I 3D print a ton. Having the ability to print multiple things at once is a lifesaver when you are in the process of designing enclosures or functional products. But, my printers accept different sizes of filament. This incompatibility made it inefficient and hard to utilize both the printers as I would have to buy both sizes of each material.
As it turns out, Lulzbot is a company that prides themselves on being 100% open source. I decided to build a version of their new Aerostruder, but with a 1.75mm Titan Aero hotend instead of the standard 3mm Aero hotend that came with it.
Plus, the retail cost was $375 at the time, and I built this extruder for under $100.
I ended up buying a cloned version of the hotend off of Aliexpress for two reasons, one, it was half the price of the real one, and two, the real one was out of stock and I was on a time constraint before school started back up. The other parts such as the stepper motor and blower fan I happened to already have on hand in the spare parts bin (aka the remnants of past projects.)
Assembly of the extruder was pretty straightforward, I just followed the instructions over on the OHAI page, but installed the 1.75mm hotend instead. I did run into issues due to the fact that for some reason the clone version of the hotend isn't long enough to protrude past the fan duct. This caused the auto leveling sequence to fail and I almost ended up breaking the whole X carriage when I left it to print by itself for the first time. Thinking back, I probably shouldn't have done that ;).
I had to completely redesign the mount and fan ducts for this extruder to work properly, but the ability to use one size of filament for both of my printers is priceless. Now, I can print two parts of the same design without having to worry about if the tolerances will play nice with each other.