ben mdm c10 - hong kong polytechnic university training materials... · 2002. 7. 23. · prefix...

BEN MicroStation Drafting (Metric Edition) Bentley Education Network 10-1

10 Dimensions

Dimensioning is an essential component of most drawings, the designed objects cannot be fully defined without them. In the MicroStation context, Dimensions are labels combining geometry and text into one Element which are generated automatically. We can create linear, angular and radial dimensions for any element or combinations of elements. There are many types of dimensioning, with a large number of individual tools to enable us to create each type. A dimension label may optionally be Associated with the element or points being dimensioned. Dimensions automatically update to remain accurate after elements have been manipulated if this Association is established.

Dimensioning styles may vary to comply with state and country standards, with the particular discipline we work in, even with our personal preferences. Every component of the dimensioning style can be customized to suit the requirements of the project being undertaken.

When you have completed this chapter, you will be able to:

• Recognize the components of a Dimension Element

• Use the Linear Dimensioning tools to dimension distances

• Use the Radial dimensioning tools to dimension arcs and circles

• Configure the various dimension components to create a Dimension Style

• Modify existing dimension elements.

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10-2 Bentley Education Network BEN MicroStation Drafting (Metric Edition)

DimensionsThe Dimension Element

The Dimension ElementA Dimension Element may be a single dimension or a “chain” of dimensions, all placed in a single operation. The element is composed of several components, which, depending on the type of dimension, may include:

• Extension Lines - lines extended from the dimensioned points

• Dimension Line - a line the same length as the dimension, usually parallel to the direction of the dimension

• Dimension Line Terminators - symbols such as arrowheads used to define the ends of the dimension line

• Dimension Text - the dimension in the chosen units of the design file

• Prefix or Suffix - may be used to indicate that the dimension is of a diameter, radius etc.

These components are illustrated in Figure 10.1

Figure 10.1 Typical Dimension Elements

Extension Line

Dimension Text

This is a single Dimension Element, placed as a “String” or “Chain” of dimensioning.

Dimensions of Size

Angle Between Lines

Radius

Diameter

Prefix

Suffix

TerminatorDimension Lines

DimensionsThe Dimensioning Tools


The Dimensioning ToolsThese tools are all highly configurable to create a large variety of types of dimensions.

Figure 10.2 The Dimension Tool Box

Quick Dimensioning of ElementsIndividual elements and segments of elements may be dimensioned by using only two clicks of the data button, or only one “press, drag and release” action. The Dimension Element tool automatically adapts to suit the element being dimensioned.

We will use this tool in the following exercise, which uses the supplied DGN called “BEN_Dim1-m.dgn”. This DGN is saved using a Lock we have not used so far in the course, Level Lock. When this lock is checked On, we can only select elements that are on the Active Level, elements on other levels cannot be manipulated. This feature is used to prevent the guide numbers and circles being accidently identified for dimensioning instead of the intended geometry. The circle and bar symbol will appear when the pointer is moved over elements on locked levels.

Note: This means Level Lock will need to be turned Off temporarily if we need to delete any dimension elements placed in the next exercises, as they are being placed on a level named Dimensions, which will not be Active.

Dimension Elements and Segments

1. Open “BEN_Dim1-m.dgn” from our allocated student directory; select the view group Dimension Elements from the combo box in the View Groups tool box.A group of simple elements will display, along with some numbers and circles for guidance. Clicking the Lock icon in the Status Bar will reveal that the settings of this DGN were saved with Level lock On.

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2. Ensure that the Sample Elements level is Active.If this is not the case, Level Lock will prevent the elements for dimensioning being identified.

3. Select the Dimension Element tool, with the default tool settings as shown in Figure 10.3.

4. Identify the line at location 1, move the pointer to location 2 and accept.The horizontal line is dimensioned with the Dimension Lines outside the extension lines and the Dimension Text inside them.

5. Identify the circle at location 3 and move the pointer to location 4 and accept.The tool has changed to placing a Radial instead of a Linear dimension. Since we identified a circle, it dimensions the Diameter.

6. Identify the Arc segment at location 5 and accept at 6.The tool is now dimensioning an arc, so it dimensions the Radius.

7. Identify the line at location 7 and accept at 8.The vertical line is dimensioned with the Dimension Line and the Dimension Text inside the extension lines.

Figure 10.3 Dimensioning Elements

DimensionsDimension Alignments


Dimension AlignmentsThe Alignment of a dimension element is basically the direction the Measurement is made for the Dimension being placed. The alignment setting also defines the direction of the dimension line and (usually) the text.

Place Dimensions with Various Alignments

1. With “BEN_Dim1-m.dgn” open, select the view group Alignments from the combo box in the View Groups tool box.A group of angled lines will display, along with location numbers and circles.

2. Select the Dimension Element tool, Alignment: View (as before), identify the line at location 1, accept at location 2.The dimension is aligned with a view axis, y in this case. The dimensioning is placed at the left side, as we moved the pointer to the left after we identified the element.

3. Select the Rotate View tool (page 1-26), Method: 2 Points.

4. Keypoint snap to the lower end of the line at location 1 as the first point, then define the x axis of the view with a snap to the upper end of the same line.The view is now rotated to make the lines appear in the view to be horizontal and vertical.

