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merddyn

STL files show okay but don't print okay

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Hi,

A friend made some STL [sKP] files for me with Sketch Up. They load okay in Cura but don't print despite showing they have sliced okay.

I have tried using Slic3r and when file loads whole sections of the walls are missing and are triangular instead of rectangular in places. It reports that it has fixed hundreds of manifold areas.

I have tried Rhinosceros 5 64 bit and GOM 7.5 SR2 to attempt to sort these problems out manually as it appears the automatic fixing of errors selects the wrong lines as the outer and inner edges. This shows up well in GOM where one wall will be shown with the diagonal on the top being part of the outer wall instead of the parallel one to the other, and in some case at the corner posts using the diagonal in the post instead of the parallel inside and outside lines. You can even get a diagonal from say the topinside right corner to the bottom outside left corner becoming an edge of a wall.

Have tried manually deleting incorrect mesh lines but this only allows a small number to be removed unfortunately.

According to Nettfab it says there are 180 triangles, 318 edges and 80 points. It has a big warning sign on screen when it loads although it claims the unit is 100mm x 100mm!

Now according to my working out and looking at the drawing there should be 32 points for the four posts 10mm x 10mm [8 each, four top and botton] that are set on top of a 100mm x 80 mm x 5mm base and 8 for each of the four walls that are inset 2mm from the edge - another 32 - giving 64 points in all. The walls are 5mm thick and 35mm high.

The top of each post has, correctly, 8 points - 4 for post angles and 4 for where two walls attach giving 32 in all. The bottom of each post has 12 points giving 48 in all. The problem is how the mesh triangles connect them AND MORE IMPORTANTLY how the slicing programs read which are the lines that are the real edges, and which are meant to be internal lines.

I have replicated part of one model - one post on base - and printed with no problems.

If anyone has any ideas I do have small jpg images to illustrate, but haven't worked out how to post them.

Thanks for any help offered. Can send images to you if you think they will be of use.

Cheers

Garry

 

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Sketchup is great, but it is not a solid modelling (3D manufacturing) tool. Creating solid models with SketchUp is possible, and easier with the pro version, but even then you need to be careful. Missing walls is a classic sign of a non-watertight 3D model.

What kind of shape is it? You might find it easier to do it yourself. If the shape is simple I would use OpenSCAD.

Yes, a picture of the model might be useful.

 

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Hi Don,

Thanks for reply.

It is a simple square item 100mm x 100mm and 35mm high. Can easily do myself and get it to work. My friend was trying Sketch up - He does lots of architectural drawings and 3D animations - his business, and we are looking at going into producing models to accompany.

It also seems to insinuate that there are two models superimposed - the other 100mm x 80mm but only in the floor area :sad:. He swears he only drew one, so who knows. The tower is in 7 files, and the roof shows as only 100mm x 80mm, but each other is 100mm x 100mm.

This does actually show as such in Nettfab Studio, so I'm inclined to agree with you - its Sketch Up. I actually asked him to use OpenSCAD, but try telling someone how to suck eggs that's been doing it for years :smile:))

Cheers

Garry

 

Sketchup is great, but it is not a solid modelling (3D manufacturing) tool. Creating solid models with SketchUp is possible, and easier with the pro version, but even then you need to be careful. Missing walls is a classic sign of a non-watertight 3D model.

What kind of shape is it? You might find it easier to do it yourself. If the shape is simple I would use OpenSCAD.

Yes, a picture of the model might be useful.

 

 

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Well, that is one of the things that makes SketchUp not a solid modelling tool. SketchUp will quite happily let you have objects which intersect, walls with 0 thickness, enclosure surfaces missing altogether etc. With great care you can avoid these defects, but you would have to have this in mind from the moment you started to the create the model.

I do now try to make all my SketchUp models watertight, even though I only currently use SketchUp for woodworking designs, not 3D printing.

p.s. Does your friend make use of the Outliner Window feature in SketchUp? I use it zealously, making sure that all model components are part of a named group or component. That way I can easily enable and disable drawing elements - and it should be easy to see objects that are in the outline but not obvious (e.g. because they are hidden inside something else).

 

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