YOUR 3D Printed Airless Basketball Might Not Bounce

Can You 3D Print a Wilson $2500 Airless Basketball?

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3D Printing Nerd
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[aviphysics]

It's actually impressive how much energy that white TPU can dissipate

[davydatwood]

Speaking as a librarian, I must say that Andrew's answer is deeply unsatisfying. Basically, all he said was "the different balls performed differently because they're different." I would have much preferred someone pointing out that the reason the TPU ball didn't bounce is because its more flexible material returned to the original shape fairly slowly, and so did not provide enough force to push the ball back up. Whilst the more rigid PLA returns to the original shape fairly quickly and thus pushes back against the floor hard enough to bounce. Well, up until the point that the energy involved exceeded the PLA part's structural strength and it just failed. (That last issue being why you don't make a real sword out of stainless steel.)

This video did a good job of showing us all *what* happened, but failed to really get into the *why* it happened.

On a side note, since no-one else has mentioned it, have you seen Slant3D's video about a 3d printed American football? They make the point that in the real world, if you're trying to transition to a new method of manufacture, you need to maintain user-experience expectations and so at least at first a 3d printed sportsball needs to not just *act* like the air-filled rubber ball but also *handle* and *feel* the same to the player.

[MrGerhardGrobler]

This was a really fun video to watch. Both as someone who 3D prints for a living, and who does STEAM workshops.
The reason the TPU doesn't bounce as much is the same reason a mattress in a gym doesn't let you bounce much when you fall on it. The material properties absorbs the impact, dispersing the energy upwards as the impact progresses. It folds in on itself. So most of the energy is gone. Stiffness stores the energy for the bounce back. reason the PLA could bounce, sortoff. But the downside is stress fractures caused by storing all that energy in an unforgiving material. Just basic impact science.
I also posted this on Uncle Jessies video

[UncleJessy]

😂🤣 wall slam might have been my favorite

[BirnieMac]

What you want is a TPU with higher dynamic hardness (note not shore hardness, that’s indentation type hardness - we want rebound type) Rebound type or dynamic hardness is effectively a rough measure of a spring constant (realistically its the coefficient of resistution you derive from this testing data too like Andrew mentioned)


Reason PLA bounces is because of this, but because its not not flexible enough to handle the loads (the UTS between layers is much lower than the typical UTS for PLA)
PLA’s got quite a good young’s modulus, it’s a bit stronger than we typically associate it being
But because of it being a ball, as it deforms as it compresses to rebound, the deformation effectively goes in every direction meaning it doesnt matter how you oreitnate it before bouncing (it’s also why they designed it like this for the material theyused, really good stress distribution, except you need the right properties for it to work properly)

Am working on my university’s EV racecar project atm and I’ve been doing lot of materials research than I normally would for fun
trying to address parasitic in a flanged insanely low friction bushing has been pretty cool (Iglidur Z was the material we’re using, it’s got effectrively the same friction coefficient as teflon but much better structural properties - though evenentually realised that low friction coeficcient has lead to slippage of the conical fastener that also was deforming the flange and have together caused the issue - now just gotta figure out how to fix it)

[pileofstuff]

It would be interesting to see more experiments.

ABS, CF-nylon, PETG, and some of the more exotic materials that are available to the consumer printing community.

Maybe some of the different resins (if there is a consumer resin printer big enough to do a full basketball)

[cybernetix]

It would be interesting to see it printed in nylon. Or you could ask your friends at PCB Way to sls print you one …pretty it’s the way the original was made

[TheOneAndOnlyTed]

I just finished printing an airless tennis ball as I saw this this morning. I used Flashforge Flexible PLA and it came out great. It bounces higher and for longer than an actual tennis ball. Just a PSA if you use this stuff, make sure you dry your filament first. It looks awful if you don't. Even fresh out of the bag, it didn't print great, at least not the small details of the hexagons on the ball. Dried it, and it works much better.

[GeneralRasp]

That was an excellent transition to Uncle Jessy. And of course we want to see the 3d printed baseball in a bating cage, just make sure to wear eye protection.

[TheDepep]

I printed my ball in Flexable PLA. It bounces somewhere between a real basketball and a deflated basket ball.

[Brainstormer_Industires]

Rubbery things aren't actually that bouncy. Steel ball bearings are actually very bouncy. It's not about using squishy material, but material with low internal dissipation, which are actually ususally very stiff.

Something stiff like the PLA, but more durable, like a nylon or CF-nylon would probably be ideal. SLS nylon would probably be ideal, and may be what the real ball is made of.

[JohnSmith-tuhv]

Those things are better than airbags!!!! There's gotta be a use for something that dissipates that much energy!!!

[hellothere]

PEBA would be a good material to try, it is a flexible 90A and has excellent energy return. It is also expensive and not many places sell it.

[DJapan]

There are different hardness levels of TPU. I wonder if more or less firm would help.

[nufnuf]

Hey Joel! If You want it to bounce - print from PEBA material. It has probably the best energy return value out of all flexible filaments. But its expensive :( Good thing is - its freaking impossible to break that material :D

[LegendaryJim_YT]

Love hearing from Mr. Mayhall. If anyone ever wants to geek out and has the opportunity to talk with him about the science of Gloop, I highly recommend it. Dude is so smart and awesome to talk with. Keep up the collaboration Joel. ✋🏽

[toyotaboyhatman]

What if the interior of the ball had a sparse honeycomb lattice so it could evenly transfer that energy so the force isn't traveling along the circumference? Its impossible to injection mold, but not hard to 3d print.

[Jrheaton]

My adidas shoes are 3d printed soles with a lattice kinda similar but meant to be squishy for comfort. They have a sweet video with Adam savage explaining the material science behind it

[OwenBuckingham]

This is a cool showcase of the different material properties. Love it!

[vodzurk]

You probably need to tension each of the "plates" by bending them. That could force some energy into the system/ball, so when it impacts a surface, it REALLY wants to push back, as opposed to dissipating the energy.