Shredder box – assembly guide – v3.1

I started dumping of footage about the shredder v3 fixes and also addressing issues in an assembly guide. It’s work in progress but more or less the hard part is done; what’s left is a complete guide for the 3phase wiring, over-torque and auto-reverse code as well an updated component source list.

I am sure the generosity of @btmetz and @andyn and eventually others can add more on the subject … 😉
We already tried multiple times to merge hotfixes/pull-request in the download kit but PP Eindhoven seems on permanent vacation.

btw. the page (full fledged multi – user/language) needs a new maintainer; there are still 3 TB being processed to unveil all connected spots on the map such as injection molding, etc… in a user friendly interface but the hard work is done : internal items as guide, components, machines, faq,… with templates and neat interface to make neat write ups.

here to show just the hopper and shields

Hey everybody,
since there was no update for the v3 shedder at the end, we started designing a new update.

There is as said already since long the 32 mm hexbar version which received a thousand clicks and til today it’s still our standard.

However, it turned out that the long knifes are not really needed and waste just too much energy, not to mention, jam way too quickly. So here’s the design in progress and we update here once again when it’s tested. As you can see it’s also incorporating a 30mm hexbar & shaft but best part is, this is backward compatible and so you can upgrade your shredder 🙂 In the other folders you can also find the laser files for the shields, the hopper, as well the control box to house auto-reverse, called the HAL 9000B which currently also receives a major firmware update.

happy shredding – please reach out on the new forum.

The teeth on my small paper shredder are V shaped with two sharp points. I assume they did some optimization to minimize the torque required. Perhaps getting a sharp point initial penetration is helpful.

I tried a different method for the blades yesterday.  I ground the side of the blades to a point from one side so it was more of a pointy chisel like a lathe tool.


We shredded a very large sack of material in a hour.  It handled material almost as fast as we could feed the machine.  The only difficulties were LDPE plastic bags.


HDPE shreds fine, LDPE is more greasy and can build up in the machine.


A few times I had to reverse the machine to clear it out, and a few times it jammed, but it was really a huge improvement.


I think next up changing from case hardened blades to armor plate.  Although will have to re-draw the cad files as the material is only available in imperial thickness

hey @btmetz. please find below the cutting (manual, round file goes best).
i took good guesses with the help of the machinery handbook regarding cutting  angles. the cutting edge is more or less 1.3 – 1.6 mm. there is a decrease of drawn amps of 18% – 25% and it’s noticeable better with harder/thicker stuff.

I am updating the guide page (using your input as well) over the weekend ( still have to cleanup the mess of the teletappi attack, lol and not so lol)

Re stall detection + reverse.


I have heard from  tech a one of my clients that they use components from a local company that has the anti motor stall-auto reverse in a single unit for single phase motors.


I will be persuing this as soon as I can.


Meanwhile.  Yesterday I ran my first double shredder.  Not the first set of parts I have made, but the first I personally assembled.


Interestingly the double size seems to shred plastic easier than the smaller unit with the same 5hp motor and gear ratio.


We shredded for about 45 min last night of various foams, plastics, and cardboard.


Also could someone post some dxf of photos of the improved blade designs.  I already have modded my personal files for the last 20 shredders to 32mm (1.25inch) hex shafting, however the other blade geometries remain the same.



sorry but your request isn’t in the scope of the subject. this here is only about the actual shredder – box. the drive part and it’s variants deserves a few more pages. however, i am not aware that a shock absorber is really needed. to minimize damage it’s best to follow the guide (32 mm hexbar, proper mount, proper frame) as well the mentioned over-torque/stall protection via inverter & arduino (guide in progress).

Lots of great work on this.

I am looking at using a belt pulley system for coupling the motor to the shredder as a way to limit any damage from any shock loads. Is there a reason I am missing that this is not a method that is used?

no, i have only the laser files for 32mm uploaded. for now, i can only recommend to file at least a 1.5 mm edge on the tip, with a 5-10 degree twist.

Do you have the DXF for the improved cutter blades?  Have to send in files to laser today, I really would love to try out the new blade design.

yeah, M12-M14 is definitely better 😉

interesting how you did the bolts.


I changed the bearing bolts to m14, and TIG weld grade8 stud bolts both front and back.  I cut off the head of the bolt first so it is flush on the inside before welding.


