Shredder 2.1

Hey everyone

As you might know we are working on V3 of the project, here you can have a look at our full plan. This time our focus isn’t on re-developing the machines but trying to get the most out of them. That said we do have a few tweaks and things we could improve on the shredder. Mainly making it easier for the plastic to be pulled into the shredder so you don’t have to do it manually. And looking for a way to make it easier to change/clean the mesh. This wouldn’t be a full update but more of a hack. So if you already build the machine you can simply upgrade only a component (the advantage of a modular build 🙂

@morrentrading is going to help us with his expertise in building shredders. If you guys have any updates/hacks/suggestions let us know.

Our first try-out. A different blade-set

Wow! Nice to see further improvements on the machines! Looks amazing!

However the exchangeability of the shredder blades ends when welding the shredding unit, right? This leads to the question: Is it necessary to weld the stainless steel case of the unit in the first place? Aren’t the 10 screws enough? 😀
EDIT: Wow, I’ve overlooked how the shredder design is even more amazing than I thought before. 😀

Hi All friends,
Very thanks you to share them, and I will try to build new one to test my idea, and feed back to you.

Because I refer to the wood chipper and resource recycling PET, PP, PS characteristics, I plan to try 3 blade. According to my previous CNC machining experience, try to see the different speeds.

Thanks you!



If you want a custom shredder axle like this I can make one for you. I sell the standard design in the Bazar, But I have made custom ones for people using different bearings, couplings etc. I think the UCFL205 is a better choice anyway, 20mm is a little on the small side for the shaft for the amount of torque some people are using. Also adding a keyway is a good idea, the plain 20mm shaft can slip easily.

I can also supply raw lengths of 27mm hex cut to length if you want to machine your own shaft.

AAA Hi All, I will start to built my shredder in May and I am looking a solutions to make the shredder cheaper and easier to built, The solution I fiond are:
1 aluminium frame without welding
2 Hex axel with round end 25mm for bearing UCFL205 and final 24 mm with keyway to go directly inside motor, no coupling needed.
3 Monophase motor with 750w / 1 Kw max with electronic, double directions, safety stop and variable speed included, double output for shredder and extruder (I found it)
4 Shredder without weld fix end profile (you didi it on upgrade files)
So I would like if anyone can hel me, I need Cad file for the side plate of shredder and round spacers, the side olate must have new bearing holes, now they are for UCFL 204 90mm center to center, I need 99mm, then the 2 spacer has the inside diameter of 20 and I need 25 mm. i am not sure is there are more modification to do.
I’m quite sure it is possible to built a shredder for 800€ with new motor or buy it from a builder for 1200 / 1300, consider that you will use the same motor for extruder so it will be very cheap.
Please feel free to contact me, actually I am in Lima (Perú) but I will be in Italy from The end of March.

Hey there, it’s all in the Download Kit!

In the “BUILD”-Folder you will find two folders: One for the Shredder itself (V2.1) and one with the Shredder Upgrades (Hopper and Sieve). 🙂

Hi Dave! We are a group of basicyear students from the Gerrit Rietveld Academie making the shredder at the moment. The thing is that I cannot find version 2.1 anywhere to download (the precious plastic website is only in v2.0!) Thank you!

any reason that shims aren’t used?

Hello @luisgamez
That’s correct, there’s a small gap between each rotating and fixed knife, and that’s how it’s intended.

In a perfect world, 3mm thick metal is 3.000000000000000mm thick, in the real world, 3mm metal is something around 3.01mm thick. Due to this, a small gap is required to avoid friction between the knives or having a shredder that doesn’t spin at all.


HI, mi name is Luis, im from mexico.
im trying to build the shredder but on my autocad inventor drawing found a gap between the rotating blades and the small and big fixed blades.

the total lenght of the rotating blades assembly is 148 mm
The total lenght of the fixed knifes is 149mm
Taking this in consideration there would be a gap of 1mm horizontally between fixed and rotating blades.

Please let me know if im doing something wrong.

thanks in adavance for your help with this issue


Is 2.1 tested yet ? Does it make sense to change the blade format ?

At the workspace it is now a spiral shape. But my idea is half spiral- half random. So the plastic is transferred to one side of the shredder and then shredded by multiple knifes. Maybe we can check this soon. But it takes a lot to take the shredder apart.

@mathijsstroober Nice! How exactly did you set up the blades there? Just randomly or do you have a pattern?

Hi everyone! I write from Argentina! I am working on a new design attempt for the shredder. I am thinking in somethin like this…
where it is used one or two big blades and a lot of small blades and it is not necesary a mesh. The size of the particles is fixed by the small blade size. Did you already think in something like this?
I am trying to make the shredder cheaper because here in Argentina there are a lot of people interested in start with plastic recicling but build the machines are not cheap enough.

With a stronger coupling we sometimes have problem with plastic melting instead of getting shred. The blades are not extremely hot by friction so the plastic melts by compression. I think it is due to the spiral shape of the blade set up. All the plastic is moving to the end resulting in two blades cutting the plastic (see drawing). To resolve this I think half of the blade setup should be spiral and the rest should be more spread so different blades are cutting the plastic all the time.

@agile, what do you think about this?

Because it takes a lot of time to take the whole shredder apart, I did not do it yet.
Is someone willing to try this? Otherwise i will do this probably in the future.

In the PP hq I worked a lot with the shredder.
I made two improvements:
The hopper is now straight so the material needs to be a bit smaller but therefore it gets less stuck
With the elastic rope you can create tension on the press stick, resulting in shredding without needing to press all the time by hand

With shredding PP we had a lot of problems with the axle connection so we made a coupling of 2 plates welded to the axle of the engine as well to the axle of the shredder. The 2 plates are connected with 4 bolts so it is still possible to take it apart.

We did. But the material was not always getting into the shredder. The spiral seems to works better but results in jamming the shredder when too much plastic is shredded at one specific spot


Have you tried arranging the blades in a chevron pattern, one half a mirror image of the other so that material is pulled towards the centre?

I read a lot about people having to push material (by hand or with a stick etc.) into the blades. I don’t have personal experience with the PP shredder, but I have built a twin shaft shredder and I have no problems with this, it just grabs anything and feeds it through even though the blades are half the size and the teeth much smaller. I have an interlocked lid on my hopper that only needs to be opened to add more plastic. The only added complexity is that you need a pair of gears to link the shafts.

I love the look of the new blades and the design changes look like great improvements! I am curious as to why you did not go with a 3 or 4 blade rotating knife? Every other shredder I can find uses this style. Like the ones below. I am not criticizing, I merely want to understand. The machine is well designed so I am sure there is a reason! Off the top of my head: cost of materials – a two blade knife uses less material and/or rotating mass is less as well, also most other shredders are dual axle and thus more complex – so minimizing complexity. Anyway, I drew up a few blades that would fit right into the current housing. I mostly modified the original design. Any feedback on these would be great! Thanks! Again, love the machine!

Ah! Okey, now I understand 🙂