I do not like the filament holder solution on the stock Prusa XL, so I created this to improve the user experience. It handles 5 1kg spools but can also be configured to handle larger 2kg and 3kg spools as needed. 

0.6mm Nozzle, 0.32mm layer height on SPEED, no supports. 

I plan on updating this design with better modular filament sensors as the stock ones are terrible, but that will take time for me to reverse engineer the pcb and create a new one. Don't expect it any time soon, I have a day job. 


Assembly is pretty straight forward. Print and combine each roller assembly first, then attach it to the center 500mm rail and align with its twin. Then add a divider plate and add the next section of rollers. The 608 bearings are press fit into the spools.

Do not cut your stock teflon tubes. Do not modify your original filament sensor cables. You need a way to go back if you don't like this design. Save your original parts.  

Buy new teflon tubing, do not route it through the bottom of the extruder mounts. Only attach it to the printer via the orange plastic clips and let it hang off the back of the printer. Route it from the Nozzle to the caddy, not the other way around. Use a sharp box knife to cut the tubing to maintain the shape of each end. 


You will need to buy quite a lot of hardware to assemble this and if you want to use your filament sensors, you will have to crimp longer cables. Please see my forum post here for information on crimping longer cables for the filament sensor:

https://forum.prusa3d.com/forum/original-prusa-xl-tool-changer-user-mods-octoprint-enclosures-nozzles/connector-type-filament-sensors

Required Hardware Breakdown:

10x Spool Assembly:  3x M3-16mm
                                      2x M3 T-Slot Nut
                                      2x 608 Skate Bearing
 

5x Filament Guide:     1x M3-10mm
                                      1x M3 T-Slot Nut
                                      1x M10 PTFE Push-Fit Connector
     
1x Filament Sensor:    2x M3-16mm - Attach to Filament Sensor
                                      2x M3-10mm - Attach to 2020 Frame
                                      2x M3 T-Slot Nut
     
4x 2020 Frame Coupler:    3x M5-8mm 
                                               3x M5 T-Slot Nut
     
2x 2020 500mm Extrusion
2x 2020 300mm Extrusion
5x Large Run Bowden Tube
5x Short Run Bowden Tube

Totals:
32 M3 16mm Screws 
7 M3 10mm Screws
27 M3 T-Slot Nut 

12 M5 8mm Screws
12 M5 T-Slot Screws


If you don't already have any of the above hardware required, you can use anything similar to the links below from Scamazon:

m3-16mm: https://www.amazon.com/Fullerkreg-Socket-Stainless-Machine-Quantity/dp/B07CK1LFL8/

m3-10mm: https://www.amazon.com/Fullerkreg-Socket-Stainless-Machine-Quantity/dp/B07CK3RSN3/

m5-8mm: https://www.amazon.com/10-9-Alloy-Steel-Machine-Quantity/dp/B08P1PC7B4/

M10 PTFE Push-Fit Connector: https://www.amazon.com/gp/product/B01KHN1HWY/

M3 T-Slot Nut: https://www.amazon.com/Zorveiio-Sliding-Fastener-Assortment-Aluminum/dp/B0C9D8T647/

M5 T-Slot Nut: https://www.amazon.com/Boeray-Sliding-Aluminum-Extrusion-Profile/dp/B01GCDG2QO/

608 Skate Bearing: https://www.amazon.com/Bearing-Miniature-Bearings-Skateboards-Scooters/dp/B08DR6L5CJ/

500mm 2020 Aluminum Extrusion: https://www.amazon.com/European-Standard-Anodized-Aluminum-Extrusion/dp/B092Z35X3V/

300mm 2020 Aluminum Extrusion: https://www.amazon.com/Bitray-Aluminum-Extrusion-European-Standard/dp/B0C9MGHQQ5/

I ordered 5 sections of 5m each and it came packed as a single roll, there were 2 kinks in the tubing that I had to cut around, I don't know that I recommend them but finding 2.5mm ID tubing is difficult:
4mm OD 2.5mm ID Teflon Tubing: https://www.ebay.com/itm/263583709138