How accurately can the Fab@Home build an object?

For the Model 1 and 2, the accuracy and repeatability depend upon the material you are working with (does it flow?, does it change shape with time?), the time you have spent tuning the deposition parameters, and the nozzle diameter, as well as on the positioning accuracy and repeatability of the machine. For a "good" material that does not flow, the X-Y (layer plane) resolution is roughly twice the diameter of the nozzle, and the Z (height) resolution is roughly equal to the nozzle diameter. In theory, this holds until you approach the positioning resolution of the machine. For the Model 1 it is roughly +/-25 micrometers. The accuracy and repeatability of the positioning system of the Model 1 have not been measured. At a rough guess, without special attention paid to setup, the repeatability will be roughly +/-100 micrometers. The Model 2 can operate at a higher speed for the same resolution as the Model 2.