Calibration check on disc probe

[TheDudeAbides]

Hello,

I did a calibration check program reporting results from X,Y,Z axis plus ball sphere diameter.
I set tolérances at +/- 0.005 for X,Y,Z coordinates and +/- 0.0025 for sphere diameter.

Everything is fine except disc probes due to calibration method (the angle is very narrow on the Z axis +/-7°) :

CASE 3_TIP 1_RES	Emplacement des dimensions (CASE 3_TIP 1)		X		0	-0.00324	0.005	-0.005		-0.00324	0
CASE 3_TIP 1_RES	Emplacement des dimensions (CASE 3_TIP 1)		Y		0	0.00069	0.005	-0.005		0.00069	0
CASE 3_TIP 1_RES	Emplacement des dimensions (CASE 3_TIP 1)		Z		0	0.01786	0.005	-0.005		0.01786	0.012861682
CASE 3_TIP 1_RES	Emplacement des dimensions (CASE 3_TIP 1)		D		24.99775	24.99829	0.005	-0.005		0.00054	0

What should I do to properly check this probe on Z axis ?

Thank you

[NinjaBadger]

I wouldn't bother. You're not going to be using to measure the location of anything in Z.

[TheDudeAbides]

Yes it's true for one of my disc probe.
But on the second one I'm using the roller.
Altough it doesn't seem to be officially supported.

[louisd]

get out a micrometer. measure the distance between rollers. write it down. this will be your 'constant' like you use during a thread wire measurement.
measure Z location using top roller.
measure Z location using bottom roller.
subtract the two, but add your constant into the evaluation.
that's about as accurate as you can get.

If you are using a TP20, you need to be using a 6-way TP20 module, or your negative Z hit will be totally inaccurate.

Don't expect the roller to be something that you can depend on. Orientation of the roller (Polar angle relative to probe CL) will be different each time you change any probing component.

[Douglas]

louisd I have not yet bought one and tried but I'm under the impression that pcdmis can calibrate the roller using not a sphere but a plane as the calibration tool, could I not put my height standard on the table, define a plane artifact or two and get quite accurate on Z calibration of the rollers?

EDIT: I would need to add 1 level of error from the master probe as it has a very short A0B0 only, I'd need to locate sphere, calibrate 1 other probe then use that one. Is there more trouble I just don't see yet?

[louisd]

I don't have any further experience other than what I've described above. If PCDMIS actually has some type of roller calibration process baked into the software, this will be the first time I've ever heard of it, and greatly appreciate you teaching me (and likely others) something new.

[Douglas]

I'm going to experiment a little on this, I could save hundreds of probe changes a week using a disc with roller. Maybe I will take an old disc removed from service and hot glue a ruby or two on it to play with... I guess I only have ideas not answers so far