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Probe problem... maybe

Caemgen
I had a calibration done a couple weeks ago.
I reset all the probes in the rack and re-qualified them.

Run a program and get results that don't match what I had before calibration and don't match my customer.
One probe (2mm ball on a 62mm carbide shank that is 1.5mm diameter) has me worried it might be shanking, so I get a compound swivel and tram the thing plumb.

Reset the build and requalify all positions.
One position gives me the error attached. The head rotates, rapids to approach, rapid feeds in to about a quarter inch off the sphere (I have a .22 approach/retract in the cal window, so this is ok) and that error. The probe never moves to contact the sphere, just throws the error. Twice in a row, same position. ONLY that one position. I MAN+DCC and it quals.

After, the results from a part program are not good.

Ran a part on another PcDmis machine get results I expect.
Programmed it on a Mitutoyo machine, results match within .0005".
Run on the machine with the potential problem, it has different results by .015 on one axis only.

I then reset all the probes in the rack and requalify. Maybe I made a mistake. Maybe when I got that error and saved partial something happened, I don't know, so I do it all over.
No errors on any styli in any positions.

I run that part again, and it is now off .010 on one axis only.

I get a 20" gage block.
I make a three plane alignment, primary the end of the gage block and measure the length on X with a 5X90 stylus that I aligned the part in the program with. I measure the block length, .0001" off.
Switch to the 2mm stylus described above, .0001". Rotate to A45 B-45. .0001".
Spin the block along the Y axis.
Same thing.
5X90 is off .0001".
2mm probe off .0014".
Rotate to A45 B45 so no chance it is shanking, it is off .0015".

I delete the 2mm probe file completely.
Rebuild from scratch.
Try to qualify A0 B0 and get that stupid error again.
Try to move to change out on the rack and pushing the dead man's switch elicits a beep while the switch is depressed.
PcDmis stops working, crash to desktop.
Again, the head was at A0 B0 so no rotation there, the machine just rapids to some 4" over the sphere or something, then rapids down to about .25" over the sphere and stops with that error. It never makes the move at contact speed to try and touch anything. There is no contact speed motion, just rapids.
This probe had 86 positions before I deleted it. It qualified all the positions by itself lights out after the machine was calibrated. Then when I added the swivel, one position ONLY of those 86 gave me this error. Then, when I cleared the results and ran the qualification again yesterday, all 86 positions went through DCC+DCC with no errors. This is intermittent and I don't remember ever seeing it before.
The machine is 18 months old. I'm not the only one to run it, but this wasn't reported to me. Could it have happened and no one told me, ABSOLUTELY!

My extremely long winded question is, does this sound like a probe file problem and I'm on the right track, or does it sound like a head problem or does it sound like a machine calibration problem?

I'm going to continue with the stupid probe file, but if I'm beating my head on the wall over something that isn't the issue, and someone has an inkling of what it is, I'd like to know.

Thank you

  • It might be useful to know what kind of machine this is, what kind of rack, and what kind of probe it is. That error makes me think it might be a Leitz probe on a B5 controller perhaps? Maybe the probe is not properly seating when it changes from the rack?
  • Fair question, and one probe not QUITE seating would explain much of the weirdness. Maybe the stylus holder is damaged or something, I'm going to clean them all and the probe with that putty stuff.

    From the quote we ordered on, not sure how to get this out of the machine itself:
    Global S Green 9 15 8
    Controller DC241
    Kit Cilma thermal comp
    Next jobgox
    motorized head HH-AS8-T2.5
    Scanning probe HP-S-X1H
    Rack HR-X-900, X1, X3
    Ports HR-X1-P-SF
    PcDMIS 2021.2 SP4 build 411
  • I would try the block test with A0B90.
    I would also clean the ball stylus (once, the ball was unglued, but it was not visible- it fall down during the cleaning).
    I would also put a little oil on little spheres on the "cup" of the LSPX.
  • I would also clean the ball stylus (once, the ball was unglued, but it was not visible- it fall down during the cleaning).
    Did this three times just in case the first two missed something lol

    I would also put a little oil on little spheres on the "cup" of the LSPX.
    Never heard this, I will do this now.

    I would try the block test with A0B90.
    I didn't do this, but I did get a ball bar out and checked from "near" machine home, down to +X +Y and -Z so I'd have all three axes.

    The probe I am using in my part alignment is crap.

    What I find odd is that it is only off on X and Y, Z is good.

    Would a bad probe qualification really miss X and Y but have a good Z?

    I only used A0 B0 on this, but rotating the 2mm X 72mm stylus was giving me consistent errors.
    I know A0 B0 on my 5X50 stylus is shot, so why bother with rotating, I am just going to scrap the probe file and rebuild it, then qualify complete.
    Once I get A0 B0, THEN I will check other head angles, though, absolutely.

  • Check for cracks on the probe module. Also check the magnet for cracks or metal shavings. Maybe even try switching the suspect one with one that calibrated good.
  • I would measure the gage block along X with A0B0, and along Y with A0B90 (along Y with A0B0 is already done).
    If the defect turns with the probe, it comes from the probe.
    If the defect still the same after the head rotation, the problem comes from the cmm (dirts in air bearings or on pathes for example - it can be serious !!!!!)
  • Check for cracks on the probe module. Also check the magnet for cracks or metal shavings. Maybe even try switching the suspect one with one that calibrated good.

    I did this for the stylus build that ended up being confirmed bad, didn't see anything in any of the shafts, but I didn't like the SiN ball on the tip, so I changed it. Looked like just light bouncing wierd, but $100 stylus is a LOT less than the $3000 parts I'm trying to inspect.

    I didn't look at the magnet though, I didn't think about it being cracked. Thank you for that. I will be looking, and I have another holder in back up so the calibration people don't have to play with one of my builds.



    The same stylus that gave me that error ran 20 positions, then error-ed out with a counterbalance timeout. I hit go, and it went, then gave me that above error after positioning but not moving to touch. Picked the head up, went to A0B0 and ran that one position DCC+DCC and it went just fine.

    Something funny is going on there, I will be checking into that more.

    ​


    I would measure the gage block along X with A0B0, and along Y with A0B90 (along Y with A0B0 is already done).
    If the defect turns with the probe, it comes from the probe.
    If the defect still the same after the head rotation, the problem comes from the cmm (dirts in air bearings or on pathes for example - it can be serious !!!!!)

    I will be doing this next.

    I just ran every stylus in the rack on the ball bar after deleting probe files, rebuilding and qualifying.
    This was at A0B0 (other than the cranked probes) only.
    This is repeating now, both ends of the 600mm ball bar.

    I'm not going to run multiple angles on the head all on the qualification sphere for most of the probes (might skip the disk, will skip the cranked since I already spun the head on those).

    Then, I'm going back to the gage block.

    I like what you said about spinning the head on the block, to check for probe vs. machine. I hadn't thought about that even though I'd spun the head. Thank you. I'll definitely be doing this.



    Also going to force this program to be run every week (I think, shouldn't be more than an hour) so that I'm in front of any problems in the future.

    Thanks all!
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