The 3D4D Dreambox Emergence Challenge asked GrabCADrs to develop highly cost effective sunglasses for children as a preventative measure for Pterygium (known in the US as Surfer’s Eye.)
Matthew Hayto put together a quick summary that sheds some light on the manufacturing constraints their team and Challenge participants needed to overcome. The winning glasses and the full results are available on the Dreambox Protective Sunglasses for Children Challenge page. Dreambox Emergence was very impressed with the quality, variety and creativity of the 3D4D contest submissions.
We’ve gathered our favorites, but wanted to shed some light on our reasoning, since we know not all entrants had access to a 3D printer to prototype their designs, and printability was one of our deciding factors. - Matthew Hayto, Dreambox Emergence
Fused Deposition Modeling
Most consumer 3D printers use a process called Fused Deposition Modeling or FDM. While this makes additive manufacturing accessible and affordable, there are some serious limitations to the shape of a print such that it is not only possible, but also reliable (our end goal here).
Layers
The key to FDM is designing something that can be printed in horizontal Layers. If a layer is larger than the layer below it, the filament has a very difficult time solidifying in place, and will often warp (printing software is able to design in supports to allow for “overhangs” in models, but we’re aiming to use as little of this as possible, since it hasn’t proven as reliable as printing flat models). Because of this, the first model below would print much more effectively than the second, which would require supports along the entire frame to print in place. While the second design is very effective for solving the problem we face with eye irritation in Nebaj, printing it en masse would take significantly more material and post-processing.
Below, we’ve printed the first layer of a set of glasses arms. Since the bottom surface of the model is completely flat (and flush to the build plate), its a simple design for an FDM printer to handle.
Hinges
One element of the challenge that was deliberately left open-ended was the hinge portion on a standard pair of glasses. Hinges allow for glasses to be stored safely, with a lower risk of breaking, but are also intricate and challenging to print using FDM technology. We saw 3 main designs:
Snap-in hinges, in which the arms snapped to the frame using a number of variations on small nub and recess joints, proved successful in a number of cases, but ultimately many required a degree of post-processing in order to fit properly, mostly due to the imprecision of FDM printing
Pin hinges, which called for metal pins to be threaded through corresponding holes in the arms and frame were widely successful. The obvious downside here is sourcing pins, since the fewer elements to assembly required, the better for our purposes. We’re investigating further how much of an impact this could ultimately have.
No hinges, many designs featured no hinges at all, and a continuous frame/arm assembly that prints in one piece. While conceptually this is reasonable, printing vertical arms was challenging (see final video).
Frames
This design was attractive since it was overall low volume (meaning low cost to manufacture) and very simple (no hinges to complicate assembly). The first video shows the face-down frame assembly in process.
In the second video, the frame is complete and the printer has started on the arms. Because such a small amount of filament is deposited at each end, a systematic drip has started after each one, allowing a second arm to grow out of nowhere. Furthermore, this process is extremely time consuming, since most of the print head’s time is spent in transit, moving from one arm to the other. Another advantage of lay-flat designs is that the print head is almost always depositing filament.
We hope this information helps GrabCADrs and anyone else designing for consumer 3D printing machines build better products. You can view, download and print the glasses that took finalist positions in the Challenge.
