I decided to reprint the "chest rig core" in a flexible material. Originally it was printed in PLA because it's such a large piece and my Kobra Max couldn't print TPU. In order to put it on I used a rotary tool to split the front open and used elastic webbing as "hinges." While this
worked, it was incredibly uncomfortable and difficult to put on.
So, naturally, when I heard about this new foaming TPU Air from Siraya Tech, I jumped at the chance to revisit that particular piece of my build. TPU Air is a foaming TPU that changes its shore hardness (i.e. pliability) depending on the temperature it's printed in, so it can range anywhere from 65A to 82A. In principle, it's comparable to Colorfabb's Varioshore TPU.
Naturally I went for the lowest shore hardness at 65A by printing at 270°C, which also causes the TPU to foam and expand during printing which yields a matte texture.
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Because my P1S has a somewhat smaller bed size at 256³ I had to split the chest rig into 8 pieces. These were joined together using CA glue with activator spray. It does hold up to flexing, though that has more to do with the material itself being so pliable that not much stress is placed on the seams.
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The new chest rig is much easier to put on and is much more comfortable. It also weighs next to nothing compared to my old one. To fasten the back seam I'll use some velcro tabs.
A few things to note about this material:
- ADHESION - TPU is notorious for sticking to the print plate a little too well, and can damage PEI coatings if you're not careful. Make sure to use an intermediary layer for easier, risk-free removal. Adhesion aids like Magigoo or 3DLac work great. Glue sticks can also work in a pinch, and you can use IPA to thin it out. You can also use painter's tape over the print plate - just ensure that the strips don't overlap or have gaps between them.
- SETTINGS - Siraya Tech offers print profiles on their website for their products, and TPU Air is no different. They're a great starting point for tuning your printer for this material. What's nice is they offer specific TPU Air print profiles for different printing temperatures, which is crucial because the flow rate needs to be adjusted to account for material expansion. Make sure you're selecting the correct profile for your desired temp/shore hardness.
- SUPPORTS - Supports have been a bit challenging for this material. For generic 95A TPU I've been able to use organic supports with one layer's z-distance (0.2mm). Not so for this stuff. Organic supports at 0.2mm adhered too well. I even doubled the z-distance (0.4mm) with very little improvement. I've found that Grid supports (not Snug supports - too many small, unstable towers) worked the best for me at 0.4mm z-distance, since the support interfaces had a more continuous structure that way which made them easier to peel off. I might give it a shot at 0.6 to see if I can get better removal without sacrificing surface quality.
- STABILITY - When printing for 65A shore hardness, I found that any tall, thin structures can get really unstable and will wobble during the print, which results in some unevenness in the walls. I believe slowing down the print/travel speeds will mitigate this. Luckily for me, none of these areas will be visible with the suit on.
Also, worth mentioning, I was able to print this whole thing with less than 1kg of filament, compared to almost twice that in PLA (maybe more, I can't recall). My assumption is that due to the expansion during foaming, the filament has to be printed at half the flow rate which uses less material overall.
