Blades

Polymer Craft General
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I’m in the process of looking at exactly what I need for the shredder, I don’t have an engineering background or anything of the sort, but have family that are more than capable of building most of the machine.

I’ve been looking at the blades, and how for some, they are proving very costly.

I’ve also been thinking that I’d like a twin shaft set up, as I (rightly or Wrongly), believe that it pulls the plastic in better

Anyway, this has led me to look around for blade alternatives. Whilst doing so, I came across the attached blades on ebay.

Would these work? Or do they have too many teeth? Or not thick enough, or strong enough? Or one of a million other things I haven’t thought of?

Thanks in advance for the help.

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this has been tried a few times, and it doesn’t look or work great at all… i would just forget the whole idea, it’s insane, dangerous and just not fit for the job.

the laser cut set should cost you not more than 300 Euro in the EU and the required 2.2 Kw drive part with couplings is around 600 Euro (check second traders and machine shops around you)

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Thanks for that, I’ll check out the link.

I’m pretty certain we can’t buy granulated plastic from the recycling plants here, the other problem is that our recycling centres only recycle a very limited range of plastic (literally just plastic bottles), so we want to recycle more for eg our yogurt pots.

Appreciate the help, and know there is a long road between here and making anything of any use.

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you’re welcome! ebay (‘plastic granulator’) , here you go : https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2380057.m570.l1311.R1.TR2.TRC1.A0.H0.Xplastic+gran.TRS0&_nkw=plastic+granulator&_sacat=0

it will take some time to find one and make sure you can deal with blade maintenance or part replacements. however, it’s quite a good fit if you consider to shred a lot.

But honestly, I think buying it from your next recycle spot, is way more economic, green and clean = noble, since you get it pre-sorted, washed and at price 1/10 of what you could ever manage with a PP shredder.  A proper shredder should have at least 4KW,  running usually at 30% of it’s max (1.5 KW) – efficiency wise…

I should mention at this point that PP machines and know-how is just the first step, it’s called material development. Once you’ve got the chips, it can take months to figure out what you actually want or could do with it.

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Thanks for taking the time to write all that, I can see the issues now thank you.

With regards to the machines, yes, we’ll be having a good think about what we’ll be making and therefore what we’ll need, long before we start making anything.

The shredder is obviously the starting point for it all for us. I’ve not really seen any plastic shredders on ebay, not of an appropriate size? The only ones on there seem to be large industrial ones.

I’ll certainly keep looking though, and will definitely be looking into the other machines on there too.

Thanks again

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hey,
can you please search the forum for ‘saw blades’, there are couple of posts about. on you tube you can find quite some stuff as well : ‘saw blades shredder’, ie:  https://www.youtube.com/watch?v=Us1NIza0V3k

the main reason why saw blades are just not fit to shred common house hold waste is that there is no clearance enough to tear plastic apart. I saw Dave trying a few shapes with way less clearance : it’s just not working, period. you won’t get chips out of such thing with the dimensions needed : 2 – 4 mm.

From a machining standpoint it seems rather difficult that you get spacers with such large diameter, fitting properly on an hexbar or whatever axle. If don’t put spacers between such blades, the blades could eventually break, jumping out of the shredder, killing you, your dog or the birds next trees. Nobody want’s this (well, not me at least) !

kidding aside, the only re-fitting chance i see for saw blades is to grind totally different things out of it but that’s it or build something which cuts some larger plastic down to shredder friendly sizes, ie: bottles, etc…but that’s better done at a vertical band-saw.

costs 4 machines: count on 1000-2500 Euro (mostly using second hand stuff), another 200-500 for the tools : grinder, drill press and a stick welder; well, and plenty of spare time (see you in 2 months mate!).

tip: you are better off by knowing what you actually want long before you spent $$. In 80% of the cases you just need a shredder (sometimes cheaper and better on ebay btw. or better: just buy it from your next recycling center, much cheaper and cleaner,….) and the machine(s) which spits out your product/project which are more likely not PP machines but rather second hand injection mold machines, hydraulic presses, pizza-ovens, vacuum tables, blow tables,…etc…did i mention the insane expensive molds too ? …

good luck man! and dont forget that i can be of course totally wrong 🙂

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Thanks for the swift reply.

I’m not too concerned about the look, but can I ask why its dangerous? Are these sorts of blades liable to fracturing etc,?

The idea was a row of these (or similar), with spacers, connected up to a similar set up as the original designs

The blades would obviously be moving a lot slower than they would be on a saw.

I’m happy to accept that this doesn’t work, but I’d appreciate an explanation as to why.

€300 is a considerable sum, for what is a small part of the overall set up (the 4 machines).

If it comes to it, I’ll pay it of course, as the safety and useability are paramount, but blades like this are obviously much cheaper, and easier to replace when needed

Thanks again