According to [Alex] it is easy to make your own rolls of 3D printing filament, even though existing off-the-shelf solutions don’t work very well. His explanation for this is economics. He built a filament extruder using a high torque induction motor and gearbox that was locally sourced. He argues that shipping heavy gear around would make a similar extruder commercially unattractive. He sunk about $600 into the device but estimates that a company would need to charge at least $1,500 or more for the same thing. That may seem steep but as [Alex] points out, a 1 kg roll of filament really only has about 750 grams for filament and plastic pellets cost $2 to $3 per kilogram.
There are other costs, of course, like the electricity required to heat and move the plastic. Still, the system appears to use about $1 of electricity for every 10 kg of filament. You can see the process in the video below.
If you think about it, the mechanism isn’t too different from a 3D printer. You heat plastic, force it through a nozzle, and it cools off. The big differences are you are not moving around and have to manage the pellets using a screw feed. It turns out the screw and associated components make up a large part of the machine’s cost.
The other key component is a 1 HP motor. A typical motor will run at 1800 RPM, so you also need a gearbox to slow things down. You’ll also need drive electronics, heaters, and temperature control. If you pay retail for everything, you are going to have trouble matching the $600 price tag. However, the motors and quite a bit of it can be found used or salvaged. A lot of the details are in the second post. The details of the part of the machine that winds the new filament are in yet another post.
If you don’t want to spend quite as much, you can also make a smaller version that can produce about 2 kg per hour as opposed to the 5 kg per hour that the big machine makes. The little sister uses an eBike motor and the whole thing should come in for well under $500. There are several other posts linked from the original ones, including notes on the water bath required, measuring filament thickness, and even selling filament for profit.