Mechanical Design, Fall Semester
For the Mechanicals, the first semester was spent primarily working out the best configuration for our project. Below are various approaches to achieving motion on three axes.
XY table, Z router
Advantages: This configuration allows the table to move in the horizontal plane while the router moves along a vertical axis. Functionally, this means the router, which is the heaviest component of the machine besides the frame, is relatively easy to support. Also, the router has a power cord, and this design results in minimal movement of the router, so the trailing power cord becomes an almost non-issue.
Disadvantages: Using an XY table means that the area available for the table to move in must be four times as large as the table itself (twice as long as the table in both the X and Y directions). This results in a large footprint, which is at odds with our objective for a small machine.
X Table, YZ Router
Advantages: Since the table only moves along one horizontal axis, the total footprint of the machine can be reduced. This is right in keeping with our goal of a small machine.
Disadvantages: Moving the router along two axes makes it difficult and rather ugly to control the power cord to the router. In addition, the weight and force of the operating router would create large stresses on the complex machinery necessary to support the router.
Advantages: This design includes a stationary table. This allows for an extremely small footprint - not much larger than the circuit board itself.
Disadvantages: This design is really complex to build. Having so many moving parts support the router means each moving part will have to be quite strong, resulting in a heavy machine. And the problems with managing the router's power cord are only magnified in this design.
Advantages: Since the table is stationary, the foot print of this design is quite small, which is a major positive. And best of all, this design just plain looks amazing!
Disadvantages: This design is exceedingly complex, not just to build, but also to control. In addition, it would be very difficult using this design to position a router with the precision we need.
We decided to go with an XY table design. Despite the disadvantage of its larger footprint, the advantages in build simplicity, router stability and power cord management make this the best design for our project.