## Using Unequal Tolerance Zones with Profile Feature Control Frame Dimensions

PC-DMIS 2010 and higher support the use of the Unequal Tolerance Zone symbol as specified in the new ASME Y14.5-2009 standard. This allows you to have a profile dimensions with unequal tolerance zones.

Requirements

- You must select ASME Y14.5 from the Advanced tab of your Profile dimension's GD&T dialog box.

- You must use a Feature Control Frame (FCF) Profile dimension (legacy dimensions do not support this).

- The FCF Profile dimension must have a datum as specified by the Y14.5-2009 standard. Unequal tolerance zones are not supported in ISO 1101 because in that standard, a profile dimension's tolerance zones are always equal bilateral.

The FCF Editor

If you have met the above requirements, the Feature Control Frame Editor area of the GD&T dialog box will look something like this when you begin to create your FCF Profile dimension:

Feature Control Frame Editor for a Line Profile Dimension

Notice the addition of the <UZ> and <UTol> fields.

- <UZ> - Unequal Tolerance Zone

- <UTol> - Unequal Tolerance value

Using the Unequal Tolerance Zone

From the <UZ> field you can choose to display the Unequal Tolerance Zone symbol. If you display the symbol, you must enter the unequal tolerance value into the <UTol>.

The value you enter into <UTol> is the plus tolerance. This value is always positive and must be between 0 and the total tolerance value. The minus tolerance is not visible but is calculated behind the scenes by subtracting the plus tolerance from the total tolerance.

For example, if you have a total tolerance of 0.3 and an unequal tolerance (plus tolerance) of 0.1, like this

then PC-DMIS will take the total tolerance of 0.3 and subtract the plus tolerance of 0.1, leaving you with a minus tolerance of 0.2 as shown here:

Without the Unequal Tolerance Zone

If you choose not to use the unequal tolerance zone for your profile dimension, the total tolerance zone is split evenly between the plus and minus tolerances. So, using the above example of 0.3, you would end up with a plus and minus tolerance of 0.15 each.

PC-DMIS Version Compatibility

If a 2010 or higher part program contains FCF Profile dimensions with unequal tolerance zones and you load that program into a version older than 2010, the unequal tolerance zone symbol and the field in the Edit window command block will not appear. However, the unequal plus and minus tolerance zones will still be applied.

If your part program was created in a version prior to 2010, and you load it into 2010 or higher, any FCF Profile dimensions with unequal tolerance zones will cause the Unequal Tolerance Zone symbol to appear. If the tolerance zones are equal, the symbol will not appear.