[Za...] Posted May 7, 2020 Share Posted May 7, 2020 Hello everybody, it's me again 🤣 I'm having some issues getting these mounting holes to come into tolerance. The part is a casting and has some rough spots, but I'm using all machined surfaces for all of my alignments. The machine programmers assure me that there are no major adjustments that can be made and these are still checking way out of tolerance. I have a strong base alignment that is looped to not exit unless the sigma is less than .0002". I'm using a secondary alignment using the OD and plane pictured to get my mounting hole distances from the middle of the OD: Does anybody have any advice to check these in a better manner? Thanks, Zach Link to comment https://qualityforum.zeiss.com/topic/15830-mounting-hole-locations/ Share on other sites More sharing options...
[Cl...] Posted May 7, 2020 Share Posted May 7, 2020 the picture doesn't match the alignment. Translate from the BA to the cylinder (ZX origin) make the -Y Plane Spatial &Y origin. Link to comment https://qualityforum.zeiss.com/topic/15830-mounting-hole-locations/#findComment-86638 Share on other sites More sharing options...
[Ke...] Posted May 7, 2020 Share Posted May 7, 2020 Are the machined surfaces that you are using in your base alignment specified datum targets? Is the -Y plane specified as a datum? ... wondering if that should be removed from the Planar rotation, and just use your XYZ origins. Link to comment https://qualityforum.zeiss.com/topic/15830-mounting-hole-locations/#findComment-86640 Share on other sites More sharing options...
[Me...] Posted May 7, 2020 Share Posted May 7, 2020 What's the callout for the holes? Do you have any unconstrained degrees of freedom you can best fit, like rotation around the center axis? Link to comment https://qualityforum.zeiss.com/topic/15830-mounting-hole-locations/#findComment-86642 Share on other sites More sharing options...
[Za...] Posted May 7, 2020 Author Share Posted May 7, 2020 Please sign in to view this quote. I'm confused? Is my alignment not good from this view? Link to comment https://qualityforum.zeiss.com/topic/15830-mounting-hole-locations/#findComment-86644 Share on other sites More sharing options...
[Za...] Posted May 7, 2020 Author Share Posted May 7, 2020 Please sign in to view this quote. My base alignment isn't using any of the datums that are called out. I'm using a cone from one of the cavities, the same circular plane from the pictures above, and the .656 ID of the OD I'm using for my secondary alignment. Link to comment https://qualityforum.zeiss.com/topic/15830-mounting-hole-locations/#findComment-86646 Share on other sites More sharing options...
[Za...] Posted May 7, 2020 Author Share Posted May 7, 2020 Please sign in to view this quote. One thing I have not been able to understand so far in my short time of CMM programming with Calypso is constraining degrees of freedom (which ones to use and why I would use them). Here's the only callouts for this view:Pic6.png Link to comment https://qualityforum.zeiss.com/topic/15830-mounting-hole-locations/#findComment-86648 Share on other sites More sharing options...
[Ri...] Posted May 7, 2020 Share Posted May 7, 2020 Look at the same trihedron, the space axis is flipped. Link to comment https://qualityforum.zeiss.com/topic/15830-mounting-hole-locations/#findComment-86650 Share on other sites More sharing options...
[Ri...] Posted May 7, 2020 Share Posted May 7, 2020 But it looks like you are creating an alignment, measuring the feature to that alignment, and then reporting the X,Y axis deviation. Are these circles that you are reporting or cylinders? If they are circles, you shouldn't have any issues doing that, but if they are cylinders then you are reporting the deviation of the feature coordinate system Link to comment https://qualityforum.zeiss.com/topic/15830-mounting-hole-locations/#findComment-86652 Share on other sites More sharing options...
[Cl...] Posted May 7, 2020 Share Posted May 7, 2020 Please sign in to view this quote. I thought the first pic was the secondary alignment. Link to comment https://qualityforum.zeiss.com/topic/15830-mounting-hole-locations/#findComment-86654 Share on other sites More sharing options...
[Ma...] Posted May 7, 2020 Share Posted May 7, 2020 How does your data look from your base alignment features using a cartesian distance? Also for the datum -B- Cylinder is that the smaller highlighted OD in the pictures? If so try using this a circle instead of a cylinder feature. A good rule of thumb I have been told also the cookbook mentions, if the bore depth is <1 x diameter you should use a single circle in place of cylinder features. Link to comment https://qualityforum.zeiss.com/topic/15830-mounting-hole-locations/#findComment-86656 Share on other sites More sharing options...
[Ke...] Posted May 7, 2020 Share Posted May 7, 2020 Ooh... Threaded holes, not just "mounting holes" How are you measuring the threads? How do the Actuals look? (open feature - right click - Show Actual Points)... I ask, even though it looks like the holes are "off" in the same rotational direction, but could be a contributing factor if you're not using True Pos Pins. Link to comment https://qualityforum.zeiss.com/topic/15830-mounting-hole-locations/#findComment-86658 Share on other sites More sharing options...
[Cl...] Posted May 7, 2020 Share Posted May 7, 2020 Should be at least 3x the diameter. Link to comment https://qualityforum.zeiss.com/topic/15830-mounting-hole-locations/#findComment-86660 Share on other sites More sharing options...
