Name X

6mm tip, and that almost makes sense.

Unfortunately, that would mean that PolyWorks is improperly showing my CAD surfaces because the CAD surfaces appear correctly oriented.  The original program was written using the fixture CAD, which would (should) have set the vector correctly for the actual measurement.  Then changing to part CAD (which would be inverted compared to the measurement) the exact same things happens.

I will try inverting those surface elements, when I get a chance.

Thanks  :)

Anyone have a lot of experience with PolyWorks + Romer Arm + Part Fixtures? I'm losing my mind, pulling out my hair, banging my head against a wall, etc.

I'm having an issue with aligning to a part holding fixture with the Romer arm on PolyWorks versión 2014 IR18 (build 7338).

We have a part fixture which we have aligned to 3 bushings using the Reference points alignment. At this point, everything seems to be fine. All of our deviations are 0 along the alignment axes. Watching the probe in real time on CAD shows the prone touching exactly where it is expected.

When we go to align on the datum nets that the part will actually sit on, using a reference points alignment (after the first iteration, when you get to fine-tune the points locations), all of the data drops ~6.00 mm. Looking at the bushings locations, they all show -6.00 in the primary axis (Z). I cannot figure out why the data no longer stays on CAD. I have tried linking to the part CAD as reference object, linking to the fixture CAD as reference object, and linking to no reference object. Oddly, the alignment deviations show up within tolerance, even though all of the hits, and the 4-way and 3-way locators show up 6 to 8mm low in Z. It's not even skewing the data, its just straight shifted by about the diameter of the ruby...

I've even re-programmed everything from scratch and still no change.

Also, I have checked the fixture on the CMM. The bushings and the datum nets are NOT 6mm out in relation to each other.

The easiest way to dimension a composite position is to use a best fit to modify the alignment.  I'm not sure how to handle this in PolyWorks.

If your position is ABC and your composite is only A, then you can rotate and translate to fit the holes.  If AB, then you can only translate.  It all depends on what degrees of freedom are 'unlocked' by your FRTZ.  Again though, I am unsure how to handle such alignment changes in PolyWorks.  Have you tried defining datums from the part? 

It is more necessary on a print, because the number of decimal places is useful in conveying tolerancing information with title block tolerances.  A lot of times, if you go out 4 or 5 decimal places, you'll start to see rounding, all over the place.  Typically though, the rounding is orders of magnitude smaller than the tolerance and present very little in the way of conflict.   Then, occasionally you will find places where the print numbers were overridden manually, and then you start seeing issues measuring from CAD.  I usually just report everything to whatever my largest number of decimal places happens to be, but I also am on PC-DMIS 99% of the time, and I can change decimal places back and forth throughout the program, anytime I want.

Excellent.  Glad to be of service.

Yes, it is possible.  If your data is a point cloud, you can mesh it and, in turn, use the mesh as the reference object.

The procedure for this is different depending on scanning or probing.

Since you mentioned scanning, I will answer that.  It's not highly intuitive.  (Doing this from memory, as I am nowhere near our PolyWorks laptop).

First, scan the part and do a best fit.
In the RPS alignments, select RPS points.
Select features from the drop down, and the feature type from the selectable icons.
Hit next and select anchor for points, or pick from cad for other features.
Select your points, using the XYZ check boxes as you go to define what degrees of freedom get locked by the features.
As you create RPS features, nominal features should be automatically created.
When finished, select your features and Extract Measured.
Then, select the RPS features and in the RPS menu, select the option that is NOT Align by Probing (it should be the only other option).
The menu that comes up should have a box to check for "Use Constraints" (ignore it).
Hit done, Viola!  (note that it doesn't seem to properly iterate as PC-DMIS would, and you end up with, EG Datum B not at 0 deviation.

I don't know that there is any other way to achieve this without probing.  (If any of these steps isn't quite right, my memory isn't what it used to be  ;))

You could go about it the long way.  Construct sheet metal points (edge points), then construct a plane from the points.  After doing the same on both sides, you should be able to get the distance between the two planes.

Did you verify that the nominals of the top, and sides of your base plate are 0 along the appropriate axis?  Where are you getting numbers from for the base plate?  Basic dimensions?  I see quite often that basic dimensions will be rounded to 2 or 3 decimal places.  Which can account for differences in nominals, in which case, CAD would be master.