Hackaday Prize 2022: Recycled Plastic Skateboard Decks Demonstrate Small-Scale Injection Molding

Injection molding is usually focused on high-volume production, but that doesn’t always need to be the case. The Recycled Plastic Skateboard Deck project centers on the use of injection molding for a relatively low-volume production line using open-source tooling.

RPSD is part of the Precious Plastics ecosystem and uses the existing and open-source shredder and extruder to turn locally-sourced plastic waste into melted plastic. The core of the tooling is in the aluminum CNC-machined top, bottom, and edge mold sections bolted to a thick steel support structure that give the skateboard deck its shape. The edge section defines the deck’s perimeter, and 64 cartridge heaters are inserted into it to bring the mold up to temperature. The mold is mounted on a scissor lift mechanism to allow it to be aligned with the extruder, and temperature control electronics are housed in a laser-cut metal enclosure, which is bolted to the base of the mold structure.

To be clear, this is not a cheap way to make a couple of skateboard decks, but rather a way for small shops to do injection molded decks in-house. At ~$7500 for the components of this relatively large mold, excluding the extruder, you’d still have to sell quite a few decks to make it economically viable.

Although small-scale injection molding has become a lot more accessible, the cost of machined metal molds will remain high for the foreseeable future. However, if you only need small, flexible parts, you could probably do it for under $50 using 3D printed molds and silicone.

25 thoughts on “Hackaday Prize 2022: Recycled Plastic Skateboard Decks Demonstrate Small-Scale Injection Molding

  1. Hm… I have been skateboarding for 35 years now, and I somehow doubt these plastic decks have the same “pop” (it´s a thing) as the wooden boards. Wood skateboards are initially quite stiff, they will lose that stiffness, depending on the abuse you put them through, over time. In my prime I replaced a deck every month at least, even if it did not have terribly visible wear around the edges. Since I have never ridden these plastic boards I can only make assumptions here, but I would guess the material has different properties. Skaeboards are typically made out of 7 plies of laminated maple, with 5 layers orientated being orientated in the long direction, and 2 layers 90° to that. When I ran a small longboard company I experimented a lot with materials to get a certain springyness (is that a word?) yet torsion-stiffness, all catered to the riders weight. I ended up using bamboo and triaxial glassfiber laminate. It is easy to build an object that looks like a cool skateboard – making one that actually rides well is decidedly more difficult.

      1. Oh, but they do. Well, if you want to generalize the term “skateboard” anyway. There is for instance a distinction between a “skateboard” and a “longboard”, the latter being a much broader family of … things. It is actually quite common to find glasfiber, kevlar, aramid and/or carbon combined with various woods in those. It depend on what you want to do. Like in every other sport the equipment has undergone quite the evolution, and you are totally able to spend top dollar on a specialized and often custom made deck. This does not apply to the average “trick” skateboard tho, those are mass produced 7ply maple boards where the graphics (and the association with a pro rider, for that matter) are the primary selling point, seconded by the shape (which is not only the outline, but the wheelbase, the angle of the upcurve on nose and tail, and the concave. Skateboards are not flat planks, but very much 3D Objects). Anyhow, you do not want a skateboard to feel like a steel plate or a wet towel under your feet. Maple is very much fine for a trick/street skateboard, a downhill rocket or a “dancer” require different materials. If the recycled plastic boards are the next big thing then I am totally up for it. Still I remain skeptical.

    1. Plastic also starts out stiff and loses strength over time with use. And it doesn’t have to be a completely plastic board, you could modify the properties of the plastic by mixing in some fiberglass or wood, or mold in some sort of frame or reinforcement.

      It doesn’t really matter that it’s not 100% the same ride quality as wood, the point is to reuse waste plastic that would normally go into the ocean or a landfill. Making home injection molding more accessible to the average consumer is a great way to create demand for waste plastic and reduce the amount we throw away, as otherwise we’re solely dependent on big business to eliminate plastic waste. And they’re not motivated by environmental concerns, they’re motivated by money, which is how we ended up with the Great Pacific Garbage Patch in the first place.

      I mean really, this still deserves a prize even if the skateboards suck. It’s plastic; you can mold whatever you want with it.

      1. I guess the properties of the specific wood used and the orientation of the grain is key for making a skateboard. Google the basic trick called “Ollie”, which is basically a jump initiated by a kick on the tail end and a complex shifting of body weight and footwork. The board will flex quite a lot (way back then a friend got hold of a camera that could record at a whopping 200 frames/sec or so and we had much fun doing ultra slo-mo recordings – at the time when VHS was king). Much like on a bow the board does bend and spring back, giving off the energy put into it by the flexing part. I agree that the “injection molding for the masses using recycled plastics” is a great thing, and I would love to have access to such a machine. I just dont think that “real” skateboards are an application for such a process. For kiddie boards that are just used to cruise around it WILL work, there are plenty of plastic boards around.

