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V4 Shredder Single Axis – [INDEX+BLOG]

This topic contains 72 replies, has 28 voices, and was last updated by  Garrett Cadou 2 months ago.

Friedrich friedrich

V4 Shredder Single Axis – [INDEX+BLOG]

08/11/2018 at 22:25

This is the main blog where the updates for the development will be shared and general questions will be answered and discussed. Beside that, there are a few important sub-topics which I will give you an overview in here:

First a short overview about certain Sub-Topics of the development:

Drives (Motors and Gears)
Cutting Technology (Shredding principles and fine tuning)
Feeding System (Hoppers, Conveyer Belts, new Systems)
Control System (Electronics)


So here the Development Blog starts:


Hey community,
I’m Friedrich from Germany – a Industrial Designer and Engineer. I will work on the next revision of the Precious Plastic shredder in Eindhoven until the beginning of the next year.

As most of you know there are some things about the shredder which can be improved to build a more reliable/productive and safer machine. The recent weeks I ran some tests with the current shredder, a fast-spinning shredder and a double axis shredder to compare them against each other.


Some points which we are sure we want to improve:


Right now we have a max output of ~10kg/h – to run a workshop or small business with our shredder we need at least 40-50kg/h. The goal should be to shred in half a day (or less) the complete plastic for a week.



The next version should not jam that often as the current shredder does. This is not just a problem of the motor power only but also concept related. Furthermore we want to implement automatic reverse (Torque detection) and back to normal operation.

This is very related to the topic of reliability, due it is not possible to build a save shredder if it is not processing the input material in a reliable manner. The shredder should run without any correction of the user during the shredding process. The shredding blades must not be accessible during the operation, this is ensured by mechanic constraints or sensors.



Some of you report a fast wear down of the shredding blades. The new version should have a way to reduce the necessary time for maintenance and changing of blades. I will try to increase the lifetime of the blades by optimizing tolerances, cutting angles and material selection.



The revision of machines will come with a guideline for a easier part-selection process depending on personal needs.



So how will we start? 

Our biggest problem right now is the huuge variety of plastic we recycle – small/big, thin/thick, flat/geometric and different materials. And most of the shredders are specified on one particular task. E.g. slow running Granulators to recycle runners of the injection process.


I found a different concept from our existing one which i want to adapt to a smaller size shredder. I think it can solve the problem about the big variety in the best way. The biggest benefit of this shredder type is that, the process is more reliable and you can throw in even bigger rests of plastic like left-overs from the extrusion machine or half injected parts.


Its called single shaft shredder which looks like those ones here:


Of course our shredder will be a bit smaller 😉

The build will be similar to the current one (stacked blades on a hex-shaft) – just the blades will be between 10-20mm thick, to assemble the teeths on them. The width will be the same for all, but the length will be adjustable to your needs (education vs. production)


What do you think about this concept?

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06/02/2019 at 12:37

sorry but those components and the total weight will be very expensive to ship and to produce for us machine builders (who probably serve 90% of the PP folks). This will increase the bill for Precious Plastic newcomers about 30% – 40%.
Also I can’t see how this will be more easy to build in regions with supplier/resource problems.

Dudes, the idea was to make PP affordable, lighter, cheaper and greener, not inaccessible! The steel plates alone are 200 – 300 Euro, the shipping alone will increase by 80%. the pushing part is cool, I would have love to see that as v3 upgrade.

Dudes, but please go back to drawing board! That’s a clear no-go from us (and pro machine builders who where just laughing at it) !
Btw. it took us 6-8 months to optimize and secure stable suppliers for v3, it’s going to take another 10 months to build this one cheap.

@andyn, would love to see your input here 🙂
@davehakkens, what the heck is this please 🙂

06/02/2019 at 11:56


It look awesome, we wait a running clip, if it will be possible!
I think is looking very good, professional.

Very good work Friedrich

06/02/2019 at 11:49

And the electronics 🙂


The schematics were created in https://qelectrotech.org which is a really simple program to draw your diagram.

22/01/2019 at 02:08

Hi Friedrich

How the project work?
I’m looking forward for this and hope everything will be just fine!

Congratulation for all your work! I admire it and wait to see the final phase!

