Mid-run Stylus Calibration

[[Br...]]

Is it possible to manually change the values of the probe position/calibrated mid-run without pausing, or without cancelling the run? We have a 500mm long disk probe that runs parallel to the CMM table. It repeats to within 3 microns from once measurement to the next; however, every 2-3 features the program needs to be stopped mid-run to 'calibrate' the probe to the right position. This has to be done at least twice throughout the program which adds 2-5 minutes to the program. We've just finished the first article, so the program function is already proven, but there are at least 100 more parts remaining.

Currently I measure a circle with a repeatable and newly calibrated probe, make a secondary alignment with that circle, measure another circle with the exact same X,Y,Z, and diameter dimensions with the 500mm long probe, then adjust the stylus geometry values from the difference of the position until the probe measures within 1-2 microns.

I know it's possible to add a stylus calibration to the characteristics, but this won't work for the probe as the calibration isn't consistent enough with a probe of that length. I have to manually stop and start the program each time, which then restricts me to waiting at the machine. My solution was to make a feature that recalls the points from the 500mm measured bore, then use a formula that changes the nominal value to adjust for the difference of the 2 calibration circles. It seemed to work for the 1 part, but I don't think I can prove anything until I've tested several parts. I was hoping to have this ready for our production run in the next week or so.

If anyone could help of give some feedback, that would be much appreciated!

[[Ow...]]

Not sure what you're trying to explain, been a long day so it might just be me.
Are you having to tell the probe exactly where the hole is to get it to measure correctly?
If so, if I remember correctly, in the circle feature click on the projection tab and in the drop down menu where it says no working plane, choose three points. It will then measure the circle with three points to find the exact location and then measure the circle at that position.
I could be completely off on what you're asking but, with a little more communication, maybe we can help.

[[Br...]]

Sorry if its a bit confusing. Basically the issue is that the 500mm probe doesn't give the correct actual value when I measure the hole (compared to a reliable/repeatable probe). So I manually change the geometry of the 500mm probe (XYZ coordinates) in order for it to measure correctly. I have to do this manually in the middle of the run (measure the same hole with two different probes and change the 500mm probe geometry by the deviation), which will be a pain and very time consuming when there are 100 parts to run. Maybe I'm trying to do too much in a single program, and it's not possible. But if I can save 5 minutes a part, that would be great.

[[Da...]]

500 MM is a long probe, and with a disk it adds to the weight. Have you considered a counter weight?

[[Br...]]

Yes, it is a long probe. There is a counter weight on it right now to help, but unfortunately I can't add anymore weight to it to make it perfectly balanced as it already weighs about 480 grams.

[[Ri...]]

Any way to change from a disc probe to either a t or a star probe? I'm not a fan of disc probes, and to this day I've never measured a part that I just HAD to have one. I'm not saying that there aren't products that this is the case, but I've just never seen one.

[[Br...]]

I could go to a star or T, but it would restrict my measuring length. With the bore size that needs measuring; even with the shortest 2mm probe I can find, I would still only be able to measure about 120 - 150 degrees with a T and about 90-120 degrees with a star. There is also a small undercut at the bottom of the bore, about 5mm long, that also requires measuring. I'm not a huge fan of disc probes either, only had to use three in the last 4 years. We've had these parts before: however, there was only a 300mm long bore instead of 500mm.

[[Ow...]]

Did you try selecting the 3 points option to find position before measuring in the projection tab of the feature?

I had decent <0.003mm luck with this Disk, balance was critical. Using the smallest disk you can is also a difference maker,I didn't have as much luck using a 50mm disk in the same measurement.
_

[[Br...]]

I'm using a 30mm disc currently, but we have an XTR head which only allows for 500g weight instead of 600g.
And it isn't so much about the probe not measuring the correct location (It doesn't crash or have any probing errors), its more about the repeatability every time I have to pick up the probe. Once I have the probe calibrated, I can pretty much measure whatever I want and the error is less than 3 microns. As soon as I put the probe away and then pick it up again for the next measurement, that's when it seems to change position (I'm assuming because of the weight and how its balanced). Which is why I'm wondering if there is a way to 'calibrate' (change the nominal geometry of the probe) mid-run so I don't have to manually change it myself each time.

[[Ow...]]

Aha, I see.
Quick response without reading everything again. Have you tried using Gage Correction Qualification?

On a production environment CMM many years ago, I used to use it inside a program where every time the disk probe was used it would measure a precision ring gage close to the size the probe is measuring. It fixtured in specific location to qualify it automatically using the Gage Correction Qualification feature.

It can get a bit muddy to explain quickly but, I've attached an old document explaining the basics of it.
"if" you haven't tried it, you should.
Again quick reply, just trying to help.

[[Br...]]

I just talked to an expert about Calypso, unfortunately there isn't a command that does what I would like.
They basically said to probe a ring gauge with two different probes and offset measured values by the error between them.
Thanks for your help everyone!

[[Ch...]]

You're right. You did just talk to some experts in Calypso.