Part 2 of a two-part series on AutoCAD’s powerful dimensioning utility
This is a continuation of Part 1, where we introduce Power Dimensions. We will cover much of the detail of what was touched on.
Use Chamfer to create dimensions for bevelled edges. Start by selecting the chamfer line. Then select the lines forming the chamfer. The output is dependent on the active dimension settings (AM:Standards).
Power Dimensioning extends past just the annotation tools. You can also apply dimensioning when creating the chamfer with ACM’s chamfer command.
And insert radius dimensions as you create fillets.
Dimensioning can be tedious. Because of this ACM includes tools to streamline the dimensioning process.
After adding a linear or angular dimension use the command options to add the subsequent dimensions as chain or baseline dimensions.
All dimensions chained align to the original base dimension. Baseline dimensions add above or below the base dimension keeping the set dimension gap.
You can also start baseline and chain directly. The first step is selecting the base dimension.
Depending on selected base dimension, ACM may rearrange existing dimensions automatically to align with the new dimension sets.
Use Multiple Dimension to add several dimensions at one time. This command starts with the Multiple Dimensioning dialog, where you select the style and set the dimensioning options.
Select the Parallel tab when wanting to add baseline or chain dimensions.
With baseline additionally set the Alignment. Use Inside Out to align the dimensions starting from the points closest to the baseline then to the furthest. Select Outside In to align the dimensions, beginning from the points furthest to the baseline to the closest.
Enable Both axes when wanting to add the dimensions in two directions and Rearrange into a New Style when wanting to change existing dimensions into the select parallel style such as when converting existing chained dimensions to baseline dimensions.
ACM adds the dimensions from a selected point to all vertexes on the contour of the selected objects. You can dimension separate objects, even the objects within blocks.
As the tab title says, select Ordinate when wanting to create ordinate style dimensions. Ordinate dimensions show the x and y distances of the feature relative to a specified origin. Set the type to use the Current Standard or to Equal Leader Length or Center Cross on Edge.
Use Equal Leader Length when wanting visual consistency. ACM sets the dimension leader lines to all have the same length.
With Center Cross on Edge ACM places a center mark on the objects you are dimensioning. This is most useful with circular objects, like holes
The third choice, Shaft/Symmetric, creates symmetrical dimensions. It works with any object, not just those generated by ACM’s shaft generator.
Intended for dimensioning symmetrical objects (hence the name), you add multiple dimensions about a centerline, like shafts and other revolved features or mirrored parts where the left and right side are similar. It places the dimensions on both sides of the selected centerline.
Set the type to Shaft (Front View), Shaft (Side View), or Symmetric. To force dimensions inside the profile, enable Place Dimension Inside Contour.
When dimensioning a front view, after selecting the objects to dimension you then select the centerline or specify the centerline location. This specified centerline is what ACM dimensions about. Note that ACM dimensions all selected objects even if there is no matching object on the other side of the centerline.
Power Dimension Formatting
By selecting dimensions, ACM activates the Power Dimensioning contextual ribbon tab. This happens even when the dimension was created with non-Power Dimension-tools. Use this tab to apply formatting, fits and tolerances.
Change the Representation, making the dimension an inspection and/or reference dimension. Or tag the dimension as theoretically exact or not to scale.
With inspection dimensions, additionally select the frame type, set a label and specify the inspection frequency.
Use the Dim Text features to set the units, adjust the precision and toggle alternate units.
If you double-click the dimension (instead of selecting it), not only do you get access to the contextual ribbon tab, but it opens the dimension text for editing. You can also select Edit Dim Text from the contextual ribbon.
While editing the text, insert symbols and line breaks from the gallery. The ribbon panel updates with the last used symbols.
Power Dimensions can incorporate Tolerance and Fit List information directly into the dimensioning. From the ribbon, turn on the display of fit or tolerance information. Then select the desired representation (Fits) or method (tolerance).
With Fits, select the symbol, or with representations including both, select the hole and shaft symbol.
Use the Fits dialog as an alternative to selecting a fit symbol for the dimension. From this dialog, select the hole and shaft fit and review the fit combination graphically.
With tolerances, set the upper and lower limits for the nominal dimension and the desired precision. The precision of fits and tolerances is independent of the dimension style precision.