        1. Hey Cree! We also recorded some slow-mo footage! Check it out:

          Its also worth mentioning that our project is not trying to replace the wooden deck completely, we know it will always hold a special place in the hearts of seasoned skaters. Our project is about expanding accessibility, to people who live in situations of hardship, and normally would not be able to afford a deck. For many, having a deck that performs 95% as good as a wooden deck, is better than having no deck atall 😊

  2. The reason that popsicle Deck skateboards are made out of wood is because the amount of Pop you get from hard maple. I can’t see anyway that is plastic especially recycled plastic where you’re using many different types of plastic would have the same characteristics. I think this would be better suited for different types of skateboards like longboards, cruising decks.

    1. Hey Johnny, thanks for the feedback! We have tested all of the common recyclable plastic types and got validation from skaters say the feeling of PP (Polypropylene) has a very close feeling to Canadian Maple. Its also worth mentioning that our project is not trying to replace the wooden deck completely, we know it will always hold a special place in the hearts of seasoned skaters. Our project is about expanding accessibility, to people who live in situations of hardship, and normally would not be able to afford a deck. For many, having a deck that performs 95% as good as a wooden deck, is better than having no deck atall 😊

  3. While the concept is great… repurposing bottles found in the forest.

    Most tricks involve grinding and anyone every skating on the street knows his deck is gradually grinded down….
    This means micro plastics that CAN’T be recycled.

    A good way to tackle this might be one wood layer on the bottom and top.
    and possible the edge somehow shielded so it won’t grind up and pollute even worse than those big bottles…

    1. Dumb question, aren’t the boards glued or sealed with something? If that something is like epoxy resin or another plastic/non-bio degrading material, won’t it also create microplastic?

    2. We have considered this point a lot from the beginning and still think it’s a step in the right direction to get the plastic in to one big manageable block like a deck, instead of lots of little bottle caps e.g. Sure there is a small amount of micro plastic but it’s a tiny % if you look at the overall mass of the deck (~1.7kg), which otherwise would have all ended up in the environment. A single solid piece is much easier to manage at the end of its life. We appreciate the concern though so if you have any ideas about how to solve the micro plastic problem, please share them with us so we can integrate it in to our next research publication!

    3. Lots of folks don’t care about tricks on a board at all anyway – its just a fun way to get around. I did play a little with grinding myself but mostly I just enjoyed the speed and balance challenge of romping around on one (was always more of a two wheel fan though)…

      And I’d be very surprised if the top coatings of wooden boards are plastic derived too, still going to shed micro plastics as the all natural shellac/wax options etc isn’t cheap enough…

  4. Thanks guys for sharing useful tips. Plastic skateboards aren’t always useless. While they are limited in functionality compared to wooden boards, that doesn’t mean they don’t work. They are still better than cheap skateboard decks or free skateboard decks.

  5. Besides the best wooden skateboard decks, I have gone through the plastic skateboard decks in recent years. What I found that the quality and recommended plastic material is competing with the maple wood. I’m writing these words on my personally testing. But the plastic has to be made of best of the best material to compete with normal maple wood deck.

  6. “I recently learned about the RPSD (Recycled Plastic Skateboard Deck) and was blown away by the ingenuity of the design. The use of existing and open-source shredder and extruder technology to turn locally-sourced plastic waste into melted plastic for new skateboard decks is truly impressive. The CNC-machined top, bottom, and edge mold sections, along with the thick steel support structure, give the deck a professional and durable look. The edge section and cartridge heaters work together to give the deck its shape and the scissor lift mechanism makes it easy to align the mold with the extruder. The laser-cut metal enclosure for the temperature control electronics is a nice touch and shows the attention to detail put into this project. Overall, the RPSD is a great example of how we can take something as simple as waste plastic and turn it into something useful and sustainable. I can’t wait to get my hands on one!”

  7. This looks like it would make a sick wet weather board for London’s Streets init.. Whack on some waterproof bearings i.e. stainless (or ceramic if u can afford it). If it really has 95% of the pop of a Maple deck defo has its place. + think of all the squirrels!

    A Kung-fu Master only needs a broom handle..

  8. Why wood aint wood pony for slides anyway (I think you mean boardslides not grinds?)? I mean yeh most slides are done on wood.. cos skateboards are generally made of wood.. but that doesn’t mean wood is good.. I thought wood was too grippy and everything has to be waxed up all the time..

    I’m not a materials expert person but perhaps some sort of PTFE paint or ceramic layer or something? Not wood..

  9. Well buyer beware.. I brought one it cost me €130 Euros and it snapped within 3 days and I’m a pretty light skater I only ever snapped 1 deck before and I’ve been skating about 20 years off and on..

    Maybe I was just unlucky the way it came out of the mold? Am willing to work with Jason but he says he won’t talk to me anymore because I said to him ‘Oh come on man don’t be a nurd’.. heh

    If you gonna buy one of these I’d strike a deal with Jason first.. like if it breaks..in less than 1 month he has to melt it down again and make you a new deck at cost ‘cos I think these are perhaps still at the prototype stage.

    Obs there is also the problem with microplastics, not just with slides but every time you do anything with the deck like try to pop an ollie etc..scraping the tail- microplastics gonna get into the water table.

    Good luck with it all tho..

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