Hello,
I have seen lots of people using som nifty function checking if the item is solid or not and if not where to find the errors. Is there something like this to use in free web version?
I think my design looks ok in Sketchup but when slicing in Cura the “floor” is missing,
Looks like internal surfaces are the main issues? you can do some sections through to locate or view in x-ray mode.
Attached a corrected version if it works.
coin.skp (786.7 KB)
How do I enter x-ray mode in web version?
Thank you for the file but somehow the holes are gone now 
I think the fastest way to solve my problem is to redraw in sections and then put them together as whole image.
Sorry, x-ray not avail in web version.
Not sure why the holes are missing??
They show up for me?
There is an amount of cleanup but I don’t think it would take long to redraw it if needed.
Try these files. I cleaned up WR’s SKP file.
coin.skp (225.3 KB)
coin.stl (93.6 KB)
This is what I see when I import the STL to the slicer for printing. Holes seem to be fine.
I’m guessing you’re thinking of “Solid Inspector” extension, which is not available on the web version. Extensions are only available on desktop versions at this time.
The only way currently to verify “solid” in the web version is to make your object a group/component as is usual.
Then when you select the group/component, the Entity Info Window will report “Solid Group” or “Solid Component”. If “Solid” doesn’t appear before Group/Component, then you have some investigating to do.
It looks as if it will work 
I put it in my slicer and the result looks good. Thank you very much!
You’re quite welcome. As Ian said, in the web-based version, the only thing currently for determining if your model is solid is what Entity Info shows. He’s surely right that you’ve seen some people using Solid Inspector which is indeed very handy.
As much as possible, you can and should use modeling methods that naturally result solid shapes. Things like the internal faces in your model can be avoided, for example, by using a logical workflow. Also avoid creating stray edges which can create problems. For small things like those that are typically 3D printed, set the units to meters and work with them as if they were millimeters. STL files are unitless so it doesn’t matter that the model is drawn 1000 times larger than the real thing. You’ll just tell the slicer the units are millimeters.
Actually, the reason you didn’t see any holes when you tried WR’s file is he used (his likely default) Architectural units. When you exported his file, with model units and used millimeters for the slicer units, those holes would have a diameter of about 0.394 mm. Probably not printable.
FWIW, I noticed that some of the circles in your model were not drawn with the radius dragged out on axis. It’s a good idea to get into the habit of drawing circles by dragging out the radius on axis. It will result in better, easier to work with models. Especially when you have concentric circles or other geometry joining the circles.
…and in future if you have an issue with an stl it’s actually more useful to attach the .skp file so we can see what you used to create the .stl
