Once you set these tabs, you will be able to dimension any drawing usingstandards dimensioning techniques. Advanced dimensioning will be covered in theAutoCAD Customization Modules.

Step 6 In the

Modify DimensionStyle dialogue box,enable the Linesand Arrows tab asshown in FigureStep 6.

Figure Step 6

Step 7 In the Extension lines area, change the Extend beyond dim lines: box to 0.1750and the Offset from origin: box to 0.075 as shown in Figure Step 7A. Figure Step 7B shows

what dimension style variables you are setting.

Figure Step 7A

Figure Step 7B




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Step 8 In the Arrowheads area, set the Arrow size: to 0.175. See

Figure Step 8A and 8B.

Figure Step 8A

Figure Step 8B

Step 9 In the Center Marks forCircles area, set the Type to Lineand set the Size: to 0.1000. See

Figure Step 9A and 9B. Figure Step 9A

Step 10 Enable the Text tab as shown in Figure Step 10.

Figure Step 10



Figure Step 9B

Module 34


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Step 11 In the Text appearance area, select the ...

box as shown in Figure Step 11. This means thatyou want to open the Text Style dialogue box and

create a new text style. Figure Step 11

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Step 12 Step 11 will open the Text Style dialogue box. This is the same dialogue box that

the STYLE command opens. Create a new text style and name it Module English with thefont romans.shx as shown in Figure 12.

Figure Step 12

Step 13 In the Text appearance area, pull down the

list of available test style in the Text style box andselect Module English as shown in Figure Step 13A.Set the text height to 0.1500 in the Text height box asshown in Figure Step 13B.

Figure Step 13A

Figure Step 13

Step 14 In the Text Placement area, set the Offset from dim line to 0.1000 as shown inFigure Step 14A and 14B.

Figure Step 14A

Figure Step 14B




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Step 15 Enable the

Fit tab as shown inFigure Step 15 and

study it. Do notchange any of thedefault setting for thisstyle. Ensure yoursettings are the sameas the figure.

Step 16 Enable the

Primary Units tab asshown in Figure Step16.


Figure Step 15

Figure Step 16



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Step 17 In the Linear dimensions area, set the

Precision to two decimal places as shown in FigureStep 17.

Figure Step 17

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Figure Step 18

Step 18 In the Angular dimensions area, set the

Units format to Degrees Minutes Seconds. Set thePrecision to 0d00'00" as shown in Figure Step 18.

Step 19 Click OK and you will return to the Dimension Style Manager dialogue box.

Select the Style Module English and then click the Set Current box. Ensure that ModuleEnglish is the current style by checking the top left corner of the dialogue box. See FigureStep 19.

Step 20 Save and

close the drawing.

Figure Step 19

A very common error

when using the DDIMcommand is not settingthe current style.Ensure you set the

style you want to use isset to the current style.



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Drafting Lesson

Center LinesIn multiview drawings, the center line is used to indicate the location of the axis of symmetry.Placing center lines on all objects that have a symmetrical shape will help the reader andsave the drafter from inserting a lot of dimensions as you will see in future modules. Beloware some examples of typical applications of the use of center lines in a multiview drawing.

A ?C with an ?L through it is the symbol

for a center line. Center lines are drawnas repeating long and short lines.

This example shows acenter line indicating thecenter of the circle withtwo short lines called acenter markintersectingat the center. Note inthe right side view, the

center line follows thelength of the cylinder.

When the symmetry ends so does the center line.

Note how the center line ends on the leftside of the arc.

In this example, note how the center

lines shown along with the hidden linesthat indicate a hole going right throughthe object. The center line on the topand bottom circles stops at thecomplete circle.

Note how center lines are drawn for an array of circles.



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AutoCAD Command: DIMCENTERThe DIMCENTER command is used to insert center lines or center marks on circles or arcs.

Shortcut: none

2004-2008

2000-2002

AutoCAD Command: BREAKThe BREAK command is used to break a piece out of or off an object. It can also be used tobreak an object into two pieces.

