Creating Driving Dimensions

This task shows you how to create dimensions that will drive associated geometry. 

You can create the following types of driving dimensions:

  • length
  • distance (and distance offset in the case of two concentric circles)
  • angle
  • radius
  • diameter.

 
Go to Tools > Options > Mechanical Design > Drafting > Dimension and select Activate analysis display mode. Then, click the Types and colors button. The Types and colors dialog box is displayed.

Make sure the Dimensions driving 2D geometry check box is selected, and identify the color that will be assigned to driving dimensions (you can change it if you want).

Create a line. Click the Dimensions icon from the Dimensioning toolbar and create a length dimension on this line.

  1. Double-click the dimension. The Dimension value dialog box is displayed.

  2. Make sure the Drive geometry check box is selected. This dimension will now drive the geometry.

  3. Modify the dimension value, entering 40 millimeter as the new length.

  4. Click OK to validate and exit the dialog box. The geometry is updated according to the new driving dimension value.

  5. Click elsewhere in the drawing to deselect the dimension. You can see that the driving dimension is assigned the colors defined in the Types and colors dialog box.

Limitations
You cannot create driving dimensions between the following types of elements (in this case, the Drive geometry option is deactivated when double-clicking the dimension):
  • Between an interactive element and a generated circle center. 
    To bypass this problem, create a point that is concentric with the center of the circle and create the dimension between this new point and the other element.
  • Between an interactive circle and a generated circle.
  • Between an interactive line and a generated one that are not parallel.

    To bypass this problem, create a point that will be coincident with line A and line B at the same time and create the dimension between this new point and the other element.

  • Between two fixed elements, that is to say:
    • generated elements
    • axis lines
    • center lines
    • 2D components
    • interactive elements that are fixed by constraints or driving dimensions.
  • If created using Force Dimension on element , a distance offset dimension (i.e. a distance dimension created between two concentric circles) cannot drive geometry.
    To bypass this problem, force an horizontal or vertical dimension. See the example below:

    Created with Force Dimension on element ,
    distance offset dimension cannot drive geometry.

    		 Created with Force horizontal dimension in view 
    or Force vertical dimension in view ,
    distance offset dimension can drive geometry.

 
  • Once the Drive geometry check box is selected, you can access a contextual menu and customize the values properties according to your needs. For more information on the available options, refer to CATIA Knowledgeware Infrastructure - Tips and Techniques - Summary, available from the Using Knowledgeware Capabilities section in the Infrastructure User's Guide.
  • When a driving dimension is created between two parallel lines, then their parallelism is constrained. Therefore, if a geometrical parallelism constraint was previously applied to them, this constraint is destroyed. This avoids an overconstrained situation.