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Building a Hand Cranked Shredder for Recycling Plastics 💪

Building a Hand Cranked Shredder for Recycling Plastics 💪

Today, I‘ll show you how I built a hand-cranked
shredder for recycling plastics. Let take a look at the building process and
what I want to use the processed material for! Guten Tag everybody, I’m Stefan and welcome
to CNC Kitchen! This video is sponsored by Squarespace. Create your own, beautifully looking website
by browsing More on Squarespace at the end of this video! Almost one and a half years ago I released
my most popular video to date in which I recycled failed 3D prints into new filament using the
Filastruder. One of the steps in this process is chopping
down the material that you want to use. I tried a blender and a modified paper shredder
in the past, which worked for small parts and supports, but things even only like a
3D Benchy were just a no-go. The paper shredder was overwhelmed with everything
bigger than support structure and the bender, either wasn’t able to chop down material
or it pulverized it. Having a consistent particle size for the
subsequent processes is very important and I wasn’t able to achieve that so far. I also recently received a direct pellet extruder
made by Mahor that I want to feed with recycled plastics and which is very picky with the
particles you feed it. Since there is quite a lot of interest in
that field in general, I thought I finally get back at it and in order to do it properly
and have the possibility to also shred things like PET bottles, I bought myself a beefy
plastics shredder. Since I’m lacking space, I tired to make
it hand powered, which was a bit of a challenge. If you don’t want to miss that stay until
the end and for more recycling projects make sure that you are subscribed to the channel
and have selected the notification bell! So I thought about buying a used, professional
shredder but since my workshop is not the biggest, I had to find an alternative. Until the last video released, I wasn’t
aware of Precious Plastics, that is an initiative with the goal to reduce plastic waste. They provide a bunch of open source tools
that everyone can use to start recycling plastics. One of those machines is their shredder. It’s mostly made out of sheet metal, that
can quite easily be sourced in any laser shop around the world. The even better thing is the Precious Plastics
Bazar, which is a market place where you can buy parts and materials, so that you don’t
need to source everything on you own. I browsed around, compared prices and decided
to purchase a fully stainless steel shredder unit for 320€ plus 50 bucks of shipping
that arrived within around two weeks. I basically received a box with a bunch of
laser cut parts plus the turned axle, the bearings and a couple of bolts. Most of the parts were deburred but it’s
usually a good idea to check them before assembly and use a file for cleanup if necessary. Assembly was pretty much straight forward
and Precious Plastics provides a nice instructional video that goes over all steps. The only slight modification I did, was to
drill holes in the end of the axle and thread them to later attach a stop for my hand crank. I also learned during that process, that it’s
a good idea to use the right tool for a job… Stacking the shredder blades was kind of satisfying. I followed the manual but depending on the
material you run, other stack configurations could make sense as well. The good thing about this kit was that it
was fully welded together so I only had to do the bolting job without the need of additional
tools. A screen with specifically sized holes is
placed below the blades. The part is responsible for only letting particles
go through that are properly sized for the later application so that the shredding will
not jam the extruder. Unfortunately, I just recently noticed that
my screen has 8mm holes instead of the 5mm ones that would be better suited for the Filastruder
or the Pellet extruder, so I will need to source another perforated metal plate. The first run was a bit rough because some
of the parts rubbed together. I used a file to remove some material at the
locations where I felt that the parts binded up. The unit still doesn’t run 100% smoothly
but that will change after the first couple of times when using it. And there we have it, that’s the basic shredder
unit. To properly use it in a more industrial application,
you would now attach it to a frame and add a really beefy, geared motor to it. And with beefy, I mean around 2kW strong because
it needs a huge amount of torque to chew through materials. Since my shop is too small for the complete
set and I usually only process small quantities of material, I really wanted to make it work
with a hand crank. So I got an adaptor cut from steel that I
then filed to the proper dimensions, to which I attached an 80cm long 25mm thick, hollow
square steel pipe. And this is really the bare minimum that I
need because, I tried using a 16mm pipe, that just was way too weak! I printed a handle in which I pressed two
skateboard bearings and attached it with an 8mm bolt to the end of the handle. The assembly is attached to the shredder,
that itself is attached to the table via vice clamps. Not a perfect solution yet, and I need to
raise it a little for a material drawer below but a starting point. It really works, sometimes requires a tremendous
amount of force, but it’s now even able to chew through thick bits of material. I might get myself a decently sized flywheel
cut out to add some inertia, but if I’m not going through a couple of kilos of material
at a time, a workable solution at this point. The only thing that still need fixing is,
that it’s horribly dangerous and also the shredded material flies everywhere. Lacking a welder, I had to make myself a kind
of funnel out of wood. I cut OSB to the proper dimensions and added
a small hole for a window with my multitool. Then, I screwed everything together and here
we finally have my, for the moment, finished, hand cranked shredder! And shredding it does! For the moment I mostly went though PLA but
I also tried PET bottles and HDPE bottle caps which it cut down to small pieces without
any major issues. Really cool. The big hand crank is definitely necessary
because even with only little material in it, I sometime have to pull with my whole
weight, which results in a torque of around 500Nm! If you have ideas what I could be shredding
in the future and then print with it, leave a comment down below! The shredded material is basically ready now,
but both my Filastruder and the Direct Pellet extruder work the best, if the particle size
is fairly similar. In order to ensure that, I designed and printed
simple stackable sieves, where the sieving part is just the exposed infill and the mesh
size is adjusted by changing the infill ratio. Link to those in the description by the way. I now stack them up, with the finest one on
the bottom and pour the shreddings into the most upper one. Then I shake everything around and finally
end up with the different particle size fractions. The most upper one is bigger than 5mm and
goes back into the shredder, the smallest one, that also includes wood and metal shavings
unfortunately goes into the trash for the moment. The remaining material is now ready for the
Filastruder as well as the Pellet Extruder and should result in way more consistent extrusions
as before! Let me know down below what you think of this
project, what you would have done differently and what I can do with it in future videos. Since quite a while I’ve been posting writeups
with additional images, graphs and code on my website that I created using todays sponsor
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you can probably find a solution to your problem in their great help center! Thank you Squarespace for supporting this
channel! Thanks for watching, I hope you found this
investigation interesting and learned something new! If you did, then please leave a like and make
sure that you’re subscribed. If you want to support my work then take a
look at the description and become a Patron or a YouTube member. Also check out the rest of my videos, I’m
sure you’ll enjoy them. I’ll see you in the next one, auf wiedersehen
and good bye!

