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Measuring step height

*...*
I have a Visio 300
PC-DMIS 4.3
I set up 2 gage blocks side by side 1 .600" and 1 .550"
I measured a the top of the .600" block with an auto focus point max zoom
set the (Z) origin to that point
measured the same point 10 times and got a range of .00222"
did the same on the .550" block and got a range of .00247"
I don't understand I feel this should be more accurate than this.
Does anyone have any settings suggestions that I can try?
Thanks
  • Try increasing the duration of the focus. You should also be on high magnefication. Also try turning the light down. Use the light ring, it is less shiny than the top light. Also turn the light down.
  • Gage blocks are shiny are they not?
    Also tested these:
    plastic .00216 range
    phenolic .00249 range
    steel grind finish .0025 range
    steel tumbled finish .00379 range
    steel lapped finish .00216 range
    brass turned finish .00242

    TOP SURFACE=FEAT/VISION/SURFACE POINT,CARTESIAN
    THEO/<0,0,0>,<0,0,1>
    ACTL/<0.00201,0.00131,0.00084>,<0,0,1>
    TARG/<0,0,0>,<0,0,1>
    SNAP=NO
    SHOW FEATURE PARAMETERS=NO
    SHOW_VISION_PARAMETERS=YES
    TYPE=AUTOMATIC HIT TARGET
    MAGNIFICATION=4.51213
    HIT TARGET COLOR=WHITE,NOMINAL COLOR=GREEN
    HIT TARGET=SA1,YES,0.01721,0.01525
    FOCUS=FULL,0.4,NO,6,NONE,NO,TOP LIGHT [OFF] : BOTTOM LIGHT [OFF] : RING
    LIGHT [ON:89%{1111}]
    DIM LOC1= LOCATION OF POINT TOP SURFACE UNITS=IN ,$
    GRAPH=OFF TEXT=OFF MULT=200.00 OUTPUT=BOTH
    AX NOMINAL MEAS
    X 0.00000 0.00201 ----#---
    Y 0.00000 0.00131 ----#---
    Z 0.00000 0.00084 ----#---
    END OF DIMENSION LOC1
  • I should have also mentioned that I know ZIP about your system - the shiny thing was just a guess.

    What are the published accuracy specs?
  • If you want to do Z measurement, don't use a Tesa viso, you must do it with an OGP or MicroVu machine
  • I have a Visio 300
    PC-DMIS 4.3
    I set up 2 gage blocks side by side 1 .600" and 1 .550"
    I measured a the top of the .600" block with an auto focus point max zoom
    set the (Z) origin to that point
    measured the same point 10 times and got a range of .00222"
    did the same on the .550" block and got a range of .00247"
    I don't understand I feel this should be more accurate than this.
    Does anyone have any settings suggestions that I can try?
    Thanks

    Welcome to vision... on the better systems, I would expect to see around .0002"-.0005" @ ~12X optical.

    This could be software or hardware.
    Can you reduce your focus target size to it's smallest?
    Adjust the speed of the focus - slower = better.
    Adjust the "backoff" and "focus through" to the smallest settings. This is the total evaluation range of Z for each focus.
    Try only using coaxial illumination if possible.
    You need a target to focus on, something with contrast. With a gage block, a finger print works nice.
  • set the (Z) origin to that point

    Just a guess. I not overly familiar with this software, but does the quote above mean that the part coordinate is "Leveling" into the Z plane or just "Translating" it from world or machine coordinates?

    Big difference.
  • Note true, in fact I'd say the reverse, though no vision system is as accurate in Z as it is in X and Y (unless you are using another sensor type like white light)

    If you want to do Z measurement, don't use a Tesa viso, you must do it with an OGP or MicroVu machine

  • TOP SURFACE=FEAT/VISION/SURFACE POINT,CARTESIAN
THEO/<0,0,0>,<0,0,1>
ACTL/<0.00201,0.00131,0.00084>,<0,0,1>
TARG/<0,0,0>,<0,0,1>
SNAP=NO
SHOW FEATURE PARAMETERS=NO
SHOW_VISION_PARAMETERS=YES
TYPE=AUTOMATIC HIT TARGET
[COLOR="Red"][B]MAGNIFICATION=4.51213[/B][/COLOR]
HIT TARGET COLOR=WHITE,NOMINAL COLOR=GREEN
HIT TARGET=SA1,YES,0.01721,0.01525
FOCUS=FULL,0.4,NO,6,NONE,NO,TOP LIGHT [OFF] : BOTTOM LIGHT [OFF] : RING
[COLOR="red"][B]LIGHT [ON:89%{1111}][/B][/COLOR]
DIM LOC1= LOCATION OF POINT TOP SURFACE UNITS=IN ,$
GRAPH=OFF TEXT=OFF MULT=200.00 OUTPUT=BOTH
AX NOMINAL MEAS
X 0.00000 0.00201 ----#---
Y 0.00000 0.00131 ----#---
Z 0.00000 0.00084 ----#---
END OF DIMENSION LOC1

    I'd say MAG=too low and LIGHT=too high for repeatable Z measurement. I tried gage block on OGP Flash (non-pcdmis system) at max magnigication and light @35%. 10 run repeatability = 0.0002". At low mag, I got 0.001". I did not test at blinding light intensity, since I know this causes measurement issues.

    I'm a cmm guy and tend to pooh-pooh vision measurements, but was fairly impressed by this.
  • I'd say MAG=too low and LIGHT=too high for repeatable Z measurement. I tried gage block on OGP Flash (non-pcdmis system) at max magnigication and light @35%. 10 run repeatability = 0.0002". At low mag, I got 0.001". I did not test at blinding light intensity, since I know this causes measurement issues.

    I'm a cmm guy and tend to pooh-pooh vision measurements, but was fairly impressed by this.

    Not so bad ??
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