Shortcut: BR

2004-2008

2000-2002

34 - 17

Disable the osnap mode when using the BREAK command. If it is enabled,

you will get unwanted results.



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Drawing Center Lines

Step 1 Open drawing AutoCAD 2D

Workalong 34-1 that you completedearlier in this module. At the same

time, open the drawing AutoCAD 2D Workalong 15-2that you completed in Module 15 and make it thecurrent drawing. Using the COPYBASE command andthe base point of the bottom right corner of the object,select all of the objects in the drawing.

Step 2 Change the current drawing to AutoCAD 2D

Workalong 34-1. Enter thePASTECLIP command and pastethe objects using the insert point of10,4. Your drawing should nowappear as shown in Figure Step 2.

Step 3 Create the necessarylayers to match Figure Step 3.

Step 4 Set the current layer to

Center.

Step 5 Using the

DDIM command, setthe currentdimensioning style

to Module English.See Figure Step 5.

Figure Step 2

Figure Step 3

Figure Step 5

Step 6 Enter the DIMCENTER command ( or click the icon)

shown below and when prompted, select the circle. It will insertcenter lines in the circle. See Figure Step 6.

Command: DIMCENTER

Select arc or circle: P1(Select the circle.)

Command:

Authors Comments:

If this command does not insert a center line as shown inFigure Step 6, go back and read Step 9 on page 34-7 or 34-12depending on the AutoCAD software you are using.



Figure Step 6

Module 34


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Drawing Center Lines - Continued

Step 7 On layer Construction, draw a construction

circle using the center of the small circle as thecenter and select the radius by eye. Make it a short

distance outside the arc. See Figure Step 7.

Figure Step 7

Step 8 On layer Center, draw lines from the

34 - 19

Figure Step 8

Step 9 Using the EXTEND command,

extend the lines to the large construction

circle See Figure Step 9.

Figure Step 10


center of the small circle to the center of the smallarcs as shown in Figure Step 8.

Figure Step 9

Step 10 Turn layer Construction off. Draw

a circle on layer Center with the center at thecenter of the small circle and the radius as

the center of the arc. Ensure you use snapmode to snap to the exact center of the circle

and the arc. See Figure Step 10.



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Step 11 Ensure that osnap mode is disabled

and enter the BREAK command as shownbelow. Make sure you select location P2 first

and then P3. Since arcs are constructedcounterclockwise, you also have to break themcounterclockwise. See Figure Step 11A.Figure Step 11B shows the results of theBREAK command.

Command: BREAKselect object: P2

Figure Step 11A

Figure Step 11B

Specify second break point or [First point]: P3(The locations P2 and P3 can be selected by eye. Thisis a center line so the exact length is not that important.

Try to make them match the figure.)Command:

Step 12 Using the BREAK command again, break the end

off of the center line. Select the location P4 and then for the

second location select past the end of the line and the BREAK

command will remove everything to the end of the line. SeeFigure Step 12.

Step 13 Using what you justlearned, break the other center lineas shown in Figure Step 13.

Figure Step 13


Figure Step 12



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Step 14 Zoom in on the small arc and break a small

part of the line as shown in Figure Step 14A. Do that 7more times to draw the center lines for the arcs. See

Figure 14B. It is best to zoom in close and break byeye. The more you practice this, the better you will getdoing it.

Figure Step 14A

Figure Step 14B

Step 15 Using what you learned in

this workalong, draw the center linefor the slot at the top. The center lineruns from the center of the circle

perpendicular to the line. Thenextend it. You will have to add aconstruction line to extend to. SeeFigure Step 15.

Step 16 Your drawing should

appear as shown in Figure Step 16.Save and close the drawing.

Figure Step 15

Step 16 Save and close the drawing.

Figure Step 16


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Module 34


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The dimensioning style Standard is a special style and exists in eachdrawing. It cannot be deleted or purged from the drawing. Even thoughthe Standard dimensioning style can be used, it is not a good practice todo this. It is much better to create your own styles giving them descriptivenames. If you are ever required to merge your drawings together with a

client's drawings (this is a very common practice), you will not have conflicting style namesand all dimensions will appear as they did in the original drawing before the merge.