[Ke...] Posted May 7, 2020 Share Posted May 7, 2020 Not to muddy the waters too much more than they already are, but, do you know how the machinists are fixturing the part for machining? And try evaluating to their set up (if different), to see if it passes using that method. Link to comment https://qualityforum.zeiss.com/topic/15830-mounting-hole-locations/#findComment-86662 Share on other sites More sharing options...
[Za...] Posted May 7, 2020 Author Share Posted May 7, 2020 Please sign in to view this quote. I changed the datum B cylinder to a circle and the results got closer, but they are still out. Link to comment https://qualityforum.zeiss.com/topic/15830-mounting-hole-locations/#findComment-86664 Share on other sites More sharing options...
[Za...] Posted May 7, 2020 Author Share Posted May 7, 2020 Please sign in to view this quote. I'm scanning the threads as circles. I've tried the TP pins and the results are very similar. I don't think it's the thread scans that are causing the issue. It's almost like there is some rotation of the part due to the casting surface. Link to comment https://qualityforum.zeiss.com/topic/15830-mounting-hole-locations/#findComment-86666 Share on other sites More sharing options...
[Za...] Posted May 7, 2020 Author Share Posted May 7, 2020 Please sign in to view this quote. I know they went back and were looking at the fixturing, but they're positive the fixturing is good ( 🤣 I know). At least these results are believable when I go back to them with my findings. Link to comment https://qualityforum.zeiss.com/topic/15830-mounting-hole-locations/#findComment-86668 Share on other sites More sharing options...
[Za...] Posted May 7, 2020 Author Share Posted May 7, 2020 I really appreciate the input/help with this. I started here as "the calibration guy" and got thrown into the fire when our CMM operator left for a new job. I feel like I'm smart enough to get by on most things and definitely have the ability to learn this, but I'm in the worst "fake it to make it" situations there is at the moment not being able to explain these results very well. Link to comment https://qualityforum.zeiss.com/topic/15830-mounting-hole-locations/#findComment-86670 Share on other sites More sharing options...
[Za...] Posted May 7, 2020 Author Share Posted May 7, 2020 Please sign in to view this quote. What would I be able to constrain to stabilize the measurements/alignment? I want to figure the constraints out so I can use them in the future as well. I'm just a noob at the moment learning on the fly 😕 Link to comment https://qualityforum.zeiss.com/topic/15830-mounting-hole-locations/#findComment-86672 Share on other sites More sharing options...
[Me...] Posted May 7, 2020 Share Posted May 7, 2020 What are datums B & C? It looks like B is the cylinder. What is datum C? There are 6 degrees of freedom for a 3d object in space. Datums constrain or "lock" degrees of freedom. If there are DOF that are not constrained by the datums then they may be best fit. So, for example, if B is the cylinder and C doesn't constrain rotation around B then you are allowed to best fit the rotation. That's why I'm trying to understand what your datum features are. Just to add: Is the feature that's stopping your rotation in your Alignment 1 datum C? (-Y plane) Link to comment https://qualityforum.zeiss.com/topic/15830-mounting-hole-locations/#findComment-86674 Share on other sites More sharing options...
[Za...] Posted May 7, 2020 Author Share Posted May 7, 2020 Please sign in to view this quote. DatumB is the OD of the cylinder (scanning as a circle) DatumC: Link to comment https://qualityforum.zeiss.com/topic/15830-mounting-hole-locations/#findComment-86676 Share on other sites More sharing options...
[Me...] Posted May 7, 2020 Share Posted May 7, 2020 Go in order of Datum precedence. B (cylinder) constrains 4 DOF: 2 rotational and 2 translational. C (plane) constrains 1 DOF: 1 translational. Any datum following a previous datum can only constrain DOF that are not already constrained. That's the Can/May/Must rule. You are allowed to rotate around the axis of B to best fit your 2 holes. Create a 2d Best Fit bore pattern, select your datums, select your holes, and in the BF dialogue box check rotation but not any translation. Hit calculate and it will best fit by rotating around your B axis. Tell me if that helps. Edited to add: You also have MMC on the thread but you can't measure that on the CMM realistically and it probably won't have a lot of impact. And you have MMB (mobility) on B. Check the MMC box for Datum B in the BF dialogue box. Link to comment https://qualityforum.zeiss.com/topic/15830-mounting-hole-locations/#findComment-86678 Share on other sites More sharing options...
[An...] Posted May 7, 2020 Share Posted May 7, 2020 See attached.Contribution_07_05_2020_1.pdf Link to comment https://qualityforum.zeiss.com/topic/15830-mounting-hole-locations/#findComment-86680 Share on other sites More sharing options...
[Za...] Posted May 7, 2020 Author Share Posted May 7, 2020 Please sign in to view this quote. I'm going to get a few parts run that I know will go smooth and then I'll go back into this and report back. Thank you again for your help! 😃 Link to comment https://qualityforum.zeiss.com/topic/15830-mounting-hole-locations/#findComment-86682 Share on other sites More sharing options...
[Ma...] Posted May 7, 2020 Share Posted May 7, 2020 I agree with everything Robert Davis but would add that you should consider using C as the primary datum and B for origins only. The short length of B relative to its diameter makes it unsuitable for controlling spatial orientation. This is not what the drawing says but it is very likely how the part will function. Feel free to attempt to educate the engineer that made that drawing regarding proper datum structure. I find it's always an enjoyable exercise. 😃 Link to comment https://qualityforum.zeiss.com/topic/15830-mounting-hole-locations/#findComment-86684 Share on other sites More sharing options...
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