I have 3D printed a new version of my monarch butterfly. This is an additional prototype (or study as I prefer to call it) for a fully animatronic monarch. This version has four servos and a herringbone gear mechanism to allow for large wing stroke amplitude and phase shifting of the front and rear wings. This is my most compact mechanism I have designed yet. I was pleased to discover that my iPhone recognizes a monarch butterfly in my sculpture.
Assembled monarch head. thorax and mechanisms 3D printed in black ABS. Resting on the airbrushed wings I created last year.
The wings of the monarch are separately being finished, and I am using last year’s airbrushed wings as my rough draft version. My new oil painted wings will be much nicer, but I don’t want to risk tearing them while I practice assembling this monarch.
The parts are printed in black ABS plastic. I find this material to be very well suited for making mechanisms and it sands and drills very easily. I would like to use light weight PLA for the exoskeleton in the future. It is a nice filament for arts and crafts because it also sands and drills easily but does not have the same risk of plastic VOCs as ABS does.
The legs, claws, proboscis, and genitals of the monarch will need to be made by hand using a variety of methods. I have had good success using fly-tying techniques to make the proboscis and feet. I’ll need to learn more about monarch anatomy with each phase of this build. A family member recently informed me about Biblio, a website for buying cheap used books. I purchased the 5th edition of The Insects: Structure and Function by RF Chapman. I loved reading an older edition at the San Francisco Public Library. It will contain a lot of helpful information about insect physiology to make sure I stay true to science and nature!
If all of these pieces fit well together, I may consider some additional 3D sculpting work on certain areas of the exoskeleton like the mesonotum. However, I have found that the scale is small enough that the fidelity of standard FDM 3D printing doesn’t allow me to include a lot of very fine features. Instead, it is better to design and print parts that will successfully complete printing. Once printed, it is reasonable to refine them later. Also, I would like to glue velvet and fake fur to the exoskeleton to simulate a Monarch butterfly’s hairy body.
I had some internal debate about why I should bother separately printing each sclerite of the exoskeleton. After I attach fur and paint them, the details do get lost. However, I think this is great practice for creating objects which can be assembled and safely disassembled. I learned from previous versions that I may need to replace parts, or reposition gears and servos. I can decorate each piece easily if separate. Once assembled, the overall look of the monarch will be quite insectoid.
The coolest thing about this version is the mechanical compliance of the butterfly’s body. The four servos and gears are all joined together with a curved thin piece of plastic. This becomes a compliant mechanism allowing each pair of wings to rotate toward and away from each other. I hope this will improve the organic quality of the butterfly flapping motion. I’ll record the motion in high frame rate which allows me to watch the wing strokes in slow motion. The wings should flex from air resistance and their own mass. I can already tell that there is some opportunity for the front wings to rotate back while the monarch dangles from its front legs. Maybe this will make it look like a resting monarch with the front wings folded back behind the hind wings.
Finally, this entire process is revealing just how little space I have to work with inside the body of the monarch. Four servos and their associated mechanism uses up most of the thorax. It leaves only enough room for the servo wires. The butterfly head is too small to include any electronics or mechanisms. I’ll need to fit servo signal electronics and perhaps a power supply into the abdomen. I plan to use my radio control receiver and a small lithium battery. I am using the MKS HV70H servos which operate up to ~8V. That is enough to safely use the fully charged voltage of a 2S lipo.
The mounting points of wing hinges to the wings may prove to be weak and a point of failure. I don’t think I will fully complete this monarch as a sculpture. Instead, I will try all the methods I’ll need to use to make a final draft. It is important to carry through the build on many components. Occasionally, I discover issues I had not anticipated in Blender. For instance, in the 3D model, the hind wings overlap and occupy the same space as each other and the abdomen. I am okay with this because in real monarchs, the hind wings fold around the abdomen and meet neatly in the middle. I hope I can do the same with my wings, but I may discover they aren’t flexible enough or the veins rub on the body parts in a weird way. Only creating things in reality reveals everything I can’t anticipate.
As usual, I have ignored any method of mounting and presenting this monarch. I only design it to be a self contained unit. I may need to incorporate some kind of mounting point for the final version. I also haven’t figured out a good method of rendering my designs. I use a simple sky texture for world lighting and really simple materials.
Top view of the monarch exoskeleton and wing mechanism. This was 3D printed in late 2024 to verify the positions of components, and ability to be assembled.