5. Reset back to the Dimension Element tool, Alignment: View (as before), identify the line at location 3, accept at location 4.

6. Repeat step 5, except this time set the Alignment to Drawing.

7. Note that the view rotation is ignored this time, the dimension is aligned with the y axis of the Drawing or the Design Plane.

Figure 10.4 View and Drawing Alignments

These dimensions were placed using View alignment and located to one side, thus the measurement was made vertically.

The view has been rotated here. The angled dimension was placed using Drawing align-ment, which ignored the view rotation.

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8. Select the Rotate View tool, Method: Unrotated to restore the view to its usual rotation.

9. Reset back to the Dimension Element tool, Alignment: True, identify the line at location 5, accept at location 6.The measurement is made along the line, regardless of its angle.

10. Set the Alignment to Arbitrary, identify the line at location 7, accept at location 8.This is a version of True alignment, but it allows the arbitrary angling of the extension lines to suit the situation. A typical application is on Isometric views.

Figure 10.5 Various Dimension Alignments

This was the dimension placed using View alignment while the view was rotated.

DimensionsAssociating Dimensions


Associating DimensionsThere is another Lock setting involved here, Association Lock. When this lock is enabled, we are able to place our dimensions with associations created to the points in the drawing that they dimension. The effect of this association is that when the point on the element changes position due to a manipulation or modification, the dimension automatically updates. This association is similar to that used with the Place Note tool on page 9-33; it applies even when the dimension point is on an element in a reference attachment. The lock may be controlled from the Tool Settings windows of the dimensioning tools, or from the locks menu in the Status Bar.

Placing Associated Dimensions

1. With “BEN_Dim1-m.dgn” open, select the view group Associated from the combo box in the View Groups tool box.Two horizontal lines will display, with location numbers and circles.

2. Select the Dimension Element tool, Alignment: View, Association: Checked, identify the line at location 1, accept at location 2.

3. Remove the Association checkmark from the Tool Settings window, identify the other line at location 3, accept at location 4.

4. Select the Modify Element tool, use AccuDraw to change the length of each line in turn to 150mm.The top line was dimensioned using Association, the bottom one was not, so its dimension was not updated.

Figure 10.6 Association of Dimensioning

This dimension was placed with Association On . . .

. . . this one with Association Off.

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DimensionsDimension Size Tools

Dimension Size ToolsThe Dimension Element tool provides a quick method to do exactly as its name implies, Dimension Elements. What it cannot do, however, is dimension across multiple elements or segments. The two Dimension Size tools are available for this type of dimensioning, Dimension Size with Arrows and Dimension Size Stroke. The only difference between the two tools is the type of Terminator (see “Typical Dimension Elements” on page 10-2).

Placing a String of Dimensions

1. With “BEN_Dim1-m.dgn” open, select the view group String from the combo box in the View Groups tool box.The drawing shown in Figure 10.7 will display without dimensions.

2. Select the Dimension Size with Arrows tool, Alignment: View, Association: Checked. Identify the line at location 1, “Define length of extension line” at 2, “Select Dimension Endpoint” at 3, 4 and 5.The prompt will still read “Select Dimension Endpoint”.

3. Reset (the prompt will change back to “Define length of extension line” in case we want to continue the string of dimensions around the corner), Reset a second time to complete the string.

4. Place a new dimension string from 6, define the length of the extension line at 7, an endpoint at 5, finishing (Reset twice) at 4.

Figure 10.7 String of Dimensions with Stacking

There was insufficient room for the dimension text between the extension lines here, so a Stacked dimension was automatically generated.

A string of dimensions as placed here is a single dimension element.

DimensionsDimensioning Angles


Dimensioning AnglesThe most commonly used tool for dimensioning angles is Dimension Angle Between. This tool will dimension an angle between two elements, or two segments of the same element.

Dimensioning Angles

1. Open “BEN_Dim2-m.dgn”; select the view group Angle Between from the combo box in the View Groups tool box.The drawing shown in Figure 10.8 will display without dimensions.

2. Select the Dimension Angle Between tool, identify the segment of the triangle at location 1 to “Select first line”, “Select second line” at 2, position the dimension element at 3.

3. Repeat the above for locations 4 to 6, 7 to 9 and 10 to 12.

Figure 10.8 Dimensioning Angles Between Lines

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DimensionsRadial Dimensions

Radial DimensionsThe Dimension Element tool was used for dimensioning arcs and circles on page 10-4, but this tool only provides enough functionality to do basic dimensioning. We need to choose from more options and make an extra mouse click or two with the Dimension Radial tool, but it offers more functions.

Placing Radial Dimensions

1. With “BEN_Dim2-m.dgn” open, select the view group Radial.The drawing shown in Figure 10.9 will display without dimensions.

2. Select the Dimension Radial tool, Mode: Center Mark, Alignment: View, Association: Checked, Center Size: 0.Center Size is an override setting; the dimension setting for the text height applies if it is left at 0 (the default).

3. Identify the arc at location1, accept the center mark away from the geometry.

4. Change the Mode to Radius and identify the arc at location 3, position the inner end of the dimension at 4.

5. Change the Mode to Radius Extended and identify the arc at location 5, position the outer end of the dimension at 6.

6. Change the Mode to Diameter and identify the circle at location 7, position the inner end of the dimension at 8.

7. Change the Mode to Diameter Extended and identify the circle at location 9, position the outer end of the dimension at 10.

