Prepare to print shows extra layer of plastic in model

[codejoy]

I have a simple little model I thought would be fun to print from here:

https://www.thingiverse.com/thing:2750463


going on an ender 3 pro. Never had any trouble before, in this model use settings suggested: .2mm height and 20% infill, yet when I goto prepare print, there is like a square of plastic that shows up in the preview and when printed. Not sure how to get rid of that. Image attached for reference.

[reddadsteve]

I looked at the model itself and it has a few non-manifold segments.

When I slice it I get some stray first layer issues as well, different than yours due to a different printer setup, but still wrong. Every slicer handles non-manifold segments differently and sometimes the model may slice correctly and sometimes it won't. So, in this case it does not get sliced as hoped for.

You might be able to fix the model by running it through netfab.

Teamwork,
Steve

[dkightley]

This is a typical Thingiverse file.....filled with errors!.

As an alternative to NettFab, if you're on Windows10, load into 3DBuilder and it will be auto-repaired...then save as a .3mf.