[papercreters] Grinding and bagging EPS (aka Styrofoam)

The best way I have developed so far to grind EPS works as follows:

-BUILD AT YOUR OWN RISK-

1) First you will need an electric foam slicer. Here's a good one on instructables .

The slicer is used to convert big pieces of EPS into ones small enough to drop into the grinder. You don't need to slice EPS that is small enough or weak enough to feed into that machine, and as you might expect the slicing process makes toxic smoke so use this tool as little as possible and of course only in a well ventilated area.

Bigger slicing machines can also be built, this can be as simple as finding the heating element from a home heating unit and making a wooden frame to create a 2" grid of wires (that don't touch each other). I just used screws into wood to route the wires, the wood will get scorched a bit but it won't catch on fire if you do it right. Note that the wires will droop (lengthen) when they are energized, and if they touch they will shorten the wire assembly, which will cause it to get MUCH hotter than if the current is forced to go through the entire length of the wire.

Build a chute that feeds into the slicer, and a frame to hold the slicer up at the right height to fit over a large cardboard box. When you drop the EPS through the slicer, it gets cut into 2" x 2" strips. these will feed nicely into the shredder. if you want to get fancy put a rheostat on it so you can control the wire temperatures. I found that if you use all the wire that comes on one loop of the heating element direct AC current will not overheat the wires. They do get hot enough to light stuff on fire, so BE CAREFUL.

2) Find a nice big (10 HP) chipper shredder. The little ones suck, trust me. Remove the screen (its at the bottom) and either add another screen onto the outside of that one or replace it altogether. The hammering action inside the chipper will tear up the screen if it is not durable. The screen you make can have holes about 1/4" or larger, depends on what kind of mix you're after. Smaller holes will make the process slower but will result in a smoother mixture, which is only real important if you are spraying it. A 3/8" hole will work fine.

Around the outside of the screen, build a plenum that can attach to an electric leaf blower (set up in vacuum mode). This blower will suck the beads through the screen and direct them into the bagger. Use the tubes for the leaf vacuum or dryer tubing to connect it together, and lots of gorilla tape :-)

3) Make a bagger. I used a large plastic garbage can. You can place a liner bag inside the can, and close the lid to seal it up. The lid of the can needs a hole for the tube from the blower, but it also needs a screened vent to allow all that air to get out (and keep the beads inside). I use a mesh bag, that prevents the screen from clogging with dust too often.

Always turn the blower on before you start shredding the EPS, and turn it off after the shredder is stopped.

I have made one of these setups using electric chippers, they are 5x slower than the gas ones and if pushed hard they will trip a 15 amp circuit. With the 10 hp gas chipper I can make about 10 cu ft of EPS beads in about 15 minutes. Next up is a 60 HP hammer mill, that will likely speed up the process up a tad :-)

If these instructions aren't enough to get you there you might not be ready to make stuff like this. I might be persuaded to make one for you for a good price, email if that's what you want.

Cheers!
Aquaponic Dave

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