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100 thoughts on “Building a Hand Cranked Shredder for Recycling Plastics 💪

  1. Hi, if you interested in recycling plastic check this channel, this man build filament extruder from crap and it work!
    Also on channel he try extrude different types of plastic junk (old printer case for example).
    All videos on russian but just watch is good too (or enable subtitles)
    youtube DOT com SLASH channel SLASH UClB8dmF UNDERSCORE GwusEM MINUS gOCnlWEQ

    Sorry for cryptography, YouTube ban links in comments.

  2. For the smallest particles couldn't you melt those in the oven and make a larger blob to then shred later

  3. Interesting concept! Have you considered using an impact wrench to power it? Not sure how you could implement a standard square drive on the input shaft without a mill or welder, but it would open up the possibility. Or at least you could use a ratchet wrench to improve the ergonomics, I nearly threw my back out just watching that lever go round.

  4. no chance i'd waste my energy cranking this thing lol i'd be hooking up a motor faster than you can say corona

  5. Their marketplace is an interesting concept for connecting local business that would normally deal with primarily commercial customers, to consumers. Rather than having to pester fab shops to find one thats willing and isnt givng you a "I dont wanna spend the time on this but will if you really wanna pay" sort of quote, you can find a place that is willing to do it, has the setup for the project done already, and understands whats being built. Plus the fab shop gets to use whatever resources they invest in setting up multiple times. (Only have to do the CAD on the laser/plasma cutter once, only have to dial in the kerf compensation once)

  6. I Belive that the catching of the mechanism could be fixed without filing, you could of tried to gape it wider before screwing together because it looked like the hole tolerances would of allowed it.

  7. Gears are your friends. Or, use a torque multiplier. That way you handle can be a lot shorter and also spun faster with a ton less effort.