Figure 10.9 Radial Dimensions

DimensionsDimensioning From an Origin


Dimensioning From an OriginWe are able to label distances along a line known as an Ordinate Axis from an Origin or Datum. The tool for this job is called Dimension Ordinates.

Dimensioning From an Origin

1. With “BEN_Dim2-m.dgn” open, select the view group Ordinates.The drawing shown in Figure 10.10 will display without dimensions.

2. Select the Dimension Ordinates tool, Alignment: View, Association: Checked.

3. Identify the outline at location 1 as the Ordinate Origin.All of the dimensions placed during this operation will be measured from this point.

4. Place a data point to the right of the origin (about location 2) to define the Ordinate Direction.

5. Place a data point at location 3 to define the length of the extension lines.

6. Keypoint snap to the ends of the lines at locations 4 through to 9, Reset to complete the operation.

Figure 10.10 Dimensioning Ordinates

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DimensionsDimension Styles

Dimension StylesA Dimension Style, like a Text Style (page 9-2), is a set of Dimension element attributes which will normally be saved for re-use, either within the DGN where it is being applied, or externally for general application. A Dimension Style may be created in one DGN and imported into others, in the same way as Text Styles. In practice, special DGNs are often created without any geometry placed in them, just to hold Dimension and Text styles.

Creating Dimension StylesIn the next series of exercises, we will create dimension styles of our own and save them for later use. The first style will be based on some dimensions already placed in a supplied drawing, “BEN_DimS.dgn”.

Create a Dimension Style

1. Open “BEN_DimS.dgn” from your assigned Student directory. The End Plate design is displayed, with some dimensioning and annotation already in place. It is shown (at reduced size) in Figure 10.11. Our first job will be to Match the current dimension settings to an existing dimension.

Figure 10.11 The End Plate Drawing

DimensionsCreating Dimension Styles


2. Select the Match Dimension Settings tool, identify one of the dimension elements in the design.This will restore the attribute settings that were active when the identified dimension element was placed.

3. Select the Dimension Element tool, Style: None, Alignment: View, Association: Checked.

4. Zoom in on the area about the top of the drawing, identify the line beside location 1 (not on the location marker circle), position the dimension at location 2.

5. Manually snap to the dimension element just placed and note the pop-up info.We find that the dimension element has been placed on a level named “Supplied Dims”. We need our dimensioning to be placed on the Dimensions level, so we need to change the Level setting of the current Dimension Style.

Figure 10.12 Matching Dimension Settings

The current Dimension Style is actually “none” according to the tool settings window. We are now going to change the Level setting and save the current collection of dimension attributes as a named Dimension Style.

When the pointer is over a dimen-sion element, it will highlight.

If we move the pointer over an element other than a dimension while we have the Match Dimension Settings tool active, the “Barred” symbol will display. This is the text component of a Note, not a dimension.

We need to use a manual snap to display pop-up info when the active tool disallows AccuS-nap on particular elements.

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6. Choose Element > Dimensions to open the Dimension Settings dialog box.We can also open this dialog box with the magnifying glass icon in the Tool Settings window of any tools used to place dimensions.

7. Highlight Dimension Lines in the left side panel, ensure that the Level box is Checked, then choose Dimensions from the Level option menu.The dialog box may be left open and moved aside as necessary. We will now use a new tool called Change Dimension (to active settings) to update the dimension we placed earlier.

8. Select the Change Dimension tool; identify the dimension at location 2 and accept away from any geometry, then manually snap to it and note that its level is now Dimensions.Now we have a collection of attribute settings that we will save as a Dimension Style.

9. In the Dimension Settings dialog box, click the Create Dimension Style icon to open the Create New Style dialog box. Name the new style 1:1 Mech Ext, with the description With Extension Lines; click OK.

10. Click the Save Style icon in the Dimension Settings dialog box to save our new style; close the dialog box.We now have a dimension style that matches the dimensioning supplied with this drawing, except for the level it is placed on. This style may be used in the current DGN, and/or imported into other DGNs.

Figure 10.13 Creating and Saving a Dimension Style

The style name has an asterisk if there are any unsaved changes. This is removed when we click the Save Style icon.

DimensionsUsing and Updating Dimension Styles


The Dimension Style we have just saved can now be put into service and checked out. If we find any deficiencies, we can easily fix them. We can also use this style as a base for other new styles, as we will see. For now, we will place some more dimensions on the “End Plate” model.

In this case we are going to place our dimensioning on the Design model, not on a Sheet model like our annotations of the “Spindle Assembly” made last chapter. It is OK to place our dimensioning in any model, although it is usually more convenient to place the dimensions on the Sheet when scaling is going to be involved. The dimensions of this model are suitable for printing out at full size, so scaling will not be an issue.

The following exercises will require identifying elements at locations marked with the usual small circles. If the location circle highlights instead of the desired element, just Reset and another element will highlight.

Using and Updating Dimension Styles

Dimension the Model

1. With “BEN_DimS.dgn” open, select the Dimension Size with Arrows tool, Alignment: View, Association: Checked.

2. Using keypoint snap, identify the line at location 3, “Define length of extension line” at 4, “Select Dimension Endpoint” at 5 then 6, Reset twice.We have placed a dimension string. The first Reset indicates that there are no more dimensions to be placed in the original direction, but we could still continue around a corner. The second Reset resets the tool ready to start a new dimension.

