The Monoprice Mini 3D printer is a fantastic machine. I'm a fan, and so are many others. But being a low-price machine, it understandably comes with a few cut corners.

One of the most notable issues is with keeping the control electronics inside cool. They are fully enclosed in a sheet metal chassis, with no active cooling and only a pattern of vent holes on the bottom. Way less than ideal.

This makes it pretty easy for those control electronics to overheat, which can introduce faults in your prints. The most common type of fault is the dreaded "extruder skipping," which puts little gaps in your layers and potentially ruins entire prints. Keeping your controller cool is the best way to prevent it. Just stirring the air inside the case slightly can have a huge effect on PCB temperatures.

I pulled together a very tidy solution using quality parts from McMaster-Carr and Digi-Key, which cost me about $30 total to source (incl. shipping). I've published some BOM info on the Hackaday.io page for this project so you can get all the stuff yourself if that's how you roll. The price here will be a lot better though, since you only pay one shipping charge, and won't have to buy 100 little screws when you only need 4.

The design uses a carefully-selected low-profile fan, so it can mount to the pre-existing vent hole pattern. It uses a patch/splice dual connector to deliver power to the fan without having to solder anything to the board. This approach makes the upgrade 100% reversible. The kit comes with a custom spacer, so you can install the fan either as an exhaust or an intake, depending on your setup.

This is available as a DIY kit, or more fully assembled for a little extra. If you order the kit, this is what you will get:

• 1x BLDC Fan
• 1x Intake spacer
• 1x Female Connector Housing
• 1x Male Connector
• 2x Small pieces heatshrink insulation
• 2x Short wires
• 2x Crimp contacts
• 4x Screws
• 4x Nuts
• 4x Locking washers

To assemble the patch/splice is not difficult but requires wire strippers, soldering iron, hot air, and a suitable crimping tool. If you do not have all of those tools, I highly recommend you let me do it for you.

Installation instructions:

• Unscrew the bottom of the printer (6 screws)
• Bolt the fan to the inside, noting airflow direction
• Unplug the main DC input to the PCB (3 pos connector, 1 pos empty)
• Plug the fan into that spot on the PCB
• Plug the DC input you initially unplugged back into the fan connector
• Screw the bottom of the printer back on (watch for wiring too close to the fan blades)

That's it. Installation only requires a screwdriver. The printer will function exactly the same after adding the fan.