Open Source Plastic Grinder

Hey there,

here the promised grinder. Please find more in the precious plastic open source library. We maintain drawings, etc… there.

Long story short, this addon, component or stand-alone machine – depends on how you build it – enables you to post process your v3 shredder flakes down to 1-2 mm. This results in better melting times but also significant overall quality for injection, extrusion and compression (you can speed it up then too). Since the flakes are that small you can also print it (I know only of PET as suitable material).

From our tests, this will also lower the horrifying energy consumption for the compression drastically; also resulting a better sheets/tiles.

License : OpenHardware License

Release – date: 10th of October – 2019, as v4 companion or v3.0 follow-up
Motor speed, recommended 700 – 1200 RPM but you can use the shredder motor at 60 – 90 RPM as well.

Please have a look at this Wood chipper & Log splitter - BUILD - YouTube and this Making Wood chipper mechanism [PLANS] - YouTube

Yeah, impatient me.
I am curious if I can adapt any of the cutter geometry to the low speed garden chipper I acquired.
OK, I’ll go watch Colin Fruze videos in the meantime.

@s2019 – As much I consider you PP VIP and you should be definitely more involved PP machine development – I am afraid you have to wait – til I think it’s presentable. The stationary counter knife mount is a nightmare since the knife edge has to be aligned around the mobile knife’s circumference but at least I know how to make it, also the DIY way – so, hang on – it’s almost there 🙂

@ppolice , do you have some pictures or video of the grinder in action?

Here we go!

Maybe we can add here the which is nicer for folks to look at 🙂

little update on the grinder :

– basically working well – in the v3 housing (a good way to recycle or hack your shredder :-). I still have to test PET dust on the new printers
– I am waiting for v3.1/4 CAD drawings to finalize all design variants – unfortunately they added flanges – making things really annoying and hard for us – so we have to maintain now 4 different versions to make this work in real productions,…
@timberstar and me started 2 different printer projects  : one small using the AnyCubic printers (around 180E for the printer, another 150E for the print-head, making a PET print farm possible) and a big one using scaffold tubes and hopefully the v3.1 extruder as print-head. Both printers will focus on PET first.

References :
– Open Source repository :
– Discord Chat :

Status :
– Small printer : parts & printer ordered – overall design unclear
– Noah printer : maintained by @timberstar – first design stages completed

We’re obviously excited- as the project name ‘Noah’ suggest – we aim at cheap ways to print trash, eg: a boat – in some cases may be even life saving.

I am creating another thread – let’s make this happen !

There are also such variants. Me personally more likes the latest .

blades ready and on their way ! 100$ from a real nice & decent vendor on Alibaba.

so what’s next is to :

1. find a suitable and rigid printer which can withstand the vibrations coming from the extrusion based print head or develop one from scratch (SBR rails suck, unguided rails suck too and HGR rails are pretty expensive…).
2. develop an adjustable mount inside the PP design(for v3, v3.1, v4) for the stationary blade
3. spent some weeks fiddling PET, PETG printing & document everything and as well upload this to the hungry PP machine repository

Developing a larger diameter printer (furniture) seems like a can of flies but I am confident this can be done this fall as well.

Corrected price: using PP shredder housing design with mild steel : 250 $, without motor and electronics but it’s a relative easy machine.

see you in bit and thanks everybody again

@PET, we’re coming !

little update: I’ve got the knifes but I have to order other ones. That will last another 20 days 🙁 . Btw. they’re quite cheap : 100 Euro in total whereby 50 is for shipping and insurance.

Yeah, I don’t think it is an option for your fine particle grinder, but may be useful. Just the 15 amp/120V motor geared down to 60 rpm is interesting.

@s2019, thanks a million. This is indeed very tempting and very possibly this just works  – with some hacks. From what I saw in the 3devo grinder, it’s pretty violent in there. Especially with PET. Possibly @sonik knows better about this (could you throw for us some flakes in there ?). Besides, this kind of machines have quite some custom & nasty housing/framework (aluminium casting as I see, horror). For now I’ve to keep going finishing what was planned, eg: make this work with v3/v3.1/v4 equipment; back and forward compatible.

@ppboys , I was looking at the drawings on page 18 in the manual I linked. The plate that the blades work against pivots and is screw adjustable (found an example from a different brand- image below). If that plate was replaced with one that has a blade at an angle and possibly the pivot was tightened up, then functionally, you have something similar to what you are going after. It may rotate a little too slow for creating the fine particles you want for the printer application but may make an low cost medium duty shredder. You would have to pre-size the plastic to fit the opening but that is not too bad (put my metal shear to work).

Unfortunately these geared down shredders are not popular in the states, but I’ll start looking.

@sharma-sagar, same bad, In Sept. we have tests for the commercial version planned of this grinder; and all other projects have to get out as v3 & v4 addons on time. including a new keyboard for Dave, etc…  I think Nov. is better for new fun stuff. But as said, the Poland guy did everything right; just harden the blades and do the stationary blade as described; the cutting edge tolerance might be in the 0.1mm range to make this work good. I am leaving here notes and updates from the tests anyway in Sept. incl. ideas/predictions for PPers 🙂

Ok, whats in September?

@sharma-sagar, as much I’d like but unfortunately not; we decided to get as much sun as possible til production kicks in Sept.  🙂

@s2019, I think so too. From what I’ve seen in the 3devo grinder, the stationary cutting edge is placed exactly along the mobile knifes circumference. And this seems to make the big difference. It’s grinds even below 1mm flakes that way.
But DIY wise, you would have to harden the knifes as well; commercial blades are done from tool steel.

I think the Made In Poland build is basically a wood shredder like this example (see page 18-19). The blade acts against a plate instead of against a sharp edge. I don’t think it produces fine particles.
There is someone on the forum using one of these.
As was stated elsewhere on the forum, these units can provide a cheap low speed drive.

@ppboys if you have access to metal and free time, do you think you could make and test the grinder that the Made In Poland guy made in the video, links of which I posted above?

@s2019, sorry, just saw your post. re interia via flywheel & pulleys : yes, that could do. not sure about diameter but more or less cracking a half hand full of PET chips at the same time would be in the 500 – 700 Watt range and a fly wheel around 40 cm at 10 – 20 KG . just guessing but those motors in this segment are enough as in the 3devo version; at worst you lower plastic feed rate. the knifes arrive here in 2 weeks; i have those motors around and will test it; hang on 🙂

regarding nice/cool design : thanks but I just copied it though. No idea who designed this for real. The last time I saw this was in the 3devo shredder & grinder combo but I think I saw that before in industrial grinders too; just a little different. The neat thing is that it perfectly fits inside or underneath the v3/v4 shredder.

What’s actually tricky is to align and mount the stationary blade; the current drawings are incorrect about. I try my best getting this sorted too.

see you in a bit.