does anybody know the best and the cheapest way to convert a Zbrush 3.1 OBJ file to a STL file?
The simplest way I found is to import the .obj to Rhino 4 and export it as a .stl. I tried some other softwares and I think Max does it too, but Max crashes because of memory as my polygon count was high.
I dont think there is quality loss using this method, but I dunno how cheap that is! ;)
Why convert? Why not export from ZBrush AS STL? 
http://www.zbrushcentral.com/zbc/showthread.php?t=071266
I think ZBrush 3.1 Exports only .obj. Thats why he might ahve asked.
Maybe I’m wrong, I’m new to Zbrush. :o
That’s why I linked to that thread. The 3D Print Exporter is a new, free plugin that lets ZBrush export STL and VRML.