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articles:optimizing_calibration_intervals [2019/03/17 18:22] – [Methodologies for the determination of calibration] rrandallarticles:optimizing_calibration_intervals [2019/03/19 21:36] – [Reducing Waste: Through Optimizing Calibration Intervals] rrandall
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-====== Optimizing Calibration Intervals ======+====== Reducing Waste: Through Optimizing Calibration Intervals ======
  
 One of the most often overlooked areas in Lean Six Sigma for reducing waste is the optimization of calibration (i.e., metrological confirmation) intervals. \\ One of the most often overlooked areas in Lean Six Sigma for reducing waste is the optimization of calibration (i.e., metrological confirmation) intervals. \\
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 If M&TE calibration intervals were optimized based upon performance, optimal calibration intervals for some instruments might be 18 months, 24 months, or even longer. This results in immediate tangible cost savings. And while a few instruments may require shorter calibration intervals (e.g., 9 month intervals), immediate intangible savings are realized through the reduction of risks. If M&TE calibration intervals were optimized based upon performance, optimal calibration intervals for some instruments might be 18 months, 24 months, or even longer. This results in immediate tangible cost savings. And while a few instruments may require shorter calibration intervals (e.g., 9 month intervals), immediate intangible savings are realized through the reduction of risks.
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 +One company I visited, had over 13,000 instruments in their calibration system. They'd contracted all of the calibrations with a metrology laboratory who "optimized" their calibration intervals for them. The number of instruments found "Out-of-Tolerance" dropped from 5% to less than 0.5%!
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 ===== Methodologies for the Determination of Calibration Intervals ===== ===== Methodologies for the Determination of Calibration Intervals =====
  
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 <note>[[http://www.isgmax.com/|Integrated Sciences Group (ISG)]] offers a free "Method S2" interval calculator (for MS Windows only) augmented by the "Method A3 Interval Tester" (adjusting for "sparse" data) called [[http://www.isgmax.com/calint_freeware.htm|IntervalMAX]].</note> <note>[[http://www.isgmax.com/|Integrated Sciences Group (ISG)]] offers a free "Method S2" interval calculator (for MS Windows only) augmented by the "Method A3 Interval Tester" (adjusting for "sparse" data) called [[http://www.isgmax.com/calint_freeware.htm|IntervalMAX]].</note>
-===== The “Staircase” method ===== 
  
 Perhaps the simplest and most widely used methodology for optimizing calibration intervals is the "Automatic adjustment" or “Staircase” method (described in [[https://ilac.org/?ddownload=818|ILAC G24:2007, sec. 3, "Methods of reviewing calibration intervals"]]). Perhaps the simplest and most widely used methodology for optimizing calibration intervals is the "Automatic adjustment" or “Staircase” method (described in [[https://ilac.org/?ddownload=818|ILAC G24:2007, sec. 3, "Methods of reviewing calibration intervals"]]).
  
-==== How use it ====+===== Using the “Staircase” method =====
  
 Each time an instrument is calibrated on a routine basis, the subsequent interval is extended IF it is found to be within a certain percentage (e.g., 80%) of the maximum permissible error that is required for measurement, or reduced if it is found to be outside this maximum permissible error. \\ Each time an instrument is calibrated on a routine basis, the subsequent interval is extended IF it is found to be within a certain percentage (e.g., 80%) of the maximum permissible error that is required for measurement, or reduced if it is found to be outside this maximum permissible error. \\
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 A critical component when using this methodology is determining the percentage of the maximum permissible error. The higher the percentage, the greater the risk of an instrument being found Out-of-Tolerance (OOT); potentially resulting in nonconforming product escapes. The lower the percentage, the greater the cost associated with lowering the risk of an OOT condition; and reducing the potential for nonconforming product escapes. This percentage will often vary based upon the type of instrumentation to which it is applied. \\ A critical component when using this methodology is determining the percentage of the maximum permissible error. The higher the percentage, the greater the risk of an instrument being found Out-of-Tolerance (OOT); potentially resulting in nonconforming product escapes. The lower the percentage, the greater the cost associated with lowering the risk of an OOT condition; and reducing the potential for nonconforming product escapes. This percentage will often vary based upon the type of instrumentation to which it is applied. \\
  
-Most often companies establish a "range" for the optimization. For example, IF an instrument is found exceeding 75% of its maximum permissible error, then the calibration interval is shortened. However, IF an instrument is consistently found below 50% of its maximum permissible error, then the calibration interval is lengthened. And IF the instrument is found between 50% and 75% of it's maximum permissible error, then the interval is considered acceptable.+Most often companies establish a "range" (or "window") for the optimization. For example, IF an instrument is found exceeding 75% of its maximum permissible error, then the calibration interval is shortened. However, IF an instrument is consistently found below 50% of its maximum permissible error, then the calibration interval is lengthened. And IF the instrument is found between 50% and 75% of it's maximum permissible error, then the interval is considered acceptable.
 ===== Initial Calibration Intervals ===== ===== Initial Calibration Intervals =====