  8. 2kW because it needs a lot of torque… best explaination ever… NOT
    kW is not a unit of torque… so this literally makes no sense what u just said…

    its beafy because it needs a lot of torque but its not 2kW because it needs a lot of torque… big differece

  9. If you don't need it to be fast you can use a not so powerful motor with a gearbox with very low gear ratio to save space.

  10. Torque doesn't have to translate to power. A cycloidal gearbox is a great way to trade speed for torque, maintaining the same puny human power output.

  11. here is an idea. if you get a nut attached to the end of the input shaft you can use a large pneumatic impact gun to drive it. pneumatic impact guns can provide up to 1200 ft lbs of torque so it should work.

  12. TFW the extruder alone costs more than my entire 3D printer did

    Hopefully direct-pellet extruders go down in price soon though. Or at least filament making equipment.

  13. Why not use a nema23 or nema34 in combination with a 200-1 gearbox. It relatively small, and not too expensive. It would definitely be slow but is that really an issue?

  14. I love this idea 😍. I have limited shop space and have limited funds but this it perfect 👌. Muscle is the way to go 💪.
    Thanks dude

  15. You really need a worm gear reduction. With the proper reduction, you could power it with a hand drill or just a 30cm handle.

  16. What you could is use a car flywheel and starter. You would have an adapter made for the flywheel to shaft connection. I think a starter would provide the necessary amount of torque

  17. if you can find an old powerchair, the motors on it would work I bet. the chairs here have a weight limit of around 600 lbs on them.. worst case you might have to gear it some..

  18. Ive been thinking about doing this myself for quite a while now. It is just so tempting to make filament out of waste and print cool things with it. with these PET bottles you might not even have to add virgin material to the mix. Really cool! I guess you will add a gear to the handcrank? The way it is now you could charge people to use it for a workout in times of this toiletpaper-noodle-pandemic.

  19. I thought about 3d print planetary, cycloidal or harmonic gear, driven by a hand drill. Cozy, beautiful and also nice fatigue test.

  20. Just thinking out loud, but those industrially shredders take too big of a cut which requires a high torque force to work properly.
    Couldn't you use or modify something like a rotary potato shredder or an electric "salad shooter", which would take smaller bites out of the plastic, requiring less force and also costs under $50.
    Although not sure if it will cut the plastic into a constant size which you need, but I think it should definitely cut it…right?

    I mean, I just tried a cheapo hand cheese shredder on a junk 3D printed plastic part and it did start to shred it……again just thinking out loud 🙂

  21. I think you should attach this thing to an old home trainer. Use a belt system as a transmission with the needed ratio (maybe you can even use the stock parts of the home trainer) and easily shred kilograms of plastic by using foot pedals 🙂

  22. Thanks for the great video! Time to look for an external gearbox or pully system. Speed does not seem to matter, so you could gear it way down.

  23. Dieses Video enthält Gewalt gegen Flaschen. Bei Risiken und Nebenwirkungen essen sie die Packungsbeilage und erschlagen ihren Arzt oder Apotheker.

  24. You need to pelletize the shreded plastic. It makes it easier to manager and mix and also dries it from any moisture it might have caught while laying around.

  25. I'd say add a geared motor. Your motor doesn't need to be as powerful then. Or at least add a gearbox as Ic3Fenix suggested. You can generate tremendous torques with a properly sized gearbox so you'll be able to drive it with a tiny Lego motor.

  26. You could run the plastics through a hot-end with a ridiculous nozzle size (1.75mm), and make a spool that way

  27. If you don't use spur gear reduction, a single stage planetary gear box will add plenty of torque although you wouldn't be able to fix a flywheel.

  28. Maybe add a chain and put the huge ass motor underneath you can source a forklift motor for cheap and add proper multiplication gears from the motor to the upper shaft just like a bike

  29. I threw one away less than a week ago.It was hand crank or motor driven.I kept the motor and tossed the thing.Had I known!

  30. For the finer particles you are throwing in the trash. You can instead collect them and combine them into larger pieces in a toaster oven. Then they can be processed with the larger ones.

  31. Eagerly waiting to see the pellet based printhead. I can't wrap my head around how they managed such a precise device

  32. Metal doesn't like rubbing especially stainless, it galls and picks up and gets worse, so it's best to fix the clearance.

