We’ll admit that most of the Hackaday staff wouldn’t get too far on a skateboard, but that doesn’t mean we can’t appreciate the impressive DIY wheels that [Chris McCann] has managed to cast using 3D printed molds. From unique color combinations to experimental materials, the process certainly opens up some interesting possibilities for those looking to truly customize their rides. Though it’s worth noting there’s a certain element of risk involved; should a set of homemade wheels fail at speed, it could go rather poorly for the rider.
Both the STL and STEP files for the mold have been released under the Creative Commons Attribution 4.0 license, meaning anyone with a 3D printer can follow along at home. Unfortunately, it’s not quite as simple as clicking print and coming back to a usable mold. Because of the layer lines inherent to FDM 3D printing, the inside of the mold needs to be thoroughly sanded and polished. [Chris] mentions that printing the mold in ABS and using vapor smoothing might be a workable alternative to elbow grease and PLA, but he hasn’t personally tried it yet.
Once you’ve got the three part mold printed, smoothed, and coated with an appropriate release agent like petroleum jelly, it’s time to make some wheels. The core of each wheel is actually 3D printed from PETG, which should give it pretty reasonable impact resistance. If you have access to a lathe, producing aluminum cores shouldn’t be too difficult either. With the core loaded into the mold, urethane resin is poured in through the top until all the empty space is filled.
But you’re not done yet. All those little air bubbles in the resin need to be dealt with before it cures. [Chris] puts his filled molds into a pressure chamber, though he mentions that vacuum degassing might also be a possibility depending on the urethane mixture used. After everything is solidified, the mold can easily be taken apart to reveal the newly cast wheel.
While there’s often some trial and error involved, 3D printing and resin casting are an undeniably powerful combination. If you can master the techniques involved, you can produce some very impressive parts that otherwise would be exceptionally difficult to produce on a hacker’s budget. Especially when you’re ready to start casting molten metal.
I don’t skateboard but that’s a great project! Best part? Open source files :)
If you have a lathe you can turn the inside of the mold to make it smooth and give it a draft angle for easy removal of the wheels. Then make a mandrel to mount the wheels in the lathe to turn them straight and true. Use a 4-jaw chuck to precisely center the mandrel at the start of each batch of wheels.
Petroleum jelly and other oil based products shouldn’t be used as release agents for urethane resins, or for silicones. Get the one recommended by the resin or silicone manufacturer. Ruining parts or molds from cure inhibition or a bumpy surface isn’t worth a small cost saving. In general, release agents that work on one brand of platinum cure or tin cure silicone, or urethane resin, will work on other brands of the same type* of silicone or resin, but do watch out for manufacturer notes on specific resins that *don’t* work with certain ones of their release agents. I use Mann 400 for most castings but Smooth-On has some resins they state are not compatible with that release. One 14oz spray can of Mann release costs around $14 plus shipping and goes a looooong way. People pay more than that per ounce for beef jerky.
So don’t get stuck on pinching every last penny when doing resin casting. The small difference in price can be the difference between a great result, an OK result, or a total waste of material.
*Don’t use a urethane based release on urethane resins or rubbers, or a silicone based release on silicone rubbers when making a mold or making a casting of the same type of material as the mold. They’ll work more like glue than a release. There’s a HaD Fail article from a while back where the author made a mold from some old coat buttons and absentmindedly grabbed a silicone based brush on release agent and his two piece mold became one piece he had to rip apart to get the original buttons out.
Much as I admire and respect the effort, this is a lot of money and time to get a set of subpar OJs. But… Negative Nancy aside there are places in the world that getting skateboard components is difficult (Iran, Cuba, etc) where I could fathom this being a solution.
Doing something very similar for an industrial product I’ve developed at work. Except I’m casting silicone (shore A25) ‘wheels’ (not actual wheels but similar mechanical properties).
Works perfectly using a PLA mold. The FDM texture is just an added bonus for this product 🤓
“The core of each wheel is actually 3D printed from PETG, which should give it pretty reasonable impact resistance.”
Yea, kinda like:
https://www.youtube.com/watch?v=zZmxnJa1ebU
Haha, after becoming curious about making my own caster wheels the other week, I found this fantastic thread for electric skateboard wheel casting; https://electric-skateboard.builders/t/diy-wheel-casting/6546
Tl;dr Use a silicone mold for the actual wheels, but 3d print a mold to pour the silicone mold around
“should a set of homemade wheels fail at speed, it could go rather poorly for the rider”
This immediately brought the skateboarding kid from It to mind–“you can’t be careful on a skateboard.” This is a good bit of work. I’m glad Gregg weighed in, or my ignorance would have let me believe it was a great bit of work. Seems like a great start, can’t wait to see the next iteration show up here.