Rework in CAD .stl  

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pingu
(@pingu)
Estimable Member

i have some basic to advanced skills in CAD ( autodesk inventor).

but i have problems when i try to do some work on designs from others, and i have only STL files. how do you manage this?

All the usual design steps like do a sketch on a surface do not work, because the surface whitch is flat when you print it (and in original design i guess) isnt in a microscopic look. when importing the stl it is a very whobbly surface then. i even cant transform them into solid objects to 3d modelling them. any ideas?

Posted : 18/10/2019 7:35 am
Neophyl
(@neophyl)
Noble Member

Its always difficult working with just the stl models.  For gross changes I've just been modifying the meshes with Blender but I think Fusion360 has a mode designed to work with an imported stl.  How good that is I don't know.Also something like Meshmixer which is designed for modifying meshes might work.

Posted : 18/10/2019 8:21 am
burtronix
(@burtronix)
Estimable Member

I have been getting some experience with importing  STL files into Fusion 360 & modifying them. My problem with importing into Mesh Mixer, Blender, & a few others is that they try to do smoothing when importing or converting STL files. Maybe there's a way to turn off smoothing, but I haven't found it. I'm typically not happy with the smoothing result, as it looses detail resolution or changes shapes & dimensions.

In Fusion 360, imported STL files show up as mesh bodies. To import an STL into a mesh body, you must first turn off Design History in the work-space. If I'm adding features or dimensions, it is simplest to leave the imported object as a mesh body & just add new solid-body objects intersecting with the mesh body.

If I'm deleting a feature or dimension along a plane, I split the mesh body along the plane & delete the unwanted part. This leaves a new planar face on the remaining mesh body.

If needing to remove material from the mesh body in a non-planar fashion, it first needs to be converted to a B-Rep body. This can be tricky because Fusion 360 limits the number of planar facets (~50k) that can be converted in a single operation. You can reduce the mesh before converting it to a B-Rep, but that will loose detail & change shapes & dimensions. Instead I prefer to split the mesh-body, convert the parts into B-Reps, then merge the B-Reps. Then you can do whatever edits you need.

Whatever you find to do with your hands, do with all your might!...
Posted : 11/02/2020 8:16 pm
Neophyl
(@neophyl)
Noble Member

I've never had blender smooth a stl.  Not automatically.   A stl is just a mesh/vertices with no history and it comes in as is, warts and all.  Usually theres much cleanup needed with a lot of imported meshes.

Posted : 11/02/2020 8:33 pm
Sembazuru
(@sembazuru)
Prominent Member

I've taken the lesson of having trouble modifying STLs so that on my designs (pitifully few, I admit) I provide the original 3d model (if I can, PrusaPrinters doesn't accept FreeCAD files) and a STEP model. That way anyone remixing has access to either the full FreeCAD file with full parametric editing, or a STEP file that should be easy to import into other solid modelers.

If you want to remix (or fix) something downloaded, it wouldn't hurt to try contacting the original author for something that is easier to remix from.

This post was modified 5 months ago by Sembazuru
See my (limited) designs on:
PrusaPrinters - https://www.prusaprinters.org/social/1448-sembazuru/prints
Thingiverse - https://www.thingiverse.com/Sembazuru/designs...
Posted : 12/02/2020 2:05 am
vintagepc
(@vintagepc)
Noble Member
Posted by: @neophyl

I've never had blender smooth a stl.  Not automatically.   A stl is just a mesh/vertices with no history and it comes in as is, warts and all.  Usually theres much cleanup needed with a lot of imported meshes.

Blender (edit: whoops, was thinking meshmixer) can be misleading due to the default lighting/rendering settings, I think. It makes geometrical models look like crap. I suspect turning that off and having it just render the faces as unshaded flat surfaces would help.

This post was modified 5 months ago by vintagepc
Posted : 12/02/2020 12:46 pm
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