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Aligning to a circle & slot feature using measured values?

Posted: Wed Dec 04, 2019 3:12 pm
by Magna 12345
Afternoon,

Forgive me if I don't use the correct terminology, i'm fairly new to this. We normally measure parts by placing them on a check fixture and aligning to tooling holes/balls.

Our customer has asked us to align to a circle (to control XY) and slot (to control X). We were going to measure a tooling hole as our primary datum and try to RPS alignment (tooling hole primary, circle secondary, slot tertiary). The issue we run into is we need to use the measured values for our secondary and tertiary aligning features because the rest of the measurements are relative to these features.

I've attached a couple images to hopefully paint a better picture of what's required. What would be the best way to align the part to measure the rest of the circle features?
Capture 1.PNG
Capture 2.PNG
Thanks,

JD

Re: Aligning to a circle & slot feature using measured values?

Posted: Wed Dec 04, 2019 5:38 pm
by CrashN8
Looks like a perfect opportunity to use RPS Alignment - see example here - https://www.cmmmanager.com/forum/viewtopic.php?p=7536

Re: Aligning to a circle & slot feature using measured values?

Posted: Wed Dec 04, 2019 6:41 pm
by Magna 12345
Thanks for the reply. Much appreciated.

I ran an RPS alignment and when I verify my tertiary feature/datum, its sitting over 3mm out in Y (locked in at X as per customers direction). When we look at the part there are attribute checks in the area and it's within tolerance 3mm+/-1.0mm. SPC's in the area are within tolerance as well (+/-1.0mm). I'm thinking the primary datum (center point of a tooling hole on fixture) isn't enough data to lock in the plane (-A- datum which is cross-car or Y axis). In hindsight I should have remeasured the tooling holes on the fixture to see if there was variation in those measurements as well.

So for the example above in the link, if that part was on a check fixture with alignment tooling holes which appears to be locked in z (or -A-), then I asked you to measure slot 2, aligning hole 1 to X,Z & Slot 3 in X. How would you align it? I was thinking to create a plane using the tooling holes somehow and using that to align the other 2 features? Currently we're using the features on the check fixture(1 hole for XYZ and the 2 others to lock in Y) and on the part (XY & X) for our alignment but we're getting an over constraint error.

Hope this makes sense.

JD

Re: Aligning to a circle & slot feature using measured values?

Posted: Fri Dec 06, 2019 4:11 pm
by Magna 12345
I had a winded message yesterday but it still isn't posted.

Long story short. What do I do to align my -A- datum with only the 2 features (called out in pictures above)? Our ABC alignment was our fixture alignment (-A- being our Y plane). We tried RPS alignment for ADE using one of the tooling holes on the fixtures for our Primary and we were seeing -E- datum out by over 3mm.