Personal Mini Shredder (Page 1 of 2)

How fine does it shred?

needs to be able to take scrap ABS filament pieces or chunks of failed prints and make all about BB sized pellets to feed into a Filastruder. repurposed paper shredder cant do it. this is needed with Filastruder so we can recycle support material etc and stop waste. food processors wont either tried both. need like a coffee grinder style with maybe a diamond rasp blade or mini wood chipper.

Exactly.

That... isn't true.

I've been looking at this for a long time, and I can't make anything outside of centralized recycling (like Ggalisky's setup) work out. Lets take a look at the numbers.

Lets assume you're able to machine those teeth out of hard steel (or conversely, soft steel and then heat treat them) for $5/ea. Even a small shredder needs 10 teeth per shaft, plus the cleaning spacers (do not need to be hardened). You're looking at ~$150 before you've even made a chassis (6061, I'd assume) and bearings. You might be able to do it with a BoM of $175. Maybe. It is commonly accepted that your retail price must be at least 2.3x BoM, even in maker businesses. Now you're looking at $400/ea - lets assume you do free shipping just to make the numbers easy.

$400 buys a lot of pellets. Lets take a look at the three options:

Virgin Pellets
It buys 120lbs of 4043D PLA (shipped, from OS3DP) or 100lbs of MG94 ABS. That is a lifetime supply for most folks - in fact, I'm only aware of one Filastruder customer that has extruded more than this from their machine.

Centralized recycling
You can fit about 10lbs of failed prints in a large flat rate box, which costs $15 to ship. It can be returned in a medium flat rate box, which costs $10 to ship. It takes about 10 minutes to granulate and reship, so figure on $5 for that - now you're looking at $30 for 10lbs of regrind (recycled prints). Your $400 buys 130lbs of either ABS or PLA worst case, maybe more if you live closer to the recycler and can use by-weight shipping for a lower cost.

Distributed recycling
As noted above, the cheapest a shredder could realistically be sold is about $400. Note that this would be cheaper than the cheapest shredder on the market. However, such a shredder would be hand cranked, so now we need to value time as part of the equation. Let optimistically assume you can shred 1lb in 15 minutes by hand. Based on reports from other shredders on the market, this is likely optimistic. You're then looking at 32 hours of time to shred 130lbs, which at reasonable wages ($15/hr) is already more expensive per pound than centralized recycling - and you haven't even started to pay off the shredder yet.

That raises the next point - in order to pay off the shredder, you're looking at needing over 100lbs of failed prints. Remember how I said 100lbs would likely be a lifetime supply of filament? Very, very few people are going to have enough prints to even break even on a $400 (or $300, if you make the mistake of selling for less than the rule of thumb) shredder. I print on average 6-8 hours a day, every day, and I've amassed about 30lbs of failed prints in total - on over 200lbs of filament.

I'd love for the economics to work for personal shredders - but I can't in good conscience go down that road until either shipping gets much more expensive, or heat treated blades get cheaper. Like real cheap.

yep I see both sides but still dont see how 1 location way out on the west coast can get others thousands of miles away to save, package and ship scrap plastic to and from a 'NON centralized' long distance recycler. maybe if every local recycling station world/nation wide offered this service then not only would it take shipping/packaging cost out but also lower the 'carbon footprint' of all the fuel used doing so which is 95% of what drives people to recycle. also I dont pay myself or my family to help recycle so... for this to work it MUST be so easy even in-house easy that people have no excuse not to recycle their waste what ever it is. plus as you said lifetime of plastic so that means those that can recycle can resell their excess to locals that use that material. same thing applies to all "green tech" look at the Bio fuels they come from same place as PLA. thats why you here pro 3D printing reporters saying you can literally grow your material on site, print, recycle whats left, repeat.

The shipping costs I quoted above are flat rate (same cost throughout the US). It takes less than 5 minutes to print a label, fill a box, tape it shut and stick the label on. USPS picks up from your house, no need to do anything besides set it outside.

I'm glad you brought that up. USPS has to deliver to every house ever day anyway, adding a 10lb package to a 5000lb truck does not produce a significant increase in the carbon footprint or fuel costs.

Which is easier? Cranking a shredder for 3 hours (to do 10lbs) or spending 5 minutes to slap a label on a box?

"Which is easier? Cranking a shredder for 3 hours (to do 10lbs) or spending 5 minutes to slap a label on a box?"

well considering how low my fixed income is thats a no brainer LMAO aint got the postage money nor money for packing materials. nor gas/leg power to take it to post office. plus when I can buy a 2 pound roll of ABS or PLA for under $20, wheres the motivation to spend the money on postage etc.?

That's even worse! The product liability is enormous! There's a reason all the shredders on the market are manual.

Also not sure how I could have "done my homework" when you haven't released such details. I assumed there was no way you'd sell a motorized shredder capable of removing fingers to the general public. I guess that was an assumption though, you're right.

Interested to see where you're sourcing 150N-m gearmotors at this price point as well. You're making a lot of promises!

Here's an example of the type of motor and gearbox you need for a shredder:

https://www.youtube.com/watch?v=wzA4tgpsEHY

If you can source those brand new and in quantity for under $100, I'll take a truckload!

Btw, that guy recycles TVs using a Filastruder:

http://forum.seemecnc.com/viewtopic.php?f=80&t=6285

Pretty cool setup he has there. He has about $1200 in the shredder alone, though.

And you should check out their website if you haven't been.  They have a printer that is about 10' tall.  As for him being cranky I'm sure he would love people to be able to recycle at home.  That opens up the market for his extruder.  Unless I'm completely missing something.

I'm not sure why you continually feel the need to insult me.

You must not be reading what I'm saying, so I'll try to clarify for you.

There's a reason all consumer-oriented shredders on the market are manual.

There is definitely liability in that.

http://tucson.com/news/local/crime/judg … 65918.html

Kit airplane manufacturers get sued all the time for injury/death.

I am not cranky one bit - Its just that I've designed exactly what you showed in your CAD rendering in the OP. I've been there, done that... and I'm trying to save you the trouble but you seem to be uninterested in listening to those that have come before you, so I wish you the best.

Apparently not. I'm not sure why you'd come into this forum and be so adversarial. I'm quite happy to share my experiences openly, you on the other hand don't seem as open to receiving them.