MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.
Z axis is not possible to modify without changing most of the printed parts and many rods. Actually it is not so crucial as Z axis is used only when layer is changed and the backslash of gearbox don't make artefacts on prints. If you want to speed up the movement of Z axis, it would be a better idea to change Z axis to use trapesoidal rods 6mm dia 12mm pitch. It will be less complicated as only two printed parts have to be changed (along with the threaded rod).That will result in 3mm/s with resolution of 0.003mm/fullstep. I have the rods and nuts at home ready for this upgrade, but not enough time to make models and publish this.