"Verification of Calibration" - CMM arm

[Kchnwtch]

Hello!
I have a CMM arm that at the moment has a yearly calibration schedule, which means I have to pack it up, send it back to the mfr, and pay hideous fees both for shipping and for the calibration sticker.

I had a (certified) lab rep come to me today and say he can offer "calibration verification," i.e., he can verify whether the arm is in or out of calibration. If it's in, we're fine; if it's out, we have to send it back to the mfr. He can do it onsite while he's calibrating some of our other tools (like an optical comparator) that have to be calibrated on site.

My question: Would a verification like this meet the calibration requirement?

Thanks for your help!

 

[normzone]

Re: "Verification of Calibration"?

The answer is dependent upon your situation and regulatory constraints, but in general yes, that is just fine. People get all whupped up about calibration, since there's an adjustment implied in that useage, but in reality what the manufacturer does may be exactly what the alternative supplier you're considering is proposing.

Both of them look at the amount of error in the device and either pronounce it within acceptable limits (that's a can of worms, depending on your useage requirements) or not and adjust it.

Does the manufacturer provide "as received" and "as returned after adjustment, if any" kind of reports, or do they just tell you "it's been calibrated" ? Generally outfits charge more for more data, so sometimes you only get the latter.

Others with more professional statements should show up shortly. But if you have history of the device remaining in cal and not requiring adjustment, then that can be referenced to justify your decision to change the cal provider.

 

[Tyler C]

"Where necessary to ensure valid results, measuring equipment shall be calibrated or verified, or both, at specified intervals, or prior to use, against measurement standards traceable to international or national measurement standards; where no such standard exists, the basis used for calibration or verification shall be recorded."

As long as the lab rep is certified and can prove he is not making "adjustments that would invalidate the measurement result" and is performing against a traceable standard, or a documented standard of verification from your organization, there should be no issue. And, of course, you must maintain these records.

This is quoted from the ISO 9001:2008 standard.

 

[JoShmo]

Re: "Verification of Calibration"?

Hello!
I have a CMM arm that at the moment has a yearly calibration schedule, which means I have to pack it up, send it back to the mfr, and pay hideous fees both for shipping and for the calibration sticker.

I had a (certified) lab rep come to me today and say he can offer "calibration verification," i.e., he can verify whether the arm is in or out of calibration. If it's in, we're fine; if it's out, we have to send it back to the mfr. He can do it onsite while he's calibrating some of our other tools (like an optical comparator) that have to be calibrated on site.

My question: Would a verification like this meet the calibration requirement?

Thanks for your help!

Some wacky statements here, like "calibration verification" sounds like something they made up to sound good. "he can verify if...is in or out of calibration"? He can either calibrate it or verify it and that's all. You decide if it's calibrated, based on the results... It's your choice, really. It sounds like you're using a Faro arm or similar which seems to me to have both options

 

[Ninja]

Re: "Verification of Calibration"?

We do this on-site ourselves, FWIW. We bought a traceable standard and simply run a verification and get a report printed out. Only if the max error or RMS error are out of acceptable limits do we then have any adjustment made.
Historically we've made an adjustment every ~5yrs or so...the CMM holds tight pretty well in our usage level.

The standard itself is pretty hard to change without breaking it (etched glass) so we verify it at a much longer cycle.

HTH

 

[ncwalker]

Re: "Verification of Calibration"?

Step back and look at your bigger picture.

You told us that your optical comparator gets calibrated on site. Why?

The answer is most likely it's too big and bulky to ship out and have it done. (Also, it has to be shipped BACK. THAT's a scary thought... trusting it to a common carrier after it has been calibrated).

The better question becomes - if your comparator can be calibrated on site, why cannot your Faro arm be?

Answer - it absolutely can. And in reality, it SHOULD be if at all possible.

Again, look at it the other way.... If you purchase a new CMM/Faro arm and they test it on the factory floor, after they ship it, aren't you going to want it tested again at your location to make sure it has not been damaged in transit? Of course you are.

So why then would you not want the same care with your calibration? And if you can verify a new piece of equipment is OK on your floor, why can you not also calibrate current equipment?

We tend to fall into this trap of "do it this way because that's how it is done" with not enough thinking about "what" it actually is we are trying to do.

 

[Kchnwtch]

Re: "Verification of Calibration"?

Last year we had to ship it anyway for repairs along with calibration, but yes, I was thinking inside a very small box and making the assumption we needed to send it back again. This should save us a ton of money--thanks everyone for your help!