True position reports the location of a feature relative to specified datum planes or axes. It can be used with bonus tolerancing.
To create a GD&T True Position item:
- Open a Geometric group in the inspection sequence.
- Click Geometry tab > GD&T panel > Location > True Position.
- Enter a Name for the item.
- To exclude this item from the report, deselect the Output in report check box.
- To restrict the features that can be selected to those which are close to parallel with the
Primary datum, select the
Use angular tolerance to filter the available features check box, and enter the maximum angle by which the features can vary from parallel in the
Angular tolerance box.
If a circle's orientation falls outside the specified tolerance, you can use the position of the centre of the circle.
To show all datum items in the list, deselect the Use angular tolerance to filter the available features check box.
- Enter any extra information about the item in the Comment box.
- Click Next. The Datum Definition dialog is displayed.
- In the Workplane list, select the datum you want to use for this GD&T item.
- To measure the position relative to the datum specified in the
Workplane
list, select the
Lock Datums
button. The button changes to
, and
PowerInspect selects the Z, Y, and X planes of the workplane as the primary, secondary, and tertiary datums. Select the button again to unlock the datum lists.
To measure the position relative to specified features:
- In the Primary datum list, select an item to determine the plane on which you want to project the true position feature.
- To specify a Secondary datum for this item, select the Use datum check box in the Secondary datum area, and select the feature you want to use.
- To specify a Tertiary datum for this item, select the Use datum check box in the Tertiary datum area, and select the feature you want to use.
- If you select a circle or cylinder as a datum, select a material condition modifier to specify whether you want to include a bonus tolerance in the calculation.
The order in which the datums are selected can affect the results.
- If you are measuring the position of a circle or cylinder, select a Material condition option to specify whether you want to include a bonus tolerance in the calculation.
- In the
Tolerance box, enter the position tolerance. If you selected a
Material condition of
MMC or
LMC, and you want to limit the bonus tolerance that can be applied to this item, select the
Maximum check box, and enter the maximum bonus.
The control frame at the top of the dialog summarizes the tolerancing requirements.
- Click Next. The Feature Selection dialog is displayed.
- In the
Feature
list, select the feature whose position you want to report, then click
Insert nominal position relative to Datum Definition, and select:
- From CAD entities to load the item nominals from the CAD model.
- From Active Measure to load the item measurements from the current Measure.
Alternatively, type the nominal values of the feature in the Distance along X and Distance along Y boxes.
The details of the position are displayed in the Feature list.
- Click
Next. The results of the GD&T calculation are displayed in the
Result Preview dialog. If the result is:
- Accepted, the measurement is in-tolerance.
- Out of Tolerance, the measurement is out-of-tolerance.
- Not Calculated, the measurement cannot be calculated because one or more of the selected features or datums is unmeasured.
- Click Finish to create the item and save the results, or click Back to change the item definition.