Can anybody help with this TP callout?

[[Za...]]

Hello all, long story short, I'm being asked to help one of our other companies out by being a 3rd party inspection of a part for them. However, I don't deal with too many complex parts like this one.

I've been able to determine that the angles are all good, but I can't get the true position callouts to come in and I think it's due to an unstable base alignment/incorrect secondary alignment. Any help is appreciated.

The part is fixtured like this:
This gives you a better view of the part:
These are the three print views that I'm focused on getting results for:


Here is my base alignment along with the theoretical features being used (I think this is the problem with the alignment). -A- is the Giant Cylinder at the bottom, -B- is the machined surface of that cylinder, and -C- is the tiny cylinder at the top that appears in one of the views posted above.


I have all of the angles in the CMM and everything is scanning correctly, but the TPs are not close to what the other two companies are measuring. If anybody can help, that would be great. Also please post if you need more information. I think I got everything on here, but it's possible I missed something.

[[Lo...]]

Couldn't find Datum B but it looks like you might have to rotate a few datums in your alignment.

[[Ma...]]

Same for me - can not find B, but i gues it will be face of cylinder A

I would use compound surface profile to get basic overview how planes and TP are in alignment.

[[Za...]]

Sorry about that, here is the view with Datum -B-

[[Za...]]

Please sign in to view this quote.

In my Base Alignment? or in the Secondary Alignments?

[[Mi...]]

Use a 2d feature as the rotational feature in your Base alignment, it will orient the BA in a more predictable way. I would likely

Your base alignment is just for finding the part so don't complicate it if you don't have to, you can make the more complicated coordinate systems either in the Position Characteristic (don't overlook the special button there to rotate/translate as needed), or with secondary alignments to help you program.

Your fixture looks solid, but I would still apply a base alignment loop.

I would likely do -A- as the Rotation in space, and the YZ origin, B would be the X origin, and a Circle of C would be the Planar Rotation.

Then each position characteristic you fill out the appropriate datums in the correct order - use the special button to rotate the coordinate system as needed, don't use secondary alignments( they most likely will not be formed with the correct datum rules unless you tell it to) or especially not with the base alignment.

[[Ch...]]

The first issue I see is DRF = A-B-C however you are using C (tertiary) as rotation in space. Yes, you can use anything you like for Base Alignment, however small/short cylinders are typically not ideal especially for larger parts.

I can see how -A- can be a problem due to being an incomplete 360° bore, etc.

I would agree with what Michael said above and use a circle for tertiary.

Also add "LOOP" to your base alignment, at least 3x.

Good luck.

[[Za...]]

Please sign in to view this quote.

I'm going to start from scratch here once I get some of our production parts run and see if I can't get this going from your suggestions above. I'll be back to update once I've had a chance to mess with the part again. Thank you for reading into this!

[[Za...]]

Please sign in to view this quote.

My loop is set, I actually have the full 360º -A- even though it doesn't appear on the print, and I'll switch those features to circles and see what I can come up with. Thank you for the response!

[[Lo...]]

Please sign in to view this quote.

The alignments used for that specific Characteristic, if applicable.

[[Za...]]

So my main issue was having the cylinder for -C-. Once I used the circle instead of the cylinder, the alignment clocked to the correct feature. Everything looks correct the way I have it, but I'm still having some issues getting the .13 TP callouts back to -K-.

[[Je...]]

Please sign in to view this quote.

Zachary,

Is that John Deere? This is unrelated, but I've been impressed with the discipline that John Deere applies to their drawings and GD&T, not to mention the fact that they are longtime Zeiss customers and have one of the largest CMMs in the nation. They have had people sit on the ASME GD&T committees and help write the standards.

I'm glad you got your base alignment to cooperate. I'd still recommend considering changing your base alignment because Datum feature C does not offer as much stability as A or B. You could constrain rotation to Datum feature C, though. Here's one example, although you could use Datum feature A as the primary as well:

.
.

I would recommend not using your base alignment to evaluate position. You should use either a secondary alignment or input datum features directly into the position characteristic.
.

.

Can you screenshot the position characteristic that you are using to evaluate Datum feature K? Are nominal values populating in inside this characteristic window?

[[Za...]]

Please sign in to view this quote.

I hope to get back into this today at some point. Trying to clear my plate before the New Years weekend gets here. And yes, it's a Deere part 🙂

[[Za...]]

I haven't forgotten about you Jeff, but I also don't have the part to play with anymore. It will be just playing with the data that I already have from the previous scans. The new year brought me many parts to work on this week 🤣 🤣 🤣