The Key to Standardizing Annotation in CAD Files, Part 3: Dimension Styles

By Jennifer DiBona

This month’s article is the third in a series covering the different aspects of CAD standardization regarding annotation. Part 1 (June 2011) explains how to standardize text, and Part 2 (March 2012) explains how to standardize and create new linetypes. This month’s topic, dimension styles, is probably the least understood and most intimidating, but, by the time you finish reading this, you’ll be talking about parent and child styles like a pro!
 

Components of a Standard Dimension

There are several different types of dimension objects that you can create in an AutoCAD or IntelliCAD drawing. Some of them are linear dimensions, aligned dimensions, angular dimensions, radial dimensions, and diameter dimensions. Even though the various types are used to dimension different objects (lines, circles, etc.), all dimension objects have the same general components and can be easily managed using dimension styles.

Before diving into dimension styles, it is helpful to understand the terminology and know the different components of the dimension object itself. Knowing these details makes it much easier to navigate the seemingly endless settings that are available in the Dimension Styles Manager (Figure 1).

Defpoints/Origin: Defpoints (Definition Points) are CAD points and are placed at the origins of the measurement. For instance, in Figure 1 the side of the figure has been dimensioned as 4.0” long. The origin points for the dimension are at the endpoints of one side of the figure. Although they can’t be seen, the defpoints of the dimension object are at each endpoint.

  • Defpoints are nested as part of the dimension object.
  • They reside on layer defpoints (which does not plot).
  • Their size and visibility can be controlled by typing DDPTYPE at the Command: line.
Dimension Line: The dimension line component is made of one or two lines with terminators (arrowheads, tick marks, etc.) on the ends that show the space being measured.

Extension Line: The extension line component is made of one or two lines that run from the origin perpendicular to the dimension line and then beyond the dimension line for a short distance.

Dimension Text: Text that is centered or placed above or below the dimension line.

Arrowheads: The more generic term for this is “terminators”; it is the symbol that is placed at the ends of the dimension line. Rather than arrowheads, you can use architectural ticks, dots, or various other symbols as terminators.
 

The Dreaded “S” Word: “Scale”

Whether it’s text or linetypes or dimensions, standardizing annotation always comes down to the question of how to develop a standard that works for a 1:1 drawing as well as a 1:100 drawing. Believe it or not, dimensions are one of the easiest to manage regarding scale.

Just as with text and linetypes, the key to standardizing dimensions is getting everything to look and work right at 1:1. You can draw a line on your screen that’s four units long and dimension it with a linear dimension and decide what you like about it and what you don’t.

For instance, maybe the dimension text is positioned in line with the dimension line and you’d prefer it to be above. Or, maybe it is already above the dimension line, but it’s too far above the line for your taste. Maybe the extension lines start too close to the origin points for your liking or extend too far beyond the dimension line.

Once you make the appropriate changes to the dimension style and it is formatted properly, it’s a simple matter to change the scale factor to have it work with other scales. I recommend that you define a custom dimension style for every drawing scale you may need.
 

Parent and Child

Just like text entities, every dimension object added to a drawing is associated with a style. And, again like text, the default dimension style is “STANDARD.”

When you first open the Dimension Style Manager, you can see there are two available styles: annotative and STANDARD. I recommend that you leave the existing dimension styles intact and create a custom one of your own.

Follow the steps below to create a new custom dimension style for a 1:1 scale.
 
  1. Type DDIM to open the Dimension Style Manager.
  2. Left-pick on STANDARD and then pick the New button on the right.
  3. This opens the Create New Dimension Style window.
  4. Enter a “New Style Name.” The style name should indicate that the style is based on scale of 1:1.
  5. The new style should “Start With” the STANDARD style and is to be used for “All Dimensions.”
  6. Pick Continue (Figure 2)
  7. When the Dimension Style Manager pops up, notice that the style you are modifying is TCG_Scale_1.
  8. Switch to the “Fit” tab of the New Dimension Style dialog box and make sure the value for “Scale for dimension features” is set to “Use overall scale of: 1.00.” This means that this dimension style will be used to dimension objects to be plotted at 1:1 (Figure 3).
  9. You can then switch to the other tabs to make needed changes or adjustments. Figure 4 can be used to identify some common style changes.
  10. On the “Primary Units” tab, you can make changes as needed. (For this and the remaining steps, the preview window may or may not truly reflect the expected results. Some recommendations are highlighted in Figures 5, 6, 7, and 8).
  11. On the “Lines” tab, you can make changes as needed.
  12. On the “Symbols and Arrows” tab, you can make changes as needed.
  13. On the “Text” tab, you can make changes as needed. When developing a dimension style standard, I recommend creating a new text style named  “DIMTEXT” (or something similar) that has a fixed height of 0. This text style should be used for all of your dimension styles. This allows you to manually control the dimension text height and manage it separately from other text in a drawing.

