Cheers all, and hope everyone is having a happy and safe festive season.
Aaron, I just received a set of HO scale locomotive body sections that I designed from Shapeways. The material is the white and flexible, the quality is acceptable for what I need and to the level I expected in using a cheaper material (there is some visible stepping that can be cleaned up).They seem to have maybe got a little better then, but you're right about the axis rotations, and that is generally why I find their repeatability to be rubbish.
Using digital callipers (not the greatest, rated accuracy of 0.02 mm) and referencing against the digital model. In 2 axes, walls below 2 mm in width are consistently +0.05 mm greater than what they should be, above 2 mm they are accurate to the digital model (to the level I can measure at). In the vertical axis (assumed from the stepping pattern) there is an approximate +0.1 mm (range +0.09 to + 0.12) increase. For my uses this is perfectly fine and is well inside Shapeways stated accuracy for the material (± 0.15mm, then ± 0.15% of longest axis). The biggest problem with Shapeways is that there is no consistency between printings of which axis which, that is one of the horizontal axis could be the vertical next time around. In this case it is not an issue but if it was something with ultra-fine detail and especially if it fitted together it might be a major one as one printing may be fine and the next printing problematic.