DCF - Dual Cylinder Fit

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Contents

About the Feature

Vtube-laser v2.8 cylinderfit DualCylinderFit.png

DCF (Dual Cylinder Fit) is the major enhancement for VTube-LASER in version 2.8 (April 19, 2017) because...

  1. It replicates measuring the tube TWICE in one pass when the user measures the tube the first time.
  2. It requires 4 total pass-fail checks for cylinder calculations.

The goal is to ensure repeatability of the cylinder measurements on-the-fly using a LASER scanner.

Vtube-laser v2.8 DCF logo.png



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.

As of VTube-LASER v2.8.1, it works in both UNISCAN and MULTISCAN modes.

*(Note: DCF is not used tactile measurements because it is assumed that there isn't enough data to perform DCF properly with ball probe measurements.)

The DCF Point Repeatability value is reported in the Cylinder Fit window (see CHECK 4 below).

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.

Vtube-laser v2.8 DualCylinderFit model.png

Vtube-laser v2.8 DualCylinderFit model step3.png



Introductory Video

See the five-minute video of the feature explained by Michael Cone - the developer of VTube-LASER.

Vtube-laser v2.8 dualcylinderfit intro video.png



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.

When using the laser scanner in Uniscan mode, VTube cylinders must pass a total of FOUR checks to be qualified as good cylinder scans.

(Versions before 2.8 only required CHECK 1 shown below. This 4-level check is only available in version 2.8 and newer.)

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 - CYLINDRICITY and OOR%

The new CYLINDRICITY value reports the difference between the lowest and highest points on the measured diameter relative to the centerline. If the values get too far from each other, then VTube-LASER will warn you.

Also, the OOR% (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.

Vtube-laser v2.8 cylinderfit window sections.png

Cylindricity graphic.png



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.

RED PANEL

This would indicate a major problem in the cylinder fit calculation. VTube requires a remeasure of a straight section.

Vtube-laser v2.8 cylinderfitwindow redpanel.png



GREEN PANEL

All green indicates that no issues were found in all four checks. You can trust the calculation.

Vtube-laser v2.8 cylinderfitwindow greenpanel.png



Intersection Pass Distance Warning Test

This is an example of the Intersection Pass Distance warning test.

Vtube-laser v2.8 IntersectionPassDistance.png



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