How can I improve inspection process

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  • How can I improve inspection process

    Evening gent,

    Hope you are all well, I am here to ask for an advise how can I improve inspection program of component from the sketch Part is made from carbon, with approx 6mm thick walls. Part have to be bolted down through 4 off holes at size 8.000 / 8.012mm (yellow, later on used for locating studs) to the inspection plate while is being measured, due to datum B plane is bowed along side Y axis. Inspection plate is mated with datum B and has only 4 small holes to allow 4 points taken for DCC plane (normally comes up around 20um).

    manual alignement

    Z LEVEL -> plane B
    Z ORIGIN -> inspection plate
    ROTATION X+ -> to 'D' holes (4 off in total at size 10.000 / 10.018)
    X/Y ORIGIN - Datum D hole

    DCC alignement

    Z LEVEL -> plane B
    Z ORIGIN -> plane B
    ROTATION X+ -> constructed cylinder -> c2 off circles from the 2 bearing bores (approx 120 mm diameter) located on the left and right from the largest centre bore
    X ORIGIN -> line from datum C
    Z ORIGIN -> intersection cylinder and line C

    - total runout is than reported for all other bores with requirement to be max 0.03 mm
    - true position for 'blue holes' - max 0.05
    - every bore {apart from 1 on either end) than has a groove which is 2.5mm bigger than bore diameter, groove width 0.7mm, max runout 0.03
    - all bores tolerance is +/- 0.02 mm

    All features used during alignment are within 0.03 in form. Hatched area is trimmed away prior assembly,

    Parts gets NCR every time due errors, occasionally up to 0.15mm. I have had not measured many carbon components previously and therefore I am asking if you guys are seeing something I could improve ? Your inout is much appreciated

    Regards JJ

    Attached Files

  • #2
    Try rotating to your datum C line in the Y axis instead of the constructed cylinder.

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    • #3
      I cannot comment on the material, as it is outside of my personal experience, but I can offer some general comments on the measuring strategy:
      • Personally I prefer to DCC align to the datum reference frame (in your case, level X on A, Zero YZ on A, rotate Y around X on B, zero X on C) but in theory it should not matter
      • I do see bigger issues in your datum A as per attached sketch, which seems ill-defined to me. What features constitute the datum? The two "bearing bores" seems like a reasonable assumption, but it is just an assumption. You should try to clarify this with the designer if possible.
      • How many points are you taking to measure the datum features? How many for the other features?
      • Have you tried to correlate your CMM measurements with other instruments? if so with what results?
      • In general, measuring circles/cylinders with 180 degrees or less available is (and always will be) a problematic area, as the software struggle to assign deviation from nominal as a position or form error. This is magnified in your case by the main datum being such feature.

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