A - Best Fit Cylinder constructed from eight points
You can construct a best fit cylinder from six or more points. The first three points must be on an approximately planar cross section of the cylinder that is normal to its centerline. The best fit construction method takes the actual measured points, rather than the ball's center (as in the case of best fit recompensate). In both cases, PC-DMIS computes a least squares cylinder, one for which PC-DMIS minimizes the average squared distance from the data points to the cylinder.
Be aware that certain patterns of points, such as two rows of three equally spaced points or two rows of four equally spaced points, result in multiple ways to construct or measure a cylinder. The Best Fit algorithm may then construct or measure the cylinder using an unexpected solution. For best results, measured or constructed cylinders should use a pattern of points that will eliminate unwanted solutions.
To construct a Best Fit or Best Fit Recompensate Cylinder, do the following:
Open the Construct Cylinder dialog box (Insert | Feature | Constructed | Cylinder).
From the Method list, select either the Best Fit or BF Recomp option.
From the Feature list, select your input features by either choosing at least two appropriate circle features or at least six features of any type.
For at least two circle features, they must be constructed Best Fit (BF) / constructed Best Fit Recompensate (BFRE), or measured circles. The total amount of hits in each circle must be at least three.
For at least six features, they can be of any type.
However, if you selected BF Recomp, at least one feature must be a point.
For Best Fit (BF) or Best Fit Recompensate (BFRE) constructions, while you can use any feature type for your input features, BF and BFRE fit types are typically used with point features or point sets (a scan of points, a feature set with points, or an expression that resolves to an array of points).
From the Best Fit Type list, select the type of best fit algorithm to use. For details, see the "Best Fit Type" topic in this documentation.
Click the Create button.
The math routine that PC-DMIS uses to gets the points from the input features behaves differently depending on the type of input feature. Constructed features other than the appropriate input circles described above return a single point. The constructed BF circles, constructed BFRE circles, or measured circles described above return their input points.
The Edit window command line for this option would
read:
CONSTR/CYLINDER,BF,feat_1,feat_2,feat_3,feat_4,feat_5,feat_6
(Uses the actual measured points for construction.)
or
CONSTR/CYLINDER,BFRE,feat_1,feat_2,feat_3,feat_4,feat_5,...
(Uses the center of the probe for measurement.)
A - Best Fit Cylinder constructed from eight
points
Constructing a Cylinder from Six or More Points
More: