Procedure:

1.Create a new GD&T Measure from the Measures dialog or the right-click menu.

2.Assign the new GD&T Measure a Name and Description (if desired).

3.Select [Add] and select any features from the graphics window or the Model Navigator that will be included in the Concentricity Measure. When finished select [OK][Close] in the Pick FeatureSelect dialog.

4.Select Concentricity (icon only) from the Measure type list.

5.Select the desired DRF from the DRF list. Note: if needed, define the DRF by selecting [Edit DRFs...]. Also Create Datums if needed.

6.Set the Upper Spec. Limit and Lower Spec. Limit to whatever values this measure is meant to check against (typically found on Assembly level drawing). Note: Can also turn off Upper Spec. Limit and Lower Spec. Limit if desired.

Single Point Analysis:

The Concentricity Measure is most easily thought of as a combination of four Point Distance Measures. Using the DRF, 3DCS will calculate where the Reference Point is for each build. At Nominal, the Reference Point is at the same location as the Measure Point, however as there is variation of the Datums relative to the Measure Point or variation of the Measure Point relative to the Datums, there will be a distance between the Reference Point and the Measure Point. For each build, 3DCS performs a Point Distance Measure in four different directions between the Reference Point and the Measure Point. The four measure directions are each divided by 45° such that the measure directions could be described as 0°, 45°, 90°, and 135°. The example below shows the four directions for a measure as well as a single deviation of the measure.

Above: At Nominal these are the measure directions 3DCS will use for the four Point Distance Measure that combine into the Concentricity Measure

Above: At possible deviation, the Measure Point is measured along each of the four directions from the Reference Point.

Note: 3DCS does not display what these four directions of measure are for the Concentricity Measure. See Position Evaluating Points on Feature for information about how to find the exact measure directions of 3DCS.

3DCS is not combining the four Point Distance Measures on a "per build" basis (like the Combination Measure does). Instead, 3DCS internally keeps these four measures and then only shows a single distribution at the end. The distribution shown is the one that returns the largest Recommended GD&T Value (see Recommended GD&T Value section for more details).

For an example case, we could have these four results:

In this case, the 90° direction has the largest Recommended GD&T Value so for the Concentricity Measure results 3DCS will only display the Monte Carlo Simulation, GeoFactor Equation-Based Analysis, and Contributor Analysis results for the 90° direction.

Note: Because 3DCS is only displaying Contributor Analysis results for one of the four directions, it is possible that there is a Contributor that is affecting the variation in one or more of the other three directions but is not displayed in the Contributor Analysis list for the measure because it is not adding variation to the measure direction that had the greatest Recommended GD&T Value.

Multiple Point Analysis:

When using multiple coaxial points in the Features list of the GD&T Measure dialog, the Concentricity Measure still follows the same analysis method but it is reporting the maximum of a larger sample of measures if there is more than one point. If there are two points in the list then it will have eight total measures internally but output only one, likewise if there are three points in the list then there are twelve total internal measures.

For an example case, we could try adding two points to the Feature list and get these results:

The 45° direction of Point 2 has the largest Recommended GD&T Value and therefore it will be the output for this Concentricity Measure.

Single Axial Feature Analysis:

An Axial Feature such as a pin or a hole can also be selected in the Features list of the GD&T Measure dialog. If a Feature has no Feature Points on the Center of the Feature, then the Concentricity Measure will follow the same procedure as the Multiple Point Analysis described above, checking points at each end of the Feature's Axis.

Above: At Nominal these are the measure directions and points at the axis's ends that 3DCS will use for the Point Distance Measures that combine into the Concentricity Measure

Above: At possible deviation, the Measure Points are measured along each of the four directions from the Reference Points

For a single Feature without any Feature Points there will be eight total measures that the Concentricity Measure checks and returns the largest Recommended GD&T Value.

For an example case, we could have these eight results:

The 0° direction of Axis End 1 has the largest Recommended GD&T Value and therefore it will be the output for this Concentricity Measure.

If the Axial Feature also contains Feature Point(s) on its axis, the Concentricity Measure will also check the Feature Point(s) in addition to the two Axis End points.

Above: At Nominal these are the measure directions and points at the axis's ends as well as a Feature Point on the Center Axis that 3DCS will use for the Point Distance Measures that combine into the Concentricity Measure

For an example case, we could have these twelve results:

The 135° direction of Axis End 1 has the largest Recommended GD&T Value and therefore it will be the output for this Concentricity Measure.

Multiple Coaxial Feature Analysis:

Multiple Coaxial Features such as a pin or a hole can also be selected in the Features list of the GD&T Measure dialog. If a multiple Features are selected, then the Concentricity Measure will follow the same procedure as the Single Feature Analysis but it will check Axis End points on each of the Features selected (as well as any Center Feature Points any of the Features may have). Features and Points can also be combined in the Features list and 3DCS will simply follow the analysis for each of the Features or Points and return the one with the largest Recommended GD&T Value. Here are a few examples of features along with how many Point Distance Measures will be used internally for the Concentricity Measure:

Example 1: 3 Features

Feature1: 0 Center Feature Points

Feature2: 1 Center Feature Point

Feature3: 0 Center Feature Points

Example 2: 2 Features, 3 Points

Feature1: 1 Center Feature Point

Feature2: 0 Center Feature Points

For an example case, where we have two Features selected in the Features list and neither Feature has a Center Feature Point, we could have these sixteen results:

The 45° direction of Axis End 2 for Hole 1 has the largest Recommended GD&T Value and therefore it will be the output for this Concentricity Measure.