UZ True Position of a Plane Xactmeasure GD&T

[JayKin]

Evening all,

Having a bit of a head scratch moment.

The drawing I have specifies True position of a surface to a primary perpendicular plane datum UZ +0,10.

Nominal is 2.04.

U or UZ isn't showing up in exact measure when I'm using ISO1101, is there an update I'm missing or in my version (2016) did UZ not exist as we're currently on ISO 1101:2017 which this part was drawn in.


Any help would be appreciated

Regards,

J.K

[louisd]

huh, I don't quite understand how an Unequal tolerance Zone (UZ) applies to a tolerance of position...

Do the dimensions or any pictorial element of the drawing clarify how this unequal zone apples? UZ should only apply to PROFILE measurements from what I understand, that's why it likely isn't showing up.

[JayKin]

Afraid not, only what I could gather from the ISO spec itself, it seems to work similarly to how profile of a surface would work with UZ, as its a plus indicator its material on.
Certainly the first drawing I have seen it on, it seems strange to me.

[louisd]

What is B? perpendicular plane? Parallel feature of size (bore/boss)?

[JayKin]

perpendicular plane

[louisd]

So you have a UZ attached to a perpendicular element. Where are you going to apply the UZ? To the left of perpendicular? To the right? does it depend on the wind? lol.
UZ is not remotely equivalent to a projected tolerance zone, this is technically baffling.

I'd bet my paycheck (all $0.10 and a gumball) on this boiling down to a fail on the engineer's application of GD&T.

[JayKin]

Wouldn't UZ normally apply dependant if it is a plus or minus before the 0,10? Plus is the direction of material on while a minus is the direction of material off. That's my understanding as far as iso goes.

However I do agree there could be a better way of controlling this feature.

[louisd]

Plus or minus of what though? the height of the B plane? it's still perpendicularity normal to the B datum, regardless of B plane height. It's a bogus call-out on the drawing. There's no location or rotational control defined, so +/- deviation values about the polar coordinate X/Y grid, from true zero cannot be attained.

[AndersI]

It is mentioned in ISO 1101:2017, for planar features only:

1101uztp.PNG

[louisd]

Effectively controlling parallelism and thickness. I can totally see this as valid, as it's essentially controlling the plane the same as profile would.
JayKin has this case, which is attempting to apply to a feature perpendicular to datum. this seems to confirm that it isn't a valid application of GD&T.

[JayKin]

Oh my goodness apologies!
Just realised my mistake in a previous comment, its not perpendicular to the plane it Is parallel.

Its been a long week and its still Tuesday.

With that said how would I then apply that to PC-Dmis?

[louisd]

if your situation mirrors what AndersI posted, you would be measuring parallelism & thickness plane parallel to P, offset a basic distance of 20mm thick, with a tolerance zone equating to 19.993 - 20.003, I think?

[JayKin]

unfortunately our customer can be more than a little fussy when it comes to reporting to drawing and would expect us to report true position, do we know if UZ for planar true position in Xactmeasure is available in post 2017 software updates?
Or is there a download I can use that updates the GD&T standards in PC-Dmis?

[AndersI]

The current version, 2019 R1 (SP3) does not allow UZ on position. There will be changes in the PC-DMIS GD&T in 2020 R1, but I don't know if that will cover UZ for position.

The only way I can Think of for accomplishing that is to nudge the theoretical position to be in the middle of the actual tolerance zone.

[JayKin]

Thank you AndersI, very helpful.