[Cl...] Posted April 21, 2022 Share Posted April 21, 2022 One of our Conturas is having its annual calibration done by Zeiss. While this is being done, we moved several programs that run exclusively on that machine, over to another Contura. Both CMMs have the RDS/XXT/TL1. We are seeing a .0005" difference between the two CMM's running the same program with the same "Master Part". As well as the same styli. Thoughts? Link to comment Share on other sites More sharing options...
[Da...] Posted April 21, 2022 Share Posted April 21, 2022 Wait till after the calibration. Then check again. Link to comment Share on other sites More sharing options...
[Cl...] Posted April 21, 2022 Author Share Posted April 21, 2022 I told management that if one CMM is at the - side of the Zeiss spec and the other one is at the + side of the spec, then yes I might not be surprised by a .0005" difference. They are under the impression both CMM's should correlate within a tenth or so. Link to comment Share on other sites More sharing options...
[Ke...] Posted April 21, 2022 Share Posted April 21, 2022 Please sign in to view this quote. So many questions, like: For what types of evaluations? Something simple, like point to point distance ...or something more complex, like profile or position? Obviously, I would give more complicated evaluations more "tolerance" How many times has the Master Part been inspected by CMM1? What is the range of the Master part reaults by CMM 1? Is the Master Part only checked after a calibration, or before & after calibration, or on some other frequency? Are the Calypso evaluation settings the same? Do the styli use the same calibration methods? Link to comment Share on other sites More sharing options...
[La...] Posted April 21, 2022 Share Posted April 21, 2022 I've seen this happen to some customers who don't have the right information for the reference sphere in their system. I.E they just use 15.0000 for the radius when the cert says 14.998 (for example). Link to comment Share on other sites More sharing options...
[SH...] Posted April 21, 2022 Share Posted April 21, 2022 Please sign in to view this quote. This is why OEM company uses fixed head CMM. A Zeiss application engineer told me , he had complaints from company ( fixed head prismo) related to .0005mm repeatability issue 😮 😮 Link to comment Share on other sites More sharing options...
[Cl...] Posted April 21, 2022 Author Share Posted April 21, 2022 Please sign in to view this quote. Two diameters, and two positions (using those diameters) Master part ran once a week, after qualification. Exact same program, exact same styli used on both machines. Link to comment Share on other sites More sharing options...
[Ow...] Posted April 21, 2022 Share Posted April 21, 2022 1st thing I'd look at is temperature differences, the bigger the part, the bigger the difference. 2nd, what is the probe radius after qualification and does it match what it is on the other CMM. If it does and the reference spheres are of the same type and size, try using the other reference sphere on the other CMM to qualify the probe. Calibration technicians will sometimes change the reference sphere diameter to match the outcome of the sphere they use (sometimes different). Are the diameters ID or OD? Are the diameters being scanned a full 360° (or greater) or are they just partial sections? Are the diameters measured in the X,Y or Z axis? Does the diameter measure different measured in a different axis? 0.0005 (.013mm) is a lot in my opinion. I've run articulating CMM's 20 years ago that would be more accurate than that. Link to comment Share on other sites More sharing options...
[Cl...] Posted April 21, 2022 Author Share Posted April 21, 2022 Thanks for the valuable input everyone. Our value stream managers have decided to just run as is for now. Link to comment Share on other sites More sharing options...
[Je...] Posted April 21, 2022 Share Posted April 21, 2022 Please sign in to view this quote. A Contura with an RDS/XXT setup? .0005" repeatability is within my expectation in a normal environment between machines. A Vast dynamic sensor would be required to repeat tighter than .0005". . Link to comment Share on other sites More sharing options...
[Da...] Posted April 22, 2022 Share Posted April 22, 2022 Please sign in to view this quote. Don't they all say its OK ! 🤣 Link to comment Share on other sites More sharing options...
[Mi...] Posted April 22, 2022 Share Posted April 22, 2022 He have 3 CMM's that all the same specs. The machinist usually/Always run their own parts and complain the 1 CMM has zero kick outs and the other has multiple. Usually the roundness on diameters are was kicks out on the other CMM. We use a Glastonbury Gage to to see the machine differences. They are usually always have .0003 - .0005 difference. Glad we are not the only ones that see this. I guess this is the downside to having the RDS/XXT TL3. Link to comment Share on other sites More sharing options...
[Ow...] Posted April 22, 2022 Share Posted April 22, 2022 I'll retract my statement regarding the 20 year ago repeatability on articulating Renishaw head CMM's. Of course different sizes of parts/probes and the number of rotations made a difference but, generally, on the standard size most commonly used the they would repeat to around 0.0002 tenths of an inch on diameter sizes. Location is a different story but, also not mentioned is that they both had touch-trigger only point capability, no scanning. Now if I got 0.013mm [0.0005 inch] difference between two Vast Gold cmm's, I'd be calling the CMM doctor. 😭 Link to comment Share on other sites More sharing options...
[Ri...] Posted April 25, 2022 Share Posted April 25, 2022 The number one reason I have found for correlation between CMM's, is Styli. Users simply do not clean the styli. Wiping off the styli with isopropyl alcohol lint free wipes will help. Visually inspecting by 1X is, well, not going to help. Use at least a 10X eye loupe or microscope. Build up from scanning leaves bands of material on the styli that is typically not seen by the unaided eye. You can clean scanning build up off of styli (Ø2mm or larger) with an electric eraser. I use Mylar erasers with a low speed electric eraser, a little bit of time and the build up is removed. I have yet to damage a stylus with this method. I've extended the life of styli for 2 or more years. Link to comment Share on other sites More sharing options...
[Ow...] Posted April 25, 2022 Share Posted April 25, 2022 Please sign in to view this quote. Link to comment Share on other sites More sharing options...
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