cecilio

starter

09/04/2018 at 01:31

hola
I have a 5.5kW 3 phases motor with a gear reductor to +/-80 rpm, complete with the switch box. It comes from an oil extrudder.
Do u think it will fit to a shredder I made?
saludos
cecilio

xxxolivierxxx

hero

11/04/2018 at 10:30

Hello @cecilio
Yes, it has more than enough torque so it won’t have any problem shredding any plastic. The RPMs are a little high, ideally we would like to keep them close to 60RPM because if the shredder spins too fast it tends to make plastic fly away, but you can probably work around that problem by making a square hopper and push the plastic into the shredder with a cover with a handle, like this one https://bazar.preciousplastic.com/listings/548935-star-usa-star-hopper-for-shredder

fabirihotmail-com

dedicated

22/06/2018 at 06:32

Used a 750w monophase 4 pole Motor with finaln28 rpm and it doesn’t work, so with a 1100w 28 Rpm it will work for sure or it’s possible to use a 750w 14 or 17 rpm and it will have enough torque to work.
At the moment I change my mind And I will use the same shredder of Olivier with a 250w motor and 17 rpm, it has more torque than the one he was using (370w 35 rpm?) If it doesn’t work I will use a 370w 17 rpm and recycle the 250w for the extruder.

xxxolivierxxx

hero

22/06/2018 at 07:33

@fabirihotmail-com 0.37kw at 17rpm should give you 207.83N.m.
Theoretically that should work, but is still far away from the minimum 300n.m recommended to shred plastic

fabirihotmail-com

dedicated

22/06/2018 at 23:44

This is a list of monophase motor with the resultant torque, the data must be lower about 10% due to the reducer efficiency but he give us an idea of which motor can work.
As you can see is no sense use a 2.2 kw motor with 70 rpm, i think we must think in how can be sustainable this project and the first thing is the efficiency.

fabirihotmail-com

dedicated

22/06/2018 at 23:54

@Olivier, this 200 Nm will work perfectly with the filaMaker I will use for built next shredder machine, the final sell cost is quite the same of de PP shredder, due to the cost of the motor, the easyer frame and the lower shipping cost, in add the electricity running cost are minimum 1/3 of the PP shredder, in country where the electricity is expensive this make a lot of difference.
I think in the forum we will put a similar post with the really needed power of the machines, when I read post where people says they usa a 5Hp motor to run the shredder, I feel bad, electricity is no 100% produce from renewable sources so we are fighting plastic pollution but we will create other kind of pollution.

sonik

dedicated

23/06/2018 at 10:08

@fabirihotmail-com Concerning power consumption: 17 rpm will produce more or less 25% of a 70 rpm shredder, Which means that you shredder will run 4 x longer to produce the same amount of plastic.
And of course don’t forget the cosinus phi of your motor for real calculations.

fabirihotmail-com

dedicated

23/06/2018 at 15:53

@Sonik, this is in theory, as you can see in a lot of videos, many times bottles jump from the blades due to the high speed, in add up must consider the dead times between a bottle and the next, so maybe a 70 rpm will probably produce more kg/hour plastic than a 17 rpm but I think no more than twice. The pp shredder run well at 28 rpm, about the Filamaker that run at 17 rpm it has 2 axes so when it takes a bottle it shred all without bottles jumping. By the way I prefer a 20 kg shredder machine that I can transport and use everywhere, with sunpower or windpower instead of a 70 or more kg machine that need high power energy. what do yo think about it? 😉

sonik

dedicated

23/06/2018 at 16:32

The bottle jump can be avoided with the new straight hopper. Did you succeed to run your shredder on wind or solar energy or are you working in that direction?

type: 3 phase
Voltage: 230v
RPM: 1440 rpm
Reducer: 1:20 , SITI – Service Class 1
Output RPM: 72
Power: 4kW
Inverter: 4kw
Quality: Low, I assume a proper ABB motor can do magic here
Result: fail

jams with a few bottles already, i assume the shredder blades/box has to be redesigned.

video here

xxxolivierxxx

hero

24/06/2018 at 06:53

Thanks a lot for sharing your experience @anne-barbier, I’ll add the info to the main topic.
Your motor/gearbox combination should give you close to 530.49N.m which is plenty to shred plastic, I’m surprised to hear that your shredder jams considering how powerful your motor is.
One option would be to add more reduction, that would exponentially increase the torque. I heard that shredders that have double axles and knives with smaller teeth require less torque, so another option would be using a different shredder box, such as the filamaker shredder

sonik

dedicated

24/06/2018 at 09:36

your shredder isn’t finished ?? At 4:11 you see it is just hold with acme-threads. Before assuming redesign of the shredder, maybe you could built it like it is supposed to be built.

@sonik, yeah, this part isn’t done right. still have to work out a better quick release for the hopper before locking it up. seems we need 3 different hoppers: a large one, a straight one, and another straight one with a better feed to re-shred chips again.

