Why Can't I slice Wheels or Rims face up without getting a plug/disc covering it?

Has anyone tried to print wheels or wheels and tires face up? Why do three different slicing programs (MakerBot Desktop, Cura, and ReplicatorG) all put an extra disc or plug of material over the top of the wheel, completely blocking it?

See also photos...

Here's a photo of the STL

Attachment 8235

These next images are progressive screen captures from Cura - MakerBot Desktop does the same thing.
Attachment 8234 so far so good...

Attachment 8236.... wait, what? Where'd the disc come from? The settings are no support material!


Attachment 8238 total fail.


Why does this happen when I select no raft and no supports?

Printer is a Flash Forge Creator Pro but I don't think its the printer.

Attachment 8239 ....here's the STL file

Pic of failed Prints, facing up. The wheel is in there, but it's covered with the unrequested plastic.
Attachment 8240

Am I crazy?

Oh yeah and I am using the STL import/exporter in Sketchup.

I also just downloaded Slic3r and tried it, also total fail with Slic3r.

Thanks!

I have the same issue with Simplify3D.

Its a problem with your model. You have an open edge or something.

I ran it through netfabb basic (free download), and now it slices fine.

Oops actually Cura and MakerBot Desktop is still showing the disc despite the repaired file. It actually changed the model at the base of the wheel and the center cap as well.

Hmm...the repaired file slices fine on Simplify3D for me.

You can try fixing your model in sketchup or try makeprintable.com

Thanks for the help guys. Still not there though.

Here's another STL that doesn't work and is a wheel. I borrowed this from a Karmann Ghia model on 3Dwarehouse for sketchup. Same problem different wheel.
Attachment 8248

Sketchup is awfully particular whenever I make or edit solids, so I'm finding it hard to believe that there's something wrong with the model I made, and it just so happens to be the same, exact, identical problem with some other wheel (the wheel from the Karmann Ghia). Just doesn't make sense that it's the models.

For the folks that ran the model through netfabb, here's the sliced screen captures I see...
Attachment 8249 only 5 lug holes now
Attachment 8250 filling in the area above the wheel lug flange
Attachment 8251looking like a wheel again
Attachment 8252 oops here's the disc again.

Whether Simplify3d does this properly or not, I've gotten in contact with their tech support. I'm hopeful! I don't currently own their software but would consider it if their product fixes the issue.

Does anyone know if Replicator, Cura, MakerBot and possibly others have a less than ideal slicing engine (or engines)?

Thanks,
Kris W.

Hi Kris,

I believe that the problem is with the stl model. I use Simplify3D and have made a number of similar wheels with no problems. When I loaded and sliced your stl and the repaired stl I had the same problem namely the flat disk on the top. I did a cross section on the stl model and found it to have a lot of oddly intersecting thin-walled surfaces which I suspect is the source of the problem.

Chris

Kris,

I modeled a similar tire and made a cross section. The thin walls of my stl file are clean intersections with no walls passing through another. The slice was good with no top plate. I am convinced that the stl model you downloaded is causing the problem.

Chris

Kris,

Here is the stl file I made. It is larger than yours but you can slice it for an example.

Attachment 8280

Chris

Can I suggest you stop using sketchup - which isn't a solid modelling program and start using something which is.

The autodesk freebies are a good place to start: http://www.123dapp.com/

Also openscad - my favourite.