"SP600" probe measures too small

Good day,

I have a problem with the "SP600" probe head.
The diameters are, regardless of whether they are scanned or with an auto-element circle, it is always exactly 0.010mm smaller than it should.

Tested on a purchased ring with a certificate

Calibration says 1my standard deviation.

Maintenance says everything is ok.

Temperature compensation is off, but the room temperature is 20.5 ° C

Is it possible that the calibration is set incorrectly?
or is it a hardware error?

what can i do differently?

Useing pcDMIS 2020R1

Thank you for your time

Matthew D. Hoedeman over 3 years ago

are you absolutely SURE you didn't fubar the size of the gage you are measuring? And I would check both the ring and the cal-sphere for a typo on the size.
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JEFMAN over 3 years ago

First, you have to check parameters, in F10 / opt probe, and in the setting editor.
ftp://ftp.wilcoxassoc.com/docs/FilesInHelps/Scanning%20Parameters%20-%20H006908%20PRB%20Params.pdf

Once parameters are checked, you have to perform a lower matrix calibration.

Then, you can create a circle scan around the sphere, and look at the difference of radius (it should be close to zero).
You can also check the roundness of the ring (your measured circle), to see if it could be an alignment problem.
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Cris_C over 3 years ago

First, you have to check parameters, in F10 / opt probe, and in the setting editor.
ftp://ftp.wilcoxassoc.com/docs/FilesInHelps/Scanning%20Parameters%20-%20H006908%20PRB%20Params.pdf

Once parameters are checked, you have to perform a lower matrix calibration.

Then, you can create a circle scan around the sphere, and look at the difference of radius (it should be close to zero).
You can also check the roundness of the ring (your measured circle), to see if it could be an alignment problem.

I'm just curious. I have never worked with an SP600. How does PC-DMIS handle the calibration of probe tips? Does the lower matrix calibration only need to be done once in one angle? When different probe angles are being calibrated, does it just take touch points the way you would calibrate a TTP probe angle?
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JEFMAN over 3 years ago

The lower matrix just define the orientation of the head from cmm axes.
A "static head" (or measuring head) is a kind of cmm, with 3 deformable parallelograms perp between them (this def is wrong for a SP25 !)
When the ball touches the part, the parallelograms are deformed, so the cmm moves in a direction that equilibrates them.
The orientation of parallelograms is measured while the lower matrix calibration.
So this calibration is done only with A0B0...
Take a look at this old doc, it's really interesting about parameters and matrix...
ftp://ftp.wilcoxassoc.com/docs/How%20To%20Docs/Sp600.zip
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Henniger123 over 3 years ago

Good day,

Thank you very much for your feedback

I'm not sure about the diameter of the "cal-sphere", but the certificate for this should still be around somewhere. Afterwards dig a bit.

"lower matrix" hasn't been done for a while, so that could also be the problem. (why does that influence the measured diameter? just curious)

So what do I have to consider with "lower matrix" or simply press the button with the reference probe?

Thank you for your time.
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Henniger123 over 3 years ago in reply to Henniger123

i have found certificate for the calibration ball. There is no typo in diameters for the ball and the ring
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Henniger123 over 3 years ago in reply to JEFMAN

i can't access this file
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Cris_C over 3 years ago in reply to JEFMAN

Nice Resource. Thanks!
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JEFMAN over 3 years ago in reply to Henniger123

clean the tip and the sphere
select the L50D8 (length 50 mm - diameter 8 mm : it's the "standard tip" for the SP600)
select "reset to theo", and "yes, the sphere moved"
calibrate by selecting "lower matrix", then re calibrate.

I'm not sure that it will change lot the diameter, maybe more the circularity.

For the sphere, you should look to the stem, the diameter is often write on it.

Hope this helps.
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