V4 Shredder Single Axis – [INDEX+BLOG]
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:
So here the Development Blog starts:
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?
Hey people, just reading through and thought I’d share what I’m doing. So first bottles get soked in a chlorine rich water. Killing all bacteria cleaning and loosening labels. Then I remove labels and rings. Then use a guillotine to cut in half and then straight into a strip cut industrial paper shredder. This makes it easier to handle and literally stretches every bit of plastic so any stubborn dirt automatically gets detached ready for a final rinse and dry. Then finally put through the precious plastics shredder. simplistically the easiest way I’ve found to clean large amounts of plastic at once. Cheers
I like this design a lot, though the shape of the cutters look a little hard to resharpen, and like you wouldn’t get many sharpenings before they are too short to work. Maybe square tool steel held by simple grub screws perpendicularly would be better? Just advance it slightly each time you sharpen. Some relief on the cutting edges would be good too.
For the pusher, you could use a ‘self reversing screw’ driven by the same motor that powers the shredder, saving on extra components. www.youtube.com/watch?v=9UbnvtJ2qMk
Yes I agree with you!
The question in the end is if the ratio is reasonable, between how much extra money the user has to invest for the machine versus the gained output/h. One option would be indeed to create two separate shredding units which can be mounted on top of each other. Or depending on the mainly type of processed plastic could be also specificly picked and used as a single unit.
The clear advantage is that we probably cut the costs maybe by using motors with belts instead of high-ratio gearboxes.
One option would be to go with 20mm insert-cutters for very rough particles. And then granulate those in a smaller ready-to use particles with a double axis/ fast spinning shredder under it.
Thank you for the information!
I was already planning to measure the current of the motor consumes, to create a torque-amp relation. So there you would see the torque curve raising up if the motor stalls.
I will look into the electronics more after I finished my current mechanical build. Propably it’s worth to check which option is cheaper and easier to build. I assume the output will be usable in both ways for our purpose..
Nice shredder 🙂
Looks like a very nice shredder!
I would be interested to hear why you decided for an encoder based solution to detect jams?
I tested also a 1.1kW dual shaft shredder quite extensively, they work perfect on thin materials such as bottles, single use plastic products and especially flat items.
My big problem with them was, as soon as I inserted harder and bigger pieces it tended to jam due as soon as they cut deeper into the material, the direction has to be reversed, the part removed and repositioned by hand. This is always a dangerous process, due the machine is running while you have to hold the part in the optimal position to be feeded inside.
Where in other cases the parts just are not feeded and jam the inlet of more material (see picture below)
You would need enough pressure from a pusher which breaks those parts. You cannot just fill the hopper with material and walk away -> so in a workshop there needs to be always one person standing next to the shredder and feed the shredding material in the best direction – piece by piece.
For bottles and parts that are under a certain ratio to the blade thickness/size a double axe shredder is propably the best choice, but for random plastic I don’t belive its the best choice. Unless you build a really big one with a blade-diameter of >20-30cm.
Just reporting back on my development here.
After sharpening the v3 blade teeth to a sharp chisel point, and the 1.25 inch hex shafting with 25mm bearing. Upping the power to 5hp.
I am getting 50 kilos of bottle caps shredded on the existing design. However this is without a screen. I have to feed the material thru a second time to cross cut the material. It still does not like pet bottles much without crushing first. The blades wont grab it easily.
My double size shredder on the other hand grabs pet bottles nicely. Same 5hp motor. That machine has been running 4-8 hours per day for 2 months now at a plastic foam factory.
My other clients who shred mostly sachet do not get 50kg per hour. Mostly due to the bulky nature of the plastic. They feed the hopper as fast as they can with big handfulls of material. It digests plastic bags nice too.
So far jams result in the belt spinning not the motor stopping. On 2 latest machines, the belt is very tight and no jams despite over feeding it.
The use of a 63 amp transfer switch to reverse the motor has made life easier.
Initial supplier ripped me off with a german switch that cost 90usd. I since found indentical China switch for 15usd that i imported.
