Great, Michael, works like a charm, thank you !

It's important to delimit the parameters of fileExport with ";" and inclose them in " ' " like here :

moi.geometryDatabase.fileExport(filename,'NoUI=true;Angle=12.0;Output=quads;Weld=true;Display=shadedwithedges');

Perhaps the script could be added to the script collection.

Another question
Is there a way to compute the minimum size of the exported object
for an uvmap size of, say, 2048 pixels ?
I want to keep my obj files as small as possible before being unwrapped and uvmapped in 3D Coat.

TIA