TPU and flexible 3D printing
Not every part should be hard. Flexible plastics can come out firm and tough or soft and bouncy. Here's what they're good at, where they struggle, and the options I have right now.
What flexible plastics are
TPU is a rubbery plastic you can bend, squeeze and stretch, and it springs back to its shape. You've held it as a phone case, a watch strap, or the soft edge of a kitchen tool.
The number with an A after each name tells you how hard it feels. It's the same scale used for rubber, and a lower number means softer. A skateboard wheel is near the top of it, a pencil eraser is a bit lower, and a gummy candy is lower still.
That number is only half of the story. A thick, solid part feels much firmer than a thin, hollow one printed from the same plastic, so tell me how soft you want it and I'll print to that.
What flexible prints are good for
Parts that need to grip, cushion, seal or take a hit: handle grips, protective corners, feet for furniture and gadgets, vibration pads, gaskets, cable strain reliefs, watch and camera straps, and RC car tires.
They're also good wherever a hard part would crack. A flexible clip or cover can take being bent over and over.
What to know before you order
Flexible plastics print much slower than hard ones, because pushing a soft thread through the printer too fast makes it bunch up. Expect a longer print time, and a price to match.
They can't handle fine parts that hang out in mid-air, like a thin ledge or the underside of an arch. The temporary scaffolding I'd print beneath them tears the soft surface when it comes off. The shapes that work best sit flat or build straight up.
If your part needs to stay rigid under load, or has lots of overhanging detail, a hard plastic is the better choice. PETG gives a little without being rubbery.
Finish, heat and outdoor use
Flexible prints come out with a soft, slightly satin surface that's grippy to touch. You can't sand or paint them the way you can a hard plastic, so what comes off the printer is the finish.
They cope with a warm car or a sunny windowsill better than PLA. They also shrug off rain and stay bendy in the cold, which suits outdoor bumpers and seals.
In the notes on your order, say how you'll use the part — a firm bumper, a soft pad, a bouncy spring. That's what helps me set it up right.
TPU 95A — the everyday flexible
This is where I'd start for most flexible parts. It's firm enough to hold its shape and tough enough to take rough use, with enough give to grip and absorb knocks.
Pick it for grips, bumpers, protective covers, gaskets and furniture feet.
How it holds up
- black
TPU 85A — softer
A noticeably softer, more rubbery TPU that squashes under your fingers even when it's printed fairly solid.
Pick it when comfort and cushioning matter more than toughness: soft grips, pads, straps and parts that press against skin.
How it holds up
- black
TPU-LW — lightweight and foamed
This one puffs up with tiny air bubbles as it prints, a bit like a foam sponge. Parts come out much lighter than regular TPU, with a soft, velvety surface.
Pick it for insoles, wearables, padding and RC car tires, where low weight and softness count more than strength.
It's also the hardest one to get right. A new shape can take me a couple of tries, so it costs more and may take a little longer. If you have a particular softness in mind, mention it in your notes.
How it holds up
- black
PEBA — high rebound, very light
PEBA is a lighter cousin of TPU with a lot more bounce. Press it and let go, and it springs back hard instead of slowly settling, a lot like the foam in running shoes.
Pick it for springs, bouncy parts, sports gear and anything that should return energy rather than soak it up. It also stands up to oil and grease better than TPU.
It's a newer material in my workshop, and I'm still fine-tuning how I print it, so allow a little extra time.
How it holds up
- black
Parts I've printed in it
Questions people ask
- Which flexible material should I choose?
- Think about how the part should feel: firm, soft, light, or bouncy. The options below each say what they're best at. If you're unsure, tell me what the part does and I'll suggest one.
- Why does a flexible print cost more and take longer?
- Soft plastics have to be printed slowly to come out clean, so they spend more time on the printer. Some of them also take more tries to get right. The price follows that time and effort.
- Can I print a shape with overhangs in TPU?
- Gentle slopes are fine, but parts that hang out in mid-air need temporary scaffolding, and removing it leaves marks on the soft surface that I can't fully avoid. If your shape needs that, I'd suggest a hard plastic, or I can help you find a way to print it flat.
- What does the number with an A in the name mean?
- It's a hardness scale for rubbery materials. A higher number is firmer: near the top it feels like a tough phone case, and further down it's closer to a soft shoe sole. How thick the part is changes the feel too.