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Trying to measure a 3mm hole with a 1mm probe

I am trying to measure the position of a 3mm diameter hole using a 1mm probe tip. I tried using the auto circle measure tool and it positioned the probe incorrectly. It didn't move over the hole, but was off by about 2mm. Why would this happen? The hole is dead on position and the part matches the model to within .001". I measured the alignment with a different probe on three square faces of the part. Would this impact where the machine thought the hole is? Is there something wrong with the hardware? Both probes were calibrated before measurement with no errors. Any help would be appreciated. 

Also, I still need to measure the hole, but taking hits moves the probe too far back. how do I change it so that the probe can measure the 3mm hole?

Parents
  • After some more experimenting, the 5mm probe I use to do the initial alignment finds the hole exactly when I use the "move to" button. The second 1mm probe is off in both x and y. I am going to try to do another alignment after using the 1mm probe and see if that fixes it. Is that normal behavior for PC DMIS?

  • That sounds more like a probe calibration problem - the relationship between the two different probes is incorrect.  Search this forum, there are many, many, many posts on the topic of probe calibration.

  • Both probes were calibrated before I started measuring. I just calibrated them again for good measure. I also manually took some hits with the 1mm probe. It is now off by -1.127" in x, .025" in z and .924" in y. It looks like the probe thinks that the part is somewhere completely different than where it is. I think there must be something that I have to do with alignments when changing probe tips. I use a probe rack and the machine does it automatically. I think that there is something very basic that I am missing that is so basic that nobody here would even think to respond with the answer. Here is the code for my program so far. 

    PART NAME : measurement test 1
    REV NUMBER :
    SER NUMBER :
    STATS COUNT : 1
    
    STARTUP =ALIGNMENT/START,RECALL:USE_PART_SETUP,LIST=YES
    ALIGNMENT/END
    MODE/MANUAL
    FORMAT/TEXT,OPTIONS, ,HEADINGS,SYMBOLS, ;NOM,TOL,MEAS,DEV,OUTTOL, ,
    LOADPROBE/5MM50L PROBE
    TIP/T1A0B0, SHANKIJK=0, 0, 1, ANGLE=0
    MAN_ALIGN =GROUP/SHOWALLPARAMS=NO
    ENDGROUP/ID=MAN_ALIGN
    DCC_ALIGN =GROUP/SHOWALLPARAMS=NO
    ENDGROUP/ID=DCC_ALIGN
    SCN1 =FEAT/SCAN,LINEAROPEN,NUMBER OF HITS=397,SHOW HITS=YES,SHOWALLPARAMS=NO
    MEAS/SCAN
    BASICSCAN/LINE,NUMBER OF HITS=397,SHOW HITS=YES,SHOWALLPARAMS=NO
    *A BUNCH OF HITS*
    ENDSCAN
    ENDMEAS/
    MOVE/POINT,NORMAL,<1.8409,-1.1827,1.4011>
    LOADPROBE/1MM PROBE WITH EXTENSIONS
    TIP/T1A0B0, SHANKIJK=0.0001, 0, 1, ANGLE=0.0959
    MODE/MANUAL
    PLN4 =FEAT/PLANE,CARTESIAN,TRIANGLE
    THEO/<1.063,-3.6554,-0.1457>,<-1,0,0>
    ACTL/<-0.0641,-2.8459,-0.1078>,<-0.9999983,-0.0001729,0.0018597>
    MEAS/PLANE,3
    HIT/BASIC,NORMAL,<1.063,-2.2793,-0.175>,<-1,0,0>,<-0.0644,-1.4773,-0.1108>,USE THEO=YES
    HIT/BASIC,NORMAL,<1.063,-3.5447,-0.0538>,<-1,0,0>,<-0.064,-2.8064,-0.0567>,USE THEO=YES
    HIT/BASIC,NORMAL,<1.063,-5.1423,-0.2083>,<-1,0,0>,<-0.064,-4.2542,-0.1558>,USE THEO=YES
    ENDMEAS/
    PLN5 =FEAT/PLANE,CARTESIAN,TRIANGLE
    THEO/<1.7903,-2.646,-0.0098>,<0,0,1>
    ACTL/<0.5752,-1.938,0.0156>,<0.0000849,-0.0000348,1>
    MEAS/PLANE,3
    HIT/BASIC,NORMAL,<1.4314,-4.7782,-0.0098>,<0,0,1>,<0.2498,-3.7312,0.0155>,USE THEO=YES
    HIT/BASIC,NORMAL,<1.5476,-1.8087,-0.0098>,<0,0,1>,<0.2462,-1.5491,0.0156>,USE THEO=YES
    HIT/BASIC,NORMAL,<2.3918,-1.3511,-0.0098>,<0,0,1>,<1.2295,-0.5336,0.0156>,USE THEO=YES
    ENDMEAS/
    PLN6 =FEAT/PLANE,CARTESIAN,TRIANGLE
    THEO/<2.8752,-0.9843,-0.1258>,<0,1,0>
    ACTL/<1.6836,-0.0602,-0.0896>,<-0.0005733,0.9999913,-0.0041359>
    MEAS/PLANE,3
    HIT/BASIC,NORMAL,<1.9252,-0.9843,-0.0888>,<0,1,0>,<0.7465,-0.0607,-0.0615>,USE THEO=YES
    HIT/BASIC,NORMAL,<2.9035,-0.9843,-0.1953>,<0,1,0>,<1.608,-0.0605,-0.146>,USE THEO=YES
    HIT/BASIC,NORMAL,<3.7969,-0.9843,-0.0934>,<0,1,0>,<2.6961,-0.0595,-0.0615>,USE THEO=YES
    ENDMEAS/

  • Is it possible for you to edit this post and cut your program text, and paste it into an Insert > Code block so it's more readable?

  • I tried, but do you know which language I was supposed to select to actually format the text? PC DMIS is not an option for type of code.

  • It looks like an alignment that is done using one probe is not carried over to other probes. I assume that this is normal and expected behavior and I should be creating new alignments for each probe that I load? Will I also need to create new alignments when I change the angle of the probe head but keep the same probe?

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