NX Creating 'Arc length' dimension Outside arc, with Extension lines passing through the arc center

As designed behavior:

The arc length dimension’s linear extension lines are oriented perpendicular to the chord of the arc segment being dimensioned when dimension is positioned on the outside of the arc.

However, in certain situations we would need the arc length dimension’s extension lines to pass through the arc center & dimension needs to be positioned on the outside of the arc, so that additional details can be shown on the inside area of the arc.

In the simple example shown below, users may need dimension’s extension lines to pass through the arc center (Figure b) , instead of the ‘As-designed’ behavior (Figure a).

The steps given below, lists the method to create ‘Arc length’ dimension as shown in ‘Figure b’.

The trick is to use ‘Angular Dimension’ & insert an associative measurement of the arc length into the dimension. This can be used in NX Drafting application, as well as PMI application.

We will use the example shown above to take you through the steps.

Step 1: - Create an Associative arc length measurement from the ‘Analysis – Measure’ command. Ensure that you check on the ‘Associative’ option in settings.

Step 2: Now let’s start the Drafting application. We will initiate creation of an Angular dimension on the arc entity, as shown below. Keep selection mode as ‘Vectors and Objects’.

Step 3: Make the selections as given below:

       i.          Select any end point of the arc as the ‘First Object’

      ii.          For Input of the ‘Specify First Vector’, use the ‘Two points’ option.

iii. Now select the arc center & the point selected as the first object to define the vector, such that the ‘Vector’ is seen as shown below.

v. Click on the ‘Text settings’ option as shown in the right-side image above. In the ‘Text Settings’ dialogue, go to ‘Format’ & activate the ‘Override dimension Text’ option.

vi. Replace the Angular dimension text with the associative arc length measure, created in ‘Step 1’. This can be done as follows:

a. Click on the ‘Edit Text’ option as shown in image below. A Text input box opens up.

b. User can access the ‘Arc length’ expression from the Expressions button on the ‘General’ tab. Select the ‘arc length’ expression & It will appear in the Text field. 

c. Users can choose to add the ‘arc length’ symbol from the ‘Expression’ window.

Thus, the Arc length dimension can be created on the outer side of the arc, with extension lines passing through the center of the arc, for which the arc length dimension is created. 

Summary: - Outer Arc length dimensions with extension lines passing through the center of the arc, can be create with the trick detailed in the steps mentioned above, to achieve the result given below.

Note: - An enhancement request (ER9507642) has been filed for including the above mentioned functionality in OOTB NX.