I learned how to use SolidWorks in high school robotics, and, considering that my final project idea is a CNC mill, thought that the ability to make complex assemblies would be important.
For this project, I looked at a lot of the work from the Machines that Make project and an online forum written by hobbyist CNC builders. Having the spindle move in three dimensions with respect to the stage is difficult because it means that either the workpiece or the spindle must move in two dimensions. The image to the right is of my design for the spindle carriage, which moves in the X and Z dimensions. It currently has a couple of flaws that would make the CNC as currently designed not very good, namely that the spindle would only be attached to the 1"-tall plastic piece in the middle, and that the nut for the Z-axis leadscrew doesn't currently fit between the two Z rails.