My Shredder form Tim in Cornwall
This topic contains 8 replies, has 5 voices, and was last updated by Anonymous 9 months ago.
I have just completed my shredder which seems to work well.
The motor is a three phase 2.2 KW unit with a worm gearbox giving 100 rpm at 50Hz.
I do not have three phase but I sourced a very nice little inverter at the same time which gives me full control forward /rev plus speed which I have set from 30- 80 Hz on the control pot.
Drive shaft alighnement is almost impossible to get 100% accurate especially in your shed. I have a solid drive (no flexible coupling) from the gearbox to the shredder box. This is .25mm out of centre I have “accommodated” this by mounting the shredder box on rubber mounts. They are very cheap! This gives an acceptable (for me) .5mm total wobble as the drive shaft rotates.
I have a 5mm screen / sieve to grade the shredder output.
All stainless parts on the shredder box which were cut by Laser master http://www.lasermaster.co.uk down here in Redruth who offer a great service.
The axel I made myself which was asking allot of my Myford 7 lathe (only little) but it worked well.
Here is a short video of it working without a sieve. https://youtu.be/37opr_W8FR8
Many thanks to Dave and his team for making this excellent project available to all.
I will be comentating the technical part when my knowledge en the matter is good enough,
All i have to say in the first point is WOW, your schredder seems to be doing the work !
I wonder though if your machine is not turning too quick ! (doesn’t it get a bit messy once the sieve is installed?)
Once again, congratz ! i’m so looking forward to build my own (or as part of a group) !
Hi Nick yes as the motor is running at 1.5 times normal speed it would want to throw the plastic out of the hopper. I have added a lid to help with this. This is a common addition people make to stop things getting messy.
Shredding like most things is a compromise for your 2.2 KW you can have speed and get the job done quick with thin material or you can have torque to rip through thick material you can’t have both.
The inverter or VFD gives some addition speed control by varying the freqency of the three phase AC power the motor receives.
that machine looks very powerful in the video. how did you wire your motor? im connecting power directly to a 220v 1.9 kw motor. seems like a wrong way to do so . would be nice to get some tip from you .
Thanks for sharing, this looks brilliant.
Do you still have links for the motor parts that you bought?
I’m interested in finding out what sort of cost I’m looking at
motor + gearbox + inverter
@jeanbono, you get really good results with a 4kw (5hp) motor (around 100e), a service class reducer for around 500-600 euro, and the inverter for that power is around 210 euro (make sure it’s not the cheapest, take an original Huanyang ! ). So you’re looking at 800-900 euro but you can run 2 shredders and one extruder on this drive at the same time since it’s pretty efficient setup. btw. we also added 5 more blades :-). however, with such setup you can shred also wood, PVC and all other hard plastic. others say here you could use 2-3 kw only but it seems to stall often and is sensitive to the kind of plastics or feedrate of plastic entering the shredder.
Thanks @anne-barbier that’s really helpful.
Can you specify what a service class reducer is? I’m having hard time finding out. Is it something like a worm gearbox? Do you have any links by any chance?
@jeanbono: here the reducer, it’s ‘SITI’ (italy), pretty much the best choice in the long run(5 years+). about reducers, here’s a rule of thumb of mine: if you have an average shredder torque of 300 Nm (300 times of holding an apple with a fully stretched arm) you can image an sufficient wear in the worm drive! if you go for cheaper reducers, it’s a matter of time you have to replace it (2-3 years, 200-300 euro each time). however, the reducer in the link is one model bigger than you actually need for one shredder, so just google for SITI, look for a MI90 and find distributor in your country :-). if you need a drive shaft and good couplings, i have some stuff in the bazar (catalonia connection :-). here our list.
and here the calculations about the required service factor/class
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