Best regards,

10/01/2019 at 12:20

hoping for an quick update. keep on going 🙂

07/01/2019 at 17:18

hey @leoroth
thanks! we are still working on a proper documentation. I think we will publish the video and the files during february. furthermore you can contact me personal via direct messages and i will give you some unpolished files, so you can start to work on that shredder!

much love


07/01/2019 at 04:19

Did some work on shredder blade design with my friend Max who is a sophomore at the University Central Florida in Engineering and helps look after the Fab Lab here in Sarasota, FL when on winter break.

Here’s the google drive- open source!


23/12/2018 at 14:59

hello there .
it is so nice to see that many designs . everyone has an a littlebit other approach to shredders. I wanted a shredder wich caould work still with an motor 1.5kW -2.2kW but bigger. And I made something . actually the very first prototype is being buildt rigth now. it should be able to process about 150kg of plastic per hour.
But it would be made out of thick plates of steel – 25mm , blades from 16mm thick stell. it would be rather 4times big as the pp one.
Ill post ,more of it when it will be buildt. we will see.

for me the most important thing was to build it ASAP   – As Simple As Possible 😀


21/12/2018 at 07:10

I did some research on the finger joint cutters.  I see that the standard size is 160mm with a 6mm thickness.  they are kinda expensive though.  Possible instead just TIG some leaf spring bits to the end of the existing blades.


Alternately there are wood plane cutters that are ready to add into a hopper feed mechanism.



30/03/2019 at 19:08

There is some development going on at OSE on this as well, so feel free to look there;


25/03/2019 at 23:37

That sounds really good guys! Do you have more pictures of it? Maybe a video?

16/12/2018 at 22:06

So I’ve gone and bought a VINTAGE 😉 industrial Plastic Granulator. Wortex(now Conair Wortex) HA-811 – made some time in the late 1980’s and she is a beast of metal weighing upwards of 200 kilos.

This machine was designed to be used in conjunction with plastic injection molding equipment that produces LOTS and LOTS of spruce, runners, channels and all the other plastic byproduct pieces of the framework in the molding process that are all snapped off. Because this is good usable virgin plastic it only makes sense for factories to have this recycling stream in the manufacturing process.

This machine a a few main mechanism-
THE AUGER BIT which is chain drive driven by a 1 HP motor with a gear reducer that spins and acts as a screw drive to pull the plastic into:
THE SHREDDER BOX – The part of the machine housing the back of the augur bit and THE ROTARY SHREDDER – which is a big gnar gnar set of heavy blades, belt drive powered by a 1.5 HP motor that spins the shredder wheel at about 300 rpm and smashes the plastic against another stationary set of steel blades.

The guy who sold it to me use to use it for the intended purpose- shredding smaller bits of plastic that can be easily turned through the auger. The hooper is huge and this thing could take a lot of plastic at one time. In NEEDS to be full to properly function. The other drawback is that it DOES NOT self clean. As in there is space in the shredder box out of reach of both the AUGUR what I will call the flat “FLAPPER” and the bottom of the shredder box, also out of reach of the rotary blades. So about two handfuls of plastic just always sit back there in near granulated form. Also below the auger

The machine does produce BEAUTIFUL Pellets pushed through the have iron screen. That also needs more plastic to keep being forced through to push out the pellets through the screen. For my purposes of shredding different types of plastic sorted by color and type these things are draw backs. I called the company trying to get a schematic or manual of this machine and it seems during their merger they misplaced it – though the engineer there did know the type of machine I had and he said that they’ve don’t really make em like this with the auger drive anymore- soooo, confirming what I already wanted to do- I took the auger out and covered the holes with plexiglass – the rotary shredder definitely still needs something like a “Flapper” inside to compress the plastic materials into the rotary blade. I am thinking to fabricate one that will fit in the hole as the same sprocket as the auger used roughly 2 3/8 inches. Looking for suggestions on what kind of steel I ought to use for this piece

orrrrr I’m thinking to upgrade with another set of blades on a shaft in the box. The only issue is there will still be space for the plastic to pool in the back.

My idea now with this giant auger screw I’ve taken off is to possibly make a giant extrusion machine! We shall see…

And I want to replace the old circuit board with a Variable Frequency Drive or some other smaller computer that can control the speed and direction of both motors. Looking for suggestions, please!

Trying to do this before I ship the machine to Costa Rica in January and then fly to go meet it and start shredding all the plastic I can get my hands on.

I will post more pics and videos as this restoration/upgrade continues

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