  33. Braze or weld a socket on the end of the shaft and use a mechanics impact gun to drive it. you can get them as electric plug in units but the battery ones are more handy but a bit more pricey. the air driven ones are good but too load and cumbersome with the air hose and stuff.
    the battery ones are about 1000-2000 ftlbs of impact torque and the plug in ones are 3000-10000ftlbs. Air ones range as high as you wallets value can expend.
    That and a fly wheel would work well. You might be able to borrow a mechanics one if you take you contraption down to a local engineering shop.

  34. what about turn the axis trough an Gearbox by the Impact wrench? it would be smaler than the Handle and make the Work without much strenght by you

  35. Hi Stefan.

    first of all, i really hope the notorious covid 19 isn't doing too much damage there.

    I think the machine you bought is very interesting but I think it really needs a lot more power to work.

    You could try adding a (very robust) grid above the entrance to limit the amount of material that is sheared by the knives, as an electric planer would do, while in the current configuration the whole thickness of the piece comes to stand between the rotating knives with greater effort on your part, then adjusting the height of the grid you would get better control in the size of the ground material.

    To compensate for the loss of efficiency then since the effort would have decreased, you could increase the speed of rotation.

    I hope I have been helpful, otherwise I apologize.

    P.S. another solution would be to use a branch grinder for the garden, it is an idea that has come to me now, the operation is similar to a food processor: two blades on a disk placed under a tube from which the vegetables to be sliced ​​fall , if you know someone who has one you can test its efficiency and if it doesn't work you can send me to direct the traffic :-))

  36. What we would do differently? Oh, let my try a short list:
    – Diy for the Shredder (requires you to mill tool steel)
    – Gears for the Shredder (requires you to mill tool steel)
    – Attach a motor anyway. If Time is no problem, together with gears a small motor could do the trick. Just do the math

    Why diy Shredder with hardened tool steel? The shavings have multiple reasons. Metal to soft, wrong clearrances (repeating), maybe even to sharp of a teeth (it will break if to sharp)

    To get rid of the steel shavings: Strong (REALY STRONG) neodydlium maaagnet. Best with a "thick" plastic foil in between, so you can easilly pull it of for cleaning the magnet.

    Maybe convert it to filament. And to do so, I recomment you to use a nozzle with a metal mesh, to further pull out impurities.

  37. Could you use a worm gear drive with a motor or by hand to reduce the effort? There has got to be a cheap enough one somewhere.

  38. I can't figure out why you haven't taken an Arduino along with a 48V DC Power supply and a Nema 34 Stepper Motor to power your Shredder. A 906 Oz. In. Stepper shouldn't have the slightest problem turning your shaft efficiently.

  39. Very spiffy. You might consider putting a motor through a planetary gear to amplify the torque, so you can have it motorized.
    You could probably take the particles that are too small, and melt them together to make bigger chunks that can be re-shredded?

    Certainly being able to recycle all of your test parts is a good way to save money and plastic. (might have to do this myself. Been making a lot of draft prints, lately)

  40. You'd better put a reduction gearbox. About 1:20 up to 1:50 depending on the hardness ot rhe plastic. Besides, if you put a larger gear ratio gearbox, you can fit a small motor. That way you will have a motorised shredder with small footprint in your shop.

  41. Thought you'd find this interesting

  42. Great video! Could you melt the plastic into thin sheets in an oven, then shred those? The thin sheets might be easier to shred.

  43. I think the gap between your teeth is too far apart. It's not making small chunks. Whole parts are getting in the way.

  44. It would be interesting to test the strength of a print after being recycled multiple times comparing each one to fresh pla

  45. Please, please for the love of god make a gearbox so that you can increase your torque output and shorten your hand crank, please I cant watch any more of this struggle

  46. Normally unusable plastics can be mixed with sand and or gravel heated and molded to form tiles and bricks add some carbon dust for UV protection and color uniformity you can tile your roof pave your driveway, garden path, the back alley behind your home and so on.

  47. A car differential would be perfet to convert this to true hand cranking

    Could be bought from a wrecking yard cheap look for the locked dif type

  48. You wouldnt need a 2kw motor, a 0.75kw induction motor with a gearbox attached, sutible for the job would cost you 120€ and it would run on normal "lichtstrom" at 230v.

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