We’ve had a love affair with the Monoprice Select Mini since it came out. The cheap printer has its flaws, though. One of them is that the controller is a bit opaque. On the one hand, it is impressive that it is a 32-bit board with an LCD. On the other hand, we have no way to modify it easily other than loading the ready-built binaries. Want to add bed leveling? Multiple fans? A second extruder and mixing head? Good luck, since the board doesn’t support any of those things. [mfink70] decided the controller had to go, so he upgraded his Mini with a Smoothie board.

On the plus side, the Smoothie board is also a 32-bit board with plenty of power and expansion capability. On the downside, it costs about half as much as the printer does. Just replacing the board was only part of the battle. [mfink70] had to worry about the steppers, the end stops, and a few other odds and ends.

Luckily, the stepper connectors are compatible. Some of the motors were reversed, but the Smoothie board can handle that sort of configuration with a simple change to a text file. The end stops and most of the other wiring required connectors to come off (the Smoothieboard mostly uses screw terminals).

Of course, the new board won’t drive the old display, so he also replaced the display with an MKS touchscreen (driving the cost up to well over half the machine’s cost). The payoff, though, is you wind up with a wealth of expansion options.

There are plenty of other mods you can do with less expense, of course. If you are interested in our original review (of the first generation model), it is still out there.