Sticky Oni: materiality and birthing shapes with TPU

It’s a powerful feeling to pop a tangible object from the print bed, knowing it only existed as a thought in my mind not so long ago. 3D printing allows me to express who I am through body augmentation; very much in the moment. I may not have been born with horns, but if I wake up in the morning and decide that I’m a demon, with some effort I’ll be sure to have horns by the time I go to bed at night.

I love the very real sense that the shape is being birthed by the 3D printer. I select my zcode on the little screen of our PRUSA, knowing it will take time before the object I wish to exist is ready to be held in my hands. This ‘gestation’ period demands hours of tense anticipation. I woke and eagerly leaped out of bed Monday morning to see if my over-night print had been born while I slept.

Creating devil horns is my current passion. I’ve made a few different sets now. The ones I’m working on this week are in an “oni” style: delicately curved. They’re a challenging print because in order to diffuse light, they’re comprised of merely a thin shell; like hairs stacked on-top-of one another. The print could easily have failed, or produced less-than-fantastic results… but somehow the technology pulls it off and I wake to the glorious sight of two perfect pointy forms… with an added ooze bonus:

When I noticed the thin strand of filament between the tip of each horn (created when the extruder jogs from one body to the other), I felt myself blush a little. It was as though I had interrupted a private moment between my two shapes spent within their birthing fluid. The fibers of vinyl connecting them felt very visceral and organic… like organs inside a volume of tissue.

This is one of the lovely byproducts of printing with TPU (vinyl). Though this material can be fussy to work with, it does yield fantastic results once properly loaded into the printer. In this case, the transparent quality of the vinyl makes for gorgeous light diffusion with a candy-like luster.

Printing with TPU

So, what is the cause of gorgeous goopy birthing scenes like this one? TPU print settings call for a high temperature and slow speed. Due to this, I ran into problems if I tried to print the horns one at a time. Once the extruder made it to the end of the print at the very tip of the horn, the material was unable to cool down and solidify between layers. It would stay molten and swirl around with the nozzle… creating a giant goopy-glob instead of a solid point:

devil horns

The easy fix for this was to print both horns at the same time and place them some distance away from one another on the print bed. This forced the hot extruder to move way from the tip completely for a time, allowing each body to adequately cool between layers.

Printing both horns at once did have its own byproduct however. Each time the print head jogged over to the body of the opposite horn, it’d leave a thin hair-like fiber in its wake, sort-of like when you use a hot glue gun and it creates a strand from the tip of the nozzle to where you pulled away from. As the extruder moves back and forth between bodies over dozen of layers, it produces the same amount of sticky-looking hair-like connections:

devil horns

These fibers aren’t difficult to clear away. I’ve accepted that “cleanup” is necessary if I intend to print with flex filament. I plan for it and tell my printer to choose a uniform location on the back of the shape where it may finish the layer and then jog to the next body. This step allows me to literally slip straight down a singular seam with a set of nippers to remove the… extra ooze:

The light effect this material creates is truly stunning. With just one 3mm LED and no additional material for light diffusion, I saw great results. It feels like if you licked them they’d taste like cherry hard candy, which just makes me love them more.

As makers and engineers, we tend to get swept up in the momentum of creation. We get carried off in problem solving with a desire to arrive at a finished object. It’s easy to overlook the beauty wrapped within the process we move through along the way. Having recognized this, I really wanted to take a moment to share the messy-beauty that captivated me this week when I started to learn about printing with this filament.

Paying this level of attention to creating objects prompted me to reconsider how I view creating objects. What I once called, “3D printing parts for my project” I now think of as “gestating new pieces of myself”. In and of itself, saying those words out loud fills me with magnitudes more energy than the later.

Sometimes we must challenge how we’ve been taught to view things. Doing so can change how we see the world, and thus actually change our entire world.

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