Use the various features in the Format panel to:
- Move rotated dimension text back to its default position
- Rotate dimension text by a user specified angle
- Slant extension lines by a user specified angle (creating oblique dimensions)
With radial dimensions, add a landing line and toggle the location of the arrow heads.
When editing a dimension (text edit is active) Edit Geometry becomes available. This presents a dialog in which you can change the dimension appearance graphically. Selecting a component in the dialog toggles its visibility. When selecting an arrowhead, ACM displays a list of arrowheads to choose from.
When you have selected multiple dimensions, the contextual tab shows property values that are the same across all the selected dimensions. When the properties differ across the dimensions, they will be blank or displayed as VARIES. Regardless, changing the property applies the setting to all selected dimensions.
To speed up the process, you can apply predefined text from stock templates and copy the formatting and settings from other dimensions.
[Predefined Text & Copy From]
Editing Dimensions
Use Arrange to rearrange linear and ordinate dimensions. This applies the dimension gap spacing, placing the dimensions at the appropriate distance from the selected contour point. Or use the automatic option and let ACM determine the outer location.
When selecting dimensions in both directions (axes) you do not need to select the outer contour as ACM uses the endpoints for the extension lines.
Arrange is not perfect. When wanting a baseline output, you may need to manually move the dimensions into the proper order from the outer contour prior to running arrange.
When dimensions overlap or when dimensions cross other objects it is common to many standards to break the dimension. Use ACM’s Break (AMBREAK) to insert gaps at specific points on the dimension.
Start by selecting the dimension to break. By default, where you select the dimension becomes the first point of break. Although you can respecify the first point. Then select the end of the break.
The break with this workflow is not associative as by moving the crossing object the break does not update. By adjusting the position of the broken dimension, ACM removes the break. This is a feature where AutoCAD’s DIMBREAK is superior as the break stays regardless of moving the broken dimension.
An alternate workflow is using the multiple option. This only works with dimensions but allows you to select several dimensions. ACM sets the gap sizing. With multiple the break is associative and does update as you move the broken dimensions.
Linear/Symmetric Stretch is an interesting take on the stretch command. You specify the amount of stretch by setting the value of the dimension. This adjusts not only the dimension but also the selected objects.
Start by setting the type, Linear or Symmetric. Then select the dimension text to change and set the desired value. Finish the operation by selecting the objects to stretch. This command defaults to a crossing window.
Note, you can only include one side of the dimension (DEFPOINTS).
Linear stretches the objects in one direction. Symmetric resizes the objects in both directions from the selected centerline.
In the expanded Dimension panel…
In the expanded section of the Dimension panel.
Join (AMDIMJOIN) is a great shortcut for taking dimensions of the same type and merging them into a single dimension. This works with linear and angular dimensions. The first dimension selected becomes the base and sets the position for the newly combined dimension.
The dimensions do not need to be aligned nor need to touch. ACM creates the new dimension for the extents of the selected dimensions.
Insert (AMDIMINSERT) is the opposite to join as it allows you to two split an existing linear or angular dimension into two. This command splits the dimension at the point you select.
ACM applies the active dimension style to the new dimension, regardless the styles set on the selected dimensions.
The Align (AMDIMALIGN) is a great clean-up tools as it lines-up linear, ordinate and angular dimensions to the selected base dimension. The first step is selecting the base dimension. The selected base sets which type of dimensions you can then select for alignment.
The dimensions do not need to touch to be aligned. ACM does not recognize extension line suppression with this command.
Use the DIMTEDIT alignment tools to change (or restore) the location, justification and angle of the dimension text. You can also adjust the location of the dimension line. The options are:
- Left and Right to justify the text along the dimension line
- Center to move the text to the center of the dimension line
- Angle to adjust the angle of the dimension text.
Home, available from the command line only, moves the dimension back to its default (dimension style set) position.
This feature works only with linear, radius and diameter dimensions. The vertical location of the text (above, below, or middle) is set by the dimension style.
Check finds dimensions with overridden text. Still useful but not nearly as much of an issue compared to the good-old-days of non-associative dimensions. When finding a dimension text value not containing the default (<>) ACM highlights the dimensions and shows the number found at the command line.
There are a lot of dimensioning features in AutoCAD Mechanical. This makes it difficult to cover all the ins-and-outs and explain all the options and features. The best thing to do is dive in and try everything there is.
