How are you smart guys editing .stl files?

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How are you smart guys editing .stl files?

Postby Corey Warren » 2016-Feb-Tue-20-Feb

I see people all over Thingiverse making design changes to other's .stl files. I've never been able to do this. I use Autodesk Inventor to do make my creations. I did install some addin a while back to Inventor to assist with the import of .stl files, but, it was very difficult to deal with. Everytime I end up starting over from scratch and recreating what others have already created in order to add or remove.

How do you guys edit .stl files? What software do you use for that?
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How are you smart guys editing .stl files?

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Re: How are you smart guys editing .stl files?

Postby sgibbers17 » 2016-Feb-Tue-21-Feb

Sketchup with these extentions.

https://extensions.sketchup.com/en/content/cleanup³
https://extensions.sketchup.com/en/cont ... -inspector²

cleanup³ will cleanup all the extra lines in the stl and solid inspector² will make sure the stl has now holes and will "hold water"
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Last edited by sgibbers17 on 2016-Feb-Wed-08-Feb, edited 1 time in total.
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Re: How are you smart guys editing .stl files?

Postby frankv » 2016-Feb-Wed-04-Feb

I don't think that's quite what he was asking. I think he's after importing an STL file to a CAD app so that it can be modified to create a new object.

I've done this once or twice, without having a good way to do it.

I import the STL into FreeCAD and use that to convert the mesh to a shape to a solid. Then export it as a STEP file and load that into OnShape.com. However, typically I end up "tracing" the STL shapes to make new sketches and extruding a new object. I'm also dabbling with Meshmixer and Meshlab. There's also some CAD conversion utilities, but they don't seem to be very successful either (limited set of source & destination formats, and the few that do have IGES or STEP output often refuse to work on most STL files.

I look forward to replies by smarter guys than me.
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Re: How are you smart guys editing .stl files?

Postby WayTooManyHobbies » 2016-Feb-Wed-06-Feb

I don't know about qualifying for smart, but you can open STLs in OpenSCAD and edit them as solid objects directly. Fair warning, there is a learning curve involved. http://www.openscad.org
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Re: How are you smart guys editing .stl files?

Postby sgibbers17 » 2016-Feb-Wed-08-Feb

frankv wrote:I don't think that's quite what he was asking. I think he's after importing an STL file to a CAD app so that it can be modified to create a new object.

I've done this once or twice, without having a good way to do it.

I import the STL into FreeCAD and use that to convert the mesh to a shape to a solid. Then export it as a STEP file and load that into OnShape.com. However, typically I end up "tracing" the STL shapes to make new sketches and extruding a new object. I'm also dabbling with Meshmixer and Meshlab. There's also some CAD conversion utilities, but they don't seem to be very successful either (limited set of source & destination formats, and the few that do have IGES or STEP output often refuse to work on most STL files.

I look forward to replies by smarter guys than me.


Once the mesh is cleaned up using the extentions I mentioned, it is much easier to edit the stl in sketch up then export it as a new stl.
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Re: How are you smart guys editing .stl files?

Postby cacb » 2016-Feb-Wed-12-Feb

WayTooManyHobbies wrote:I don't know about qualifying for smart, but you can open STLs in OpenSCAD and edit them as solid objects directly. Fair warning, there is a learning curve involved. http://www.openscad.org


I suggest those interested in this topic read the following discussion in the OpenSCAD mailing list archive:
http://forum.openscad.org/CGAL-errors-w ... 15928.html

In short, I state that using STL as intermediate storage with the intention of performing further booleans is never going to work well. The reason is that STL is just a topology-less collection of triangles and therefore very vulnerable to numerical issues, among other problems. This view is contested in the thread, but you can read it yourself and see what you think. The interesting part is that if we had a better format available, with explicit manifold or non-manifold topology, it would also be a much better basis than STL for printing multi-color prints from the same file.
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Re: How are you smart guys editing .stl files?

Postby Mooselake » 2016-Feb-Wed-15-Feb

cacb wrote:The interesting part is that if we had a better format available, with explicit manifold or non-manifold topology, it would also be a much better basis than STL for printing multi-color prints from the same file.

Well, there's AMF - but that just looks like stl with XML and curvy triangles from a quick google search. I remember reading something about a standards effort to produce the best solid model description file ever, but can't remember what it's called.

I've tried editing stl files in Freecad, but it wasn't a very productive experience. Fusion360 might work.

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Re: How are you smart guys editing .stl files?

Postby cacb » 2016-Feb-Wed-16-Feb

Mooselake wrote:
cacb wrote:The interesting part is that if we had a better format available, with explicit manifold or non-manifold topology, it would also be a much better basis than STL for printing multi-color prints from the same file.

Well, there's AMF - but that just looks like stl with XML and curvy triangles from a quick google search. Kirk


Although AMF isn't the ultimate format, there is more to AMF than what most people recognise immediately. STL has zero topology, nothing is really connected, everything must be inferred from coordinates. In AMF it is different, the vertices may be mentioned exactly once and the faces refer to the vertices. I.e. you have a basic topological model. That makes it possible to describe things you cannot describe with STL and the model can be interpreted exactly, without having to evaluate coordinates. AMF would therefore be much better suited than STL as a format for intermediate storage (re. the topic of this thread) or model exchange between different programs.

I have worked with meshes in other areas (Finite Element Analysis), and the way AMF does it is the conventional way to describe a mesh, even though that too is very much simplified.

With STL it is assumed you describe only the outer surface of the thing you have modelled. Such a model is called manifold, i.e. exactly 2 faces will share each edge, and each face has material on one side (inside) and no material on the other side (outside). However, it is useful to also consider non-manifold models, where some faces have material on both sides. Such faces are internal to the model, and could for example describe the internal boundary between two colors. You could do this with AMF, but not with STL.

So if AMF or something equivalent to it could replace STL, it would be a good thing.
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