Using dimensions to control sketch geometry

Dimensions are a type of constraints that use numerical values to define sizes, angles, or distances in a sketch. Dimensions control sketch geometry by preventing changes to the dimensioned quantities. To change a dimensioned quantity, you must modify the associated dimension.

Related Topics
Modifying objects by changing dimensions or adding parameters
Customizing the Sketcher
Constraining, dimensioning, and parameterizing a sketch

The following dimension types are available in the Sketcher:

  • horizontal

  • vertical

  • oblique

  • angular

  • radial

The first three dimension types correspond to linear distances between two points (including the endpoints of a single line), two lines, or a point and a line. Angular dimensions always indicate the angle, in degrees, between two lines. Radial dimensions indicate the radius of a circle, arc, or fillet or the major and minor radii of an ellipse.

You can use the following techniques to add dimensions to a sketch:

Adding dimensions automatically

After you create a sketch, you can use the auto-dimension tool to add dimensions to the entire sketch or to a selected group of entities. Use the sketch options to control the dimension types that Abaqus/CAE can add automatically. For more information, see Customizing the format and use of dimensions in the Sketcher.

Adding individual dimensions

After you create sketch geometry, you can add individual dimensions. This method gives you the most control, but it is also the most time consuming. For more information, see Adding individual dimensions.

You can modify any dimension in a sketch. When you edit an existing dimension, you can modify it in several ways. You can

  • edit the numerical value to modify the sketch,

  • convert the dimension to a reference dimension, or

  • link the dimension to a parameter.

Reference dimensions annotate quantities that are already controlled elsewhere in the sketch or quantities such as projected reference geometry that cannot be controlled within the current sketch. Reference dimension values are enclosed in parentheses, and Abaqus/CAE updates them automatically to match changes in the associated geometry. Dimensions that have been linked to parameters are assigned a variable name for use in creating mathematical expressions (parametric equations) to define other parameters in the sketch. For detailed instructions on editing dimensions, see Editing dimensions.

When you add or modify dimensions, you must not overconstrain the sketch geometry. Geometry is overconstrained when multiple controls are applied to a single degree of freedom (for more information, see Fully constrained geometry). Abaqus/CAE colors conflicting constraints magenta to indicate an overconstraint condition. You must resolve any overconstraints before you can use a sketch to create a feature or save it with the model database.