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Understanding Calibration Results

TheBradish
I don't usually look at the probe calibration results because I don't really understand what I'm looking at. I'd really like to gain a firm understanding of the data and what it should mean to me.

I've been digging through old threads, and I'm getting closer. What I think I get is that StdDev is the standard deviation of single-point error of the measured sphere for each tip angle. (I was told by another inspector here that that number should be .0002 or less.) I also understand that the MEAS D determines the effective probe diameter for each tip, and is used for probe size compensation.

I don't fully understand the THEO/MEAS XYZ (where the THEO comes from, what the MEAS means), or what is a maximum permissible error. What do you guys look for when you read your calibration results? What do you hope to learn from the numbers? What do you consider to be a red flag?
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  • So the XYZ is a coordinate for the center of the ruby?

    I drew a quick sketch to see if I understand where the XYZ origin is, according to Vinni. Do I have it right?



    As far as I know. I asked the Hexatech some questions last time he was here. He said Z zero is set at the bottom of the z-rail during the initial machine mapping. So, when your machine homes, the probe tip isn't at Z0, but at Z0 - probe head - probe build. For me this tends to be 0,0,-230 at "home".

    You can verify this at A0B0. Modify your build to include or remove a 50mm_CF extension. The Z will shorten by 50mm. The pivot point of the head makes calculating the XYZ awkward when at any other angle. But you can see the PH10 dimensions in its data sheet. I think there is some compensation for your master probe. For mine, A0B0 is 0,0,230 (which makes it looks like it calculates backwards from the probe center). It forces A0B0 then to be 0, and where it calculates everything else from.

    This isn't really "Official" information, but from what I have gathered out of curiosity. As such, it might be mis-informed, but it probably is correct, in general.
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  • So the XYZ is a coordinate for the center of the ruby?

    I drew a quick sketch to see if I understand where the XYZ origin is, according to Vinni. Do I have it right?



    As far as I know. I asked the Hexatech some questions last time he was here. He said Z zero is set at the bottom of the z-rail during the initial machine mapping. So, when your machine homes, the probe tip isn't at Z0, but at Z0 - probe head - probe build. For me this tends to be 0,0,-230 at "home".

    You can verify this at A0B0. Modify your build to include or remove a 50mm_CF extension. The Z will shorten by 50mm. The pivot point of the head makes calculating the XYZ awkward when at any other angle. But you can see the PH10 dimensions in its data sheet. I think there is some compensation for your master probe. For mine, A0B0 is 0,0,230 (which makes it looks like it calculates backwards from the probe center). It forces A0B0 then to be 0, and where it calculates everything else from.

    This isn't really "Official" information, but from what I have gathered out of curiosity. As such, it might be mis-informed, but it probably is correct, in general.
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