I built the first moving prototype of my Digital Fern Branch (tentative title), or as my instructor likes to call it, a potato. Not sure of the etymology of that phrase, but we’ll go with it. It was meant to have all of the moving parts built in. While I continue to wait for more stepper motors, I used the one stepper motor that I had to push this along.
I cut the pieces out of a laptop box I found in the shop. This proved to be super useful as the coating was actually waterproof. This arm is going to be controlled by hydraulic cylinders, and sometimes water finds its way out of those cylinders.
The syringes had to be modified somewhat to work in the assembly. Threaded rods formed the main hinge component for these.
I used a Dremmel to punch holes through the syringe plungers and pushed threaded rods through as a way of securing them to the cardboard. This beats the toothpicks and crazy glue used in the Instructable that inspired this manner of actuation.
The second threaded rod was secured to the syringe using zip ties and a fat rubber band to act as a gasket of sorts. This kept it from sliding around and actually held pretty tight. The syringes I used have luer locks built into the tips, so it made it easier to take a hose and plug it into various cylinders without causing a tone of leakage.
After assembling it all together I cantilevered it over the table edge and hooked it up to my stepper motor. The stepper motor I used
I taped a syringe to a stepper motor that had a built-in threaded rod. This would act as the primary source of movement. Ideally, there would be four of these sitting next to each other pushing and pulling in symphony.
I used a potentiometer as an input to control the speed of the motor. The results can be seen in the following video. More pictures below.