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What is to be measured in Measurement System? What type of characteristic is it? Is it a mechanical property? Is it dynamic or stationary? Is it an electrical property? Is there significant within-part variation?

For what purpose will the results (output) of the measurement process be used? Production improvement, production monitoring, laboratory studies, process audits, shipping inspection, receiving inspection, responses to a D.O.E.?

Who will use the process? Operators, engineers, technicians, inspectors, auditors?

Training required: Operator, maintenance personnel, engineers; classroom, practical application, OJT, apprenticeship period.

Have the sources of variation been identified? Build an error model (S.W.I.P.E. or P.I.S.M.O.E.A.) using teams, brainstorming, profound process knowledge, cause & effect diagram or matrix.

Has a FMEA been developed for the measurement system?

Flexible vs. dedicated measurement systems: Measurement systems can either be permanent and dedicated or they can be flexible and have the ability to measure different types of parts; e.g., doghouse gages, fixture gaging, coordinate measurement machine, etc. Flexible gaging will be more expensive, but can save money in the long run.

Contact vs. non-contact: Reliability, type of feature, sample plan, cost, maintenance, calibration, personnel skill required, compatibility, environment, pace, probe types, part deflection, image processing . This may be determined by the control plan requirements and the frequency of the measurement ( Full contact gaging may get excessive wear during continuous sampling). Full surface contact probes, probe type, air feedback jets, image processing, CMM vs. optical comparator, etc.

Environment: Dirt, moisture, humidity, temperature, vibration, noise, electro-magnetic interference (EMI), ambient air movement, air contaminants, etc. Laboratory, shop floor, office, etc? Environment becomes a key issue with low, tight tolerances in the micron level. Also, in cases that CMM, vision systems, ultrasonic, etc.
This could be a factor in auto-feedback in-process type measurements. Cutting oils, cutting debris, and extreme temperatures could also become issues. Is a clean room required?

Measurement and location points: Clearly define, using GD&T, the location of fixturing and clamping points and where on the part the measurements will be taken.

Fixturing method: Free state versus clamped part holding.

Part orientation: Body position versus other.

Part preparation: Should the part be clean, non-oily, temperature stabilized, etc. before measurement?

Transducer location: Angular orientation, distance from primary locators or nets.

Correlation issue #1 – duplicate gaging: Are duplicate (or more) gages required within or between plants to support requirements? Building considerations, measurement error considerations, maintenance considerations.
Which is considered the standard? How will each be qualified?

Correlations issue #2 – methods divergence: Measurement variation resulting from different measurement system designs performing on the same product/process within accepted practice and operation limits (e.g., CMM versus manual or open-setup measurement results).

Automated vs. manual: on-line, off-line, operator dependencies.

Destructive versus nondestructive measurement (NDT): Examples: tensile test, salt spray testing, plating/paint coating thickness, hardness, dimensional measurement, image processing, chemical analysis, stress, durability, impact, torsion, torque, weld strength, electrical properties, etc.

Potential measurement range: size and expected range of conceivable measurements.

Effective resolution: Is measurement sensitive to physical change (ability to detect process or product variation) for a particular application acceptable for the application?

Sensitivity: Is the size of the smallest input signal that results in a detectable (discernable) output signal for this measurement device acceptable for the application? Sensitivity is determined by inherent gage design and quality (OEM), in-service maintenance, and operating condition.

source : Analysis of measurement systems

Post Author: ghaemi mohammad

This site has been established to provide updated and specialized information in the field of quality management systems and to share my experiences in the field of conformity assessment and promotion and promotion of this science.

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