Step file resolving some parts as surfaces

Reece_Isaac

I have several different models from different sources imported as Step/stp files. One or more of these models has a part/s reduced to a series of surfaces. Apart from using a program like Freecad to convert to solid these part and update them in the folder, is there a method of resolving these surfaces back into the parts as intended with in Onshape?
Here is my motor example https://cad.onshape.com/documents/4850a464c7f84b06a621df01/w/374d09f403a249e88b3b4b67
Railway bogie
https://cad.onshape.com/documents/91e6aace4239468ab3a40505/w/3ac6a4ebd5bc4bf6a12ff5ee

Reece_Isaac

My apologies if I poorly explained the issue. The 1200 was built in VariCAD. For some unknown reason the end cover has been reduced to a number of surfaces rather than a solid like the other end.

len_1962

For the 1200 KV Motor
the problem is on one surface, it has what is called "Zero Thickness Geometry". 
It is surface 107, the hole face is at the same level as the planer face.
The part was modeled in one of the solid software's that allow this like Inventor or ProE, Parasolid Bases modelers cannot.
since OS doesn't have surfacing you would have use another software to fix the problem first, the re-import.

haven't looked at the other file, but I would assume the same thing is happening, zero thickness 

len_1962

Reece_Isaac

My apologies if I poorly explained the issue. The 1200 was built in VariCAD. For some unknown reason the end cover has been reduced to a number of surfaces rather than a solid like the other end.

peter_hall

@Reece_Isaac I had a similar problem when importing a step file from Grabcad. One part of the model was a quantity of surfaces. I made a copy part using the Onshape software as to resolve the surfaces into solids was too difficult. I expect these problems are likely to occur when using cross CAD software...plus you are importing someone elses design work and so are reliant on how they approached the design.

3dcad

I've ran into same issue while importing models from Geomagic.

Usually this happens with stuff that I have replicated from real world part just with enough accuracy to use in assembly instructions. They tend to have these problems since it is fast modeling and many times bodies get constrained so that they only share one line (which is Zero thickness geometry aka Non-manifold body - not supported by parasolid modelers like Onshape or SolidWorks).

I have tried to fix these in various ways without major success and often I end up creating new model in Onshape. Imported surfaces are good reference for sketches to extrude solid model with Onshape, a lot faster than copying shapes and dimensions manually from another cad system.

I wish there was a way to 'boolean' surfaces back into solids after manually fixing zero thickness issues inside Onshape. 

andrew_troup

3dcad said:

.....

I wish there was a way to 'boolean' surfaces back into solids after manually fixing zero thickness issues inside Onshape. 

Indeed, and not just for zero thickness issues. 
We need "knit surfaces", with or without "Try to form solid" (in SW terms)

As for capabilities missing in SW, needed in Onshape: one crucial one is "Un-knit surfaces"