The 2 lower ones can be filled in with planar surfaces, after you delete each one, select the main object and run Construct > Planar to fill in the hole. Do those one by one so you don't open up a larger non-planar hole as would happen if you deleted both of them at once.

Then the upper one runs into some problem trying to do that I think because of a teeny tiny edge in this area here:






That little edge is only 0.0004 units long and something around that size under the fitting tolerance tends to get collapsed down and cause topology problems.

That may need to be dealt with by drawing in a line from its end and making a triangle on the left side there first, then the remaining area will probably behave better. Let me know if you're stuck with that part.

- Michael

FYI, yes, I left it long enough and eventually it *DID* export. :-D

@Chipp
<< The places you point to are obvious errors introduced in Onshape or when exported as STEP from Onshape.

Yon know that you can now also use again 123D Design between Moi for delicate fillets ! ;)
http://www.123dapp.com/design
Because Step / Sat format import export have made their return for Free version! ;)
DIfference than Onshape : it's a local application! ;)

Thanks Frenchy, DID not know that. Much appreciated!

FWIW, I really like the Autodesk 123D program. I don't see where it exports STEP, but SAT works fine. I was able to quickly cobble together a basic widget in short order:


Create the basic shape in MoI


Export as SAT to 123D, fillet there using dynamic filleting, and bring back as imported SAT. Next add some kitbash:


Exports as OBJ to KeyShot and Voilà

@Chipp

<<I don't see where it exports STEP, but SAT works fine.

Don't know what format is the best for you? :)
But your results seems yet convincing!

PS Free version is of course for no commercial use! ;)

>

When you press it you have that! :) (Windows user)

>

Interesting. Mine is different (I'm using free commercial version downloaded from Mac App Store)

@Chipp

Maybe an "advantage" or more "disadvantage"of the Mac World! ;)
In any case one format is yet sufficient for Nurbs world! :)