Profile / Constraint

[[Cl...]]

I'm starting a new post on something that I've asked about a few times. I'm just not understanding the
answers I get. The bottom shaft (OD) is the primary datum (-A-). The square inside has a surface profile
callout to -A-. I'm using FFS in that ID square. Its failing a type-2 miserably. The base alignment is the large
OD cylinder (Spatial & XY origin).

The inside walls (there are 4) I'm using two opposing walls to create a symmetry plane for the planar (X+),
and the top surface (plane) as Z zero. My BA is looped 3x with a 0.005 delta value. How do I allow the FFS
to rotate without using a best-fit alignment of the FFS which I'm told I cannot use because a datum is in the
profile callout.

Also, I'm performing the Type-2 because this program has been transferred from a Contura (VAST XT Gold)
to and O-inspect 543 (fixed XXT TL3). I can't imagine that it's failing because of the differences between machines.
Just thought I'd add that little tid-bit.

[attachment=0]Profile_Clocking.PNG

Profile_Clocking.PNG

[[Ky...]]

Hello Clarke,

So, a couple thoughts:

First, by "type-2", I assume you mean a GR&R? Have you done a type-1? Because if this is passing a type-1 and not a type-2, I don't think your issue is the program. It would either be your fixturing, or environment or something else like that. I understand this has been moved from another machine, but if it is repeatable on the other machine, why wouldn't it be repeatable on this on, which is all the profile characteristic would effect.

Second, what do you have as the datum reference frame in the profile? Do you have the base alignment? In that case, I would probably just change it to datum A (if that's the only thing in the DRF). There are other ways as well. I don't know who told you you can't make a best fit alignment. You just have to make sure the alignment of the feature uses the same datums (i.e. make sure the alignment's spatial and origin is set to A) and just turn on the rotation around the A axis (and translation along it... though that shouldn't really make a difference).

I hope that helps.

[[Cl...]]

Yes, a Gage R&R. It can't be the fixture, because I used the same fixture for the same part
at an earlier op. that passed a type-2. The "original" program (ran on the Contura) was poorly
written and it failed the type-1 when I ran it as found on the O-inspect. The Datum -A- was a cylinder.
The depth was < 3x the Dia and used only 180° circle segments. The base alignment spatial was the
ID cylinder, again, depth was <3x the Dia. Looped 2x with a 0.05 delta value. I took this program and
improved it by making the cylinders depth at least 3x their Dia. Making the 180° circle segments 360°
And using a much longer 3d line for the BA spatial. and adding a symmetry plane for the BA planar.
Looped 3x delta value 0.005.

[[Ky...]]

Fair enough, but it still seems to me you are throwing several variables at the set up and then thinking it's an issue with the program, when program issues would be more clearly seen by a type-1 GR&R, at least in my opinion. If it passes a GR&R type-1 but not a type-2, then we're usually considering issues beyond the programming strategies and characteristics settings, are we not?

Beyond that, I don't see any issue with the base alignment. Generally I would not really be worried about looping the alignment when it comes to features like cylinders/planes/circles/etc. Looping I usually reserve for point based alignments (3D best fit and RPS mostly) since the evaluation of those points are going to be dependent on the alignment, at least to a higher degree than something like a plane. The symmetry plane might be a little short to define the rotation very well, so maybe it might repeat the alignment once or twice (hard to tell without the part in my head) but I still wouldn't expect it to repeat too much. So long as it measures the features reasonably, I would not be concerned with it.

As far as the profile with the freeform is concerned, here is how I usually set it up with an unconstrained reference frame:
Go into the feature under the evaluation menu. Turn on best fit and select Chebychev (if you can depending on version) and then allow it to rotate and translate in the correct orientation based on the datum reference frame (I'm assuming Z based on the image you showed). No need for a secondary alignment here.

Then go into the profile, select the freeform as the considered feature and datum as as the only datum. This should be the best situation for the callout. I can tell you that this definitely gives a better value than just putting in the datum (or the base alignment). It also doesn't allow for degrees of freedom controlled by the DRF to move even if they are checked in the feature.

[[Ma...]]

If there is no feature to stop rotation, then you have to use bestfit with only rotation in main feature axis.
I would keep base alignment as simple as it can to be assured to scan on right spot.

I don't know if i am doing this correctly, but if i don't trust BA to have problematic features measured on right place and i have profile callout for FF, then i tryout curves -> alignment from them -> measure problematic features with that alignment. Then evaluate profile on callout's datums.

[[Cl...]]

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Thank you, Kyle.

As for machine differences there are some subtle ones. Due to the different styli, I was forced to move a few features up in Z so the stylus wouldn't shank. The fixture can't be the problem because like I said previously. I used the same fixture on the same part for a typer-2 at an earlier operation and it passed. Datum -A- is only half cylinder made from three 180° circle segments. With datum -A- like that I don't know how it passed a type-2 initially after it was created. I believe the loop is necessary as I loop all my programs base alignments. Especially if the part is clocked by eye and not metallically. I can watch it correct and get better as it loops. I'm running a type-1 again and will make some adjustments based on the results. I will try the best-fit in the FFS.