|
| Higher Risk of Inspectors/Metrologists Accepting Non-Conforming Parts! |
| |
The risk of rejecting parts that conform to specification requirements, and the higher risk of accepting parts that do not conform to specification requirements, is increasing. This risk is influenced by feature tolerances getting tighter and the level of confidence (or lack of confidence) the metrologist has in the full measurement process.
This article highlights the key areas of concern and offers guidance to increase confidence and reduce the risk. Mechanical drawings that state compliance to the ASME Y14.5-2018 “Dimensioning and Tolerancing” includes compliance to ASME Y14.5.1-2019 “Mathematical Definition of Dimensioning and Tolerancing Principles.” This would also apply to earlier versions of the Y14.5 and Y14.5.1 standards. |
 |
 |
| |
| Common Misconception of Maximum Permissible Error on a CMM |
| |
A major problem throughout all industries is individuals commonly are under the misconception that the stated 3-dimensional “maximum permissible error” (per ISO 10360-2) of the coordinate measuring machine (CMM), often stated as a baseline error plus some length dependent factor (e.g. E0, MPE: 3.1µm + L/1000mm), equates to the measurement uncertainty when measuring features on a given manufactured part.
Everyone needs to understand that this can be far from the true task/feature-based uncertainty required to make accept/reject decisions, which is influenced by many other key factors. Metrologists, inspectors, supplier engineers and anyone charged with the responsibility of ensuring manufactured parts truly conform to specification requirements must have this foundational knowledge. |
 |
| |
|
