40mm fan duct / pressure booster

thingiverse

I was searching for a way to mount a high CFM 40mm fan and use it as a filament cooler and I've stumbled across a design by phil38. It does it's job of concentrating airflow, but very poorly. So I combined it with a pressure booster (scaled 200% in axial direction) by Adam_86, which increased airflow at the exhaust by A LOT. Though there was a small problem with combining both of these parts together - inside diameters were mismatched by 4mm, smaller one being the duct, which (by thought experiment) restricts the flow by a considerable amount. So I decided to solve this problem by combining both of these parts in one and smooth out the transition between the two so there are no abrupt transitions from one surface to another. The fan mounting surface is made to mate with a standard 40mm fan hole pattern using M3*0.5 screws and nuts. You can design your own mounting bracket to suit your particular printer, you can find the original design for it in phil38's fan duct. Please share your thoughts and suggestions on how to improve the design further!