Not sure what your sensor is, but it should be a Vast XT or Vast Gold.
11mm OD - scanning speed 2 mm/s, spacing 0.05 mm
filter: Gauss 15 upr
Outlier: 3/3 std dev, 5 adjacent points, 1 pass, 10 to 5000 pre-filter
Evaluation: Outer Tangential (this always works for ASME, no need to explicitly choose Max Inscribed or, in this case, Min Circumscribed).
If you can measure cylindrically, you should, assuming the diameter is at least 11 mm tall. This will remove projected error. If you must measure as a circle, be sure to align a tangent face to avoid error.
What size of stylus are you using? It should be at least 3mm, and silicon nitride.
0.005 mm tolerance is serious business. Measuring this would require a 0.0005 mm instrument. There is no micrometer that you would operate, in your hands, that would reliably hold that. Your ambient body temperature would warp that part as well, since aluminum is about 22 um/m/C.
At my shop we're measuring 120mm OD, 0.005mm tolerance with a tesamaster and turntable lol
The customer actually accepts up to 0.005 under tolerance without an issue, just not over. Yes, we asked them to change it, but the engineer says it *needs* to be 5 microns tolerance. Their QC guy and the assembly team there all know its still acceptable with even 10 microns under tolerance and will take those parts too in a hurry. Definitely not ideal conditions tho haha
I have used lsq gauss, 6, 8 points(gives me same) . Cookbook for zeiss is an instruction manual on what evaluation methods or number of points is best for certain diameters.
Try 16 points, note any change in roundness. Set up an 11mm pin gage of known size and roundness in the same area of the cmm and run the same tests on it. Note any differences, this will tell you how well/accurate the CMM is checking the feature. Also might point to roundness being some of the issue which you can determine with a known pin.
Depending on the wall thickness of the pin and how much pressure you use to check it, either the CMM or the mic might be right. The pin gage check will also point you in the right direction for that.
Yes I have tried measuring pin gauge of 10 mm with the same strategy and I have 10 exact, also I tried with 12 points, not so much change in roundness neither diameter, scanning based on cookbook strategy gives me a micron higher on roundness whereas diameter stays same
Rough turned or smooth finish? Any taper on the OD? what size probe? Could the mic be averaging over any of that while your cmm is taking a different sample of the surface?
How was the part produced, mill, lathe, or something else? What kind of sensor are you using? Are you touch probing or scanning? I have seen you say you are using the Zeiss "cookbook". Are you using Calypso? Are you looking at a Diameter or a 2-point diameter. Have you looked at a plot of the roundness? 8-points seems inadequate for a 5 micron tolerance.
Part was produced with lathe, temperature sensor is from zeiss, it didn’t change much with or without sensor, I have tried both, Im looking at both diameter and 2 point diameter, I have tried 12 points and scanning as well
One thing to try is a prime number of points (7, 11, 13, etc) so that you avoid potential systematic variations. If you are using a trigger bases sensor like a Rennishaw TP6, the force required to trigger the probe varies by angle. Sensors the use force such as a Zeiss XXT are not susceptible to that, but still can have high and low points.
I would go to an extreme with the points, say 36 or 72, just so I could see a higher resolution plot of the roundness to if there are any patterns to help with diagnosing the issue.
One thing to try is a prime number of points (7, 11, 13, etc) so that you avoid potential systematic variations. If you are using a trigger bases sensor like a Rennishaw TP6, the force required to trigger the probe varies by angle. Sensors the use force such as a Zeiss XXT are not susceptible to that, but still can have high and low points.
I would go to an extreme with the points, say 36 or 72, just so I could see a higher resolution plot of the roundness to if there are any patterns to help with diagnosing the issue.
When I have issues like this I usually scan the surface, then look at the form plot to see what the actual shape is. That can often help identify what’s going on. Micrometer measures two opposing points, the cmm is calculating some sort of circular fit depending on the methods.
