I'm printing some gauge blocks to set the height of a focusing lens in a Lasersaur. I'm used to the shrinkage and expansion problems with ABS and PLA, so I will print a test cube of N mm then measure what is actually printed and change my model. I'll print at 20mm cube, measure the X, Y, and Z, and discover it's a 20.5 x 20.4 x 20.6 mm cube and adjust my model for that particular media and printer.
However, I've run in to a really strange problem with Simplify3d, the BigBox, and Edge.
My 20mm cube measures out at 20.25 x 20.16 x 20.84. X and Y aren't an issue with my gauge, but the Z is off by almost a mm. That seems odd, but when I try printing the smaller 17.3mm test cube, Z is off almost a full mm. My 17.3 cube is 17.36 x 17.41 x 18.3. I've tried printing it at .2, .19, and .10 layer heights from a .40 nozzle and I see the same errors. I've done test prints with the defaults for spoolWorks Edge Fine/Fast and seen the same error.
When I print the actual gauge (which has a block and an upper alignment panel, see the attached STL) I get the same 1mm error on the gauge, 18.3 instead of 17.3, but the 40mm alignment piece is only 40.8mm tall. My 20mm test cube was also .84mm too tall, so I think there's one bug/problem causing these errors.
Any ideas on where to start debugging this? I've imported the STL in other apps and the heights look correct, so I don't think Rhino isn't f'ing up the STL export.