Thanks very much @deeemm for the feedback. We appreciate it so much!!
One of the conclusions drawn from the test is:
– Use normal blades (like double shaft shredder) makes simpler the building process of the SSSS.
Totally agree with you, we think is the best option. As you can see in the photos, the last version has blades without replaceable teeth.
You say that “On your new design, the angle of shear is the angle that the rotating teeth present themselves to the fixed plate – the end of the tooth should touch first.”
That is what really happens. You can see it in the attached photos.
I have also attached a photo that shows the three prototypes of the shredder we have developed so far.
apologize accepted; just don’t do it again. normal science work involves around 40 hours on the job, 20 hours to publish a new paper and another 20 hours for volunteer activities whilst still working on a few pet projects.
yes please, no hardened steel; mild steel can be processed and hardened on demand; in this case easy to grind or cut a knife mount and weld or bolt a grinded HSS blank on it; easy also for our buddies in the more urgent countries.
We are a prototype engineering company in Johannesburg. We just designed a double axial version with the same concept as version 1 shredder but with 3 teeth per cutter. Also we bad the tooth much shorts to the axis of rotation to generate more torque through the cut. we are using a single phase 2.2Kw motor that controlled by our in-house controller that detected when the motor spins to slow (lets say 50% if 1400rpm. I measure with a hall sensor at the fan and glue a magnet on the fan itself. the mass of the magnet is to small to induce a vibration. I was looking at the other alternative to detecting a jam by measuring the raise in current with a simple current transformer.
It’s an industrial shredder and will be somewhere around 2k$, meant for production rather than education or hobby use. People who don’t need an industrial version are still welcome to go for the v3 shredder. Feel free to share and publish your improvements on the current shredder.
Eventually the v4 design will be easily adaptable to smaller engines and a smaller design. But first the current prototype has to proof it’s principle.
Thx for your input, I will check that later 🙂
Let’s see how it works first! I think it has potential.
I like the insert idea and think it will be both cheaper and better than the stainless blades, the bulk of the blade being cheap steel and the hardened teeth out-performing stainless by a long way.
@friedrich I’m not sure it’s a good idea to put switches in between the output of the inverter and the motor like that, disconnecting the load while the inverter is running can destroy the output stages. You shouldn’t need the direction switch at all, most inverters have a low voltage direction input and will ramp the motor speed down before restarting in the other direction.
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.
I really like the thought process so far. My biggest concern is cost mainly in getting cut parts. I’ve been trying to find somewhere local to do it and only run into ridiculous pricing in the thousands of dollars. And that’s without trying to find the motor or someone that can weld etc. Most places that have the equipment to cut parts won’t deal with anyone that wants to do a one off small projects. (I’m in Indiana) I am moving to a different state soon though hopefully I’ll have better luck.
Hey @kunststoffschmiede that design it’s awsome. I would love to start developing something like that here in Argentina. Are those files and experiences available? Would be great if our team could continue your footsteps between now and March, when we start with the University’s work.
Thanks Garett for sharing this manufacturing Video 🙂
Yes I consider this option, however it’s a bit difficult because if you rely on commercial available shredder inserts, they are not standardized as far as i know…
Means that you can only buy those parts from one company (as long as they support their product).
The type of OEM shredder blades I am looking into getting.
Two different types pictured and a nice little video of how this company WANROOETECH water jets there own:
I have been meaning to share this experience- and the last time I typed this all out the post was lost so….I shall tell the story again!On Black Friday November 23, 2018 I purchase a “Vintage” Wortex HA-811 plastic granulator made around/before 1989- that I found searching the keywords “shredder” “grinder” “chipper” on Craigslist- and now will add “granulator” to those terms . This machine is a BEAST- weighing somewhere between 600-800lbs. It’s output is tiny plastic granules that can be used easily with plastic injection molding machines. This machine is intended to be used in conjunction with injecting equipment in order to shred up and recycle into usable grains once more all the spruce, runners, channels, and all the other plastic framing that is involved in injecting plastic parts. The parts are usually snapped off this perfectly good virgin “waste” plastic which is then thrown back in the granulator to be recycled.
