The conflict between the production floor and the quality lab is legendary. A machinist measures a part with a micrometer and sees it as “in spec.” The CMM says it’s “out.” Who is right?
Stability vs. Compensation
Manual tools like micrometers are often kept at the workstation. They are at the same temperature as the environment. If it’s 30°C in the shop, the micrometer and the part have both expanded. If the operator zeros the micrometer on a gauge block that is also at 30°C, they are essentially measuring in a “shifted” universe.
The CMM, however, uses thermal probes to calculate the part’s size at the standard 20°C (68°F). This discrepancy is where the “war” begins. Success in shop-floor metrology requires education. Operators must understand that the CMM provides the “True North” of measurement by compensating for variables they cannot see. Without this culture of measurement, the CMM will always be viewed as an “enemy” rather than a tool for process stability.
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