Prusa XL Buddy Box Cover with fan - uses spring contacts, no wiring to printer needed

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My XL is located in a workshop room that reaches 85°F (30°C) at night when the room air is off. The machine ran fine for months until I added the Prusa enclosure, ran my first job, a big job, with PC-CF and it errored out with the above message. Selecting continue resulted in a loss of the print job due to the printer rebooting.

A few days later Prusa released 6.0.4FW to address this. But I'm not sure how well FW will address an extremely hot running board in an enclosed environment with no passive or active cooling.

With the additional radiated heat entering in from the back wall of the printer, and the downdraft from the enclosure fan (my printer sits with its back against a wall), the board reached the 100°C (212°F) threshold in FW6.0.3. So I decided to engineer a solution of my own that would provide active ventilation to the Buddy box and didn't require removing the splitter board to make the electrical connection.

With this solution the Buddy Board runs way cooler; has not exceeded 60°C (140°F) with higher temp materials and a full print bed.

I wanted a solution that didn't require me to remove boards, attach wires, or allow me to accidentally forget to disconnect something in the future. So I added battery terminal contacts to rest on the screw heads of the 24Vdc terminal block of the splitter board. Making it easy to remove the cover and not have to worry with it.

This Buddy Box Cover uses a 40mm x 10mm fan with a JST-XH connector: Amazon

I added this 40mm filter housing assembly to help keep dust out: Amazon

The fan mounting screws (M3 x 18mm flat head): Amazon

M3x0.5 Hex nuts came from Amazon (4x): Amazon

The JST-XH male connector pigtail: Amazon . Male pigtail is on the right in the photo below, Female side is already on the above fan.

To aid in extracting heat from the X, Y, and Z stepper drivers, I added this heatsink to the underside of the Buddy Board where the 3 stepper drivers were located: Amazon

I also added this heat sink on top of the Buddy Board MCU: Amazon

NOTE: I think heatsinks can be considered optional. They were a slight improvement, but it appeared just getting airflow through the Buddy Box was the main improvement. The Buddy Board and Splitter Board both contain large copper pours on both sides to spread and dissipate heat.

Used battery terminal contacts for connection to the 24Vdc screw terminal header available on the splitter board, got these from DigiKey. (2x): Digikey

I also saw these offered on amazon by the seller uxcell. I did confirm they are dimensionally identical to the DigiKey offering: Amazon

Ring Terminals for the JST-XH Pigtail leads came from McMaster-Carr. (2x): McMaster-Carr

No. 2 x ¼" long thread forming screw for plastics came from McMaster-Carr (2x): McMaster-Carr

The cover has a JST connector holder added to aid in wire management. I cut the leads of the pigtail just to the length required to reach the battery contact mounting screws.

With this it's easy to plug the fan in and tuck/loop the excess wire length behind a wire retention hook

NOTE: the fan mounting fasteners seen in the image above were 20mm long, they work just fine, but the 18mm recommendation above will be a better fit for the assembly.

Cover seen in the images was printed with Overture PETG. I printed again with Prusament PETG and came out way better in print quality. Not really relevant here, but I thought I'd add that I think Prusa materials are amazing.

Battery contacts seat on the tops of the splitter board terminal screws, just well enough for positive engagement. not much force or resulting displacement is required to fully seat the cover.

Included are STL, STEP and native SW2023 part files.