I checked the website and called the now “Conair” Wortex manufacturer and spoke to someone in the service department who was familiar with the type of machine I had though could not locate the manual for it. He could only send me a questionable wiring diagram that told very little. He did tell me that they steered away from this design of plastic shredder due to the big bulk auger bit which I will get into in a moment.
The machine has some main parts – THE HOPPER which is the huge inverted rectangle thing above the outstretched right arm- THE AUGER ASSEMBLY. Inside the assembly is the AUGER SCREW which is turned by chain drive by a 1 HP motor with gear reducer which spins at about 70 RPM. The auger screw turns thereby “pulling” the plastic into the SHREDDER BOX which is full of the aft portion of the auger screw after it stops spiraling and becomes just a straight “FLAPPER” as I have grown to call it. The FLAPPER and AUGER SCREW are very much the same piece of metal.
Inside the SHREDDER BOX is a ROTARY SHREDDER comprised of massive blades that turn belt drive by a 1.5 HP motor on a separate switch and directional control than the AUGER MOTOR. The ROTARY SHREDDER spins at WAY more than 100 RPM and takes plastic that is pulled into the SHREDDER BOX by the AUGER SCREW into the FLAPPER and is smashed into two STATION BLADES, one on the top one on the bottom. You can peak into the top of the machine by the TOP ACCESS DOOR to the SHREDDER BOX above the FLAPPER. The plastic is then forced through the bottom where there is an IRON GRATE/SCREEN that plastic is pushed through into the form fitted BIN that also has a vacuum attachment(I will get ideas for this later).
These existing assemblies have some serious draw backs. As the AUGER SCREW does it’s thing it also plays a roll in the smashing of the plastic to smaller bits. The guy who sold it used it for it’s intended purpose – shredding lots and lots of small little plastic spruces and getting grains out of the bottom. The machine LOVES TO EAT!” He told me. The more material you have in the machine weighing the bottom material into the AUGER and filling up the SHREDDER BOX – pushing more plastic against the ROTARY SHREDDER as the box is full. I ran the machine with a good amount of material and getting great grains for some time until I ran out of material to feed it. I let it keep running and realized- as expected- Some of the bits will ALWAYS sit in the bottom of the AUGER ASSEMBLY as the screw is unable to “self clean” the area due to lack of contact aka a clearance of maybe 2 milimeters or .5 Inch. Also as the ROTARY BLADE does it’s thing and the FLAPPER turns feeding it more and more plastic there is also some clearance at the back bottom of the SHREDDER BOX leaving some room for plastic to pool and sit as well. The only way to clear the machine completely out of plastic is to shut it off and open compartments and do it by hand. A big drawback in my opinion and for those wanting to change between shredding different types and colors of plastic.
Since the machine is super bulky and these assemblies fall short of doing what I need my idea was to take the HOPPER, AUGER ASSEMBLY, AUGER SCREW completely off, which I have done. I covered the holes left by the AUGER ASSEMBLY and aft drive shaft which fits the sprocket for the chain drive with some PLEXI glass because it’s what I had and I wanted to be able to see in the machine. I ran the machine with only the ROTARY SHREDDER going, feeding from the TOP ACCESS DOOR and as I imagined it would – the plastic pools in the empty space left by the FLAPPER in the SHREDDER BOX.My idea is to customize my own FLAPPER. OR just to use another set of ROTARY SHREDDER BLADES on a driveshaft and fit it into the existing sprocket and bearing combos. Looking to do this drive shaft out of an upcycled car axle though also very open to options of what kind of steel I could use for this experimental FLAPPER. And also just the idea of adding another shredder stage on top sounds really good to me.
