3d printed squishy turtle – design process

This deceptively simple looking toy presented many obstacles in the design process. This is a post detailing the Industrial Design approach working through these challenges, which I thought might be interesting to curious people who make models for 3D printing. The 3D printed turtle has flexible geometry to allow the legs to bounce and scurry around when tapped. The head can also retract into the shell. Download the free model and print it for yourself here.

Solidifying a concept

The idea for this hit me right after creating the Mini Monster Truck. I really liked the way this toy truck turned out and it was a hit with the Thingiverse community, so I was thinking about other applications of the flexible design.

A toy animal with springy legs would be able to utilize a similar geometry as the monster truck, but with a slightly different function. People seemed to appreciate the novel functionality of a springy design that was easy to print and I wanted to have this same spirit in the new model.

I thought a turtle shape would be best for this design, because it could easily be done as a 2 part clam-shell type enclosure. I started putting some ideas down on paper, sketching on spatial considerations of the features and part strategy. The way a flexible structure could fix the legs to the model became a clearly important consideration and it was worked out gradually as I continued through the design process.

Concept refinement: keep it simple stupid

From the start, this idea seemed possible, but I spent a lot of time toying with the idea, trying to simplify the shape and part count as much as possible. From my experience, Thingiverse uploads with minimal support cleanup and assembly have been most successful with the community.

I came up with the basic construction and worked out a few more details on paper before I started modeling. At this point I was confident that the design would be fairly simple to print and would not need supports.

The monster truck design worked well because the flexible suspension was integrated into the main body. This gave it a low part count and the wheels were the only other parts to print.

While 3d modeling the turtle, I realized that the lower half, the flexible part, and the legs could all be one piece. This really simplifies the construction, and is possible because of the 3D printing technology’s limited ability to print overhangs. I made sure that most overhangs were “bridged” and some of the surfaces still look a little crusty when printed, but it isn’t too visible and shouldn’t affect the function of the print.

After some trial and error, I got the base and shell each print in one piece and made a clip to hold the model together so no glue would be needed.

Taking it further

The retractable head was not initially planned when I was sketching, I thought the head and tail could also have their own flexible supports. When I started making the 3D model, I knew I wouldn’t have room to add those features while keeping the turtle at the size I wanted. The retractable head was my solution to make the model smaller and add some extra functionality. I actually like this feature much better than the original plan. I built in special geometry which puts tension on the sliding part to keep it from falling out.

After the 3D printed proof-of-concept worked exactly how I wanted, I got a little crazy and created some shell design variations. It was a lot of fun making these alternate designs. The swirly spiral and line pattern designs are my favorites. Some other ideas I might make in the future are other low-poly designs, a pixelated voxel shell, and even a blank shell that other people can use as a base for their own designs.

Overall, it seems like people really like the turtle design and Adafruit even used the design in their Timelapse Tuesday Youtube series.