Designing Articulated Fidgets for 3D Printing! (Print in Place)

This short guide will show you how to create awesome 3D printable articulated fidgets! I'll be making the fish shown in Fig 2 above! STL files for all 4 designs featured are below:

Final Fish: https://www.thingiverse.com/thing:6463828

Dog and Cat: https://www.printables.com/model/747211

Heart: https://www.printables.com/model/748120

All you need is Autodesk Fusion 360, a popular and powerful design software (download the free personal license), and an image to convert into a flexi.

In the end we will create an STL file, which you can do anything with. I'll have some printing tips at the end!

You can find great silhouette vectors at vecteezy.com. This is what I used before I started commissioning my own art. If you already have an image in mind, make sure it's in an SVG format. If not, you can use convertio.co/png-svg to convert it. I'm going to go with a fish, shown above, but you can choose any silhouette image. Make sure to respect all applicable licenses!

Create a sketch on the top plane. Now make a rectangle that is the rough size you want your flexi to be. I'll go with 100mm by 50mm. Highlight it all and hit "X" to convert it to a construction line.

Click "Insert" then "SVG" in the top toolbar. Now click the Insert from Computer button in the bottom left of the pop up window. Find your SVG file. Now use the handles to manipulate the image. The curved one (highlighted blue in Fig 3) does scaling, the box does movement. Once you're happy with the placement and scale of the image, click "OK".

This spot on my fish silhouette is a bit thin, so I'll use the sketch tools to fix it up. I'll use a fit point spline and then trim off the extra using Modify > Trim.

Click the profile and press E to extrude. Enter "8" for the thickness. This makes them more durable. Now's a good time to save too!

Now comes the hard part: Where do you want to make your segments? On the dog flexi I made I divided the body into several segments, had one for each ear, the head, and the paws. On the cat I did a similar thing. On the heart I made them evenly spaced. Once you've got an idea on where to put your segments, create a sketch on the top of the new body we just made. Create lines that are where you want to divide your shape.

Some things to consider:

Your lines can be slightly curved, but too much curve will affect the motion of the final flexi.

Make sure your lines do not touch each other like in Fig. 3. This will NOT work.

Make sure your sections are not too thin, or they won't have enough room for the joints. (Fig. 4)

Fig. 5 shows my final layout. I put as much articulation as possible, as fish are usually pretty floppy.

Modify > Offset each of your "division lines" 1mm. Finish Sketch. Extrude each of the profiles created -8mm. (Fig 1) If a pair of lines did not make a profile, make sure both ends reach all the way to the end of the design. (See fig 2). If not, create a line that connects them.

Now hit save!!

Create a sketch on the top of any of the bodies. Now hit "P" and select all of the other top faces. Hit "OK." (Fig 1) Now do the following at each joint:

Create a 3 point rectangle that is 6x8 like in Fig 2. Make sure it is constrained to the side of the segment, as shown. Offset it .5mm INSIDE (Fig 3.). If you want to, use the midpoint constraint to lock the rectangle in the middle of the segment. Simply click the icon (Fig 4), click the rectangle line (Fig 5), then click the projected line (Fig 6).

You might run into a problem like the one in Fig 7. This is because my segments are too thin. In this case, I'll "Finish Sketch", and go back to delete that segment.

Extrude the highlighted (Fig 8) outer profile (.5mm thick) -8mm so it cuts through the whole body. You should now have something like the one above in Fig 9.

Extrude the side of the small square into the next body, as show in Fig 1. Repeat for all. Your design should look like figure 2. This creates "Knuckles" on each of the segments.

This part is slightly longer. For each "Knuckle", hide all bodies except that one. Now create a sketch on the side of the knuckle. (Blue in Fig 1).

Create a line going from left middle (hover over the rough middle, a triangle icon should appear like in Fig 2) 4mm towards the center middle (Fig 3).

Now create three circles from the center point. A 3mm circle, a 4.5mm circle, and an 8mm one.

Extrude the blue profiles in Fig 5. They should be extruded all the way through the knuckle. This creates space for a "pin". Fusion 360 will automatically hide the sketch, but find it in the browser and show it again. Select the smallest circle, and hit E. (Fig 6). Now show all the other bodies again. Switch the extrusion type to "Two sides" (Fig 7) and extrude all the way into the body (Fig 8). Switch to "Join" and hit "OK". Repeat for all of the other segments.

Finally, fillet all of the inside "Pin" edges, (Blue in Fig. 9). I recommend .75mm.

That's it! Now export your design to your slicer and print! Print at .24mm layer height or finer.

Final Fish: https://www.thingiverse.com/thing:6463828

Dog and Cat: https://www.printables.com/model/747211

Heart: https://www.printables.com/model/748120

Let me know you made it by sharing a photo as a make!