The Accuracy of CAD/CAM Parts - A Critical Analysis 2012-01-0557

In October, 1987, this author wrote a paper entitled The Metrology Crisis, wherein he revealed that our nation's industries did not know how to control the shape of their manufactured hardware. This stemmed from the non-use or misunderstanding of the ASME Y14.5 standard on dimensioning and tolerancing. Shortly afterward, major algorithm errors were discovered in our nation's coordinate measurement machines. The measurements of million dollar measuring systems were not accurate. They did not conform to the definitions established in the Y14.5 standard. The revelations of The Metrology Crisis and the discovery of algorithm errors sent shockwaves throughout the government, industry, and standards agencies. It would take seven years to create the highly complex mathematical formulas, compiled in a new standard, ASME Y14.5.1M-1994. One year later, a certification program, proposed by this author, was created under the guidelines of another a new standard, ASME Y14.5.2-1995. The exams began in 1997. But the problem of The Metrology Crisis and noncompliance with the ASME Y14.5 Standard today continues to plague our nation's industries amid counter-arguments that we do not need the standard anymore. This view is often justified by those who claim we now make perfect parts. Well, if you are one of those who think you have a perfect part just because it was manufactured from a model, then this report is for you. For few people understand the complexities associated with true control of part shape.

This critical analysis will expose to you many of the anomalies associated with the control of machined hardware, particularly when designed and manufactured by computer driven equipment. Few engineers may recall or even knew of the Metrology Crisis of the nineteen-eighties. And few perhaps fail to understand the significance of the ASME Y14.5, Y14.5.1, Y14.5.2 and Y14.41 standards when it comes to CAD/CAM parts. Yet, many of these same people expound on the benefits of paperless drawings and the omission of standards compliance merely because “we make perfect parts.”