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 Position Measure. When finished select [OK][Close] in the Pick FeatureSelect dialog.

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

5.Set the desired zone to Diametrical or Non-Diametrical (blank).

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

7.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.

Options Tab

If Non-Diametrical (blank) is selected, then the user may be required to input a custom direction.

Single Point Analysis:

The Position 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 Position 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 Position 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 Position 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 points in the Features list of the GD&T Measure dialog, the Position 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 Position Measure.

Single Axial Feature Analysis:

An Axial Feature such as a pin or a hole can 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 Position 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 Position 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 Position 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 Position Measure.

If the Axial Feature also contains Feature Point(s) on its axis, the Position 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 Position 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 Position Measure.

Multiple Axial Feature Analysis:

Multiple Axial 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 Position 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 Position 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 Position Measure.

Single Point Analysis:

The Position Measure for a single point is identical to a Point Distance Measure between a Reference Point and a Measure Point. 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. 3DCS performs a Point Distance Measure between the two points along the direction of the Reference Point. The example below shows a measure at nominal and at a single deviation.

Above: At Nominal. The measure direction 3DCS will use is the direction of the Reference Point

Above: At possible deviation. The Measure Point is measured from the Reference Point along the direction of the Reference Point

The Position Measure for a measure that only has one point in it will just be the results for the single Point Distance Measure that is used internally.

Multiple Point Analysis:

When using multiple points in the Features list of the GD&T Measure dialog, the Position Measure uses multiple internal Point Distance Measures, one for each of the points in the Features list.  Each point will have its own Reference Point and measure direction based on each Reference Point's direction. The example below shows a measure at nominal and at a single deviation.

Above: At Nominal. The measure directions 3DCS will use are the directions of the Reference Points

Above: At possible deviation. The Measure Points are measured from the Reference Points along the directions of the Reference Points

3DCS is not combining the three Point Distance Measures on a "per build" basis (like the Combination Measure does). Instead, 3DCS internally keeps these three 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 three results:

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

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

Single Feature Analysis:

In accordance with ISO allowing a True Position callout to be applied to a flat face, a face can also be selected in the Features list of the GD&T Measure dialog for this case. If a face has no Feature Points on it, then the Position Measure will follow the same procedure as the Multiple Point Analysis described above, but it will check three extreme points on the surface.  The example below shows a planar surface with its three internally calculated measure points.

Above: At Nominal. The measure directions 3DCS will use are the directions of the Reference Points.  The Measure Points are internally calculated by 3DCS to be the extreme points on a surface

Above: At possible deviation. The Measure Points are measured from the Reference Points along the directions of the Reference Points

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

In this case, Extreme Point 2 has the largest Recommended GD&T Value so for the Position Measure output 3DCS will use its results.

Note: 3DCS does not display what these three extreme points will be for the Position Measure. See Position Evaluating Points on Feature for information about how to find the exact measure directions of 3DCS.

If the Feature also contains Feature Point(s) on its surface, the Position Measure will also check the Feature Point(s) in addition to the three Extreme Points.

Above: At Nominal. The measure directions 3DCS will use are the directions of the Reference Points.  The Measure Points are internally calculated by 3DCS to be the extreme points on a surface and the single Feature Point that is on the Surface

Above: At possible deviation. The Measure Points are measured from the Reference Points along the directions of the Reference Points.  The Feature Point is also included in the results

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

In this case, Feature Point 1 has the largest Recommended GD&T Value so for the Position Measure output 3DCS will use its results.  3DCS typically does a decent job internally finding the three extreme points to use in the Position Measure, however as the surface becomes more complex its ability to internally find the best three points diminishes.  If the surface is a bit more complex then it is a best practice to create a few Feature Points on the surface at locations where maximum variation is most likely.

Note: a slot in 3DCS is treated the same as a face in the Position Measure. The center plane of the slot has three extreme points and the direction of the slot is treated as the Measure Direction in this case.  Any Feature Points on either face of the slot will be ignored and only the three extreme points of the center plane will be used in the analysis.

Multiple Feature Analysis:

It is also possible to add multiple Features in the Features list of the GD&T Measure dialog. If multiple Features are selected, then the Position Measure will follow the same procedure as the Single Feature Analysis but it will check Extreme Points on each of the Features selected (as well as any 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 Position Measure:

Example 1: 3 Planar Features, 2 Slot Features

Feature1: 1 Feature Point

Feature2: 2 Feature Points

Feature3: 0 Feature Points

Example 2: 2 Planar Features, 1 Slot Feature, 2 Points

Feature1: 1 Feature Point

Feature2: 0 Feature Points

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

In this case, Extreme Point 2 for Feature 2 has the largest Recommended GD&T Value so for the Position Measure output 3DCS will use its results.