Alex info
Suggestions;
Unit display precision to at least .xxx;
Deselect snapping;
Deselect color by axis, only shows parallel not on dwg axis use inference engine ;
Keep entity info open per TIGs suggestion in SCF. As noted in attached it reports diff lengths on right vs left;
Build vol for RepRap is 200x200 mm if memory is correct. Just FYI you can scale up and down to fit.
As noted some time copy & move out edges helps find problems when faces not forming. because of required modeling tolerance. You will think closed loop but not really;
As noted before for your machine and use of FDM has possible issue with building unsupported structure. Link I post has info to help you under stand. Slicer can add infill to help also.
board3dcover_mac1_2014.skp (76.8 KB)
Additional Info; Selecting back face: Then select option align view gives view perpendicular longitudinally of item. Doing that you can see the non symmetry so, cut in 1/2 and mirrored so both sides are the same.
050216_1400_mac1_2014.skp (65.3 KB)
Good Luck