I recently watched a documentary on recycling in which they showed a machine which takes waste insulated copper wire and separates the copper from the plastic insulation.
Specifically: random lengths and weights of plastic coated copper wire are dumped into a hopper at one end. At the other end two streams are discharged into individual hoppers: clean copper; and the insulation.
My question: given that the plastic insulation is tightly bound to the copper wire, and the feed is random lengths and weights, how exactly is the copper extracted from the plastic?
I would imagine it works exactly the way a regular wire stripper works. Grabs a big of bare copper (maybe the have to strip the first inch by hand) and then holds back the insulation while it pulls on the metal. As for differing gauges, I suppose it could clamp down on the wire with two metal blades and use a sensor system to be able to tell when it hits metal and then loosen it’s grip just a little bit. Oooh, a continuity detector would work to know when it hits metal instead of a force gauge.
I don’t know how that process works. I worked for a large wire and cable company in the early 80’s, part of the time in the plant that recycled their scrap. They ground it up and used vibrating machinery to separate the copper and insulation by the density. Most insulation runs from about 1.0 to 1.5. Copper is 8.9. Their process did somewhat depend on manual adjustments.
Some of the larger wire was stripped.
This machine seems to work like a planer, but you still have to separate the two parts by hand. Note that different size wires go into different spots in the back.
i wanted to ask him how fine the end-products come out. if very fine, yes, density separation is likely used. a separation through static electricy might also be used.
I found this video on Youtube which shows a machine in action:
As you will see, the idea of grabbing individual wires and stripping them doesn’t seem either feasible or efficient; particularly since the feed is random.
Evidently, the wire is chopped into small bits (about one quarter inch lengths?), and then the copper is somehow extracted from the plastic.
Once the copper is extracted from the plastic, separation of those two components could probably be easily achieved by simple air classification and screening. This would be the easy bit.
But how is the copper extracted from the plastic???
They grind it to the consistency of coarse ground pepper, the insulation is not bonded to the copper except by elastic force, once it is ground that small they separate.
They then use air classification as you mentioned, a process more correctly known as elutriation.
Some units can separate out aluminum in the same pass also.
They could be using magnets. (This is possible despite copper being a non ferrous metal)
Yep, that’s how they separate aluminum cans - they create eddy currents in the cans, thereby making them temporarily magnetic. Amazing machine, really.
