Standard

SAE AIR6975

Published

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Abstract

The scope of this SAE Aerospace Information Report includes practical applications, theory, process management, audit and control recommendations, recommended validation intervals, verification and validation, file setup parameters, additional considerations, and process documentation. Practical Applications Modern hard balancing machines use computer-based measuring units that allow one to optimize and adjust the measuring result to reflect unusual conditions that would otherwise complicate measurement results and therefore impair the balancing process. Certain rotors demand special adjustments to achieve unbalance tolerance as quickly and accurately as possible. Rotor type-specific calibration is designed to optimize the results of a balancing process incorporating one or more of those challenges. Theory Rotor type-specific calibration is an optimized adjustment to enhance the measured results. Where permanent calibration applies to the full range of the machine, rotor type-specific calibration takes the unique conditions of a balancing system for a particular rotor type into account to yield optimized results that are otherwise impossible using hard bearing calibration. This is accomplished by overlaying and improving the permanent calibration with influence coefficients for the particular system configuration including rotor, tooling, machine, and foundation characteristics. Process Management, Audit, and Control Recommendations Caution should be exercised regarding who is authorized to perform a rotor type-specific calibration. Modern PC-based measuring instruments feature multiple user levels to define different levels of authority and limit access for modification in relation to the process specific task. This document provides recommendations for applying such a structure. Recommended Validation Intervals In the case of repair or replacement of critical parts in the measuring functionality of the balancing system, all machine calibration protocols are to be reestablished and validated. During production, the frequency of validation depends on usage (stored or individual) and management policy. The intended result is a stable and safe outcome that can be easily verified with the existing process documentation. Verification and Validation Repeatability and stability of the process can be validated by the application of known trial masses performing a response/wax check. Reproducibility is achieved by using more than one example of the same rotor type in case of stored rotor type-specific calibration. File Setup Parameters All weights and actual dimensions should be recorded and traceable to a file setup using a calibrated master with certification history and reference to source data. Additional Considerations For components that are not fixed and immobile, the process will benefit from an averaged measurement based on data from multiple runs. For some rotor behaviors, rotor type-specific calibration will benefit from further compensation and characterization of these types of rotor behaviors. The objective is to integrate these considerations into the rotor type-specific calibration process to enhance the quality of the rotor type-specific calibration. Process Documentation All process parameters shall be recorded and traceable to a known source. All critical data necessary to validate results contained in the printed report of the balancing process shall be meticulously documented.

Document information

  • Standard from SAE_AC
  • Published:
  • Version: 0
  • Document type: IS