Prusa Bear mount for BananaPi M2+

Introduction

The BananaPi M2+ is an excellent, and affordable, helper board to use with a 3D printer. Whether you want to run Klipper, or OctoPrint, this board has a lot going for it:

• Armbian support, which makes installing Klipper, OctoPrint, or similar tools easy
• Onboard WiFi, HDMI, multiple USB ports
• 40-pin header matching the RPi B+
• Affordable and accessible through a range of vendors

This mount, and case, is designed for use with the Prusa Bear frame, but can be mounted to any printer with 20XX extrusions. It has several good features:

• Hole for WiFi antenna mounting.
• Support for mounting a 40XX fan (pictured with a 4010).
• Covered design without hiding any of the IO available.
• Easy to print, no overhangs, no supports.
• Holes for zipties to help with cable management.

What you will need

Print the loft and the case, plus four spacers. We recommend using PETG, with the Prusa Bear settings (3 perimeters and 5 top and bottom layers should be plenty). The files provided (both STL and STEP) are already oriented for printing.

You will also need some other parts:

• M3 heatset inserts (designed for diameter 5, depth 4) x9. You can use wider or shallower inserts (to a point), but narrower or longer won't work.
• M3 2020 T-nuts x3. Specific design of T-nut doesn't matter, but some may be easier to use than others: roll-in or hammer nuts don't require pre-loading.

Fasteners required are all M3: choose any cap design you like. You will need:

• 8mm x3 (to connect the loft to the case)
• 10mm x2 (to connect the board to the case without going through into the extrusion)
• 15mm x2 (to connect the board to the extrusion, going through the case)
• 12mm x4 (to connect the fan to the loft, may need to be longer or shorter depending on the fan)

For the fan, any 40mm axial fan will do: the one used in the images is a 4010, but you can use thicker fans if you prefer. More precisely, the loft is designed for fans with a bolt spacing of ~32mm, and a fan aperture of ~37mm. The board itself is capable of driving a 5V fan through its GPIO pins; for higher voltages, you will have to power it some other way.

If you want to use zipties for cable management, the holes are 4mm by 2mm, which should fit many kinds of ziptie.

How to assemble

The images attached show the process. The small amount of padding on the antenna shouldn't be necessary in your case, as the images were done on test parts which weren't properly toleranced. Roughly, the process should be as follows:

1. Insert all heatset inserts into the case and loft.
2. Attach the fan to the loft (if using).
3. Attach the board to the case, using the two heatset-bearing holes.
4. Insert the T-nuts into the extrusion.
5. Attach the board-case combo to the extrusion, by passing screws through the board and case holes into the T-nuts from step 4.
6. Insert the WiFi antenna and connect it (if using).
7. Attach the loft to the case.

Supplied files

Both STL and STEP files are provided, as well as the original FreeCAD source (as required by the license). This uses the 0.22 dev branch of FreeCAD, so if you want to use the source, you will need that version (at least until FreeCAD 1.0). It might also work on Ondsel's FreeCAD branch, but this has not been tested.