You can construct a Secondary Datum Line from a plane, line, or set of points. The set of points can be multiple selected points, a constructed set of points, or a scan feature that contains multiple points.
The secondary datum construction uses the points within the input feature (or features) as well as the plane from the primary datum input to create an "orientation constrained" and "external to material" 2D line. You can use this line in alignments to simulate a secondary datum feature.
"Orientation constrained" means that the input points are forced perpendicular to the primary datum.
"External to material" means that the resulting line contacts the highest point or points from the input feature (or features), subject to the orientation constraint and the selected math type.
PC-DMIS constructs the secondary datum line in the plane that you select as the primary datum.
Examples
The examples below show the points as if viewed from the selected plane.
Constrained MinMax is the default math type specified by the ISO 1101 standard.
Constrained L2 is the default math type specified by the ASME Y14.5 standard.
L∞
The red line is the L∞ plane targeting the external envelope (constrained MinMax type in PC-DMIS)
L2
The green line is the constrained L2 plane targeting the external envelope (constrained L2 math type in PC-DMIS)
How to Construct a Secondary Datum Line
Open the Construct Line dialog box (Insert | Feature | Constructed | Line).
From the Method list, select Secondary Datum.
From the Feature list, select the input feature (or features). For valid input feature types, see the table in the "Constructing a Line Feature" topic.
From the Primary datum list, select the primary datum. This datum can be either a plane from the measurement routine, or a workplane from the active alignment.
From the Math Type area, select the math type (CONSTRAINED_L2 or CONSTRAINED_MINMAX) from the first list.
From the Math Type area, select a probe compensation option (BF for best fit or BFRE for best fit recompensate) from the second list.
If you want to change the feature theoretical values, select the Feature theoreticals check box and type in the values. For details, see the "Specifying Feature Theoreticals" topic in the PC-DMIS Core documentation.
Click the Create button to insert the constructed line feature into your measurement routine.
The Edit window command line for this option is:
CONSTR/LINE,SECONDARY_DATUM, feat_1,feat_2, …
MATH_TYPE/TOG1,TOG2
PRIMARY DATUM PLANE/TOG3,TOG4
TOG1 = CONSTRAINED_L2 or CONSTRAINED_MINMAX
TOG2 = BF or BFRE
TOG3 = FEATURE or WORKPLANE
TOG4 = This is the list of workplanes if TOG3 is a WORKPLANE, or it's the Feature ID if TOG3 is a plane FEATURE.