Circular Post Center Probe Operation - curiosity

[orbscan]

Hello Dave!

From your manual:
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Circular Post Center Probe Operation
This operation measures and finds the center of a cylinder (circular post) along the X and Y axes.
The Diameter Hint DRO is an input parameter specific to this operation. Simply set the “hint” to
the approximate diameter of the cylinder end being probed. There is no need for the hints to be
precise. If the hint value is too large, a little extra time will be expended probing air.
This probe operation should be started with the probe tip roughly over the center of the post you
want to probe. The probe will search in Z- to establish an initial Z height and then the probe will
lift above this height by Z Clearance. The center of the cylinder will be found in the X and Y
directions and probe tip will be positioned over the top center of the post.
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OK.
Works well!

But why, even if I put the probe exactly in the center, the movement is greater on one side?
For example with hint 100 mm moves 68 mm to the left and 61 mm to the right...

Then it works fine but I would not had made some mistakes...

Thank you
Best regards
Carlo

[DaveCVI]

Hi Carlo,

But why, even if I put the probe exactly in the center, the movement is greater on one side?
For example with hint 100 mm moves 68 mm to the left and 61 mm to the right...

Well, you may think you have placed the probe in the exact center, but even if you have, MSM can't know where the center is when the operations starts - after all the operations is finding the center....
The only thing that MSM can assume is that you got the probe within "step off distance" of the center.
The first thing MSM must do is calculate the amount to move in X- based on the possible worst case user positioning of the probe.
Then it mores over and down, then back (X+) to find the first edge. At that point it has learned a little about the object (where the first edge is), and it can refine it's next movement based on that information - thus the 2nd movement to the other side does not need as much overshoot when accounting for the (revised) worst case - hence the total movement required is less for that move.

Dave

[orbscan]

OK!

Thank you for your kindness!

Carlo