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  Measurement, Test and Calibration
  CMM Uncertainty

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Author Topic:   CMM Uncertainty
Marc Smith
Cheech Wizard

Posts: 4119
From:West Chester, OH, USA
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posted 17 August 2000 09:47 AM     Click Here to See the Profile for Marc Smith   Click Here to Email Marc Smith     Edit/Delete Message   Reply w/Quote
Guidance on interpretation and implementation Measurement Research Resolving CMM Uncertainties www.sme.orghttps://elsmar.com/cgi-bin/get-press.pl?7363c&2&20002798&& DALLAS, TX (7/10/2000).

The International Standards Organization is in the final phases of re-writing its 9000 series quality standard that will include a requirement that manufacturers determine the level of uncertainty they have when measuring the toleranced features of their parts and products. Coordinate measuring machines (CMMs) are capable of precisely measuring features, but there have always been difficulties in assessing the accuracy of those measurements. A new company, called MetroSage, has been formed in California by some of the nation's leading metrology and software researchers to address this tricky, technical challenge. The company is a result of a decade-long research commitment made by the Consortium for Advancement Manufacturing--International (CAM-I). Work conducted by the National Institute of Standards

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Steven Truchon
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Posts: 89
From:Fort Lauderdale, FL USA
Registered: Jul 2000

posted 12 September 2000 05:42 PM     Click Here to See the Profile for Steven Truchon   Click Here to Email Steven Truchon     Edit/Delete Message   Reply w/Quote
Speaking of CMM Uncertainty, I have harbored this possibility for years so I thought I'd toss it out for scrutiny.

Part tolerance= hole location = cylindrical postional tolerance of .002 RFS.

Machine linear accuracy (XY) = +/-.0002
Touch probe accuracy = .0001

Total machine meas error = .0003
Calculated cylindrically (true position formula)= an error zone of .00085 diameter

Using the 10:1 rule of accuracy to tolerance would this CMM configuration only be able to measure Cylindrical Positional Tolerance of .0085 diameter or larger?

Whaddya think?

Steve

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