[SH...] Posted August 13, 2020 Share Posted August 13, 2020 I have to measure concentricity between two bore one bore is 40 mm long and 47mm diameter another one is 10 mm long and 118mm diameter.47 mm diameter is my datum and I have to calculate the concentricity of 118 dia with respect to 47mm dia. Customer advised me to measure 47mm dia as cylinder and 118 as circle. Tolerance of concentricity is 0.02mm. When I measure I got 0.032 mm. For dia 118 Circle I took 8 points and 47 cylinder I took 8 points, four points per segment no scanning. When customer measured they got 0.024mm. So for verification I gave the part to zeiss inspection service center They got 0.014mm. I told Zeiss engineer to use same measuring strategy I used. Me and Zeiss using with fixed head probe, customer using articulated probe head , all three are Zeiss CMM. Why three people get three result?? I think Zeiss inspection is correct, how can I verify my program. I measure the bores with two tip , tip three and five both are qualified well both have standard deviations within 0.0003mm. Can't measure with single probe because of job shape. Anyone can shed some light to my problem?? Link to comment Share on other sites More sharing options...
[Cl...] Posted August 13, 2020 Share Posted August 13, 2020 See if Zeiss will give you a copy of the program that they used? Compare their program to yours. An aspirin might help too. Link to comment Share on other sites More sharing options...
[Ch...] Posted August 13, 2020 Share Posted August 13, 2020 My first question is what is the distance between the bores? Concentricity can be tricky especially concentricity across a distance.Profile_Concentricity_CALYPSO.pdf Link to comment Share on other sites More sharing options...
[SH...] Posted August 13, 2020 Author Share Posted August 13, 2020 Please sign in to view this quote. They told they got the co ordinate value of 118 bore y axis 0.005 and z axis 0.004 or 0.003 don't remember exactly but I got y axis deviation 0.014 and z axis 0.004 . Y axis I get more deviation that is the problem. They will not give the program. My production people says they using specially designed tool for this concentricity , they using single tool with interpolation. Can't give off set for one particular bore. Link to comment Share on other sites More sharing options...
[Cl...] Posted August 13, 2020 Share Posted August 13, 2020 Please sign in to view this quote. I'd be curious to see what the result would be if evaluated as Coaxiality? Link to comment Share on other sites More sharing options...
[Ch...] Posted August 13, 2020 Share Posted August 13, 2020 I use coax a lot as a sanity check. Link to comment Share on other sites More sharing options...
[SH...] Posted August 13, 2020 Author Share Posted August 13, 2020 Please sign in to view this quote. Depth of the 47mm bore is 17 mm not 40 ...IMG_20200808_125934.jpg Link to comment Share on other sites More sharing options...
[Ke...] Posted August 13, 2020 Share Posted August 13, 2020 Is the customer and Zeiss only using 8 points? Does the customer define where those 8 points are taken? I would also scan for form, and of course, check repeatability of the measurements. Link to comment Share on other sites More sharing options...
[Cl...] Posted August 13, 2020 Share Posted August 13, 2020 Single points = no filters and outliers. I tend to scan everything, so I can apply filters/outliers. That could make a difference. Link to comment Share on other sites More sharing options...
[SH...] Posted August 13, 2020 Author Share Posted August 13, 2020 Please sign in to view this quote. I don't know what strategy is being used by customer but zeiss measured two method one according to their standard that is scanning the 47mm bore using six segment each segment 3000 points, and scanning the 118 bore with high density point, I don't know exact points. In this method they got 0.012 mm. They told me follow their method. I followed their method still I got 0.036 ,I think some problem in my measuring. Can't understand the root cause. Link to comment Share on other sites More sharing options...
[Ch...] Posted August 13, 2020 Share Posted August 13, 2020 I am confident that you are getting projection error caused by datum E being too short. I would add a second datum to help keep things straight, Datum D looks like a good choice. I've added an example of a part with a short datum. Link to comment Share on other sites More sharing options...
[Cl...] Posted August 13, 2020 Share Posted August 13, 2020 Have you thought about re-qualifying that probe? Link to comment Share on other sites More sharing options...
[SH...] Posted August 13, 2020 Author Share Posted August 13, 2020 Please sign in to view this quote. This is a good idea I did this then I got only 0.009mm, but my QA manager don't agree this, he says no secondary datum in drawing.. 😭 Link to comment Share on other sites More sharing options...
