When I export my model to .stl file for 3D printing, the top face is missing

I cannot get the top face on this model to appear in Simplify3D, my slicer of choice.

I have made a Component of the whole object, found and fixed a few strange features inside the model, but to no avail.

I’d really appreciate some help please guys…

Thanks in advance,


PS Unable to upload the original .skp file - too largeTPM Coaster Rev Aug 2016.skp.zip|attachment (1.7 MB)

The faces of your model are reversed. You need to correct the face orientation by selecting the geometry, right clicking on it and choosing Reverse Faces.

Reversed faces:

Correctly oriented faces:


Hi Dave.

Thanks so much for this, and so fast!

The two screenshots look the same - how could I tell this had happened (is it the orange colour)?

Thanks again.


They aren’t the same, the color indicates the face orientation. You have modified the back face color from its default blue-gray to orange as shown in the style thumbnail. The back face color is shown on the cylinder while the front face color is shown on the box with the sloped top.

So the white faces show what it looks like after correcting the face orientation.


Thanks so much - the model imported fine now. I’ll bear this in mind on future (or stop fiddling with colours!).i
Most grateful…

Kind regards,


Glad you got it working and you’re welcome.

You can fiddle with the colors (just don’t make them the same) but you need to stay on top of face orientation as you go. If it’s 3D, only front faces should be visible.

FWIW, I use a green back face color because it is easier for me to see it. On one of the laptops I use, the shaded front faces tend to look like the default blue gray back face color so the green takes care of that. I find even just a couple of pixels of the green easy to see.

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Nice tip, thanks.

Many other 3d modelling application will not render the backside of polygons by default. SketchUp is a little different in that it always render the backside. That’s why people run into issues some times when exporting to other formats like STL where the direction of the face matters.


Thanks very much.

I’m learning fast here!


Hello Dave,
I have a similar issue like Jonathan’s and I followed your post / advice of reversing the faces. However it hasn’t worked for me and in my case few walls are still missing. Could you help please?

Upload the SKP file so we can have a look.

R home WIP.stl (778.5 KB)

Upload the SKP file instead.

R Home WIP.skp (278.1 KB)

So from this thread, you know that you need to have correct face orientation in your model.

All those blue faces need to be reversed so you have only white faces showing.

Hi Dave,
That’s right and I did reverse a few faces to check the same. However it still wasn’t showing the walls in the layer view in my CURA. I could certainly make everything white and then revert to you.

I have reversed it Dave, but still the walls are not showing as 3D printable. Are we missing any other issue that needs to be addressed?

There’s so much wrong, I don’t know where to begin. There are internal faces that need to be deleted, intersections that need to be made, edges that aren’t attached to anything, walls with no thickness, and gaps between areas where there should be no gaps.

How did you draw this whole thing in the first place?

Edit: I spent an hour or more cleaning up the mess and I’ve made a solid component of it. Look at this:
R Home WIP (1).skp (238.9 KB)

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Many many thanks Dave, I am very pleased to see the corrections. That’s extremely kind & gracious of you. I realise my mistakes.

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