[Jo...] Posted May 26 Share Posted May 26 Hey All, I am coming across an issue measuring a Bore ID (75.06±.015) that does not correlate with the supplier or other measurement systems. We have tried various tests comparing different methods with the attempt to troubleshoot. Below is a chart comparing different results. D probe = regular production probe (5mm) D probe new = replaced/recal (5mm) 3mm probe = choosing a smaller probe size per cookbook down probe = measuring the bore oriented upright instead of on its side smartscope A down/A up = measuring a circle on each side of the part MTM avg= average measurement of the suppliers' results Bore gage measurement We measure the Bore as a cylinder at 3 sections @ cookbook settings. Any thoughts or suggestions for what could be going on? TIA! Link to comment Share on other sites More sharing options...
[Do...] Posted May 26 Share Posted May 26 Have you compared values when adjusting your evaluation method from LSQ to outer tangential? 1 Link to comment Share on other sites More sharing options...
[Ke...] Posted May 26 Share Posted May 26 (edited) What does the Form/Cylindricity look like? What are the results for each individual scanpath? What is the suppliers measurement method? Edited May 26 Link to comment Share on other sites More sharing options...
[Jo...] Posted May 26 Author Share Posted May 26 Please sign in to view this username. Please sign in to view this username. Outer tangential shows even smaller. Cylindricity shows 0.009mm Breaking the cylinder into individual Øs shows results within a few microns of each other. 75.0363 75.0386 75.0353 We have matched the supplier's method with no noticeable change. They use a Hexagon CMM. Link to comment Share on other sites More sharing options...
[Ch...] Posted May 26 Share Posted May 26 I agree with Keith. Throw in a roundness plot and cylindricity plot; then maybe even surface finish. Is your bore gage 2pt or 3pt bore gage? Assuming your probes are clean and qualified, it sounds like a form issue. Link to comment Share on other sites More sharing options...
[Ch...] Posted May 26 Share Posted May 26 I should mention, I will typically compare an unfiltered vs filtered roundness plot when I'm getting weird stuff like this going on. Link to comment Share on other sites More sharing options...
[Jo...] Posted May 26 Author Share Posted May 26 Please sign in to view this username. 3 pt bore gage. Filtered cylindricity 0.009mm Unfiltered cylindricity 0.016mm Link to comment Share on other sites More sharing options...
[Ch...] Posted May 26 Share Posted May 26 What does the roundness plot look like? Is it oval shaped or more tri-lobed or something else? The min/max difference I see from you chart is about 35 microns or so. A test would be to evaluate the circle using max inscribed and then evaluate using min circumscribed. Then see what the difference between those two evaluations is. Link to comment Share on other sites More sharing options...
[Ke...] Posted May 26 Share Posted May 26 I suppose you don't have any certified masters of comparable size? Link to comment Share on other sites More sharing options...
[Do...] Posted May 26 Share Posted May 26 Could throw on a few 2-point diameter characteristics as well to show your min/max values at each level to confirm your roundness plots. Link to comment Share on other sites More sharing options...
[Jo...] Posted May 26 Author Share Posted May 26 Please sign in to view this quote. Read my mind, this was my next verification. We measured a 75.09mm ring gauge. The gauge came in at 75.073mm, so this is roughly 0.017mm under spec and aligns with the delta we are seeing vs the supplier. So what now? Is the vast head or CMM off? Should we look to get it checked out by Zeiss? Anything else I should do to verify? 1 Link to comment Share on other sites More sharing options...
[Ch...] Posted May 26 Share Posted May 26 The colors on your graph are messing with me, but are you saying 5mm, new 5mm, and 3mm probes were all measuring about the same? Link to comment Share on other sites More sharing options...
[Ri...] Posted May 26 Share Posted May 26 What size does it show the MasterProbe radius is, as well as the radius of your stylus. 2 Link to comment Share on other sites More sharing options...
[Do...] Posted May 26 Share Posted May 26 Was the ring gage measured using the current stylus system or the MasterProbe? Link to comment Share on other sites More sharing options...
[Ri...] Posted May 26 Share Posted May 26 If the radius is off on both the MasterProbe and your stylus, you most likely have the wrong information for the Reference Sphere. If they show correct, then you have something terribly wrong with your CMM. 4 Link to comment Share on other sites More sharing options...
[Jo...] Posted May 26 Author Share Posted May 26 Thanks for the feedback guys! I will verify the masterprobe rad and measurment probe rad now. Please sign in to view this username. That is correct. Link to comment Share on other sites More sharing options...
[Jo...] Posted May 26 Author Share Posted May 26 Please sign in to view this username. stylus system used for the measurement. Link to comment Share on other sites More sharing options...
Popular Post [Jo...] Posted May 26 Author Popular Post Share Posted May 26 Update: I believe the issue is that the reference sphere is off in some way. Please sign in to view this username. was spot on! Could have gotten dropped, not 100% sure. I did not find any noticeable damage. I verified the probe radius on the measured stylus system was coming in at 2.493mm. Luckily, we have 3 reference spheres on our reference sphere tree. I swapped out the ref sphere and recalibrated. The radius changed to 2.5001mm. When we remeasured the bore, it changed the result to 75.0518mm. This aligns very close to the supplier's measurements! Thanks for the help, everyone! 4 1 Link to comment Share on other sites More sharing options...
[Ke...] Posted May 26 Share Posted May 26 Is it possible that someone calibrated to the incorrect reference sphere selection? Link to comment Share on other sites More sharing options...
[Jo...] Posted May 26 Author Share Posted May 26 Please sign in to view this quote. No, there is a cal routine that selects what ref sphere to use; the operator only has access to use Autorun. They are all the same size (30mm Ø), just in a different orientation/elevation. Link to comment Share on other sites More sharing options...
[No...] Posted May 27 Share Posted May 27 When was the last maintenance / calibration of the CMM? Was there anything out of spec? Over the years we had two cases where the maintenance tech had to change the radius of the cal. sphere slightly to get a deviating axis into the tolerance band again. They were quite old machines and it was a last resort (and of course officially documented) before they would have had to be laser calibrated again (CAA). But we never saw any issues with deviating measurement results because of this. Link to comment Share on other sites More sharing options...
[Jo...] Posted May 27 Author Share Posted May 27 Please sign in to view this username. Cal comes due in 2 months. I verified the last cal and nothing was oos. It's interesting that you mentioned the tech updated the radius settings. Every time I have seen a tech cal the machine, they bring their own cal sphere. We just placed an order for a new cal sphere today. Link to comment Share on other sites More sharing options...
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