Prealignment & Local Best Fit

[[Jo...]]

I am scanning a square plate with a bunch of holes in it.  When I create the pre-alignment it ends up substantially shifted out of position to the CAD.  I try to bring it in using local best fit but am having no success.  What do I need to do to make this work?  Please see attached.

[[Ja...]]

Hi, you can use both the main alignment and manual alignment.

In this case, you can pre-align the item, then highlight it and use the main alignment. If the main alignment is still not perfect, you can switch to manual alignment. If your model has coordinates built in, you can select these coordinates and adjust them accordingly.

(P.S. In your photo, the target element is not selected, so it's unclear what it's aligning to.) I really hope this helps! Please feel free to message me if you'd like further assistance—I'll try my best to help. 🙂

[[Ax...]]

Hi John,

sometimes helps, if you use "additional help point":
Click at one special point, maybe the corner left top on CAD und the same point on the mesh. Suddenly pre allignment works fine.

[[Ja...]]

John , are you measuring lots of these parts? And or using automation?

If yes this would change the strategy as using help points or knife manual transformations are non parametric.

You can 'align by reference points' as an initial alignment The trick is to have a stable measurement set up...scan part in setup with a setup that allows reasonable repeatability of part placement to reference points, align the part by any means necessary by the options above , then you create a point cloud of the reference points that have moved with the object, the alignment by reference points created , then use the ' replace initial alignment' function.

I cant recall if there was a support page about this workflow...and if there is someone else would need to point you to it , but hopefully this helps.

Hope this helps

[[Ky...]]

Hi John,

Alex and James both suggested some good strategies to try. If this is a manual scan project, having a helper point and selecting the element may be beneficial. You could also consider extending the search time, as this can help with distorted parts. If this is an automated project, I would take a look at the Tech Guide https://techguide.zeiss.com/en/zeiss-inspect-2025/article/introduction_to_alignments.html this may give you some other addition alignments to try. If its automated i would take a look at the VMR work flow andhttps://techguide.zeiss.com/en/zeiss-inspect-2025/article/cmd_manage_alignment_replace_initial_alignment_with_best_fit_by_reference_points.html

 

 

[[Ti...]]

You need to set this up without a mesh for it to work. So delete the mesh.

Create a Surface on the CAD model and click the top plane with all the holes on it, but don't click the holes. Then click the left side plane and the top side plane. All 3 of those planes become your surface. We are simulating a 321 alignment(Plane-Plane-Plane)  Apply the measuring principle 'no measuring principle'

Now in your prealignment picture you posted, do you see 'target element'?  Click that on and in the drop down select the surface you created above. Click OK.

Now bring in the mesh and it should line up nicely. You are telling the software what to look for to align to. If it finds those robust 3 plane which it should the part should be lined up. Otherwise you can start tying to use certain holes in the surface, but the planes should do fine.

Edited February 13