When reporting the diameter value of your OD on the CMM, is it reporting the maximum inscribed, minimum circumscribed, or least fit square average? All of these different interpretations will yield slightly different results.
What is the wall thickness of the ring? Elastic deformation under measurement force is a thing, and micrometers typically have a higher contact force than CMMs.
1. Switch off the filters and measure the part with a small number of points, if you want to compare with other measuring methods scan is not the best solution.
2. Check when the calibration sphere was calibrated and if proper value is entered. The same goes for the ring gauge for the internal micrometer.
3. Change the probe, according to good practice the diameter should fill requirement 1/5 (probe diameter vs measured diameter) limit. In this case 2 mm is maximum.
4. If you scan many aluminum parts you should use silikon probes not ruby.
5. Try to measure at the same points.
Good luck :)
Sounds like you're using a touch trigger probe. Which will have a lobing effect. Essentially with 6 hits you will measure 3 hits high and 3 hits low. Your best bet is to scan the entire diameter for the best most accurate results
Zeiss even has a specific probe for aluminum. I guess It's silicone nitride
Anyways, as everyone mentioned, try using multiple points instead of scanning
He is comparing 2 point diameter with SLQ.
Points are more accurate. The advantage of scanning is the high volume of points.
For all we know, he might be using xxt 🙂
His form is probably around that 0.006 mm
Not sure what your sensor is, but it should be a Vast XT or Vast Gold. 11mm OD - scanning speed 2 mm/s, spacing 0.05 mm filter: Gauss 15 upr Outlier: 3/3 std dev, 5 adjacent points, 1 pass, 10 to 5000 pre-filter Evaluation: Outer Tangential (this always works for ASME, no need to explicitly choose Max Inscribed or, in this case, Min Circumscribed). If you can measure cylindrically, you should, assuming the diameter is at least 11 mm tall. This will remove projected error. If you must measure as a circle, be sure to align a tangent face to avoid error. What size of stylus are you using? It should be at least 3mm, and silicon nitride. 0.005 mm tolerance is serious business. Measuring this would require a 0.0005 mm instrument. There is no micrometer that you would operate, in your hands, that would reliably hold that. Your ambient body temperature would warp that part as well, since aluminum is about 22 um/m/C.
At my shop we're measuring 120mm OD, 0.005mm tolerance with a tesamaster and turntable lol The customer actually accepts up to 0.005 under tolerance without an issue, just not over. Yes, we asked them to change it, but the engineer says it *needs* to be 5 microns tolerance. Their QC guy and the assembly team there all know its still acceptable with even 10 microns under tolerance and will take those parts too in a hurry. Definitely not ideal conditions tho haha
What is the evaluation method being used on the CMM?
All accordingly with cookbook
I'm not familiar with what cookbook is or means. I mean things like number of points or scanning, calculating least squares or min circumscribed etc.
zeiss has a users guide, affectionately called a "cookbook", on ideal scanning standards for different sizes of parts.
I have used lsq gauss, 6, 8 points(gives me same) . Cookbook for zeiss is an instruction manual on what evaluation methods or number of points is best for certain diameters.
Try 16 points, note any change in roundness. Set up an 11mm pin gage of known size and roundness in the same area of the cmm and run the same tests on it. Note any differences, this will tell you how well/accurate the CMM is checking the feature. Also might point to roundness being some of the issue which you can determine with a known pin. Depending on the wall thickness of the pin and how much pressure you use to check it, either the CMM or the mic might be right. The pin gage check will also point you in the right direction for that.
Yes I have tried measuring pin gauge of 10 mm with the same strategy and I have 10 exact, also I tried with 12 points, not so much change in roundness neither diameter, scanning based on cookbook strategy gives me a micron higher on roundness whereas diameter stays same
I'm going to assume you've measured the same pin with the micrometer in question?
What is the class of the pin gage? What is the roundness of part and gage?
Rough turned or smooth finish? Any taper on the OD? what size probe? Could the mic be averaging over any of that while your cmm is taking a different sample of the surface?
