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problem with fixture plate

pcdmisstudent
Hello everybody

So we have this fixture plate on our cmm with some pins on it.
and all parts we measure are put in a fixture and slided against the pins, so no manual alignment requierment.

problem is that every year when hex comes to calibrate our CMM, he has to take off the fixtureplate
and when he puts it on again, the plate is in a slight different position.

This kinda screws up for alot of our parts because we have to run the manual alignment again.

Has anyone any idea for either
1. A good setup for the plate so its precicily in the same position everytime we remove it and put i back. (Currenctly we put it with 3 bolts in the graphite plate)

or
2. Work with a zero point system so that we align on our fixture plate and all other manual alignments are based on that. so if we remove /put back our fixture plate all we have to do is do a 3/2/1 alignment on fixtureplate. (instead of running manual alignment on every part)

ty guys!
  • There are "rails" you can either manufacture or buy and bolt to the granite that will aid you in placing the fixture plate somewhat in the same place each time.
  • in reply to vpt.se
    Could you send me a picture of what those rails look like?
  • ah ok.
    But wont calibration tech need to remove those too?
  • The correct procedure should be to create a routine that aligns your fixture plate and saves the alignment externally. Then, in all of your other routines, you would start by recalling the external fixture alignment. Whenever the fixture plate gets moved, you simply re-run the fixture alignment routine.

    Example FIxture Alignment Routine Code... 
    PLN1         =FEAT/PLANE,CARTESIAN,TRIANGLE
              THEO/<50.298,37.095,0>,<0,0,1>
              ACTL/<50.298,37.095,0>,<0,0,1>
              MEAS/PLANE,3
                HIT/BASIC,NORMAL,<20.398,51.307,0>,<0,0,1>,<20.398,51.307,0>,USE THEO=YES
                HIT/BASIC,NORMAL,<65.04,50.715,0>,<0,0,1>,<65.04,50.715,0>,USE THEO=YES
                HIT/BASIC,NORMAL,<65.456,9.262,0>,<0,0,1>,<65.456,9.262,0>,USE THEO=YES
              ENDMEAS/
A1           =ALIGNMENT/START,RECALL:STARTUP,LIST=YES
                ALIGNMENT/LEVEL,ZPLUS,PLN1
                ALIGNMENT/TRANS,ZAXIS,PLN1
              ALIGNMENT/END
LIN1         =FEAT/LINE,CARTESIAN,UNBOUNDED
              THEO/<29.084,0,-2.117>,<1,0,0>
              ACTL/<29.084,0,-2.117>,<1,0,0>
              MEAS/LINE,2,ZPLUS
                HIT/BASIC,NORMAL,<29.084,0,-2.672>,<0,-1,0>,<29.084,0,-2.672>,USE THEO=YES
                HIT/BASIC,NORMAL,<71.956,0,-1.563>,<0,-1,0>,<71.956,0,-1.563>,USE THEO=YES
              ENDMEAS/
A2           =ALIGNMENT/START,RECALL:A1,LIST=YES
                ALIGNMENT/LEVEL,ZPLUS,PLN1
                ALIGNMENT/TRANS,ZAXIS,PLN1
                ALIGNMENT/ROTATE,XPLUS,TO,LIN1,ABOUT,ZPLUS
                ALIGNMENT/TRANS,YAXIS,LIN1
              ALIGNMENT/END
PNT1         =FEAT/POINT,CARTESIAN
              THEO/<0,6.726,-4.011>,<-1,0,0>
              ACTL/<0,6.726,-4.011>,<-1,0,0>
              MEAS/POINT,1,WORKPLANE
                HIT/BASIC,NORMAL,<0,6.726,-4.011>,<-1,0,0>,<0,6.726,-4.011>,USE THEO=YES
              ENDMEAS/
A3           =ALIGNMENT/START,RECALL:STARTUP,LIST=YES
                ALIGNMENT/LEVEL,ZPLUS,PLN1
                ALIGNMENT/TRANS,ZAXIS,PLN1
                ALIGNMENT/ROTATE,XPLUS,TO,LIN1,ABOUT,ZPLUS
                ALIGNMENT/TRANS,YAXIS,LIN1
                ALIGNMENT/TRANS,XAXIS,PNT1
              ALIGNMENT/END
              SAVE/ALIGNMENT,Fixture_alignment.aln,MACHINETOPARTS​


    Example of how to recall the fixture alignment in your other routines... 
    PART NAME  : test
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/LSPX1_3X50
            TIP/T1A0B0, SHANKIJK=0, 0, 1, ANGLE=0​
            RECALL/ALIGNMENT,EXTERNAL,FIXTURE_ALIGNMENT
​
rest of routine
  • I would create an external alignment program just for the plate and then recall the alignment in each program. Had this setup at a facility I used to work at.
  • Ty
    so i would just create alignment on plate, save it, and recall that alignment in the beginning of each program, and then do the manual alignment?
    can i implement that to our current programs or would i have to redo them
  • Grab a cold chisel and smack in some alignment lines on the table....... (OK, that's a joke).

    BEFORE removing the plate, grab some duct tape and put the tape on the table at the edges of the plate. When the tech is done, put the plate back up against the tape.
  • Use shoulder bolts if possible to locate rails and save location to external alignment.
  • in reply to pcdmisstudent
    We have the inspection arsenal rail system on all our CMM's. The plates snap into the rail using magnets and do not need to be fastened. The only thing bolted down is the rail and we've never had issues with leaving it bolted to the table during Hexagon's calibration.
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