Hi Paul, they do seem to be just very slightly out of tolerance - there is a distance of 0.009 between them, and MoI will currently join up to 0.005 .

Which surfacing command was used to create those pieces, I mean was it a sweep, network, something like that? The likely bug that needs to be fixed is to add a bit more checking to ensure curves have been fit to the 0.001 tolerance properly, the refitting procedure let through a very slightly sagging fit curve in this case which is basically the root of the problem.

One interesting thing is if you shrink the model down by a factor of 0.1 (select it, run Transform/Scale, type 0 <enter> to pick origin point, then type 0.1<enter> for scale factor), it will then join because then the gap is within the max join distance.

If you can let me know which surfacing command was used for building those pieces, I can see if I can repeat the problem starting from the initial construction, that will give me the best chance to solve the fitting problem.

At some point I will probably be trying to overhaul the way that tolerances are used in MoI in general and try to focus more on adapting the tolerance to the scale of the object instead of having it fixed at an absolute value of 0.001 . I'm not quite sure how that will work yet or when I will tackle that though.

- Michael