Measuring with large Micrometers

If using an overhead crane, I believe your Mic should be supported on its Airy-Points (Calculated)

Guest,

Very good answer. You brought up many of the things that have to be taken into consideration. Like you, I would highly recommend contacting the manufacturer (in this case:Mitutoyo) and ask them how to take the readings without distortion entering into the process. If I have a little free time, I will try to do that myself, just for my information on how it is supposed to be accomplished when working with such big micrometers/measuring tools.

30 years ago when I walked into the machine shop that is mine now, explaining to the then owners (and their shop manager) that we would try to have the shop about 70F/21C long enough for the metal we were measuring to stabilize. Usually a couple hours was all that was needed for everything to become about the same tempature.

Like measuring pistons to see what size to bore the block, and then when honing the block, letting the cylinder cool before doing the final honing. We deal in 10ths (of a thousand), I can't imagine what kind of a +/- a person would have when measuring something being made that is 5 meters in diameter like sb is doing.

People in the aerospace industry figured it out long ago. Someone here from that part of the industry care to enlighten us please?

Maybe using a LASER measurer? How much to get one of those that would be accurate enough, I wonder.

Interesting question sb, thanks for asking it, makes a person think a little harder than normal!

Ken

Not a cheap solution but something like the Faro remote contact measuring system would work. This uses a probe to take contact measurements from your cylinder with a line-of-sight laser measuring head to track the probe.

We are indeed supporting a large portion of length (as said the micrometer is 5mt , the straight edge (surface ground ) is slightly more than 3 mt. We lift up the job by balancing the system horizontal (after trial and errors, we have the positions marked)

Laser was an option thought of but the costs do not justify (no of components needing this support may be only 10-20 per year max.

Any way we are getting new machines with renishaw. The point of discussion is the concept, and not the problems I am facing.

I dare say in engineering one proves the concept by solving the problems.

Best of luck.

Infact this was a problem when we introduced this product approx 22 yrs back. By trial and error only we got this solution and getting fairly repetitive answers. The R&R values are well within the statistics required (wrt the tolerance). Anybody has tried the concept other than us? In fact in our factory also it seems that we are the only ones using it. Even other large equipment manufacturers also didn't use it (before lasers) - eg Siemens, GE etc, any body from there to enlighten us?

You are listening to your process data. With support method, you get repeatable and reproducible results. Without the support method, you get crap.

Tell your auditors that the support is a method, not a gage.

Do they require you to calibrate an operators finger when usiung a 1" mike? how about the stand that holds a bench mike?

Listen to your process data, the Gage R&R tells you that what you are doing is correct.

As to what others did or din't do befor lasers- A) so what ; B) The fact is that they may have recognized the thermal and deflection errors from unsupported mike and made allowances ... and "adjusted" the values from their readings.

listen to your process.

milo