No fill rod on the bearing side.

article updated for ‘sieve’ and ‘hexbar – sleeves’ remarks. next on the list : single phase motors, wiring, 3 phase & inverter guide.


we use original Hyang inverters, and sometimes second hand Omron, rock solid also for CNC spindels; hadn’t a single problem, til 6Kw, work fantastic also on solar arrays, they have up-times near 5 years.

i think we understood each other wrong. i mentioned the sprockets for another device but let me elaborate this in another thread (‘automatic hopper plunger’).

I will try to harvest your details you’ve wrote in the forum about your sprocket gearing and the gas motor and put it in the library under ‘variants‘. You have a more detailed product/project page ?

thanks man, much appreciated.

thanks @btmetz ! just for your notice, we use inverters straight from beginning; here in Europe they are around 80-120 Euro for up to 3Kw, 200 Euro for 4-5 Kw. In Asia they should be even cheaper. The beauty of it is not only having all inputs/outputs for reverse, speed, emergency switch as well over-torque signal at 5V/low amps but also the functions for controlling the motor very well : acceleration, … At the end you will have it all cheaper than mocking a single phase motor with high voltage/amperage switches and relays.

I’ve tested so far the auto-reverse code (arduino), it works like charm and removes a lot of hassle using this thing. I am uploading this soon into the library. I am still looking for an analog solution which can go on PCB; it’s actually stupid simple. Doing this for high-power makes me headache but maybe this can be easy too using relays (still lots of $$).

Speaking of sprockets, I was wondering to build a device from 2 bike sprockets running a chain (bike) along a straight hopper. Along the chain there are flexible metal sticks (classic music wire, 15 cm long used to make springs) which push the plastic down into the hopper and then leave the hopper again. So there are slots along the hopper where the sticks can enter and leave.

so just to sync : inverter and eletronics is about 120E for 3Kw, 200E for 4Kw; motor goes here almost per kilogram, 2Kw is near the same as 4Kw, around 100-200 E, 3 phase. The only real expensive thing is the transmission and honestly I found your sprocket drive really exciting; despite I get a heart-attack looking at it 🙂

laser cutting hardened steel and plasma cutting is the same as mild in my experience.  I have made a lot of knives and armor vest inserts from the material in the past.


The reverse for a single phase motor was fairly simple, just a transfer switch.


I had one running yesterday on a machine that I spent a few hours torture testing.


Had a few issues with the chain sprocket and shredder performing poorly.  Traced back to machinist not making the sprocket to spec, (repaired by TIG and re–boring the shaft.  The second was the bolts for the shredder bearings were loose.


During initial assembly the bolts have to be a little bit loose to turn and then as the machine is run, the bolts are to be tightened as it wears in.  Someone forgot to tighten the bearing so there was some issues.


The ability to reverse the motor was so good.  Procedure during jam.  Switch off motor.  Turn transfer switch to reverse position.  Turn on again to clear jam.  Turn off, change transfer switch to forward, and turn back on again.


Only once did I have to repeat this more than once to clear a jam yesterday on a particularly thick garotrade bottle that was folded over into 4 thicknesses.


In regards to inverters and 3 phase, I just can not justify the added 600usd cost (my cost) to a shredder.

I can buy cheap inverters from China, but they do not last very long with heavy duty motors.


I changed over to Delta brand inverters.


Bike sprocket is way too light.  I am using type 50 chain sprocket, and double pulley B type belts.  Basically all agricultural rice mill parts.


See attached pictures and the schematic for a selector switch.


great, thanks for all the input; i wrote a follow up here. I’d like to emphasize that there are 2 different scenarios :
– DIYers with medium/low quality tooling; I estimated this segment as 30% of the audience; well and of course it’s counter part, the normal user base who’d like to do something, have a budget but no idea idea what, how, etc…
– Professionals who have to provide warranty and quality components and need to keep package size small. our smallest shredder/extrusion pack is 75 Kg, 80x60x45 cm, on Euro palette; shipping is around 100 – 200 Euro

then there are different types of motors coming with that scenarios :

– single phase : expensive to control
– 3 phase & inverter, slightly more expensive but more effective and easy to control (auto-reverse, speed,…)
– gas motors

short remarks :
– hardened steel : is hard to process, if you have nominal errors, I’d be screwed
– clamping the blades: i would have love that, seems the biggest improvement regarding durability and stability, right after bigger shafts
– prices: @btmetz: yes, it’s expensive stuff after all; alone the drive part here in Europe is about ~1000 Euro for new components; we have to add not just labor but also fees to keep the shop/machines up and running, also logistic isn’t exactly cheap

I agree with all points, thanks to Eindhoven picking this up.