3. Select the Dimension Angle Between tool; identify the lines at location 7 to “Select first line”, “Select second line” at 8, position the dimension element at 8.

Figure 10.14 Dimension String and Angle Between Lines

Angle Dimension placed using the Dimension Angle Between tool.

Dimension String placed using the Dimension Size with Arrows tool.

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4. Select the Dimension Radial tool, Mode: Diameter, Alignment: View, Association: Checked. Identify the arc near location 9, position the dimension at location 10.We were not given any chance to position the dimension text to the left or the right, which can be a problem when dimensions overlap other geometry or each other. We will change the method of placement in our dimension style to provide more control.

5. If necessary open the Dimension Settings dialog box, highlight Placement and choose Location: Manual.

6. Delete the dimension placed in step 4; select the Dimension Radial tool, settings as before. Identify the arc at location 9, position the first endpoint at location 10.

7. Move the pointer slowly from side to side and note the effect, then define the leader direction with a data point at 11, Reset. This time we were able to decide which side of the dimension line the text was placed. Since we made the Placement change, an asterisk in the style name field indicates we have unsaved changes. If we choose not to save the change, the style will revert to the original setting the next time the DGN is closed. We will assume that we want to keep the Placement > Location setting as Manual.

8. Click the Save Style icon to save our modified style, clicking OK in the resulting alert box; close or move the dialog box as preferred.

Figure 10.15 Automatic and Manual Dimension Location

The text may be placed either side with this setting.

DimensionsUsing and Updating Dimension Styles


When we make changes to any settings of a Dimension Style, all dimensions placed with that style will update, this is why the alert box appeared in the last step. It will only appear when there are dimension elements in the design that were placed with that particular style.

The next element we place will be another radial dimension, but we will use the familiar Dimension Element tool, utilizing some more of its capabilities.

9. Select the Dimension Element tool, identify the arc at location 12.The element is recognized as being an arc, so a radius dimension is immediately offered, however it is not the type we require. The existing radius dimension on the smaller arc (22) has a dimension line emanating from the arc center and we need this one to be the same.

10. Re-open the Tool Settings window (<Ctrl>+<Spacebar>), click the Next button, move the pointer outside the window.The dimension line is emanating from the center, just as we want it.

11. Complete the dimension at location 13.This tool does not support manual location, unlike the Dimension Radial tool.

Figure 10.16 Using Dimension Element to Dimension a Radius

With the Dimension Element tool, we can click Next if the type of dimension is not what we require . . .

. . . then another alternative is offered. We can keep clicking Next until the required type appears, then accept.

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Overriding a Dimension StyleWe are able to temporarily override settings if we only need to place a small number of dimensions with different settings to the main style, such as “1:1 Mech Ext”. If the main style is unsuitable for an appreciable number of dimension placements, we would normally create multiple styles, which we will experiment with later on.

We will place a dimension between two parallel lines in the next exercise, which will need to be placed without extension lines. The “1:1 Mech Ext” style obviously has this part of the dimension element turned on.

Overriding Dimension Settings

1. With “BEN_DimS.dgn” open, select the Dimension Size with Arrows tool, Alignment: View, Association: Checked.

2. If necessary, click the magnifying glass icon to open the Dimension Settings dialog box; highlight Extension Lines and uncheck the Extension Lines box.

3. Make Nearest the default snap mode, identify the line that passes through location 14, data point at location 15 to position the dimension, then snap to the line that passes through location 16 to define the endpoint.The dimension text is being positioned manually, as this is the setting we saved as part of our dimension style (page 10-16). It may tend to snap to undesired locations as was the case when we were placing text in circumstances like these. Temporarily toggle AccuSnap (page 3-29) and AccuDraw Off, but do not forget to turn them both back On after the dimension has been placed.

4. Place the dimension text between the two lines, Reset (twice).

5. In the Dimension Settings dialog box, click the Restore Settings icon to revert to the saved style.Without restoring, the setting will remain until the DGN is closed.

Figure 10.17 Placing a Dimension Without Extension Lines

We need AccuSnap when we are defining the dimension . . .

. . . but not when we are manually positioning the text.

DimensionsSettings for Associated Dimensioning


Settings for Associated DimensioningWe have already been introduced to Association with dimensioning elements on page 10-7. The association between a dimension element and the geometry it is dimensioning can be established via a Reference attachment, in the same way as our note leaders were associated via the spindle assembly reference attachment on page 9-33. It naturally follows that we generally have Association On when we place dimensions. However, we may need to make some preparations for this in our Dimension Styles.

We will start by changing the thickness of the mounting plate section of the End Plate drawing. This thickness is dimensioned as part of a “string” of dimensions in a single element.

Association With Multiple Dimension Elements

1. With “BEN_DimS.dgn” open, place a Fence block (Inside mode) about the entire length of the vertical line starting at location 5, making sure no other vertical elements are within the fence.It does not matter if the location marker circle is included, as this is a Locked element, which means it will not be manipulated.

2. Select the Move tool, Mode: Stretch, move the fence contents 4 mm to the right, thus reducing the mounting plate thickness to 7 mm.The dimension string updates to reflect the change.