The Scale for Dimension Features area on the Fit tab allows you to select

the scale factor you want applied to the dimensioning features when adimension is inserted. This canbe a very useful item and will

save you time. For example, if you set adimension style for drawing units in inches andyou want the same feature sizes for a millimeterdrawing, set the Use of overall scale to 25 sincethere are 25.4 mm in an inch. Experiment with this number until you like the look of yourdimensions. This number does not effect the actual dimensions, only the features.

The Measurement Scale box allows you to set the scale you want applied

to the object measurements when inserting dimensions. This is a veryimportant setting and in mostcases should be left at 1. If you

constructed your object at full scale or actual size,then a setting of 1 would give you the actual sizeon the object which you are dimensioning. Thereare times you have to use this item but unless thatis required, leave it set at 1.

The Key Principles in Module 34

1. Associative and non-associative dimensions are dimensions that are intelligent, similar to

an associative hatch pattern and are tied to the object they are dimensioning. Anexploded dimension is simply a collection of AutoCAD objects indicating a measurementon the object and has no relation to the object it is dimensioning.

2. Definition points are points that are automatically inserted on layer Defpoints on thedrawing by dimensioning commands for associative and non-associative dimensions.The Defpoints layer cannot be deleted or purged from the drawing.

3. A dimensioning style controls the way your dimensions appear in your drawing. When a

dimension is inserted it is assigned the property of the current dimension style and usesthe style properties when it is inserted on the drawing.



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Lab Exercise 34-1

Drawing Specifications

Time Allowed: 30 Min.

Name

AutoCAD 2D Lab 34-1

Template

N/A

Units

Inches

Text Style

N/A

Font

N/A

Note: Color, Linetype, and Lineweight are all ByLayer unless otherwise instructed.

Layering Scheme

Objects on Layer Name Color Linetype Lineweight

Center Lines

Dimensions

Instructions:

Center

Dimension

Magenta

Blue

Continuous

Continuous

N/A

N/A

1. Open the drawing AutoCAD 2D Lab 13-1 that you created in Module13 and save it as AutoCAD 2D Lab 34-1.

2. Erase the titleblock and border and replace it with the titleblock andborder from the template Module Template C. Hint: Using the NEW

command start a new drawing with the template Module Template Cand then using the COPYBASE command, copy the border andtitleblock using 0,0 as the basepoint into your drawing.

3. Move the object to center it in the new border. You can center it byeye.

4. On layer Center, draw the center lines shown below. Completed Drawing



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Lab Exercise 34-2



Name Template Units Text Style Font

AutoCAD 2D Lab 34-2 N/A Millimeters N/A N/A


Layering Scheme


Center Lines

Dimensions

Instructions:

Center

Dimension

Magenta

Blue

Continuous

Continuous

N/A

N/A

1. Open the drawing AutoCAD 2D Lab 12-2 that you created inModule 12 and save it as AutoCAD 2D Lab 34-2.

2. Erase the titleblock and border and replace it with the titleblockand border from the template Module Template A3. Hint: Using

the NEW command start a new drawing with the templateModule Template A3 and then using the COPYBASEcommand, copy the border and titleblock using 0,0 as thebasepoint into your drawing.

3. Move the object to center it in the new border. You can centerit by eye.

4. On layer Center, draw the center lines as shown below. Completed Drawing



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Lab Exercise 34-3



Name Template Units Text Style Font

AutoCAD 2D Lab 34-3 N/A Millimeters N/A N/A


Layering Scheme


Center Lines

Dimensions

Instructions:

Center

Dimension

Magenta

Blue

Continuous

Continuous

N/A

N/A

1. Open the drawing AutoCAD 2D Lab 15-1 that you created inModule 15 and save it as AutoCAD 2D Lab 34-3.

2. On layer Center, draw the center lines as shown below.

Completed Drawing


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