Quality Magazine

Other Dimensions: Keep It Simple

March 1, 2004
Step-by-step formats work best when writing calibration procedures.

Editor's note: Columnist Hill Cox has put together a multipart series that focuses on developing custom calibration procedures particular to an individual manufacturer's circumstances. Accurately written calibration procedures are critical in today's manufacturing environment, especially as new standards require detailed documentation.

The last time I checked, there were no Pulitzer Prizes awarded for writing calibration procedures. However, many quality auditors report they have seen procedures written that could qualify for a creative fiction award. Such efforts are unnecessary. Because you're not writing a book, the rule is: Keep it simple.

Write what you do, or intend to do, in a step-by-step manner. Leave the flowery language to the professionals. For example, you could instruct the technician to, "...advance the micro-

meter head in a rotational manner consistent with its normal function so that the digital display will present a starting position by reading zero (0) when the measuring faces are in intimate contact."

Personally, I would simply write, "Zero-set the micrometer." Anyone unable to work with the latter statement should not be involved in calibration work.

If you work within a set format, writing the calibration procedures should prove relatively easy. A format that has served my company well for more than 30 years is based on including the following sections in any written calibration procedure:

l Preparation

l Calibration

l Reporting

l Appendix

The "Preparation" section deals with what you do with, and to, the measurement tool before it's calibrated. This could include visual inspection for damage or rust, and cleaning. It may include a simple test to determine if a tool is in need of repair before you go any further.

Under "Calibration," list each step of the procedure and indicate what measurements to take, and where or what tests are done. There may be two different tools used that could be written in a single procedure. However, because uncertainty budgets will differ, companies should have separate procedures for each tool, but keep them under a common listing.

For example, "Procedure 23" covers thread plug gage calibration using a more popular plug gage, while "Procedure 23A" covers the other tool used for the same work. The decision criteria of which tool to use for a given application would be part of the written calibration procedure.

The "Reporting" section is where you indicate exactly what data will be reported and in what format it will appear. It may indicate restrictions in the use of the tool. This section should use common technical terms so everyone understands what is meant. Recommendations could be part of this section, so that whoever decides what is going to happen to the tool gets a "heads up" on what is expected to be done with it.

As you would expect, the "Appendix" contains everything that a manufacturer may want to include that doesn't fit in the other sections. With some equipment it may be useful to have a checklist for part, or all, of the process. Such a checklist would be placed in the appendix. When the calibration procedure refers to a form, everyone can see a copy in the appendix. Of course, if you have many forms, a binder or computer file containing only forms might be the best way to keep them organized.

The acceptance criteria used for calibration requirements could be included in the appendix, to avoid cluttering the step-by-step portions of the calibration procedure.

It is important to remember that the layout of a calibration procedure should reflect how you do what you do, in an organized way, so that anyone reading it can understand what happens when a tool needs to be calibrated. If the written procedure reflects the actual work situation, the procedure will be more useful and more easily implemented than boiler-plate text that has been borrowed, stolen or sold to you.

If you keep the format of the procedure simple enough to embrace the working situation, it will be easier for everyone to understand and follow. Happy formatting!