hexagon logo
Register Sign in
  • Replies 36 replies
  • Subscribers 19 subscribers
  • Views 805 views
  • Users 0 members are here
Options
Related

Fails: Gage R&R

bfire85
In light of a gage R&R that will fail (will post the results when complete) on a $4K that someone in my company decided to purchase without the input of Quality, what has been the worst Gage R&R results you have seen from a gage?
  • How many decimal points out are the measured and calculated results to? I've seen some fairly bad results become acceptable if more decimal points are used in the calculations. Truncating the results can result in an artificially tight control limit in the calculations.

    We went out to 4 decimal places.

    Trust me...this gage is absolutely not repeatable. We had myself, another QE, a quality tech, our manager put a part on and take it off and put it back on and got massive variation.
  • in reply to JEFMAN
    I am presuming you are validating a fixture holding multiple identical parts. Your Gage R&R should be "Crossed" in this instance, where one operator physically reorganizes the parts between fixture positions, maintaining part traceability.

    When the crossed operator's data can effectively still track those parts, you have better reproducibility, but crappy repeatability.

    Also, if you have poor work instruction that makes operator 1 load parts differently into fixture, it would produce operator bias that ops 2 and 3 might not have... which would result in crappy repeatability.
  • Our customer is designing a CMM part fixture (for injeciton molded plastic parts) with air suction cups to restrain the parts... cool idea in theory, until you realize they are still using the exact same upper clamps with springs that are producing a 0.003" constraint bias on a critical dimension.
    The whole point of redesigning the fixture was to eliminate the constraint bias. *facepalm*
  • Our customer is designing a CMM part fixture (for injeciton molded plastic parts) with air suction cups to restrain the parts... cool idea in theory, until you realize they are still using the exact same upper clamps with springs that are producing a 0.003" constraint bias on a critical dimension.
    The whole point of redesigning the fixture was to eliminate the constraint bias. *facepalm*

    That's engineers for ya! Rolling eyes
  • Our customer is designing a CMM part fixture (for injeciton molded plastic parts) with air suction cups to restrain the parts... cool idea in theory, until you realize they are still using the exact same upper clamps with springs that are producing a 0.003" constraint bias on a critical dimension.
    The whole point of redesigning the fixture was to eliminate the constraint bias. *facepalm*

    how does using suction eliminate constraint...? Rolling eyesRolling eyesRolling eyesRolling eyes


  • how does using suction eliminate constraint...? Rolling eyesRolling eyesRolling eyesRolling eyes

    Sometimes suction in the right place can free things up nicely...
© 2024 Hexagon AB and/or its subsidiaries. Privacy Policy | Cloud Services Agreement