Figure 10.18 Associative Dimension String

This example is of a modification that did not alter the distance between the dimension line and the element(s) being dimensioned. This will not always be the case, as we will see.

The fence is placed to only include vertices that we want to manipulate.

When the stretch is completed, the two dimensions involved automatically update.

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3. Pan the view to a clear area and place a 50 wide by 30 high block.

4. Use the Dimension Element tool to place dimensions across the top and another along one side, with the dimensions outside the block.

5. Use the Modify Element tool to increase the height of the block from the top by 15.The side dimension updates correctly, but the top dimension is now “buried” inside the block, not as we originally placed it. To fix this problem, we must force the dimension line to retain its relative distance from the element being dimensioned. In other words, when the element moves, the dimensioning moves with it.

6. If necessary, open the Dimension Settings dialog box, highlight Placement, check the Relative Dimension Line box. Save the changes to the style (OK the alert).

7. Undo the modification, delete the top dimension, then place it again (this time it will have the Relative Dimension Line feature); Modify the block again as in step 5.

Figure 10.19 Relative Dimension Line

Note the useful information available from the Focus Item Description panel. This displays whenever we click in a check box or make a menu choice in this type of dialog box.

DimensionsDimension Line Settings


There are many more settings that may be made, far too many to be detailed in this course guide. We will do exercises on some of the main settings, with the rest explained very well by their Focus Item Description in the Dimension Settings dialog box (see Figure 10.19). We have already seen the Placement and Extension Line categories, we will now look at Dimension Line and Text categories. In the process we will create another dimension style. To save words in the following exercises in this chapter, it is assumed that we will click OK in the alert box each time we Save the Dimension Style.

Dimension Line SettingsThe active element attribute settings may be (and usually are) overridden by settings saved as part of a Dimension Style. There is a hierarchy of overrides applying here, with those set for the Dimension Line being at the top. Dimension Line settings may have an effect on all of the components of a dimension element, not just the Dimension Line itself. The Level setting applies to all of the components of the dimension element; the Symbology (Color, Style and Weight) also applies to all components, except when the individual components (such as Text) have overriding settings of their own.

Change Dimension Line Settings

1. Open “BEN_Dim1-m.dgn”, then open the Dimension Settings dialog box; ensure that Experiments is the active dimension style.

2. Click the Save Style As icon in the dialog box, save the style as Settings with the description Style for settings practice, click OK.The new style becomes the active style.

3. Highlight Dimension Lines, change the settings as necessary to those shown in Figure 10.20.

4. Highlight Extension Lines and uncheck the Color override if necessary; click the Save Style icon to save the style.

Figure 10.20 Dimension Lines Settings

When any of the boxes are left unchecked, the setting applied will be the relevent DGN setting active at the time we are placing the dimension element.

The Dimension Lines settings apply when these Extension Lines boxes are unchecked.

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Units SettingsThe Units settings for a Dimension Style are independent of the Working Unit settings made under Settings > Design File. These settings provide a lot of flexibility - we may even choose to place dimensions in Metric units in a DGN with English working units and vice-versa.

Experiment With Units Settings

1. With “BEN_Dim1-m.dgn” and the Dimension Settings dialog box open and positioned in the lower part of the view, ensure that Settings is the active dimension style.

2. Highlight Units in the Dimension Settings dialog box, choose MU label from the Label options.

3. Select the view group Dimension Units from the View Groups tool box; use the Dimension Element tool to dimension the size of the line, then zoom in to make the dimension text more legible; Pan the text to the top of the view.The dimension will be in millimeters, with the label “mm”.

4. Remove the checkmark from the Use Working Units check box, change the Master Units to Feet and the Sub Units to Inches. Choose MU label SU label from the Label options and 1/8 from the Accuracy options; Save the style, OK the alert box.The dimension text will now be in feet and inches, with labels.

5. Change the Label again , choosing SU Label; Save.The line will be dimensioned in inches only, no feet.

Leave the “English” units for now, as we will be using them in another exercise.

Figure 10.21 Units Settings

DimensionsUnit Format


Unit FormatThis setting relates mainly to angles, where the two main formats in use are Decimal Degrees and Degrees, Minutes and Seconds (see “Entering Angles” on page 2-22). The other settings are less often used and are self explanatory, so they will not be introduced here.

Change Dimension Angle Format

1. With “BEN_Dim1-m.dgn” and the Dimension Settings dialog box open as in the previous exercise, select the view group Unit Format from the View Groups tool box.

2. Highlight Unit Format in the Dimension Settings dialog box, ensure that the settings are as shown in Figure 10.22.

3. Select the Dimension Angle Between tool, identify the lower segment first, then the upper one and position as illustrated.The angle is dimensioned in Decimal Degrees format to 4 decimal places.

4. Under Unit Format, change the Display setting to DD^MM’SS” and the Accuracy to 0; Save the change.The dimension text will change to read the angle in degrees, minutes and seconds, with the seconds rounded off to a whole number.

Figure 10.22 Angle Formats

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Alternate LabelsUnder the Units settings, there is a section relating to Alternate Labels. With this feature, we can define a separate Units setting depending on the size of the dimension. For example, building plans may show any dimension equal to or greater than two feet in feet and inches, but those less than two feet in inches only. The smaller dimensions may also be shown with greater accuracy.

