It seem to me that poldek have tightening problem in one belt, meaning that backlash exist. Perpendicularity of the belts should not be important (it is symmetrical for first and second belt). Different tightening (meaning small difference in length) have ending effect that motor from more tighten side could "still" the steps...by djordjp - CoreXY Machines
Nice thread! Since I saw design of Buccaneer 3D printer I am planing to make something similar. My budget is silly tight and I throw out linear sliders replacing it with some kind of DIY sliders with coreXY. Tightening will be with two of ball bearings. Part of Sketchup drawing have all crucial parts. Metal plate is from laser catted 3mm stainless steel. Working area is 200x200mm, 200mm higby djordjp - CoreXY Machines