I suspect that making filament is like using filament (printing) - you have to watch it like a hawk. There’s a guy in town who sells filament very cheaply - his webpage is very eye-catching because he sells lots of colors and varieties, and the price can’t be beat. So I bought 6 rolls of various colors PLA from him and most of it is gathering dust on my shelf. The two main problems were consistent thickness, or rather the appallingly dismal lack thereof. From one meter to the next, thickness could vary from 1.5 to almost 2.0mm, too thick to fit through the feeder hose. The second problem was garbage in the mix. One of the colors I ordered was actually uncolored (natural), which was clear enough that you could see tiny black specks throughout. Tiny to my eyes, that is, NOT to my printer nozzle. Clog City! In the end, a reputable filament reseller confided in me that this amazing shop was actually one guy with two homemade extruders in his apartment, and due to huge demand he was severely overworking them. In reality, you need to monitor the process closely to keep consistent speed which equals consistent thickness, and even then not always. Apparently extruding is just like printing, agonizingly slow and very tempting to speed up. That said, if I had the technical knowhow or the money to pay someone who did, I’d love to fool around with extruding my own. I would just have a few boxes of Velleman filament standing by when it came time to do real work.