DCF - Dual Cylinder Fit
About the Feature
DCF (Dual Cylinder Fit) is the major enhancement for VTube-LASER in version 2.8 (April 19, 2017) because...
The goal is to ensure repeatability of the cylinder measurements on-the-fly using a LASER scanner.
How It Works
When using the LASER scanner*, the DCF feature divides the cylinder surface data into two groups, then calculates the cylinder data and intersection points twice to verify repeatability.
What happens if the points are too far apart?
If the two DCF points are too far apart (the Point Repeatability value is too high), then VTube-LASER will warn you and ask for a remeasure. This allows you to remeasure the straight to guarantee that the measure repeats before moving to the next straight.
What happens if the points are close to each other?
If the two DCF points are near to each other within tolerance, then VTube uses the average of those two points as the final point. See the illustration on the right.
See the five-minute video of the feature explained by Michael Cone - the developer of VTube-LASER.
MULTIPLE LEVELS OF CYLINDER FIT CHECKS
As part of the DCF feature, the Cylinder Fit Data window reports cylinder fit values that help you know if the cylinder measurement is good.
CHECK 1 - MAXIMUM WOBBLE PREDICTION
The Maximum Wobble value predicts how precise the surface data fits the cylinder. This was in previous versions, but now two cylinders must pass - not just one. And we've created a single new value to display at the top rather than multiple XY values.
CHECK 2 - OD SURFACE TO CENTERLINE
The new OD Surface to Centerline value reports the low and high points on the measured diameter relative to the centerline. If the values get too far from each other (the "Delta"), then VTube-LASER will warn you. Also, the Out-of-round% is reported and used to qualify the cylinder fit. This is active for both LASER and ball probe.
CHECK 3 - INTERSECTION PASS DISTANCE
The Intersection Pass Distance shows how near each intersecting 3D centerline comes to each other in 3D space. If the Nearest Pass value is more than the Intersection Error Tolerance, then VTube-LASER will warn you. This is active for both LASER and ball probe.
CHECK 4 - DUAL CYLINDER FIT
As mentioned above, because the DCF engine creates two cylinders, it always builds and compares the resulting intersection points from both cylinders. It warns you if they don't match well enough.
The CYLINDER FIT WINDOW is NOW COLOR-CODED for DCF
The Cylinder Fit Data window is color-coded to help you quickly determine where the problem lies in the data.
This would indicate a major problem in the cylinder fit calculation. VTube requires a remeasure of a straight section.
All green indicates that no issues were found in all four checks. You can trust the calculation.
Intersection Pass Distance Warning Test
This is an example of the Intersection Pass Distance warning test.