Defining and Placing Alternate Labels

1. With “BEN_Dim1-m.dgn” and the Dimension Settings dialog box open and positioned in the lower part of the view, ensure that Settings is the active dimension style and the “English” units are still as set in step 5 on page 10-22.

2. If necessary, select the view group Dimension Units and zoom in on the dimension text as in the previous exercise.

3. Change the Label option to MU label SU label, Save the style.The dimension will read 1’ 2 3/4”.

4. Check the Alternate Label box and make the settings as shown in Figure 10.23, Save the style.The dimension will change to read in Sub Units only (inches), at the accuracy of 1/32”.

5. Select the Extend Line tool (page 5-28), check the Distance box and enter 304.8 (the equivalent of 1 foot in “English” units); identify the line and accept the lengthening.

6. If necessary Pan the view to see the dimension text, which will have reverted to feet and inches with 1/8” accuracy.

7. Uncheck Alternate Label, check Use Working Units, set the Label to MU and the Accuracy to 0.1 then Save.

Figure 10.23 Using the Alternate Label

DimensionsSecondary Units


Secondary UnitsAnother option for our Dimension Styles under Units settings is Show Secondary Units. These are typically used where a design is to be issued to a variety of constructors, some of whom may be using English units, some metric. They may also be used to display the same units in different formats, for example inches and fractions and decimal inches.

Defining and Placing Secondary Units

1. With “BEN_Dim1-m.dgn” and the Dimension Settings dialog box open and positioned in the lower part of the view, ensure that Settings is the active dimension style.

2. If necessary, select the view group Dimension Units and zoom in on the dimension text as in the previous exercise.

3. Check the Show Secondary Units box and click Settings to open the Secondary Units dialog box.

4. Make the settings as shown in Figure 10.24; Save the style and dismiss the Secondary Units dialog box.The dimension text will now show secondary “English” units under the primary Metric. Opening the other view groups will show all the other dimensions with secondary units.

5. Uncheck the Show Secondary Units box and Save the style.

Figure 10.24 Showing Secondary Units

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Dimension Text SettingsThe choice of settings may depend partly on the standards applying within the organization owning the drawing, or perhaps on National and State imposed standards. They may also depend on the personal tastes of the operator. Regardless of where the choices are made, no settings have more influence on the appearance of the style than the Text settings. These settings not only define the text itself (font, size etc.), but how the text is placed. In the text style “1:1 Mech Ext”, we had the text set to Horizontal, which is not suitable for some types of dimensioning. We will change this for our new Text Style.

Change Dimension Text Settings

1. With “BEN_Dim1-m.dgn” and the Dimension Settings dialog box open, ensure that Settings is the active dimension style.

2. Highlight Text and click on each of the settings, including the check boxes, the entry fields and the option menus, noting the Focus Item Descriptions for each one at the bottom of the dialog box. Make the settings as shown in Figure 10.25.

3. Highlight Placement; if necessary choose Location: Automatic.We set this to Manual in the 1:1 Mech Ext style on page 10-16 to suit the dimensioning we were doing at that time, but Automatic is more generally used to locate the dimension text.

4. Click the Save Style icon to save the latest changes.As usual, an alert box appeared when we used the Save Style icon, warning of changes to existing dimensioning.

Figure 10.25 Text Settings

The Color override is not checked, so the text will appear as the same color as the Dimension Lines.

The Weight override is checked, with the text weight set to 1, which is differ-ent to the Dimension Lines.

The Font, Height and Width overrides are checked, so the DGN’s active text style is overridden.

DimensionsTool Settings


Tool SettingsThere are many Tool Settings that may be applied to each of a large number of dimensioning tools. In practice, there are more tools listed in the settings than there are in the Dimensions tool box, as each mode of every tool may be configured separately. For example, the Dimension Radial tool has five modes - Center Mark, Radius, Radius Extended, Diameter and Diameter Extended. Each of these have separate settings. Fortunately, once a set of standards have been agreed upon, these settings seldom need to be changed.

Change the Dimension Radial Tool Settings

1. With “BEN_Dim1-m.dgn” and the Dimension Settings dialog box open, ensure that Settings is the active dimension style.

2. Highlight Tool Settings; select Radius Extended from the right side Tool options.

3. Set the Prefix to None and the Suffix to R.

4. Click the Save Style icon to save these changes.

Figure 10.26 Dimension Radial/Radius Extended Tool Settings

Some standards require the symbol to be placed before the dimension, some after it and some require no symbol at all.

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Prove the New Dimension Settings

1. With “BEN_Dim1-m.dgn” open, choose the String view group.

2. Turn Off Level lock by clicking the lock icon in the Status Bar and removing the checkmark. Delete the dimension elements currently in place.

3. Check Level lock back On; ensure that Sample Elements is the Active level.Having this lock on ensures that we will not unintentionally identify other dimensions, or the location guide circles and numbers when placing new dimensions.

4. Select the Dimension Size with Arrows tool, Dimension Style: Settings, Alignment: View, Association: Checked, place a string of dimensions from location 1 through to 4, as we did previously on page 10-8.The prompt will still read “Select Dimension Endpoint”. Reset twice.

