When you print your test cube, do you do that solid or with infill? My experience is that infill can affect the precision.

I run at 80% for nearly every final and 20% for rough prints. Never tried 100% as it is wasteful to me. For what I need even my carriage for the printer 80% is more than sufficient.

yes... both machines same filament and brand at at the same extruder/bed temp. I think anyway. Using XYZpro on both machines, for a 235 extruder temp and 80 degree bed temp... although the 2.0 shows bed temp at ~60 degrees, but I think I remember reading somewhere that the 2.0 reports a 20 degree under temp reading for the set bed temp. i.e. even though the control software reports 60 degrees its actually 80.

If that is the case then the steps per mm are off on each axis on the machines and need to be calibrated. Not possible on stock firmware.

While I appreciate that the mechanics of FFM are such that you're not going to get items printed at exactly the size you designed, and that there's a certain amount of tolerance you have to plan for, I was surprised to discover the differences in the exact same piece printed on the 1.0 vs the Duo.

My part in my design program has the outside dimensions:
  x = 18mm y = 22.5mm z = 43.5 mm

The printed part has the following dimensions:

  x = 17.6mm y  = 22.2mm z = 42.9mm (1.0)
  x = 18.4mm y  = 22.4mm z = 41.8mm (Duo)

My expectation was that 1.0, Duo and even AiO... using the same technology would produce more consistent results across machines. Well so much for expectations. The problem is in wanting to create files for items that will actually FIT into other parts, and I wonder what kind of tolerances would be reasonable to assume. The x dimension on my part has a +/- .4 variance, which strikes me as quite a lot.

My question to the rest of you is what your experience in precision has been. Is the lack of precision what I get for buying a DaVinci... do other 3d printers provide more dependable/more tolerant parts? Do you think my variances simply indicate I need to do even more tuning up of belts and pullies and shims... or do I just need to accept something like a +/- .5 variance for anything I design?

Are both machines using the same color filament and brand? The machines will print down to .10 accuracy once you compensate for shrinkage in the filament once it cools.

You have to print a reference object of known dimensions. Let it completely cool and measure it. You then need to add or subtract the difference to your on paper or cad dimensions. Alternatively you could modify your esteps to print the object oversized when hot so it would cool to your dimensions. Much more trouble then modifying your drawing or cad design. PLA does not have as much shrinkage as ABS, but to print 15mm holes I have to design them at 15.45mm.

The problem you are seeing is as old as the industry and is an inherent attribute of our chosen medium. Every single roll has it's own shrinkage factor. Natural being the lowest as it has no pigment. I use natural for my final print on everything.

When I buy and load a roll or cartridge the first thing I do is print a cube that i made that is supposed to be 30mm x 30mm x 30mm with a 15mm vertical bore through it. Once it is printed and cooled I can measure it to see what the shrinkage factor is for that roll and adjust my designs accordingly.

This is a hobby after all.

My part in my design program has the outside dimensions:
  x = 18mm y = 22.5mm z = 43.5 mm

The printed part has the following dimensions:

  x = 17.6mm y  = 22.2mm z = 42.9mm (1.0)
  x = 18.4mm y  = 22.4mm z = 41.8mm (Duo)

My expectation was that 1.0, Duo and even AiO... using the same technology would produce more consistent results across machines. Well so much for expectations. The problem is in wanting to create files for items that will actually FIT into other parts, and I wonder what kind of tolerances would be reasonable to assume. The x dimension on my part has a +/- .4 variance, which strikes me as quite a lot.

My question to the rest of you is what your experience in precision has been. Is the lack of precision what I get for buying a DaVinci... do other 3d printers provide more dependable/more tolerant parts? Do you think my variances simply indicate I need to do even more tuning up of belts and pullies and shims... or do I just need to accept something like a +/- .5 variance for anything I design?