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Is there a way to auto re-compute a Best Fit 3D (BF3D) Alignment?

CMM2020
Hi everyone,

I'm having a bit of an issue with regards to doing a Best Fit alignment to align a fixture, specifically the fixture datums (4-Way, 2-Way, A-Nets).

I like to start off my alignment with Iterative first off of the tooling bushings built into the fixture base,
Then I proceed to measure the datums in DCC, then I will proceed to create another Iterative alignment off of the datums if possible,
else I will do a Best Fit 3D using the datums and save my alignment to be recalled in another program.

I'm noticing that after I run the program the datums are sometimes out of spec. after BF3D,
taking a closer look I can see my Best Fit alignment needs to be re-computed! (it's even lost it's chosen directions).

Is there a way to set the Best Fit alignment to auto compute every time I run the program,
or is it rule of thumb that after performing an Iterative in DCC, that the best fit alignment always needs manual intervention?

My program is basically this:

1. Pick up 3 tooling bushings manually
2. Iterative pick up off of the same 3 tooling bushings using DCC
3. Measure datums in DCC (4-Way / 2-Way / A-Nets)
4. Create BF3D off of the datums
5. Re-measure datums to make sure they are in spec. within +/- 0.05 mm

Thanks for any help you guys can provide,
I don't want to have to re-compute manually every time I run my external alignment program.

- Pete

Parents
  • When establishing Datums on a "Fixture" or "Gage" that has Tooling Balls or Bushings, they are there for REFERENCE. Always remember the nets and pins simulate how the parts interface with the assembly
    of the vehicle. I always TRY to get the the net pads and the pins as close as possible to nominal . If the fixture is not good enough, get it fixed, with an agreed tolerance and proceed from there. Always show
    the datums in your report, that shows complete transparency to customer. Just make sure you have a good "foundation" for your measurements. Using a Best-Fit will shift datums and give false results!!!

    If someone wants you to Best-Fit, get the order in an e-mail or some paper trail to CYOA!!
Reply
  • When establishing Datums on a "Fixture" or "Gage" that has Tooling Balls or Bushings, they are there for REFERENCE. Always remember the nets and pins simulate how the parts interface with the assembly
    of the vehicle. I always TRY to get the the net pads and the pins as close as possible to nominal . If the fixture is not good enough, get it fixed, with an agreed tolerance and proceed from there. Always show
    the datums in your report, that shows complete transparency to customer. Just make sure you have a good "foundation" for your measurements. Using a Best-Fit will shift datums and give false results!!!

    If someone wants you to Best-Fit, get the order in an e-mail or some paper trail to CYOA!!
Children
  • in reply to Tater
    Tater,

    Say you've successfully established an Iterative alignment off of the 3 tooling bushings on a fixture,
    then when you go to measure the 4-Way / 2-Way / A-Nets you notice they are not within spec. but slightly out beyond +/- 0.05 mm (tolerance).

    How would you proceed to get the datums into spec.? Would you perform another iterative alignment but this time using the datum features? Or Would you update the nominals on the tooling bushings to "float/shift" the datums into spec?

    I'm trying to find the best iterative practice for solidifying a solid repeatable alignment.

    Thank you for any help in this matter, I greatly appreciate you sharing your wisdom with me.
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