Home  Applications Intro to Coordinate Metrology Measured and Constructed Features
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Measured and Constructed Features |
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Download "Intro to Coordinate Metrology" 
What's the Difference Between Measured and Constructed Features?
The vast majority of workpieces are made up of simple geometric
elements created by machining or forming. These primary elements
(planes, edges, cylinders, spheres, cones, etc.) are called features.
When a CMM can measure these features directly, by touching the
surfaces that make up the feature with a probe, the features are
referred to as measured features.
Other features, such as distance, symmetry, intersection, angle and
projection, cannot be measured directly but must be constructed
mathematically from measured features before their values can be
determined. These are called constructed features. In Figure 11 the
centerline circle is constructed from the center points of the 4
measured circles.
Constructed Features
The relationships between one feature or group of features to
another feature or group of features are critical to manufacturing.
For example, the intersect point between the cylinders on one side of
an engine block and those on the other side determines how well mating
parts fit (Figure 12). This intersect point is constructed from the
two measured features (the engine cylinders).
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Sheffield Measurement
a brand of Hexagon Metrology, Inc.
P.O. Box 1658
660 South Military Road
Fond du Lac, Wisconsin 54935
Toll Free Phone: 800.535.1236
Phone: 920.906.7700
Fax: 920.906.7701
info@SheffieldMeasurement.com
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