3D Printed Prototype(s)

Over the past two weeks we've 3D printed a number of iterations of our Yo Yo to test out a number of different features. These features included:

1. The press-fit for the finger-stop on our Yo-Yo (refer to this post for more information)
2. The retaining ring to hold down the thermo-formed part
3. The sizing for the bearing and bearing post
4. The torsion spring to Yo-Yo connections

Below are a number of our 3D printed parts:

Figure 1: Version 1 - FDM 3D Manufacturing

Figure 2: Version 2 - FDM 3D Manufacturing

Figure 3: Version 3: SLA 3D Manufacturing

Through out prototyping process we moved from using FDM printing to test the rough fit of the first iterations of our parts to the higher accuracy SLA printing for our most recent iterations. As part of the prototyping we also took images comparing the FDM and SLA finish on our Dial.

Figure 3: FDM Resolution (layer height & thickness)

Figure 4: SLA Resolution (layer height & thickness)

And a video of our most recent SLA printed version of the Yo-Yo. This version includes the bearing and spring setup we'll have in the final design, but does not have out thermoformed part or the finger-stop.

We were able to test each of these to the point where we feel comfortable moving forward with our design. During this process we changed a number of things including the size and form of the finger-stop press fit, the thickness of the retaining ring, the geometry of the bearing post, and the attachment points for our torsion spring. 3D printing was invaluable in our design process because it allowed us to quickly test our ideas without putting tons of effort and time into testing out our ideas.

Overview of the Call Me Maybe Yo-Yo

Yo-Yo Design:

The vision of team Call Me Maybe is to design a working Yo-Yo based off of the aesthetic of an old-style rotatory phone – you can see the full assembly in Figure 1. The Yo-Yo will be comprised of four injection-molded parts (finger-stop, dial, retaining ring, base), one thermoformed part (number pad), and other hardware including a dowel pin, torsion spring, and bearing (see Figure 3). The bearing, dowel pin, and spring will be used to simulate the spinning dial on a real rotary phone. The parts will be assembled almost entirely using press fits. The retaining ring will press into the base to hold the number pad in place, the bearing will press into the underside of the dial, and the dowel pin will press into the bearing.  The torsional spring will then be integrated on the dowel pin, with its two points of contact being on the underside of the dial and the inside of the base. Finally, the dowel pin will press into the base, completing the half assembly.  The two halves will be connected using a set screw to complete the full assembly.

Figure 1: Yo-Yo Assembly

Figure 2: Exploded Yo-Yo Assembly Isometric

Figure 3: Exploded Yo-Yo with Labeled Parts

Design for Manufacturing Considerations:

The major considerations for our Yo-Yo were deciding how many and what parts to injection mold or thermoform. Eventually we settled on making the 2D shapes in our Yo-Yo out of thermoformed plastic and the dense 3D features from injection molded parts.

When designing using the thermoformed part and the injection molded parts we had to make sure to give each of our parts the correct sizing to allow for a nice interference fit between the parts. This is the most important design consideration – without these interference fits our Yo-Yo would not fit together. Examples of this though process can be seen in out retaining ring – this interference fit is used to hold the thermoformed part in the Yo-Yo. Similarly when designing the “Finger Stop” on the face of our Yo-Yo we needed to make sure that the interference fit was dimensioned correctly for the size of the small part.

Finally when designing parts we tried to use as many circular features as possible – this allows us to use the lathe to create the tooling for injection molding which will greatly reduce our time machining/fixing our molds. 

Specification Sheet:

Specifications for each Yo-Yo part and the full and half  Yo-Yo assemblies are given in the following chart.

Team Gantt Chart (w/ link):

https://www.dropbox.com/s/9l5harj9kx8vs9f/GanttChart.xlsx?dl=0

Thermoform Part Testing

Over the long weekend, we tried making a test thermoform piece with raised numbers on it. In the overall yoyo design, this piece sits behind the dial. The numbers have to be really small be seen within the holes of the dial (5/8" diameter), so we were concerned they might not form well and wanted to see if it was feasible before we committed to a design.

Here's a screenshot of the mold design that we printed:

We 3D printed the test mold on the Form2. Here's a video of the print (huge thank you to Dave D. for shooting it, and for dispensing the best advice for mold design and 3D printing!).

Here's a final photo of the test thermoformed piece.  

The numbers came really sharp! We're hoping to use 3D printed molds for the rest of the thermoforms during our actual production as well, to preserve the sharpness of the corners (as opposed to machining our molds). The next step is to figure out how we're applying ink to the raised numbers. 

Introducing Team Call Me Maybe!

                Team Call Me Maybe is here for the Fall 2016 2.008 season and all reports seem to indicate that this team of six will surely be turning heads at the upcoming 2.008 yo-yo exposition.  Team members Elliot Owen, Travis Libsack, Kerri Wu, Kyle Pina, Lindsay Epstein, and Revanth Damerla have worked together to develop a revolutionary rotary phone yo-yo design that is sure to create childhood nostalgia.  Consisting of four injection molded parts, one thermoformed part, and also including newly discovered “spring” technology, the design is intricate yet simple.  Stay tuned for developments as team Call Me Maybe makes its way through this year’s 2.008 season.