@xxxoliverxxx, yeah, i currently looking in a double shaft shredding box, according to a pdf here. those blades are relative easy to make on a cnc mill. i expect first results in sept. (getting finally a real bridgeport mill).

another update i see now is to read out the current amps with an arduino which reverses direction for some little time and then proceeds. if it’s jammed, the amperage goes up to 20 so that should work.

sorry for getting offtopic but shouldn’t we take the blade tip design into account for this data here? having done hundreds of hundreds cutters for the lathe from HSS blanks, I have the strange feeling the tip should have little a different design: 70 angle for the cutting edge and little more clearance and the tip surface should be also at least 0.5 – 1.1 mm high instead of being a perfect sharp V shape… well, i gonna try.

sonik

dedicated

24/06/2018 at 18:40

OMG this is really top-notch-amateur-style. You are not even capable to built the shredder with a video-guide? And you dare to give lessons to the whole community? At least, now, we all know on which level your “skills” are. I am speaking of your claimed 20 years experience in machine building, dozens of cnc’s constructed and all that.

yeah, there are budget & time constraints on this build, it’s blown already since long.

something else? i mean, it’s easy said 🙂

@sonik, by all you mean you ? and by the video guide you mean dave hakkens pretty useless assembly videos for components i don’t even have, nor it’s layout or requirements ? i’mean, c’mon, if you just want fool around, say it more directly, your last messages were clear enough : vomit, no substance, go ahead

@xxxoliverxxx, i had another run with a different cutting edge design, i used similar angles & clearances as recommend for any other cutting tools. no more jamming 🙂

Dave’s initial design of using straight 90 degree cutting edge is too aggressive, if you give it a 10-15 degree twist, it’s cutting like butter, no idea for how long 🙂

i guess i will have to grind or machine a 15 degree taper around the whole blades.

please update: RESULT : success

anyone else, who’s seeking for better cutting/crushing experience or plain single source of truth in that matter, please checkout ‘this old tony’, on cutter design, https://www.youtube.com/watch?v=r8oORR6jyh8 or https://www.youtube.com/watch?v=__A2xtLF0AU. when it comes to cutting, same principles can be applied.

guys, i’ve made another fine tune on the blade tip, i gave the blade tip a 30 degree cutting edge and now it’s cutting like all like butter, the ampo-meter on the inverter shows a 40% drop for the amp peaks compared to before, also way less vibration coming on hard plastic, so it’s cutting at an average of 8 amps now (not sure it’s right but the peak drops are significant). i guess i weld it together now 🙂 what a fecking ride, 3 full days to get here. always good to question EVERYTHING at the end 🙂
g

xxxolivierxxx

hero

25/06/2018 at 22:07

@anne-barbier would you mind sharing a picture of how your shredder blades look like after you modified them? I’m currently building a shredder and I’m interested in testing your mod

here you go,it’s one of the damaged ones but you get an idea, it’s 2-3 hours work with the round file, mine was just sitting in there perfectly. i tried to get more clearance but it requires better hands on the dremel 😉

now as said, it’s questionable whether this blade can survive long like this, but the plastics i tested didn’t made trouble, little to no vibrations compared with before.

stoli

helper

28/06/2018 at 06:34

Owner: stoli
Motor type: single phase
Voltage: 220
HP: 3 (2.4 @80%)
RPM: 1740
Reducer: Worm gear 60:1
RPM:29
Output calculations based on 80% motor and 75% Gearbox :
325 Ft/Lbs (440 NM)
Result: Success

Details: Good RPM, very strong. Rarely needs to reverse.
Built with (2) 4″ pulleys power to drive train so the belt can slip to save the mechanics if it does bind. Flakes in picture is using a 5mm hole sieve.

xxxolivierxxx

hero

28/06/2018 at 06:42

Awesome!
Thanks a lot for your feedback @stoli

xxxolivierxxx

hero

02/07/2018 at 20:49

@anne-barbier have you done any more testing with the filed-down blades? I recently built a shredder with a 4hp motor and it jams frequently so I’m thinking about grinding the blades like yours

@xxxolivierxxx : no, the machine is now at the client’s shop, i am visiting them in a week for inspection. i will let you know :-). but as far i remember, the blades did a real good job, i tried slices of 4cm PVC pipes, no problem! i couldn’t even get it  jammed anymore when throwing 6kg of already shredded plastic chips into the hopper. next time when i get the machine back for adding upgrades, i will install an Raspberry PI to collect data from the inverter 🙂 i believe however that the magic comes from the reducer which was easy to turn with the hand which wasn’t the case with all the reducers i tried at the scrap yard.

xxxolivierxxx

hero

04/07/2018 at 18:22

@anne-barbier I have a 5hp motoreducer that used to be 220v triphase and was converted to 220v monophase using capacitors. In my calculations, the power loss is around 0.75hp which still leaves me with plenty of shredding torque, but the shredder still jams often. I’ll try filing down the blades and see what happens.

@baas Would you mind sharing a pic of what your 220v motor conversion looks like?

@xxxolivierxxx, ack, just to let you know, the capacitor trick isn’t recommended for anything above 3kw! i speak out of experience and i’ve got this told from experts as well (they will laugh at you for even mentioning it), you can however get the  best out of it (always) and go the usual path by using a inverter just, one for 4kw = 220 euro, deal with it 🙂 also, don’t buy the cheapest, you get way more security and long life by buying recommended inverters only! (hy or omron)

xxxolivierxxx

hero

04/07/2018 at 18:56

@anne-barbier I guess I’ll use the capacitors for now and upgrade to a VFD in the future. I was thinking of something like this: https://www.amazon.com/Variable-Frequency-Inverter-Converter-HUANYANG/dp/B0775DC75F/ref=sr_1_3_sspa?ie=UTF8&qid=1530722993&sr=8-3-spons&keywords=220v+vfd&psc=1

@xxxolivierxxx, yup, that’s an original, it has always the orange sticker and a potentiometer, anything else is a crap copy. i had recently one of those cheap clones, it comes with 1/10 of the parameters only, and i burned it up right away 🙂
also, don’t forget, with the right reducer, you are only using 30% – 60 % of what the motor/inverter provides (one shredder with one extrusion simultaneously). that’s why, dont buy second hand reducers 🙂