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Achieved Measurement Value Accuracy through Calibration

In today world, most of the product will go through transformation via manufacturing process  by multiple suppliers across the globe before it reaches the consumer market.   During manufacturing process,  raw material, semi finished and final product’s critical to customer characteristics  have to be measured to ensure  it meets the intended spec/customer requirements.



From http://www.budgetdumpster.com/blog/measure-without-tape-measure/

It is important to verify that measuring device which is used to measure the product from raw material to finished goods is accurate across different manufacturing sites.  Accuracy of measurement system is define as the ability of the measurement system to  produce the true value compare to standard.   This means if different manufacturing plant were to measure the same part,  it should have measurement value as close as possible  to the true value which is eventually traceable to same national standard.  All measurement device used  by different manufacturing sites are calibrated  to a standard which is traceable to national standards. 


Manufacturing organization should establish a calibration system to ensure measurement device is able to give accurate measurement value.  A good calibration  system should comprise of the following:-

  1. Company should have a dedicated department or trained person who is responsible for calibration depending on the size of the company.  Some bigger organization with many manufacturing facilities has a centralize manufacturing facility
  2. Purchasing of measuring equipment must go through a review process from the calibration department to determine the measuring equipment require or does not require calibration.
  3. The calibration personnel need to develop an equipment masterlist to track all the measurement equipment. It should consist of equipment identification number,  description, owner, location, process, set up date, calibration due date, calibration interval internal or external calibration and other vital information.
  4. The measurement equipment  must follow a force routing process to go to calibration department to register the equipment in the calibration masterlist before release for use in the production.
  5. It is very important to track measurement equipment which does not need calibration and justification why it does not need calibration.  The actual measurement device should be identified in calibration masterlist for equipment do NOT need calibration.
  6. Determine the calibration interval that is required as most of measurement device accuracy degrade over time due to wear and tear from usage.  Only very manual measurement device such as ruler does NOT have noticeable degradation.  Calibration interval should NOT only be base on equipment manufacturer recommendation,  usage frequency should be a consideration factor as well.
  7. Verify equipment calibration status at regular interval to ensure the accuracy of the measurement value.
  8. Establish an automated recall mechanism for calibration before due date with proper escalation path to management.
  9. There should be a calibration report which stated the equipment ID per masterlist, master standards traceable to national standards and include the standard ID,  calibration environment, calibration range according to usage range,  recommended next calibration date and technical assessment of linearity and bias measurement system error and any other details.
  10. Calibration should be done with master standard with 10X higher resolution from the measurement equipment scale.
  11. Ensure that there is proper disposition for product which are measure with fail calibration equipment.
  12. All calibration measurement equipment must have proper seal to prevent from unauthorized tempering
  13. If the equipment is send for external calibration,  then the calibration report should properly reviewed by an authorized person
  14. If the calibration is done in house,  then there should be a calibration lab with proper environmental control.  All in house reference standards must traceable to national standards.  Reference standard such as master block  must be properly stored to prevent deterioration and should NOT be handle with bare hands.

Almost all electronics manufacturer which I had worked with does not have a problem with uncalibrated equipment.  However poor calibration procedure is always a problem.

Calibration must be done correctly by a reputable vendor to minimize measurement error.  If manufacturers are unable to collect accurate data from a process,  there are very high chances of delivering defect parts to customer. Manufacturers could also make wrong decision  in controlling the process leading to poor quality cost.

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