Exporting .obj for 3D printing


#1

Hi,

I ordered a 3D printer today and so I started with modeling the first object to print. I managed to create a cup but when I export it to an .obj file and open it with the printing tool “Repetier-Host” the cup is flawed.

the cup in SketchUp:

Anybody got an advice how to extract objects from SketchUp for 3D printing? (Both tools are recommended by the company which developed and sells the printer)


#2

apparently new users are only allowed to post 1 pic in a post so here is the second one:

the cup in Repetier-Host:


#3

You ‘cup’ is probably not a ‘manifold solid’.
If you temporarily make its geometry into a group Entity Info will say ‘Solid’ in the top bar if it is.
3d-printers want solids.
A ‘solid’ is an object containing only edges and faces and every edge must have exactly TWO faces - no fewer and no more.
So, no nested groups or components, no faceless edges, no edges with one face only [e.g. around a hole or forming a ‘shelf’], no internal partition faces where some edges have three or more faces, no otherwise solid parts meeting on a common edge where that edge then has four faces, no overlaid facets [more rare but possible]…
Part of your handle has a face oriented backwards - you should never see an ‘blue’ back-sides’ !I suspect that parts of you cup have internal partitions - e.g. where the handle joins the cylinder, of where its central seam has a common internal face ?
Edit the group.
View with Hidden Geometry ON., and/or use Xray mode and/or temporary Section-Planes to access the internal parts and manually delete problematical facets etc.

Thomthom made a Solid-Inspector plugin which highlights such ‘un-solid’ problems.
I have SolidSolver which tries to fix them - although it is quite possible to make an insoluble object! - so manual fixing is needed.

Once you have a ‘solid’ group you can explode it in the knowledge that the exported geometry should be compatible with 3d-printing.

Incidentally - OBJ is one format, but STL format is more standard - there is an Exporter freely available in the Extension Warehouse…


#4

thanks for your help, TIG. I installed Solid-Inspector and redone the handle, it was pretty messed up.

It works fine now. I also installed SketchUp STL and exportet it in .stl. I already noticed, that most print files are .stl but I didn’t know that you can add .stl format to SketchUp as an export option

.


#5

Hooray !

Now… you might want to look at increasing the segmentation of the circles used to make the cup’s cylinder, and also the handle’s arcs…
Otherwise I suspect that the3d-printed result might look somewhat ‘faceted’.

You need to change the segments when you first creating the arcs/circles [NNs typed as you make it], or soon after in “Entity Info” - BEFORE extruding the curves into a 3d form. Because once it’s 3d you can’t change it.

However, please don’t “go mad” - the default circle of 24s might be fine upped to 36s or 48s - making it ‘hundreds’ will show no benefit at this size ! It needs some trial and error…


#6

Thanks sir, that was useful!