Looking for Calibration Intervals 1

[bloodclot]

Hello,
I am setting up a new gage calibration system and I was looking for information or a guidline on calibration intervals for metrology equipment (tape measures, depth mics, calipers, groove mics, etc).

Thanks in advance for any suggestions,
Bloodclot

What do you see when the Pillsbury Dough Boy bends over?

Doughnuts

 

[weldtek]

What does your quality manual say?

 

[PSE]

Supplementing weldtek's response, I would recommend checking with or following the equipment manufacturer's guidelines on calibration intervals. It helps maintain traceability and confidence especially if you do not otherwise have independently traceable standards to validate the tool. If you have some equipment dedicated to measuring key or critical characteristics, you may wish to increase the frequency interval. Retain all documentation for the tool throughout it's useful life. You do not want someone coming back and saying that during a certain time period there were issues and not know if the equipment still calibrated/certified at that time.

Regards,

 

[JR97]

Bloodclot,

All the major calibration specifications - Z540, MIL-STD-45662, ISO 10012:1 - treat calibration intervals as a fluid item. Meaning periodically the intervals are to be evaluated to assure reliability. That means every so often you are to look at the calibration history for a particular type of gage. If it is out of tolerance when calibrated more than some percentage (we use 5%) the calibation interval must be shortened. If it is out of tolerance when calibrated less than some percentage (we use 2%) the calibration interval may be lengthened.

That said, the initial calibration intervals you select are not that important. I agree with PSE, the manufacturer's recommendations are a good starting point. The intervals should be based on the amount of anticipated use and the likelihood that a particular type of gage may go out of tolerance. For example a weight standard can be assigned a long interval whereas a thread plug which is routinely used should be given a short interval.

Hope this helps, good luck with your system.

 

[tgeorge]

Out of curiosity, is your work environment damaging to your metrology equipment so that you have to perform maintenance in excess of the recommended intervals?

 

[bloodclot]

Thanks to everyone for all of your good suggestions.

weldtek - We do not have a quality manual that is worth referencing. However, all that is changing as we speak. The upcoming ISO certification is changing (for the good) many aspects of how we currently do business. We have a single source for most machined items & there shipments are not usually checked (based on many years of zero defect shipments, unless assembly finds an issue. This is changing as well. New incoming receiveing stds, vendor tracking, etc.

PSE - I already have a list of all the equipment the shop has been using for dimensional checks, etc and I will be contacting the mfg's of each one for their recommendations.

JR97 - I will look into thoses standards you noted for some background info.

tgeorge - Our manufacturing facility is not damaging to the TME. On the other hand, our finished products, after they are installed, endure quite a hard life.

Thanks again for all of your suggestions,
Bloodclot


What do you see when the Pillsbury Dough Boy bends over?

Doughnuts

 

[weldtek]

One thing I would suggest is to think carefully about the requirements you impose on yourself. Obviously you want the procedure to be meaningful, but, it's easy to paint yourself into a corner, so to speak, by writing a great sounding procedure with requirements that may not be necessary, and, are difficult to maintain. The last thing we want is to have an auditor discover that we aren't following our procedures.
We try to set up most of our equipment for annual calibration, or whenever the item is damaged. Some instruments that are used infrequently can be 'calibrated ' before each use, as in the example of a rarely used caliper which can be checked against a traceable standard in 30 seconds or less.