3D Printed Hollow Clock [Tinkercad]

Seeing the ocean wave crash across the silky blue clock face on the thumbnail of the clock contest, my imagination was immediately sparked, and a wave of excitement overcame me with the idea of a new project. Going to the drawing board with no clue where to begin, I soon caught onto the idea of a hollow centered clock. Unlike traditional clocks where the pivot point for the hands is the center, this clock has no physical center! Instead, the hands are directly connected to a gear which they spin with, thus requiring no pivot point in the center. Through this instructable, I will be outlining the steps I took in order to design this clock so that hopefully you can be inspired to make one of your own! Happy reading!

• 3D printer - I used a Creality Ender 5
• Black Silk PLA - color choice based on preference.
• Gold Silk PLA - again, color choice based on preference.
• High torque clock mechanism - I bought mine at Hobby Lobby branded the "Clock Shoppe", but they can be found online.
• Clock hands - only the center piece that attaches to the mechanism is required.
• Superglue/hot glue
• PATIENCE!!!

**OPTIONAL** Digital Caliper - While not needed to complete the project, it is highly recommended in order to avoid dimensional inaccuracies, which could result in the failure of moving parts

Getting my inspiration from some projects I saw back in January of 2023, I saw potential for a clock that didn't require any fancy electronics or expensive software. I loved the look of the floating center, however in my clock I wanted absolutely nothing to be in the center, so I made my initial mockup of the model in Tinkercad, giving me a visual idea of the end product. From the initial prototype to my finished project, some major modifications can be seen, the most notable being the exposed gears in the finished project. The reason for this design choice is because it gives the clock more of a mechanical, machine type look and I found the gears to be visually appealing, especially being able to watch the gears turn and mesh together.

To begin with, cut off everything from the hands leaving only the center circles, or the parts that attach to the mechanism. After that, take measurements of both of the circular parts' outer diameter individually as they both have a different diameter. After that, take measurements of the entire clock mechanism in order to create a scale model within CAD.

The gears are the heart of the clock, allowing the motor to translate rotation to a specific number of rotations per minute, as to spin the hands, in order to provide the time.

To begin with, I used the metric gear from Tinkercad's design gallery, and added 60 teeth (for 60 minutes in an hour) and set the pitch angle to 30 and the module to 2.2. After that, I cut out a hole in the gear, and this can be however big or small you want, but I inlayed it around 7mm from the edge of the gear. By cutting a hole in the center of the gear, the weight of the gear is reduced, and consequently the material required, and print time is also reduced. In addition to the two larger gears, a smaller gear is placed in between the two bigger gears in order to transmit the rotation in the same direction as the clock mechanism.

In order to increase the dimensional accuracy of the clock and to be able to best design it so that it will print correctly, a scale model of the mechanism and the parts that attach to it is required. Using the measurements taken earlier in the project, create a scale model of the clock mechanism and, while not required, add color to it to help you distinguish the different parts. This whole mechanism can be modeled using just the cube and the cylinder from the toolbox. Following that, I designed the center circles taken from the hands so that I could design the part of the gear that clasps onto it. Again, use the measurements taken earlier using the caliper and model accordingly.

Following the design of the mechanism, a casing is required in order to stabilize the mechanism and to make it blend more naturally into the rest of the clock. To do this, I made a cube that was 5mm thicker than the mechanism on all sides and cut a hole ***.5 mm*** larger on all sides than the clock mechanism into the box. Instead of just taking the mechanism and cutting it into the box previously created, making a hole .5mm bigger on all sides allows for the mechanism to slide into and fit perfectly after printing. This prevents post print sanding. The hole that cuts into two of the walls is a space for the battery to go and allows access to it without needing to disassemble the entire clock to change it.

After having made the mechanism case and the gear to fit around the circular metal disks, now is time to fit them together. In the image above, you can see there is a bar running across the gear with a hole in the middle. This hole holds the metal circular disk in order to attach the gear to the mechanism. Remember, make sure the hold diameter is smaller than the diameter of the disk (called insetting) so that the disk doesn't just fall straight through. After doing that, line up the gears with their respective places along the mechanism. If you don't know where this is, place the physical disks on the clock mechanism and see where they fall. I knew that the hour hand was closer to the clock mechanism, so I color coded its corresponding gear blue and the minute gear red.

After aligning the first two gears, add two big gears above them (one will need to be offset to account for the depth of the top gear) and smaller gears in between. As seen in the diagram, if there were only two gears, the rotation direction would be changed from clockwise to counterclockwise, thus displaying the time incorrectly. To account for this, a smaller gear is placed in between to keep the final rotation direction clockwise.

In order to keep the gears rotating on track and not just slipping off of one another, rods are added through the middle, smaller gears to ensure that they only rotate and do not shift up or down. Supports with small rods also go along the upper, larger gears in order to hold them in track but not interfere with the rotation, and not adding so much friction that they can't spin.

After finishing all of the mechanical stuff, you can add any visual flare you want to the clock! For my clock, I added a front to the mechanism case to better hold in place and hide the mechanism. Additionally, I added a geometrical base by rotating rectangles with no center, going along with the hollow theme. I liked the open feel of the clock with the exposed gears, which was nice because it saved tens of hours of printing and lots of filament too versus making it enclosed.

Once I was fully confident that I liked my design, I began the tedious process of disassembling the clock and tweaking some features in order to make it fully 3D printable. Again, I printed these parts on an Ender 5 and the quality was good, meaning this is not a very demanding print. For the silk PLA, I found 215C for the nozzle temperature to yield the best results. For the smaller parts, such as the pins, a slower print speed and the use of a raft or a brim will be required to increase print quality and improve bed adhesion. After all of the parts are 3D printed, I assembled them starting from the bottom, working towards the top. I found that the gel superglue works best for the smaller parts, but hot glue worked better for the bigger parts like the base, larger gears and the mechanism casing. Please note for the hands, I changed filament in order to clearly display the time.

Through this process of making a clock, I have learned many valuable lessons that will translate into future design projects and into life in general. Although the process appears to be straightforward and leading only to success in the pictures, I found anything but that along this journey. More of the clock failed initially than I thought it would, whether that be failed prints or the print snapping. After printing gears and testing them, revising, and repeating, I finally found a distance between the gears that worked smoothly, and while still not perfect, they are certainly better than the original model. And when things didn't work for me, while extremely frustrating in the moment, they only showed me how much more room I have to learn and grow as I continue on with this design and others in the future.