help with surfacing

michael_stalls

Hi

these are 2d surfaces taken from a model of a 3d  aircraft wing structure im working on. these surfaces are to be used as the basis for a FEA model mesh using shell elements.  Is there any way to join them all together to form a single surface? In the past i had to import these surfaces into another software package to "stitch" them all together but this is not possible now. Is there anyway to do this in Onshape?. they need to joined together so the mesh lines up at the surface intersections. ive treid boolean union or join and it just returns each separate part unchanged.

thanks

michael

michael_stalls

I have had some progress ....by splitting the skin with both main spar webs i was able to union the spar webs to the wing skin and then by creating a plane at each wing rib and splitting the spars and skin i was able to union each rib to each spar/skin section. each yellow an purple section is a separate surface/part. but now i cant seem to union all the separate wing sections into one surface or part. It would seem that each surface part would require a common edge in order for it to join together. is that correct?

thanks

John_P_Desilets

@michael_stalls  Great example! Is it possible to share this model as public so we can take a closer look? 

To answer your question, surfaces can only be joined together if they share a coincident edge.

romeograham

....but it looks like there's plenty of good information in that model, and there might be a different way to get what you need for the study.
If you can share a public model (as @John_P_Desilets mentioned) someone can help you out!

leonid_raiz694

Onshape supports only so-called manifold surface models. That implies that there are at most two surfaces joined at every edge. In this example, Onshape is successful joining two surfaces along their laminar edges, but would not join another laminar (one-sided) edge to a two-sided edge. This restriction is not unique to Onshape, it is a common restriction of various CAD programs.  

michael_stalls

thanks i figured it was probably something to do with keeping the surface model manifold. Here is the actual wing cad model . it is all honeycomb cored carbon fiber skins ribs and spars. In the past i had tried using some of the FEA apps in the App store for stress analysis but none of these really supported 2d shell elements or composite materials so i had to go with another program (mecway) and i still needed a 3 rd program to stitch all the surfaces together and prepare the geometry for meshing. I was hoping i could skip this step some how. are there any new programs in the app store that might help with this?

cheers

michael