If I stay with setup I will be building the NEW HOPPER up off the TOP ACCESS DOOR which I have seen in most newer models of this machine.I also have the idea to swap out the big bulky ELECTRICAL BOX which houses the motors’ switches and relays for a smarter, more compact Variable Frequency Drive or something else. Both the motors are 3 PHASE, 220 volt, right now I am running them through a digital phase converter and plugging into the standard dryer 220 v plug in my grandfather’s garage. Looking for any and all advice/expertise on how to effectively upgrade this box, please and thank you!
This machine has about 2.5 inch solid plastic casters(wheels on it) so its decently easy to move on flat smooth services with a single person. One day I’d like to make a towable plastic shredder on a trailer, much like a large woodchipper that can be towed to places and events and shred plastic on the spot. Or perhaps I just upcycle a different vehicle like a golfcart or ATV and make the shredder itself driveable. I am very happy to be involved and see so many involved on these v4 shredder discussions!
I want to share my experience in the upgrading of this old model shredder in addition to having helped build a PP v2 shredder and intending to build a v4 dual axle shredder very soon. I was looking into doing this and then found this shredder on craigslist for $850 and after buying the digital phase converter and having it delivered to house, buying a new plug and some wiring, greasing the bearings I’m only into the machine about $1100 – which is a big hunk of steel and shredders and motors and wiring that already does a good job of shredding plastic which I intend to redesign to make better. There have been thousands of these machines so maybe our project will create somewhat of a following around restoring and upgrading these vintage type machines.Thanks to all those who took the time to read and anyone that is contributing to Precious Plastic! I will post more updates.
Love and Trash,
I like the replaceable teeth idea, one thing I’m not sure if you have considered yet or not, would be creating a tooth design compatible with a current commercially available industrial shredder so that we may either create the teeth ourselves or purchase the OEM teeth ready to go.
I dare say no premade teeth would be particularly cheap, although they would be made to handle industrial loads AND in some countries if fabrication availability is an issue, sourcing a commercial product might not be.
I like that upside down lawnmower. although ll bet some curved leaf spring two pieces, and curved one up and one down so same arrangement and sharpened would work too.
btmetz – I like those photos – and I think using spring steel is a great idea for the rest of the world. Dont have a laser cutter, just a torch and a drill press? Even auto/truck axels are decent, because they have splined ends. Splined ends could be mated to pulleys, or at least ground down to a specific profile, using the splines as a guide. This is what I read recently to make me think – I likey…
“Truck and Auto Axels have been a favorite for making hardies and hammers as they are one of the largest pieces of forged steel on an automobile. Note that the flange on some axels is the perfect shape for a mushroom stake with a little work. The splined end has been used for texturing. “
Grind them down for the blade, and maybe even use them as the axle of the shredder? My first world mind still loves the idea of using carbide though…
Regarding the hex or square or keyed shaft, I though that having a round shaft where all the parts are bolted together might be a good option. The end piece would be a gear or pulley also bolted through. A gear could easily be laser cut like the rest of the blades, therefore the bolt holes easy to locate. A spacer on either end gives clearance for the bolt heads and a bearing outside of them. A large gear/pulley would contribute to the gear ratio needed for the pp shredder with most off the shelf motors.
for those looking to do a 2 stage machine, have you thought about using the saw blade design to shredd in strips and then then the standard precious plastic design beneath to cross cut it. similar to some paper shredders?
Well, this seems to be almost an indusrial one, how many kilos of shredded plastic per hour ? Or you just have the blueprints in SolidWorks and have not make it in real ?
I wonder if something like this could work. This is engineered for lettuce and cabbage, but perhaps a more robust prototype could press plastic bottles into small squares.
Thanks for the video, didn’t knew something like this even exists!
My plan is to use for the automatic systems pistons (cheaper) or electric driven spindles. So we will track the torque curve of the shredder shaft, and as soon as it hits a certain limit the pusher can be stopped and reversed everywhere. In theory this can enable to use a wider Range of motors, due the jamms can be reduced.
About sharpening I’am not that worried right now, but we keep in mind to design maybe a small sharpening station with it so everyone can do it in the workshop.
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