Current Help System: PC-DMIS CMM (View Core Help)

## Creating an Auto Circle

The Circle auto option allows you to define a circle measurement. This measurement type is particularly useful when the circle is positioned in a specific plane that is not parallel with any of the working planes or if equally spaced hits are required for partial circles. At least three hits are necessary to measure a circle. The default number of hits needed to measure a circle is based on the default in SETUP mode.

To access the Circle option, access the Auto Feature dialog box for a Circle (Insert | Feature | Auto | Circle).

Auto Feature dialog box - Circle

With the dialog box open, depending on your situation, use one of these methods to create the feature:

Creating by Using Surface Data on the Screen

To generate a circle using surface data:

1. Click on the Surface Mode icon .

2. Click once either outside or inside the desired circle. The dialog box will display the center point and diameter from the CAD data of the selected auto circle closest to where you clicked on the part model.

3. Make any other modifications to the dialog box as needed.

4. Click Create.

Creating by Using Surface Data with the CMM

To generate a circle using surface data with the CMM, take a minimum of three hits in the hole or on the stud. PC-DMIS will pierce the CAD surface closest to where the probe touched. The displayed X, Y, Z values reflect the closest CAD circle, not the actual hits. The I, J, K reflects the surface normal vector. If a CAD circle is not found, PC-DMIS will display the closest point and ask that additional hits be taken.

The Find Noms option should be selected from the Mode list for this measurement method. See the "Mode List" topic in the PC-DMIS Core documentation for additional information on nominals.

Creating by Using Wire Frame Data on the Screen

Wire frame CAD data also can be used to generate an auto circle.

To generate the circle:

1. Click near the desired wire on the circle. PC-DMIS will highlight the selected circle closest to where you clicked on the part model.

2. Verify that the correct feature has been selected. The probe approach is always perpendicular to the feature, as well as perpendicular to the current probe centerline vector. The dialog box will display the value of the selected circle's center point and diameter once the wire has been indicated.

3. Make any other modifications to the dialog box and the Probe Toolbox as needed.

4. Click Create.

Note: If the underlying CAD element is not a circle or arc, additional clicks may be necessary to identify the feature. If PC-DMIS doesn't highlight the correct feature, try clicking on at least two additional locations of the circle.

Creating without Using CAD Data

To generate the circle without the use of CAD data:

1. Take three hits on the surface to find the plane that the circle is lying in.

2. Take three additional hits in the hole (or on the stud). PC-DMIS calculates the auto circle using all three hits. Additional hits can be taken. PC-DMIS will use the data from all of the measured hits until the Create button is clicked. The X, Y, Z that is displayed is the calculated center of the circle (or stud).

3. Make any other modifications to the dialog box and the Contact Path Properties tab of the Probe Toolbox as needed.

4. Click Create.

Creating by Keying in the Data

This method allows you to key in the desired X, Y, Z, I, J, K center value for the circle.

1. Type in the desired X, Y, Z, I, J, K values for the feature into the dialog box.

2. Click Create to insert the feature into your part program.

See the "Mode List" topic in the PC-DMIS Core documentation for additional information on nominals.