boolean does not return a valid part with an imported x_t file (or step file or STL file)

kees_bijker

Even though the imported part becomes a solid shape and you can do all sorts of modifications to it like extrude remove as well as add or boolean, in some instances it will not let me create a rotate of a section as an add and it will not let me create a boolean of these parts either. In other documents I could not boolean an imported part with a solid created by my own sketch.

I have solved this for myself by creating my own part in place of the import and I am working with this part as it should, but still I am interested in learning why it would stop the extrude add or boolean in some instances?

If you look at this document 

https://cad.onshape.com/documents/21c21d48b9ddb4fce00ea8f4/w/b176c82eec9913c48d40237c/e/7073195568e60a42f2d94ffe

I removed a screw stud down to the horizontal face of the rim around the perimeter. I could not use other faces because the stud overlaps two segmented faces and it would not work for me, but this is another issue.

After the removal of the stud I made a sketch that traces the outline of the hole which I want to fill with a sweep. So I created a section view down the middle of that hole and traced the outline. Then rotate it symmetrically and for any degree under 9 it works but as soon as you go over 9 degrees it fails. Why does it do that? Seems illogical that if the part to add, or boolean, gets too far into the existing part it does not want to know about it. What is the reason behind this. I have had many other instances with imported parts that reacted this way and made it very difficult to work with.

Would love to know if I could predict this behavior and find another way to work rather then get annoyed and create a new part to work with.

GregBrown

The boss can be removed and filled in 4 features.

https://cad.onshape.com/documents/112d6f7296496f9ad82459c2/w/1cf07bb08ce396795b11a6d5/e/1e36acee88d829dbadbef413 

There does seem to be something a little off with one of the edges in the imported geometry (how was it created originally?). Ignoring that for the moment, you can get a clean model as follows.

wayne_sauder

@kees_bijker

  This is another one of the non-manifold geometry issues. Filling in that recessed area is no easy task because of the way the outer surface flows. I think the only way to do it is to use some surfacing tools. 

  The only prediction that I know of for scenarios like this is to always assume that it is a non-manifold geometry issue. 

GregBrown

The boss can be removed and filled in 4 features.

https://cad.onshape.com/documents/112d6f7296496f9ad82459c2/w/1cf07bb08ce396795b11a6d5/e/1e36acee88d829dbadbef413 

There does seem to be something a little off with one of the edges in the imported geometry (how was it created originally?). Ignoring that for the moment, you can get a clean model as follows.

kees_bijker

GregBrown said:

The boss can be removed and filled in 4 features.

https://cad.onshape.com/documents/112d6f7296496f9ad82459c2/w/1cf07bb08ce396795b11a6d5/e/1e36acee88d829dbadbef413 

There does seem to be something a little off with one of the edges in the imported geometry (how was it created originally?). Ignoring that for the moment, you can get a clean model as follows.

Thank you Greg, Very well explained.

I do not know how it was created originally. I just needed the model for fitting this fan into my 3d printer and I looked for a model here on onshape global. Sometimes you get lucky and you find a stepfile or even somebody who generated exactly what you are looking for but sometimes no luck and the best you find is some other imported file, like this one.

But your solution works so if I get something like this again I will try to apply it.

Kind regards