Now, with the changes we’ve made to the TCG_Scale_1 dimension style, a linear dimension and a leader look like Figure 9.

Unfortunately, this isn’t  what we were looking for. Rather, the text for the leader should be vertically centered rather than above the dimension line. The way we want it to look is in Figure 10.

In short, we want to have the dimension text for leaders to be positioned differently than dimension text for linear or aligned dimensions. To do this, we will need a “child style” for leader dimension objects. Child dimension styles retain most of the characteristics of the “parent style,” but not all. The parent style will be “TCG_Scale_1.”

Follow the steps below to create a new child style for leaders using the TCG_Scale_1 dimension style.

  1. Type DDIM to open the Dimension Style Manager.
  2. Left-pick on the existing style “TCG_Scale_1” and then pick the New button on the right.
  3. This opens the Create New Dimension Style window.
  4. Do not enter a “New Style Name” as the style name remains the same as the parent.
  5. Make sure that “TCG_Scale_1” (the parent style) is specified as the style to “Start With:”
  6. Pick “Leaders and Tolerances” as the “Use for:” setting.
  7. Pick Continue (Figure 11).
  8. When the Dimension Style Manager pops up, notice that the style you are modifying is TCG_Scale_1:Leader.
  9. Switch to the “Text” tab and change the “Vertical” setting for “Text Placement” to “Centered.”
  10. Pick OK to close the Modify Dimension Style dialog box (Figure 12).
  11. After creating the child style for leaders and tolerances, your list of available dimension styles should look like Figure 13. Remember, the preview window may or may not truly reflect the expected results.
  12. Repeat these steps as needed to fine-tune each type of dimension object to look the way you want.
If you are using TCG_Scale_1 to dimension features in your drawing, leaders will position the text in line with the dimension line, and all other types of dimensions will position the text above the dimension line. After all of these changes, the dimensions should look like they do in Figure 10.
 

Styles for Every Drawing Scale

Our last step is to create additional dimension styles that are based on other drawing scales we may need. Now that our TCG_Scale_1 has been formatted properly, we can use it as a model for the new ones.

Follow the steps below to create a new custom Dimension Style for a 1:40 scale:
 
  1. Type DDIM to open the Dimension Style Manager.
  2. Left-pick on the existing Style “TCG_Scale_1” in the left-hand column.
  3. Pick the New button on the right.
  4. This opens the Create New Dimension Style window.
  5. Enter a “New Style Name.” The Style Name should indicate that the Style is based on scale of 1:40.
  6. The new Style should “Start With” the TCG_Scale_1 Style and is to be used for “All Dimensions.”
  7. Pick Continue (Figure 14).
  8. When the Dimension Style Manager pops up, notice that you are now modifying the TCG_Scale_40 dimension style.
  9. Switch to the “Fit” tab.
  10. Change the “Scale for dimension features” setting to “Use overall scale of: 40” (Figure 15).
  11. Pick OK to close.

Back in the Dimension Style Manager, you can see that we’ve successfully created the TCG_Scale_40 dimension style, but that the leader child style was not created (Figure 16). So, for every new style based on a different scale, the child styles will need to be recreated.

But, now you know how easy that is to do!

Although I’m sure I’ll find other CAD standards issues to write about in the future, this wraps up the three biggies of text, linetypes, and dimensions. I hope you’ve found it helpful. As always, please don’t hesitate to follow up with me if you have any questions. I hope you had a great summer!

Jennifer DiBona is an independent consultant doing business as That CAD Girl. She is a Carlson Software reseller and provides CAD training, technical support, and other CAD-related services. Visit her website at www.thatcadgirl.com to find out more.  

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