Parametric Expressions/Relations

When editing numerical values of a feature, you can assign dimensions in the form of algebraic equations. These equations can consist of numbers only (i.e. 5+6*3) or they can relate to other parameters to create equations with parametric dependency.

Simply click on other dimensions (reference dimensions) to enter their ID's into your equation, and then enter the desired mathematical operation. A dimension, whose ID is part of an expression for another dimension, is called a reference dimension (a reference dimension creates a parametric relation between dimensions).

All reference dimensions must be displayed in order to be used in an expression (you have to pick the reference dimension to enter its ID into the expression). Dimensions can be displayed or hidden while the Edit Parameters dialog is open by double-clicking on the appropriate features on the Feature Tree or in the graphics area. Reference dimensions are highlighted in the graphics area in a color that differs from the dimension being edited.

Note: While this operation can be performed from the Edit Parameters dialog or the Sketcher Dimension dialog, the examples below use the Edit Parameters dialog.

Parametric relations can be created among the following types of dimensions:

• Internal (dimensions from the same part)

• External (between parts in an assembly)

• Connect parameters

• Parameters from the Setup tool

• Catalog parameters

• Internal expressions inside the Sketcher

When a reference dimension is added to an expression in the Edit Parameters dialog, its ID appears in the expression field as bold text with a colored background, as shown below with the ID L7:

	The default background color for reference dimension IDs in the expression field, is YELLOW.
	In the case of Rerouted Relations, where one or more of the reference dimensions participating in an expression are no longer valid (the feature was deleted, the sketch modified, a connection edited, etc.), the background color is RED.

Each reference dimension in an expression is recognized by a unique prefix, depending from which source the reference dimension was selected:

Selected Dimension	Prefix	Example
Real dimension inside the same part	None	L1
Real dimension between assembly parts	Name of the part owner	Part1:L1
Connect parameters	Name of the assembly that owns the Connect + the number of the connect feature	AA_MD_Fixed Side41:Dy
From an external table	Setup or symbol	Setup_die:A (dependent upon the setup format)

When the expression field is displayed, the dimension field is grayed out and cannot be edited.

Interaction

To modify a dimension value into an mathematical expression:

1. Display the Edit Parameters dialog and access the expression mode (for instructions on how to invoke this tool, press the Access button at the top of this Help topic).

All the dimensions of the relevant feature(s) are now displayed, together with the Edit Parameters dialog showing the expression field.

1. Edit the dimension value as required, in the form of algebraic equations. These equations can consist of the following:

   1. Numbers only (i.e. 5+6*3) or

   2. They can relate to other dimensions (reference dimensions) to create equations with parametric dependency. These reference parameters are displayed with a yellow background in the expression field. These reference dimensions can be from:

      1. The current part - as shown in the example below, where L2 is the dimension being edited and L7 is entered as part of the expression.

      2. An external source (Setup dimensions - press the button in the Edit Parameters dialog).

      3. The catalog (press the button in the Edit Parameters dialog).

See the Notes and the start to finish example below.

3. Update the feature/model.

4. Exit the dialog. Note that the edited dimension now has an (f) suffix; this signifies that this dimension is the result of an expression.

Parametric Expressions/Relations Example

Double-click on both of the features below to display their parametric values. The values displayed include the extrude lengths and dimensions of the sketches.

The width of the green object (now 42 [ID=L2]) should be dependent on the distance from the cylinder center to the back of the box (now 21 [ID=L7]). Click the 42 dimension to open the Edit Parameters Dialog, and click the button.

Initially, when creating a new expression, the content of the expression field is the same as that of the dimension field. Now click the 21 dimension to enter its ID (L7) into the equation field.

This width value needs to be double the L7 value. Complete the equation as L7*2.

Note that dimensions that take part in an expression (in this example, L7), are highlighted in a color that differs from the dimension being edited (L2) and from uninvolved dimensions. (Setup parameters that are part of an expression are not highlighted). Also note that when the cursor is on a dimension ID inside the expression field (or immediately to the left or right of a dimension ID inside the expression field), the appropriate dimension is highlighted in yet another (third) color. These highlights enable you to immediately view which dimension is being edited, which dimensions take part in the expression and which dimension the cursor is currently next to in the expression field. See an example of the highlighted dimension IDs hereSee an example of the highlighted dimension IDs here.

When you exit the Edit Parameters dialog, notice that the L2 dimension now has an (f) suffix. This signifies that this dimension is the result of an expression.

To add another equation, click on the dimension for the diameter of the cylinder. Click the 44 value (whose ID is L2), and enter the equation shown below.

Now whatever the width of the green object is, the diameter of the cylinder will always be 7 less. Notice that the R3 dimension now also has an (f) suffix.

To demonstrate the parametric dependency, change the value of L7 from 22 to 27. Click the button to update the features.

The width of the green object is now 54 (27*2) and the cylinder diameter is 47 (54-7). If you open the Edit Parameters dialog for the width, you will see the equation you entered, rather than the numerical value. The L7 dimension used in the equation (27) is highlighted so that you can immediately see what values were used.

 

Some functionality may be dependent on the product package. Contact your Reseller if you require a license.