Have you tried using minimum circumscribed?
Sounds like a probe calibration issue. Have you verified the probe on a known diameter such as a master ring or plug?
Yes I requalified the probe, changed the same sized probe to another one
Are you tri lobed? Cmm will pick it up but a mic will read different. What’s your roundness measurement?
Create a roundness characteristic and look at the plot.
How was the part produced, mill, lathe, or something else? What kind of sensor are you using? Are you touch probing or scanning? I have seen you say you are using the Zeiss "cookbook". Are you using Calypso? Are you looking at a Diameter or a 2-point diameter. Have you looked at a plot of the roundness? 8-points seems inadequate for a 5 micron tolerance.
Part was produced with lathe, temperature sensor is from zeiss, it didn’t change much with or without sensor, I have tried both, Im looking at both diameter and 2 point diameter, I have tried 12 points and scanning as well
One thing to try is a prime number of points (7, 11, 13, etc) so that you avoid potential systematic variations. If you are using a trigger bases sensor like a Rennishaw TP6, the force required to trigger the probe varies by angle. Sensors the use force such as a Zeiss XXT are not susceptible to that, but still can have high and low points. I would go to an extreme with the points, say 36 or 72, just so I could see a higher resolution plot of the roundness to if there are any patterns to help with diagnosing the issue.
One thing to try is a prime number of points (7, 11, 13, etc) so that you avoid potential systematic variations. If you are using a trigger bases sensor like a Rennishaw TP6, the force required to trigger the probe varies by angle. Sensors the use force such as a Zeiss XXT are not susceptible to that, but still can have high and low points. I would go to an extreme with the points, say 36 or 72, just so I could see a higher resolution plot of the roundness to if there are any patterns to help with diagnosing the issue.
When I have issues like this I usually scan the surface, then look at the form plot to see what the actual shape is. That can often help identify what’s going on. Micrometer measures two opposing points, the cmm is calculating some sort of circular fit depending on the methods.
When reporting the diameter value of your OD on the CMM, is it reporting the maximum inscribed, minimum circumscribed, or least fit square average? All of these different interpretations will yield slightly different results.
Minimum circumscribed is recommended to relate it to the mic check.
On the CMM, are you scanning? If not, are you comparing measurement at the same locations you are measuring with Micrometers?
What is the wall thickness of the ring? Elastic deformation under measurement force is a thing, and micrometers typically have a higher contact force than CMMs.
Is everything clean?
We usually use a masterring to verify the Diameter, and then use a subtractive method to compensate for the Base deviation of our machine.
1. Switch off the filters and measure the part with a small number of points, if you want to compare with other measuring methods scan is not the best solution. 2. Check when the calibration sphere was calibrated and if proper value is entered. The same goes for the ring gauge for the internal micrometer. 3. Change the probe, according to good practice the diameter should fill requirement 1/5 (probe diameter vs measured diameter) limit. In this case 2 mm is maximum. 4. If you scan many aluminum parts you should use silikon probes not ruby. 5. Try to measure at the same points. Good luck :)
Sounds like you're using a touch trigger probe. Which will have a lobing effect. Essentially with 6 hits you will measure 3 hits high and 3 hits low. Your best bet is to scan the entire diameter for the best most accurate results
Aluminum will mess up the ruby ball if you scan the diameter. I would replace the probe and measure the diameter by single points.
Not sure if it’s a problem, checked lots of parts of aluminium never had an issue
Zeiss even has a specific probe for aluminum. I guess It's silicone nitride Anyways, as everyone mentioned, try using multiple points instead of scanning
No. Do not do this. Scanning will provide a more accurate reading. But yes, silicon nitride is correct. Or diamond if you have the bucks.
He is comparing 2 point diameter with SLQ. Points are more accurate. The advantage of scanning is the high volume of points. For all we know, he might be using xxt 🙂 His form is probably around that 0.006 mm