Forum Replies Created

Viewing 20 replies - 1 through 20 (of 20 total)
sort on most likes
starter
05/05/2019 at 21:43
2

If you get  wood chopper just be aware that there are two types. The type you want includes a gearbox which slows the blade down so it slowly grinds the wood. There is another type which has a very fast spinning disc with blades on it. The fast type doesn’t work well with plastic – it makes a huge noise and takes a very long time; eventually you end up with a plastic dust which is not very good for several reasons (hard to collect, blows around, colours get so well mixed that everything you make is brown).

starter
03/05/2019 at 22:16
2

Single phase shredding can work. The torque can be high enough if you are willing to accept a slower speed. Look at this thread: https://davehakkens.nl/community/forums/topic/shredder-bulid-idea/
I’m working on a shredder using the same basis, but it’s not finished yet.

starter
08/01/2019 at 00:00
0

OK, so “manchon hidraulico” in english is “jaw coupling” (the literal translation from spanish comes out as “hydraulic stain”). Anyway, from what I can tell, they aren’t designed to be used as a clutch (pleae correct me if I’m wrong about this). I guess they might be OK if the machine was stopped each time they were engaged or disengaged…. Any thoughts?
This video shows something that would work well, but I can’t find anyone selling these, so I’d have to make it from scratch: https://www.youtube.com/watch?v=Z93j7EaOV6Y Does this mechnaims have a name? It’s kinda like a dog clutch I think.

starter
07/01/2019 at 23:58
0

OK, so “manchon hidraulico” in english is “jaw coupling” (the literal translation from spanish comes out as “hydraulic stain”). Anyway, from what I can tell, they aren’t designed to be used as a clutch (pleae correct me if I’m wrong about this). I guess they might be OK if the machine was stopped each time they were engaged or disengaged…. Any thoughts?
This video shows something that would work well, but I can’t find anyone selling these, so I’d have to make it from scratch: https://www.youtube.com/watch?v=Z93j7EaOV6Y Does this mechnaims have a name? It’d kinda like a dog clutch I think.

starter
02/01/2019 at 23:40
0

Thanks cymek. For my project I’m planning to transport the machines for the UK to Uganda, so saving weight and size is very helpful.
I’m thinking through some different options to use the same motor for both the shredder and the extruder. My current plan is to use a very simple gear box with 3 gears, one on the main axel, one on the drill and a third in between then which can be moved in and out of alignment with the other 2. This would start and stop the extruder. To star and stop the shredder I’m thinking about sliding the shredder box (possibly on drawer runners) back and forth to engage and disenegage with the main axle. It should be possible to connect the shredder box to the middle gear so that it is not possible to have both machines running at the same time. I’m not sure if that is desirable or not.
I wondered about using a bike chain rather than gears, but I suspect that the torque would be enough to stretch or possibly snap the chain?
To connect the shredder to the axle I’d imagined something like the “manchon hidraulico” but I don’t know the english term for them (does anyone here know?). My plan is to make amould for one so I can make it on the injection machine. The idea behnd this is:
1) I can design the connetor to break at a given torque so that the shredder doesn’t break.
2) If/when it breaks I can make another one with the injection machine.

starter
28/12/2018 at 13:10
0

Great to see these updates. The power rating of the motors you’re using is much higher than the 375W that was in the old designs; this makes me think that it would be worth considering using the same motor as the shredder.
I’m almost finished making a shredder with a 2.5kW single phase motor (based on this post https://davehakkens.nl/community/forums/topic/shredder-bulid-idea/ )
If you’re now using a 2.2kW motor for the extrusion machine then I’m thinking I could save money, resources and shipping weight by using the same motor for both. Of course, the energy consumption will be a little higher, but from what you’re saying, it sounds like the productivity of the machine increases too. Unless anyone here can see a flaw in this approach I’ll crack on and let you know how it goes…

starter
27/10/2018 at 23:10
2

Nice solution. I’m planning to make a couple from plastic (using the injection machine). My logic is that I make the coupler’s thinnest point about as thick as I want to be able to shred so if I exceed this the coupler should break. Then I uder the mould to make a new one.

In reply to: Asking about the Mold

starter
27/10/2018 at 23:04
0

I see that several of the moulds are made from steel. Does it not get rusty?

In reply to: shredder build IDEA

starter
29/08/2018 at 08:22
2

Hi Leflora
Using a non-modified shredder is certainly easy but unfortunately it is not very effective.
There are 2 basic types of garden shredder:
The type being modified in the thread above grinds the wood using a slowly rotating wheel with sharp teeth. If you put plastic through this it will basically just squash it and occasionally cut through it. It will produce large pieces of squashed plastic. If the plastic is something brittle (e.g. a CD case) then it will shatter and the pieces will be a bit smaller.
The other type of shredder uses a fast spinning disc with two or more slits in it; there is a sharp blade attached to the edge of each slit. If you put plastic in this then the high speed of the wheel means that the plastic bounces around for ages. The pieces that emerge tend to be of a very wide range of sizes from a fine dust up to large flat pieces measuing up to 5cm across. The slits let through the large flat pieces, so I tried putting a mesh across the slits (drilling into the disc), but the same size pieses can also slip around the wheel. If you put in a big lump of plastic (e.g. waste from the injection machine) then it bounces around making a very loud noise for a long time. The output from this type of shredder is slow but might be suitable for the compression machine. The injection machine and extruder will need a smaller more regularly sized plastic.
So sadly using a non-modified garden shredder is not a great option unless you’re only going to use the compression machine. I have a seen a few people on PP who have found second-hand industrial plastic shredders – presumably these are more expensive? Or there are people in the Bazar who will make machines for you (generally for 1000 euros or more).

