Sound like an interesting idea, but probably quite limited in practice. They write that you can produce 20m segments of filament on a 30x30cm bed. That is alrea

Sound like an interesting idea, but probably quite limited in practice. They write that you can produce 20m segments of filament on a 30x30cm bed. That is already a somewhat large printbed, and 20m is not that much filament. So it seems like the use case would be small objects only. 3D printers can be very finicky, and I'd worry that the filament diameter and properties would be variable enough to cause issues here. My impression is that multi-color printing is far more limited by the amount of effort one is willing to spend on tuning everything until it works than just money.