I was attempting to print the More Alien Flora model from Thingiverse, and the printer was behaving oddly. The first layer consisted of a number of scattered spots of plastic in an arc halfway around what would be the edge of the print, followed by the second layer being deposited ‘in air’, resulting in it not being flattened as it was extruded, leaving it standing proud of its ‘proper’ level in the print, with the printhead dragging the nozzle through the previous layer when it started the next layer (image 1 , image 2 – large images).
I thought perhaps that the model was not flat to the build plane, and loaded it into Netfabb and cut 0.1mm off the bottom, exporting it back as an STL file. Printing this file resulted in the same scattered blobs of plastic, but this time all the way around the perimeter of the print. I stopped the print as it started the second layer, not wanting to waste further filament on what was going to be a failed print.
I was curious, so I loaded the original STL file into FS, but this time I went into the advanced settings and switched the slicer from Slic3r to Cura, and started the print. The first layer printed normally, and subsequent layers have been printing without issue.
It appears that there is something in the STL file for this object that Slic3r throws up its hands at and outputs garbage gcode, while Cura handles it without a problem. If this is a reproducible error with Slic3r, it may need to be reported.