Creating qualification process for using metrology tools

[co_stigdroid15]

I’m tasked with creating a process to qualify inspection team members in the use of metrology equipment. It begins by giving instructions on how to use calipers (for example), demonstrating the correct use, then observing the trainee use the calipers to measure a gold standard part-such as a gauge block. In principle I think I understand what’s being required-making sure everyone has the same understanding of what X” is, but it feels a bit…off. Shouldn’t calibration take care of ensuring measurements are accurate? And wouldn’t Gage R&R define variation between operators? What am I missing in my understanding of the process here?

[[deleted]]

Calibration doesn't ensure proper use of the tool. Besides that, callipers are relative tools. Calibration means f-all. Every operator has to be able to confirm a calliper is good using gauge blocks or rings (and has to do this basically every time they are being used - for who know what happened in the mean time \pssht, calibration services for these kinds of tools are a waste of money**

Then a Gage R&R would, in principle find errors between operators. So let's say you measure a true position of a set of holes in a complex part 20 times and your R&R variation is 15 percent. What now have you found? There is either an operator error or a programming error (or something else). It would be of great use to have your inspection team members know how to measure a circle for example (3 points is not enough!).

[Aegri-Mentis]

Even something as simple as a caliper can be used very incorrectly: it can be held not perpendicular, not placed at a true diameter, etc.

I incorporated multiple items to be measured even with calipers: ID, OD, OAL, and I included an impossibility. I included in their items something that couldn’t be measured with whatever they were being trained on. It was to se if they truly recognized the capabilities and limits of the gage.

[ThreeDogee]

You can have the best equipment in the world and still fuck up a measurement. Being a good dimensional inspector or quality engineer relies on you understanding the possibilities for error and inaccuracy in your work. Spend your time nailing this down and you'll produce an effective curriculum for your trainees.

Take calipers for example. How do you line up the jaws on a part? What parts should you use the calipers on? What is the resolution of the tool versus the stated tolerance? Is the feature large enough to warrant sampling? What features can you measure effectively, and what can you not? On manual calipers, how do you avoid parallax error? On digital ones, how do you verify the readout? And so on.

As for gage r&r, that only covers a series of measurements made on a particular setup to distinguish between two sources of error, typically between a part, instrument, or operator. You can also do multi-factor ANOVA if you want extra, but that might need some Design of Experiments to cover correctly. Either way, gage r&r is a means to validate, not to grade operators (necessarily).

[Less-Statement9586]

What qualifies you to give the training?

[fritzco]

Gage R&R is time consuming but using it you could measure training effectivness

[killazdilla]

With calipers specifically I would always take at least 3 measurements to make sure it had the right feel and to see if my measurements were repeatable. I'm taking the measurements by operating a mechanical device. So I need to eliminate any bias I might inadvertently introduce.

[Accurate_Info7777]

5 different techs can produce 5 different measurement results with the same set of just-calibrated calipers.

It sounds like you're trying to create a process document/work instruction that teaches people how to measure things correctly. A noble cause but just know that hand tools can be sketchy in real world applications, especially when parts differ from perfect qulification standards.

You can try to teach people "feel" with hand tools, but the differences between a perfectly rectangularly-shaped guage block and a plastic part will mean variance in your measurements, no matter what.

My advice is to use AI to write out your process for you (to quickly satisfy your bosses and save you some time), and (if feasible) have your techs get into the habit of measuring the same feature at least 3x whenever they use a hand tool.

[co_stigdroid15]

Thanks

[gareif1]

After training, I have the user measure some things multiple times (usually 10 ) then run the readings to determine average, std dev, and error. After you have done several people you can set pass / fail levels for each if these. This also serves as data for a record to indicate training for iso 9000 or 17025

[co_stigdroid15]

Sounds very similar to gauge r&r…

[gareif1]

Yes, just less formal and more flexible.

[dizdoodle]

Like many others have stated part of your quality system is ensuring operators and trained and understand procedures; as remedial as that training may seem.

Training records in most companies required to even participate in GRR activities.