5. Place a second dimension string starting at location 6, finishing at 4.

6. Select the view group Dimension Element; turn Off Level Lock and delete the dimension placed on the arc at location 5; turn Level Lock back On.

7. Select the Dimension Radial tool, Dimension Style: Settings, Mode: Radius Extended, Alignment: View, Association: Checked, re-dimension the arc at location 5.

8. Re-open the Dimension Settings dialog box; highlight Text and check the Color box, select a color (other than blue).

9. Change the Font to 23 Italics and Save the change, answering OK to the alert box.The Dimension Style has been updated, so all of the dimension elements in the DGN placed with this style will change to reflect this.

Figure 10.27 Changed Dimension Style

Saving a change to a style will apply the change to all dimen-sioning with that style in this DGN.

DimensionsModifying Dimension Elements


Modifying Dimension ElementsExisting dimension elements may be operated on by some of the same tools used to modify other MicroStation elements.

• The position of components of a dimension element may be moved with the Modify Element tool

• Extension lines may be added to a string of dimensions with the Insert Vertex tool

• Extension lines may be removed from a string of dimensions with the Delete Vertex tool

• The dimension text may be edited to change values or add text using the Edit Text tool.

Moving Dimension TextThe legibility of dimension text can often be enhanced by changing its position along the dimension line, moving it away from other dimensioning and linework.

Moving Dimension Text

1. With “BEN_Dim1-m.dgn” and the Dimension Settings dialog box open, ensure that Settings is the active dimension style. Choose the Units settings, change the Accuracy to 0. Save the dimension style.

2. Choose the String view group, turn Off Level lock, AccuDraw and AccuSnap.

3. Select the Modify Element tool and identify the dimension text 16; move it to fit between the extension lines, accept and Reset.The dimension may align itself with the other vertical dimension and the lower dimension line will reduce in length to match the upper one.

4. Identify the same text again, this time move it to above the upper extension line, accept and Reset. Turn Level lock, AccuDraw and AccuSnap back On.The upper dimension line will increase in length to remain under the text.

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Figure 10.28 Moving Dimension Text

Dimension With LeaderIt is occasionally necessary to move dimension text right away from the dimension line, either to make it more legible or to prevent it from hiding other geometry. This is sometimes referred to as “Ball and Chain” dimensioning. We can only do this if the dimension is placed with Allow Dimension With Leader enabled. When the text is moved away (using the Modify tool, as in the previous exercise) we can optionally have a line or a curve joining the text to its dimension line.

Moving Dimension Text Away from the Dimension Line

1. With “BEN_Dim1-m.dgn” and the Dimension Settings dialog box open, select the view group Unit Format from the View Groups tool box.

2. Highlight Dimension With Leader in the Dimension Settings dialog box, make the settings as shown in Figure 10.29.

3. Dimension the angled lines as shown in the top illustration using the Dimension Size with Arrow tool to place a Dimension String.

4. With Level Lock off, select the Modify Element tool and move the text away from the dimension lines, as in the lower illustration.

Figure 10.29 Dimensions With Leader

These dimensions were placed with the settings as shown . . .

. . . but the difference does not become obvious until we move the text with the Modify tool.

DimensionsDimension With Leader


Moving Dimension and Extension LinesWhen placing linear dimensions, the dimension line is positioned when we define the length of the extension line. The start and end points of the dimension are defined with snaps to the geometry. We can change both of these definitions at a later time, using the Modify tool in both cases.

Moving Dimensioning Linework

1. With “BEN_Dim1-m.dgn” and the String view group open, toggle AccuSnap On if necessary.

2. Select the Modify Element tool; identify the dimension lines one at a time and move them with respect to the design geometry, (optionally) accept the new positions.Moving one dimension line in a dimension string will move the lot. When the dimensions “stack” as on the right side of the design, the stack offset will remain unaltered.

3. Still using the Modify Element tool, snap to the inner end of the lowest extension line.

4. Snap the extension line to the vertex on the internal geometry as shown in Figure 10.30.The dimension text changes to suit the new start point.

5. Move the dimension lines again if necessary, as in step 2.

Figure 10.30 Moving Dimensioning Linework

Moving dimension lines moves the dimen-sion text as well. It is often necessary to improve a dimension layout this way.

In this case we are moving the Start Point of the dimension, so the Dimension Lines move as the first Extension Line is fixed at its original length.

The layout of the dimension is no longer appropriate.

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Changing the Number of Dimensions in a StringDimension strings are single elements, but that does not prevent us from making changes to individual components of the dimension element, as we have already found out. If, for any reason, we need to add an intermediate dimension to a string, or add an extra dimension to either end of the string, the ordinary Insert Vertex tool (page 5-34) is used. Conversely, if a dimension in the string is not needed, it can be removed with the Delete Vertex tool (page 5-35).

Adding and Deleting Extension Lines

1. With “BEN_Dim1-m.dgn” and the String view group open, select the Insert Vertex tool and identify the right side dimension string.

2. Snap the new extension line to the original start point for the dimension as shown in Figure 10.31.Another dimension is added to the end of the string in this case, but it could have been an intermediate dimension - this will depend on the point chosen on the geometry being dimensioned.

3. Select the Delete Vertex tool, identify the extension line extended from location 5 as shown in Figure 10.31, then accept when snapped to the desired extension line.

