# 3D Design / 3D Scanning / 3D Modeling > 3D Printing Slicer Discussion >  Slicer adds non-existing top layer to model (STL)

## flemming89

Hi,

I have an issue when exporting my STL file from Rhinoceros to Cura or Slic3r (and probably other slicers). In "object" view in CURA, the hole is there as it should be, but when I slice it, a top layer is created stretching over the hole. 

I have tried different kinds of resolution in my STL export, binary and ASCII, changed to .OBJ export. None of which did help. I have no clue what is going on, so I hope for some suggestions here.

2019-01-19 15_29_22-Kiosk_v1.3dm (96 MB) - Rhinoceros 6 Commercial.jpg2019-01-19 15_39_43-Ultimaker Cura.jpg

Thank you

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## curious aardvark

you need to make sure that you have '0 top layers set in the slicer. 
There are settings for top and bottom layers and side walls. 
Usually set somewhere between 1-3.

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## flemming89

Thank you for the suggestion. The setting is found under "Shell" in CURA, but unfortunately it did not solve the issue. It just removes to top layers and adds infill.
2019-01-19 16_29_29-Ultimaker Cura.jpg

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## fred_dot_u

You may have a non-manifold model. Consider to open it in Meshmixer and use Analyze/Inspector to see what is presented. Rhino isn't the "usual" 3D modeler for 3D printing and may not prevent you from creating non-manifold models. Self-intersecting faces is another failure point for some 3D modeling software, i.e., SketchUp that will create models that won't slice properly.

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## flemming89

Thanks for the reply, I did not know of that tool.
I ran the  inspector i MM, which did reveal a lot of flaws. It did however  recognize the hole in the model as it should be, so I still don't know  why CURA wants to print over the hole. Maybe it is simply a poor model,  as it was exported from a building model not made for 3D-printing.
2019-01-20 09_37_06-Autodesk Meshmixer - Kiosk_E00_v2.stl.jpg

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## fred_dot_u

Did you use the repair feature of Inspector? Many times when a model has as many errors as indicated in the image you've provided, the repair feature completely destroys the original design. If you'd care to attach the STL file, I can take a look at it for any apparent (repairable) flaws.

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## curious aardvark

might be worth installing flashprint, using the repair tool and exporting as .stl

that and simplify3d fix probalems really well - but flashprint is free :-)
It's also useful fur cutting models into bits and turning photos into extruded shapes, stamps, vases, globes etc.

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