[SH...] Posted August 13, 2020 Author Share Posted August 13, 2020 Please sign in to view this quote. I qualified three or four times ,no problem sometimes I get 0.0001mm standard deviations!!! Link to comment Share on other sites More sharing options...
[Ch...] Posted August 13, 2020 Share Posted August 13, 2020 I would argue that per ASME 89.7 that using a secondary datum is an equivalent measurement strategy. For example, in the picture I showed you, Datum A is only 2mm deep and the bore that is called back to it is 60mm away. It is absolutely impossible to establish a reliable axis on a bore that is only 2mm deep. So I use a secondary datum and justify that by proving the measurement on a granite table with a height gage. Link to comment Share on other sites More sharing options...
[Ke...] Posted August 13, 2020 Share Posted August 13, 2020 [/quote] I don't know what strategy is being used by customer but zeiss measured two method one according to their standard that is scanning the 47mm bore using six segment each segment 3000 points, and scanning the 118 bore with high density point, I don't know exact points. In this method they got 0.012 mm. They told me follow their method. I followed their method still I got 0.036 ,I think some problem in my measuring. Can't understand the root cause. [/quote] With scanning, what is your form error? Link to comment Share on other sites More sharing options...
[SH...] Posted August 13, 2020 Author Share Posted August 13, 2020 Please sign in to view this quote. I don't know what strategy is being used by customer but zeiss measured two method one according to their standard that is scanning the 47mm bore using six segment each segment 3000 points, and scanning the 118 bore with high density point, I don't know exact points. In this method they got 0.012 mm. They told me follow their method. I followed their method still I got 0.036 ,I think some problem in my measuring. Can't understand the root cause. [/quote] With scanning, what is your form error? [/quote] For 47mm bore I got 5micron form error same as zeiss but 118 bore I got 0.014 where Zeiss only got 7 micron. Link to comment Share on other sites More sharing options...
[SH...] Posted August 13, 2020 Author Share Posted August 13, 2020 Please sign in to view this quote. I don't think my QA head will accept this, but Zeiss engineer did not recommend this.. I think my customer also don't follow this. If this is acceptable , I could save the money I gave to zeiss 😐 Link to comment Share on other sites More sharing options...
[Ke...] Posted August 13, 2020 Share Posted August 13, 2020 Please sign in to view this quote. Find out where Zeiss took their measurements for the 118 bore. Look at the roundness is out & wipe down the part, and try measuring it with a couple of different probes. I would scan multiple paths on that bore to see what the cylindricity looks like. Link to comment Share on other sites More sharing options...
[Ma...] Posted August 13, 2020 Share Posted August 13, 2020 Shabu: did Zeiss mentioned scanning speed and measuring force? Also did they fully described their strategy? That coe Ø0,02 is most likely 0,01 from center - so it should by doubled, right? And there is hidden dwarf. You get almost double what they got measured. Please advise me if i am wrong - i have ISO here Link to comment Share on other sites More sharing options...
[Ch...] Posted August 13, 2020 Share Posted August 13, 2020 Another thing you can do is use the A1 A2 angles for your primary datum and use trigonometry to determine the amount of projection error you are getting. A good sanity check is to create an intersection point using the the axis of the primary datum with a plane about the some distance away. Similar to below pic. Link to comment Share on other sites More sharing options...
[SH...] Posted August 13, 2020 Author Share Posted August 13, 2020 Please sign in to view this quote. No, they did not disclose about measuring force and speed, infact I did not ask about it. Yes I get double value, they got. Link to comment Share on other sites More sharing options...
[SH...] Posted August 13, 2020 Author Share Posted August 13, 2020 Please sign in to view this quote. Ok, I will try this... Link to comment Share on other sites More sharing options...
[SH...] Posted August 13, 2020 Author Share Posted August 13, 2020 Please sign in to view this quote. Zeiss measured 118 bore using three circle, and they gave me three separate concentricity from 0.012 to 0.014. I wonder with their measurement. My customer says they got 0.024 and they are accepting the part. Link to comment Share on other sites More sharing options...
[Ün...] Posted August 14, 2020 Share Posted August 14, 2020 8 points taken at 118 diameters are very few. For a desired size of 0.02mm. If you have to increase the number of dots, I suggest you scan. That's why Zeiss got 3000 points. In addition, your ovality value of 118 diameters may be high. For diameter 47 cylindricity for diameter 118 it is useful to check your ovality values. Link to comment Share on other sites More sharing options...
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