The Brute-Force Fan Duct for Prusa i3 MK2 carriages

thingiverse

Most fan ducts I've used in the past have all had a pretty similar idea behind them: tightly constrained, small air outlets, precisely pointed right below the nozzle. Unfortunately, none of them have actually worked well for me. I always thought this approach was a bit silly: Having a tightly directed, precisely pointed airflow outlet doesn't really help if there's no air coming out of it, and pushing the air through 5 90-degree bends means that indeed, there's going to be practically no air coming out. This is where the BFFD comes in. Instead of creating a long, complex, constrained air path, I basically just pointed a 5015 blower in the general direction of the nozzle. There's a bit of a duct still just to center the air blowing at the nozzle, but apart from that, a big full blast of air comes at, below, and all around the nozzle. It's worked wonders for me. My blower isn't all that powerful, and with this duct, it cools far better than any other tightly constrained duct with a powerful blower I've encountered. I've included two pics of what this solution has been able to do: one 80-degree overhang printed with barely any drooping, and one layer shift that was saved with just a few millimeters left for the print to hang on to. (Alternatively named the "Point the damn fan at the damn part duct".)