Today I’m going to talk a bit about the extruder that I chose for my MK3 and why I won’t use the original one..


As I’ve mentioned earlier, the original Prusa i3 MK3 has an extruder that uses “Bondtech”-gears which the manufacturer charges you 50 bucks for.
You might think: “Well, let’s just get them from China!” - That’s what I did, at least! 50€ for a few grams of metal put into a 200€ printer makes no sense to me, even if cloned gears might be slightly less precise or whatnot. In the end they’ll just have to push some filament through the nozzle reliably.

The Big Issue

After having checked both Chinese and local online-shops as well as eBay, I quickly found out something kind of disturbing: This one single part was the only thing on the whole printer that couldn’t be purchased anywhere except the original manufacturer. I have no idea if it’s patented or something, or maybe this is because it hasn’t been used before the MK3 which is still pretty new… If you know more, feel free to E-Mail me! Of course, if you are reading this post in the future, it is possible that cloned gears are available for a few bucks, in that case just go for those and print the original MK3 extruder!

The Solution

So, I thought to myself: Don’t the older i3’s use a regular “MK8 gear”? I knew that fact because I use one myself on my A8’s Bowden-extruder and because I remembered seeing it on the MK2 and MK2S at our FabLab.
Of course, it’s not too big of a deal to use a different hotend; you can swap it out to whichever one you like and your printer will work fine. But my goal here is to build a more or less 1:1 clone of the original MK3 with all of its benefits, for example its extremely low noise levels that are only really possible if you use the same Noctua-fan (besides the stepper drivers). So using the MK2 extruder would only have been my last resort.
I ended up searching online for a MK2 extruder with Noctua fan mount and found something great on Thingiverse. This is the so-called MK2.3 extruder by Tijnv and I really loved the design, it’s exactly what I was looking for: Basically upper part with idler mechanism of the MK2, whereas the whole rest is MK3, so the mounting holes fit with the MK3’s X-carriage, you can use the Noctua fan, the new fan shroud and everything.

Stay tuned for the next post where I’ll print the different files and assemble the extruder!