4. Use the Modify Element tool to move the dimension element further away from the model geometry.Moving the dimension text components individually is sometimes necessary to improve the legibility of the dimensioning.

Figure 10.31 Inserting and Deleting Dimensions

Adding an extra dimension is simply a matter of identifying the dimension element (data point to any part of it) and snapping to the additional point we wish to dimension in the string.

When extension lines are deleted, it is often necessary to modify the position of the dimesion element, or at least its text.

DimensionsEditing Dimension Text


Editing Dimension TextDimension text may be edited using the Edit Text tool (from the Text tool box, see page 9-26). It should seldom be necessary to change the automatically generated value of a dimension, as it is generally possible to change the design itself to the correct dimensions. This is especially easy with Associated dimensions, see page 10-7.

It is also possible to adjust the “rounding off” Accuracy of dimensions in the Units setting of the Dimension Settings dialog box. However, apart from forcing a change of value for the dimension, we have the option of adding extra text while retaining the automatically generated value. We will use the latter option to add the Alignment settings used when we placed the aligned dimensions (page 10-5).

Editing Dimension Text

1. With “BEN_Dim1-m.dgn” and the Alignments view group open, choose Workspace > Preferences from the Main menu bar; choose Text from the Preferences dialog box, then (if necessary) set Text Editor Style: Dialog Box.

2. Select the Edit Text tool and identify and accept the dimension text associated with locations 1 and 2.A special text editor window (smaller than the “word processor” style window) opens for editing dimension text. The asterisk (*) in the entry field represents the automatically generated text.

3. Click in the text entry field to position the cursor to the right of the “*”, then key in a <Space> followed by (View); click OK.

4. Repeat the process to add (True) after the dimension at locations 5 and 6, then again to add (Arbitrary) to the text at 7 and 8.

5. Identify the text at 3 and 4, this time replace the “*” with 130.

Figure 10.32 Dimensions With Changed Text

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DimensionsDimensioning to Scale

Dimensioning to ScaleBy now, we will be quite used to creating all our models at full size. We have used scale when we have referenced these models to a drawing sheet, as we did with “Furnished Cottage.dgn” on page 8-9. We may also have noticed a Scale setting at the bottom of the Dimension Settings dialog box when we were working with the Units settings. Is this a setting we need to make when dimensioning a drawing sheet model, such as the one in “Furnished Cottage.dgn”?

The answer to that is No. In practice, this setting will only be used in unusual circumstances, such as when working with drawings created with older versions of CAD software. Dimensioning to scale is automatic, providing we always snap to the element being dimensioned, either with AccuSnap or manually. When we snap a dimension start or end point to a reference attachment, the scale of the attachment becomes irrelevant, the dimension text will show the actual size of the design model.

Dimension a Sheet Model

1. Open “Furnished Cottage.dgn”, select the Layout Sheet Views from the View Groups tool box. Zoom in on the site plan area of the drawing sheet.Before we can start dimensioning, we are going to need a Dimension Style, so we will Import some that we created in “BEN_DimS.dgn”

2. Open the Dimension Settings dialog box if necessary, choose File > Import.

3. Select “BEN_DimS.dgn” from our own allocated directory; click OK.

Figure 10.33 Importing Dimension Styles

DimensionsDimensioning to Scale


4. Select the 1:1 Mech Ext dimension style in the Dimension Settings dialog box, highlight Units; ensure the Label is set to MU .The Working Units box is checked, so we will be using the working units specified for this model, millimeters. The dimensions will be rounded to the nearest millimeter, since the Accuracy is set to 0.

5. Highlight Placement, choose Location: Automatic.

6. Select the Dimension Size Stroke tool, ensure that AccuSnap is On and place a dimension from the lower-front corner of the site to the lower-front corner of the house, as shown in Figure 10.34.The dimension (in millimeters) shows the distance to be about 14.5 meters.

7. Toggle AccuSnap Off, repeat the dimension, but this time place data points without snapping (zoom in further for more accuracy).The dimension shown this time is 29 millimeters, which is the approximate distance along the drawing sheet. This proves that we must use snaps, as when we do we can forget about the Scale.

Figure 10.34 Dimension Scale

When we use snaps, the dimension is placed with the “real” size, regardless of the Reference Scale.

Without snapping to a Ref-erence, the size in relation to the Sheet Model is shown. This distance will be inacurate due to round-ing error.

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DimensionsDesign Problem - Dimension the Mounting Plate

Design Problem - Dimension the Mounting PlateFigure 10.35 is the drawing that we used in chapter 5 to create the model in our “Mounting Plate.dgn”. Our task is now to place dimensioning on the design.

We are to create new Dimension Styles which will place dimensions that look somewhat similar those in the illustration, unless stated otherwise below:

• The dimensioning is to be placed in the design model on a level named Dimensions

• The Text Height is 2.5mm and the Font is Arial

• The Trailing Zeros are suppressed in the illustration - we must find this setting for ourselves

• The radius and diameter dimension text is at various angles in the illustration, but we are to place those appearing outside the plate outline with the text horizontal - again, we must find this setting for ourselves

• The remaining settings are our own choice, but the result must either closely resemble the illustration, or be as stated above.

Figure 10.35 Mounting Plate

ben mdm c10 - hong kong polytechnic university training materials... · 2002. 7. 23. · prefix...

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