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Question about calibration & master probe.

Morning, All.
I'm sure this question has been answered a million times on here, but I couldn't find specifics of my situation during a search. At out shop, we have 2 Global 5.5.5 CMMs that use the Hexagon/Tesa touch trigger probe system. With that said, I'll tell you how we calibrate the probes here. Both CMMs have a sub-plate. We screw the calibration sphere in the same location every time we calibrate. We will write a simple calibration program for all part numbers, so if me or the QE isn't here, they can screw in the calibration sphere, and open the program to calibrate. We use parameter sets for each part number, so we don't have to calibrate all tips. For every tip we use, we always say "No" when PCD asks if the calibration sphere has moved. Can we loose accuracy by doing this? My QE says that since we never move the actual location on the subplate, it shouldn't matter.

Also, we use one of our commonly used tips (1mm X 27.5mm A0B0) for the master probe, but we never use it to find the sphere (as its always placed in the same place on the subplate.

Here is the code for our typical calibration program:

STARTUP    =ALIGNMENT/START,RECALL:USE_PART_SETUP,LIST=YES
            ALIGNMENT/END
            MODE/MANUAL
            FORMAT/TEXT,OPTIONS,ID,HEADINGS,SYMBOLS, ;NOM,TOL,MEAS,MAXMIN,DEV,DEVANG,OUTTOL
            MOVESPEED/ 300
            COMMENT/OPER,NO,FULL SCREEN=YES,AUTO-CONTINUE=NO,
            MOVE THE PROBE UP ABOVE AND OUT OF THE WAY
            IN A SAFE POSITION.
            COMMENT/OPER,NO,FULL SCREEN=YES,AUTO-CONTINUE=NO,
            REMOVE ALL FIXTURES AND PARTS FROM THE TABLE.
            PLACE THE CALIBRATION SPHERE IN LOCATION I9.
            FORMAT/TEXT,OPTIONS, ,HEADINGS,SYMBOLS, ;NOM,TOL,MEAS,DEV,OUTTOL, ,
            LOADPROBE/EPS 1X27_5 NO EXT
            TIP/T1A0B0, SHANKIJK=0, 0, 1, ANGLE=0
            AUTOCALIBRATE/PROBE, PARAMETER_SET=EPS C504-002 1X27_5 NO EXT, QUALTOOL_MOVED=NO,
                          CHECK COLLISION=NO, SHOW_SUMMARY=NO, OVERWRITE_RESULTSFILE=NO
            COMMENT/OPER,NO,FULL SCREEN=YES,AUTO-CONTINUE=NO,
            MOVE PROBE UP AND IN A SAFE POSITION.
            COMMENT/OPER,NO,FULL SCREEN=YES,AUTO-CONTINUE=NO,
            REMOVE THE CALIBRATION SPHERE AND RETURN IT
            TO THE HOME LOCATION.  ​


Thanks!!!

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  • If the probe is located in "the same place" every single time why not say it has moved? This way whatever variance there is between screwing and unscrewing the sphere is not important. Are you wanting to save time by not picking up the master and locating the sphere?


    Pretty much the logic here. My concern would be that I may screw it snug, but the next operator may make it a 32nd of a turn tighter... I have the mode set as "DCC + DCC" so that the tip does 4 hits near the center, then starts the 10 hits around the sphere to help compensate for any variance like that.
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  • If the probe is located in "the same place" every single time why not say it has moved? This way whatever variance there is between screwing and unscrewing the sphere is not important. Are you wanting to save time by not picking up the master and locating the sphere?


    Pretty much the logic here. My concern would be that I may screw it snug, but the next operator may make it a 32nd of a turn tighter... I have the mode set as "DCC + DCC" so that the tip does 4 hits near the center, then starts the 10 hits around the sphere to help compensate for any variance like that.
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