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Phil Wiseman

Metrology

Calibration As a Risk Management Strategy

Why gamble with tolerance?

Published: Monday, April 27, 2015 - 16:41

All the technical journals are abuzz with the changes to ISO 9001:2015. One significant paradigm shift is to a risk-based management approach. Most companies already apply risk-based thinking in their planning process for organizational management. This article will take a narrowly focused approach to a key aspect of risk management: calibration.

The goal of every company is customer satisfaction

The reality is that if your customers are not happy, the long-term odds of your business viability are slim. There might be an exception if you are the only manufacturer of a product that everyone must have. However, that’s just not reasonable in the global marketplace.

To effectively manage risk, you must know what your customers need and want, and how to deliver that while maintaining a reasonable profit. If you use external suppliers you must communicate your customer expectations through the supply chain to ensure your risk is mitigated or managed as you produce your final product.

So what does calibration have to do with any of this?

Everything is manufactured to a tolerance: plus or minus some measurement so that component parts fit together.

Controls such as temperature, pressure, and force are also measurements that can affect final product conformance. Imagine you need a 1-in. diameter rod to fit a part. How close to 1 in. does it need to be? Is 1.25 in. good enough? Is 1.00001 in. necessary? This is the plus or minus we mentioned above.

Let’s say a part arrives and it doesn’t fit or perform properly. What is the first thing you do? You measure it with a device such as a ruler, caliper, or micrometer.

Or perhaps you are cutting a piece of wood. Do you saw it on the line? Cut it “skinny” or “fat?” How wide is the saw blade? What is the final measurement of the cut wood?
How do you know if it is the correct length?

Imagine the chaos if everyone had his or her own interpretation of what an inch is! To reduce the chaos and manage the uncertainty, standards must exist. We need a concerted standard so that we know what an inch is. Would you be frustrated if every gas station had its own interpretation of a gallon? At $3 or more a gallon, I personally want to know I got my gallon’s worth.

Enter calibration

Calibration is a comparison to a known physical standard. Our global marketplace dictates international standards to facilitate commerce across geographical borders, and internationally recognized standards for comparison are integral to this. Standards are extremely expensive to maintain and most companies could not afford to send their instruments to where the physical standard is located, e.g., the National Institute of Standards and Technology (NIST). Likewise, the weeks or months waiting for the instruments to return would be cost prohibitive. These economic constraints are mitigated by using an accredited calibration company that can provide an unbroken chain of traceability to the standard.

Each link in the traceability chain contributes to the plus or minus we discussed previously. The sum of all the pluses and minuses is referred to as measurement uncertainty. The smaller the measurement uncertainty the better confidence you have in the measurement. Would you want to measure a 1-in. block with a yardstick ± 0.25 in., or a comparator ± 0.0001 in.?

Your product tolerance makes that determination for you.

Now that we have had a rudimentary discussion of calibration, why does any of this matter to your process or product?

Say that one company makes lids and another company makes cups. Does anybody care that they fit together? Ask anyone that has ever had a leaky cup lid and he or she will say, “Yes.”

ISO 9001:2008 clause 7.6—“Control of monitoring and measuring equipment” requires a calibration program be in place. You can view this as a cost or revenue center. A properly executed calibration program will reduce internal rework and reduce external customer rejections. The more product produced that meets customer’s requirements, the more profit.

What should I calibrate?

Any process that can affect customer expectations needs to be examined.

Does this mean you must a hire a calibration company for every device that is used for measurement? No. If you have a properly trained staff and have master standards that have been calibrated, then you can perform calibrations internally. It can become cost prohibitive to maintain all the necessary calibration standards internally so a cost-benefit analysis should be done.

How do I select a calibration company?

The international standard ISO/IEC 17025—“General requirements for the competence of testing and calibration laboratories” exists for calibration and testing. To achieve and maintain ISO/IEC 17025 accreditation, an independent third-party assessment must occur. This independent assessment includes observation of technical competence. Companies often claim that they are compliant with ISO/IEC 17025. This is not the same as being accredited. A key risk management component of ISO/IEC 17025 is the unbroken chain of traceability back to the standard.

ISO/IEC 17025 accreditation does not mean a calibration company is competent for all calibrations. Accreditation bodies issue a scope of accreditation that delineates by line item what measurement a company has demonstrated technical competence to perform, and the scope will also list the best measurement uncertainty it has demonstrated. The end user needs to read this document to determine if the calibration company meets your specific needs.

Reduce your risk by doing the following:

• Determine what needs to be calibrated.
• Evaluate in–house expertise for calibration.
• Maintain the proper standards for calibration.
• Select an external calibration laboratory if appropriate.
• Examine the external laboratory’s scope of accreditation.
• Maintain records of calibration results.
• Review the calibration report and understand what it means.
• Analyze records to determine calibration frequency.
• Use calibration to reduce internal rework and scrap.
• Produce more product that meets specification.
• Gain market share based on quality work.

Discuss

About The Author

Phil Wiseman’s picture

Phil Wiseman

Phil Wiseman is COO of Alliance Calibration in Cincinnati. He earned a bachelor of science degree in chemical physics from Centre College in Danville, Kentucky. Wiseman is an ASQ-certified manager of quality and organizational excellence as well as an ASQ-certified quality auditor.

Comments

Tolerance vs Variation

In discussions of dimensional characteristics I have found it important to distinguish between Tolerance and Variation.  Tolerance being what designers put on part prints and variation being what the process puts into the parts.