starter
06/08/2018 at 08:24
1

Great idea with the paper comb template.
I notice that several people in the Bazar are selling non-stainless laser-cut parts for the shredder, (@xxxolivierxxx is one). Has anyone got any feedback on how well this works in the long-term?
Rehardox, I wonder how well it resists wearing against itself.
@michael5254 asked for the download link, it’s here:
https://preciousplastic.com/en/videos/download.html
Note that there is an upgrades folder which has modified versions of some machines/parts.

starter
05/08/2018 at 23:23
1

I notice you that several people are using non-stainless steel for the shredder. How well does this perform? I’d have thought that the steel would rust pretty quickly unless the plastic is always 100% dry?

starter
04/08/2018 at 13:58
1

I don’t think hardox is stainless is it? How important do people think the stainless aspect is?
Reading the discussion above, I agree that the photo looks like metal-on-metal wearing. If no metal has been dropped in the machine then the most likely scenario seems to be that the blades have managed to move/bend whilst shredding and have scraped against each other. Thicker or shorter or stiffer blades would be less vulnerable to this risk.

starter
30/07/2018 at 21:56
2

I’m starting work on the extrusion machine. I’ve been searching these forums for some info on what sorts of motor work well for this; there are loads of posts about the shredder motor but very little I can find on the extrusion motor – can anyone point me to some good threads on this or put info here (this seems like the best place for it (a sticky thread on motors, but the google doc is almost all about the shredder).
Ideally I’d like some tips on what sort of equipment has the correct type of motors and gearboxes in them; or is it best to buy a new motor and gearbox set?
This thread on the shredder motor is great:

shredder build IDEA


Is there anything similar out there for the extrusion machine?
Thanks

starter
26/07/2018 at 08:27
1

Thanks for raising this questions @billa14
I was planning to order laser cut parts for a shredder yesterday and then read this thread and I’m now not sure what to do.
It seems odd that this topic hasn’t been raised by anyone before (that I’ve noticed anyway) as the shredder design has been out for a long time now. Is it possible that this is an unfortunate rare occurrence which has affected @billa14. I notice that he/she hasn’t added any further responses on this thread and there’s no detail of exactly which stainless steel was used or pictures of how the blades have worn. Have the blades got thinner (through rubbing the neighbouring blade) or just worn away along the cutting edge?
As has been pointed out there are many types of stainless steel. I don’t know a lot about metallurgy (I’ve forgotten most of what I was taught over a decade ago now) but based on this page it sounds like a martensitic type would be good.
https://www.bssa.org.uk/faq.php?id=10
Has anyone else reported a similar wearing problem?
Two related points to consider (touched on above):
Should we be applying a hardening process to the blades?
Would it help if the blades were sharpened? A 6mm wide leading edge can’t be the most efficient way to cut through plastic. Sharpening would also reduce the torque required but may result in faster wearing if the wrong material was used.

In reply to: shredder build IDEA

starter
21/07/2018 at 17:41
1

I’ve been researching different ways to go about building the shredder (different motor options etc.) and this definitely looks like the best. Someone suggested the motor was a bit slow – looks fast enough in the video,  do you happen to know the RPM? This looks like this model from Titan (am I correct?) https://www.screwfix.com/p/titan-ttb683shr-2500w-200kg-hr-garden-shredder-230v/6887P?kpid=6887P Even new it’s pretty cheap considering I was looking at an industrial motor and gear box for £350 without any of the switches or controls included.
What’s the thickest thing you’ve managed to get it to munch?

starter
30/05/2018 at 08:02
0

Thanks. Another method which seems to work is to firstly use the plastic bags in the compression machine and then to put the waste plastic which overflows from this into the shredder. The overflowed plastic is much thicker and stiffer than the original plastic bags and so shreds much better.

In reply to: Shredding

starter
05/04/2018 at 08:20
1

Great Questions above. May I add another question?
I’ve watched all of the PP videos I can find and read most of the webpages and a lot of the forums but I don’t recall seeing anything about putting plastic bags or other thin plastic sheets into the shredder. I can imagine that the thin plastic might work between the blades and tangle around the axle. Does this happen or is the shredder tolerance so tight that it cuts the bags as intended?

starter
07/08/2017 at 23:02
0

Hi Soren. Sorry, I thought I replied already. We’re hoping to set these up in Rubanda and our main aim is to make flower pots but we have some other ideas. We have a machine design of our own which is similar to the Precious Plastic solution (developed entirely independently years ago but not managed to get it off the ground yet. My thinking now is to make some of the Precious plastic machines and use them alongside our own design to have a more flexible production line. The machine we have is a bit more complex to make (the mould part particularly, but the pot is big and strong, it’s a bit like the fruit bowls in the PP videos, but quicker and less energy intensive to make. That said, it’s not a quick as I’d like (around 30 minutes per pot) so I’m currently redesigning the machine to make it quicker. Check out some more pictures on: http://www.concino.co.uk/ and https://sites.google.com/site/gepuganda/

starter
17/06/2017 at 18:57
1

… also wondering which part of Uganda you are in. I’m hoping to develop a machine to take out to southern Uganda.

starter
17/06/2017 at 18:56
0

Hi Soeren
I’m very interested in your ideas here, especially the use of cement to make a mould. Do you make the handle in 2 parts and then stick them together when the plastic has cooled, or can you put the two halves of the mould together and make the whole handle in 1 piece?
Either way I think you’ve figured out a way to make a mould with very simple technology (no need to shape metal using a lathe, or welding etc.)
I think you could embed a plumbing attachment in the cement before it sets and then you’d be able to screw the mould on to the injection machine directly.
Ewan

Viewing 20 replies - 1 through 20 (of 20 total)