renishaw probe tip

[kwhite2]

hello,

anyone know if there is one variable that controls probe tip size, Im getting different results, up to .005 on diameter when running a bore check, even after calibrating several times, does the calibration cycle overide tip size? thx

[extanker59]

My book says Setting 63 for probe width. I think the calibration that you're talking about is for location rather than size. Accounts for the probe not being absolutely on centerline with the spindle.

[extanker59]

Probably wrong. Just checked my setting 63. It's at zero. I don't check dimensions, just locations. For you probe gurus, should I put my probe diameter here anyway? Running like this for 3 years. Set up by Haas tech when the machine was set up. Love the probe.

[Delw]

Originally Posted by kwhite2 hello, anyone know if there is one variable that controls probe tip size, Im getting different results, up to .005 on diameter when running a bore check, even after calibrating several times, does the calibration cycle overide tip size? thx

is the probe tip tight in the probe? I had mine come loose after I first got it

[behindpropeller]

Have you taken your probe out of the spindle?

If you do not put it back in the way it was calibrated you will get errors.

In the IPS screen for probe calibration it should have the probe tip size.

Tim

[renrepjnr]

you say up to .005 off.... if a probe is not repeating to within what you would expect your machine to hold don't use it until you figure out why it is not repeating. if it is off .005 every time it is a calibration issue. if it is not repeatable it can be a probe or machine problem. more than likely a loose stylus or loose probe to shank. running a ballbar diagnostic check or cutting a circle and having the form, size, and position measured on a cmm and comparing it to some other feature cut on the same part should give you an idea of how the machine is performing. make sure everything is tight and recalibrate.

[nian_id]

The diameter has to be in some variable. I'll second what the others said, check that it always goes in the same way (and the spindle is oriented). I ended up leaving the probe always on as T1 to make sure of that

Originally Posted by extanker59 Probably wrong. Just checked my setting 63. It's at zero. I don't check dimensions, just locations. For you probe gurus, should I put my probe diameter here anyway? Running like this for 3 years. Set up by Haas tech when the machine was set up. Love the probe.

The diameter of your probe IS set, otherwise you wouldn't even be able to check locations. The probe touches with the side and compensates for the diameter (radius actually).

[guypb]

Are you using the WIPS option? (Either VQC Probing Cycles or IPS?)

If so, variable #161 (base variable for probing data) will probably be set to 556.

In which case the diameter offsets are held in variables #556 & #557 (X & Y rads set by subprogram 9803) and the positional offsets are held in #558 & #559 (X & Y posns set by subprogram 9802).

Of course if #161 - something else, the variables will be different.
#556 & #557 radius values should always be fractionally undersize of the radius of the spindle probe tip as the probe is moving at the point in which it measures.

[extanker59]

Originally Posted by nian_id The diameter of your probe IS set, otherwise you wouldn't even be able to check locations. The probe touches with the side and compensates for the diameter (radius actually).

Excellent point. I wasn't thinking about any probe cycle but bore. OK. My book says setting 63 but that is at zero. Where is the tip diameter set?...Just checked guypb's answer. He's right. #556 and #557 has the radius of the tip. Interestingly #557 is .00005 larger than #556.
Thanks

[Donkey Hotey]

I don't think the 'Diameter' is stored anywhere. That's because the diameter is totally irrelevant to how the probe works. During calibration, it's not only taking into account any out of concentricity present in the probe and centering but, also the switch trip-points.

There may be a theoretical (calculated) diameter stored somewhere but, it would be calculated based on the clocking of the probe and the calculated diameter (not necessarily the diameter you might measure on the ruby with a micrometer).

Bottom line: when things seem flaky, I rerun all three calibration programs from start to finish and everything is usually fine. All of this diameter nonsense is calculated based on your ring gauge or other 'known' bore. Make sure that reference is accurate and truly round.

[guypb]

Originally Posted by extanker59 Interestingly #557 is .00005 larger than #556. Thanks

That is due to something called "pre-travel variation" where the forces on the tip differ between X & Y axis so there is a slight bending moment on the stylus which can lead to difference in values (but very very small!!!)
This is why it is so important to get the orientation of the probe right if you take it out of the machine and put it back in again.

[extanker59]

Thanks guys. I hope that kwhite2 got the answer he was looking for too.