This post will be applying to the Prusa MK3S specifically but it can be applied to other variants and clones.You can find my thoughts on the stock printer here.

In my previous review about the Prusa MMU2S, I mentioned that I had installed a PitStop Extruder on my printer to help with loading, this is only a small part of why I installed this modification.

I need to mention first, print this in PETG or better. Mine is in beautiful Prusament Orange PETG.

So, why would you want to modify your perfectly good printer? For me, it was a matter of if I could rather than if I should. I wanted the challenge of printing a complex assembly and assembling it. The benefits I will go into later were just nice bonuses alongside the main objective.

Before I get into the details, I will provide a brief overview of what this upgrade does.

The PitStop Extruder is designed to improve the maintenance accessibility for the extruder assembly allowing the user to easily access the feed motor, gears and hotend assembly as easily as possible. This is achieved with powerful neodymium magnets and some very clever design using off the shelf parts.

With the overview out the way, let’s get into the difficulties of the build. By far the hardest part is printing. Most of the parts are fine and easy to print as long as your dimensional accuracy and bed adhesion is good. But the fan duct, the fan duct is the most difficult part to print due to the constant overhang and thin walls. Once you have one of these printed, its smooth sailing. I personally added some support material to the steepest overhang to improve quality for the nut slot and part fan although it can be printed without supports.

The other problem I had was with the filament sensor. As I am using the MMU2S, there is a linkage of three parts that rotate around a bolt each. Getting this bolt tightness just right is one of the most important parts. Too tight and the idler door will not open or shut, too loose adds slop into the linkage making it unreliable for the sensor to not even feeding the filament. This is resolved with trial and error. Start with the FS lever, then the linkage plate and finally the idler door itself.

Other than those two points, everything is detailed incredibly well in the assembly video on the PitStop extruder website.

Is it worth it? For me, yes.

For everyone else, it depends on what you want out of it. A fun project? Satisfying magnetic action? Easy maintenance? Then probably yes. I think it is worth doing, especially because it is completely reversible. This extruder modifies none of the old parts except for the hotend fan wires.

This upgrade will most likely not improve print quality, it actually has more potential to reduce print quality as the extruder assembly is heavier. The key word there is potential, these prints are nothing to scoff at.

No modification is complete without more modification. I drilled a 4mm bore all the way to the gears to allow the PTFE tube from the MMU2S to feed straight into the gears. this improves feeding from the MMU2S

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One final note. If you do this upgrade and start getting strange layer inconsistencies, check the mating surface between the two halves for any obstructions. In my case, a tiny blob of printed filament caused the following prints to look awful. Easy fix luckily.

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