Bottom Layer Fusion

I was trying to figure out the 3D Printer's (Mendel 90) tolerance for moving parts when printed with single extruder with 3mm PLA. For this I created a 3D model (Cylinder in a Cube) in AutoCAD, and made a few variants of it. Each of the variant had different clear spacing between the cylinder and the wall of the cube. I had a total of 9 cubes with clear spacing ranging from 0.2mm, 0.25mm, 0.3mm, 0.35mm... to 0.6mm. They all printed perfectly well, and I thought the 0.3mm clear spacing was ideal, however the bottom layer of the model seem to be fusing together.
NOTE: The 3D prints in the image have not been completed to 100%, so please ignore the rather odd looking infill


TOP VIEW


BOTTOM VIEW

My SLIC3R settings -
Layer height:
Layer height - 0.15
First layer height - 0.1

Horizontal shells:
Solid Layer - 2 (Top), 2 (Bottom)

Infill:
Fill density - 17%
Fill pattern - Honeycomb
Top/Bottom fill pattern - Rectilinear

Modifiers:
First layer speed - 15%

Skirt & Brim:
Loops - 2
Distance from object - 6
Skirt height - 1
Brim width - 0

Temperature:
Extruder - 195 (First layer), 185 (Other layers)
Bed - 75 (First layer), 60 (Other layers)

I hope I have given enough relevant information from the settings I am using. If you need any other values in particular, please ask.
Am looking forward to hearing a few suggestions / advice. Thank you.