Folks have made all sorts of 3D printed machines before, but what set this project apart is that our clock requires no assembly by humans. This is remarkable for a number of reasons, mainly in that we are severely restricted in materials, in this case in one type of UV-cured resin from the 3DSystems Projet 3500 HDMax. All of the different pieces of the clock, from springs, to gears, to bearings, all had to be made of this same resin, and printed in place by the printer. Clearances were developed via the support material that is cleared away in the normal post-processing of 3D printed devices; for this machine wax is used as a support material and then melted away in an oven.
Since the resin the clock is printed from is translucent, it is difficult to see in photos, so I'll use some renders to highlight various pieces. The clock was designed in Solidworks with engineering calculations done in MATLAB. The core components are the case and packaging, the power input, and the frequency input and regulation.
Due to the limited size of the print area of the 3D printer, we made a design that would print in a folded state, then unfold for use. On the left the clock is as printed, 5.8" x 8.0" x 8.7", and on the right is the clock in operational stance, 4.6" x 10.9" x 8.7".
Several design options were considered for the case, from a fully-enclosed box to the skeleton design that we settled on. A fully-enclosed box would reinforce the fact that the design was in fact printed with no post assembly, but as it would obfuscate all of the interior design, so we went with a skeleton case.
The power input and transfer system starts with a helical torsion spring, or mainspring, that is wound via a key (also 3D printed, of course). We initially were skeptical about the ability of a 3D printed material to act as a spring, but after a rigorous set of testing we determined that the material (VisiJet M3 Crystal) does in fact work great as a spring and lasts many duty cycles. Once wound, the spring power is transferred through a freewheel into the gear train, driving the hour, minute, and second hands of the clock.
In order to move time forward, we used a pendulum and escapement system, which performed the dual duty of keeping time moving at the correct rate, and keeping the spring from unwinding instantly.
All in all, it was a great project and a great learning experience to not only work on such a complex system, but to move forward in such an uncharted realm of engineering!