Hi, I'd like to use Shapeways to print moulds for some lens prototypes I'm working on. The curvature is fairly subtle (say a 20-40 micron height difference from highest to lowest point). I imagine that even FUD is too imprecise for that if I build with the lens facing "up" in the z-direction, as according to this: http://www.shapeways.com/forum/index.php?t=rview&th=6108 &goto=32610 the layers are 31 microns thick. I could, however, rotate my mould 90 degrees, so that the precision that matters is on the x-y axes. What kind of accuracy is there in the x-y axes? I don't imagine that the minimum feature size is the correct number for this, as that speaks to the ability of the material to maintain a small ridge. Rather I want to know how precisely it will match my desired curvature. The surface will be gradually varying, so there are no fine ridges. Does anyone have any input? Thanks.