A Different Kind of Plastic Shredder for 3D Filament Making

Hackaday ^ | June 14, 2015 | James Hobson

[2ndDivisionVet]

Haven’t you heard? You can make your own 3D filament nowadays from plastic granules (10X cheaper than filament), or even by recycling old plastic! Except if you’re recycling plastic you will have to shred it first…

[David Watkins] came up with a different way of shredding plastic. Typically we’ve seen shrunken versions of giant metal shredders used to dice up plastic into granules that can be melted down and then extruded back into filament. These work with a series of sharp toothed gears that kind of look like a stack of circular saw blades put together inside of a housing.

But that can be rather pricey. [David’s] method is super cheap, and you can do it at home with minimal tools, and maybe $10 or less worth of parts?

It’s pretty simple actually. All you need are two steel pipes, one that will fit inside of the other. Cut a slot into each pipe, sharpen the edges of the inner pipe’s slot, and spin the inner pipe with a bit of mechanical leverage — or you can get fancy and automate it with a high-torque geared motor.

The shredded plastic does seem a bit big, but you could have various sizes of pipe in order to get it down to a smaller granule size. Regardless, it’s gotta be the least expensive way to shred plastic we’ve ever seen. Short of doing it by hand with a pair of tin snips anyway.

What do you think? [David] would love to hear some ideas from you on ways to improve the system — and if you like it, don’t forget to vote for him in the current Instructables contest — he could win a 3D printer!

[kinsman redeemer]

It looks like it will be very hot. There’s a lot of surface contact in the mechanism.

[philman_36]

He would be better served to use solid stock and bearings for the inner rotating section, similar to this. Press them on the solid stock and inside the outer pipe ends and you have it.

Also, a wood planing cutting disc would give a better cut and have a longer life.

The other benefit of the planing cutting disc/solid stock is that you would simply have to drill and tap a hole on the end of the solid stock and attach it with a single bolt, Locktite and lock washer. A hand crank in the same manner on the other end for mechanical advantage and...

Walla!

[philman_36]

Or he could build a base/table and use these...

...but you lose the outer pipe as the outer cutting edge.
Something else would have to be built for that.