Top Filament Entry for Prusa XL Enclosure

I store my filament in dry boxes on a shelf above my printers.  When I got my XL, I found that the filament sensors were in a place that didn't work with that layout very well.  I moved them to the top, and then I found that the PTFE tubes were way too long. So I designed this.  

While I designed it for an official XL enclosure, It might work with others.

 

In order to complete this as designed, you'll need

• (2) 14mm M3 pan head screws
• (4) 10mm M3 screws
• (6) M3 nuts
• (2) M3 washers
• PC4-M6 fittings (as many heads as you have x2)  I used these: https://www.amazon.ca/gp/product/B07PV8754Z/
• (optional if you don't want to cut the tubes that came with the printer) 4mm OD PTFE tube.  I found that I could cut and reuse the tube that came with the printer.
• Extended cables for the filament sensors.  I used these https://www.mouser.ca/ProductDetail/Molex/15135-0506?qs=jFK2DQXLaBzN1OZf0p2Rdg%3D%3D and extended them with some flexible cat5 cable.

The models for this project include:

• A guide for drilling pilot holes in the top of the enclosure.  Use this guide, along with a 2mm or 1/64" drill bit to drill some small holes for the passthrough to fit.  Follow up with a 10mm or 3/8" drill bit for the five middle holes, and a 3mm or 1/8" drill bit for the two end holes.  Take a look at the passthrough design if you're not sure what I mean.  
• New Cable Clips without the clip for the PTFE tubing.  I used 3 for each head, so for my printer, I used 15.  These should probably be printed in PETG or something that isn't brittle.  PLA might work, but I didn't try it.
• A passthrough manifold for the top of the enclosure.  After drilling the holes, mount this with 2 M3x10mm screws and nuts.  You'll probably want to use lock washers or liquid threadlocker on these, because if the nuts fall off, they could drop into the printer and wreak havoc.
• A mount for the existing XL filament sensors

Here's how to install

1. Remove the enclosure top from the printer.
2. Using the pilot hole guide, drill 7 holes in the top of the sheet metal.  I positioned mine centered from side to side and about 30mm from the back of the enclosure.
3. Drill out the pilot holes - for the five center holes, use a 10mm or 3/8" drill bit.  For the two end holes, use a 3mm or 1/8" drill bit.
4. Install the PC4-M6 fittings into the manifold.
5. Using 2 M3x10mm screws and nuts, bolt the manifold to the enclosure. It would be good to use some threadlocker on these screws and nuts
6. Remove the filament sensors from the side of the printer, unplug the wires, and remove the other ends of the wires from the printer control board.  
7. Remove the PTFE tubes from the filament sensors.
8. Using 2 M3x10mm screws and 2 M3 nuts, mount the sensors to the sensor mount.
9. Remove the two center top plastic rivets from the enclosure.
10. Using the holes that the two rivets were in, install the filament sensor mount using M3x14mm screws, 2 M3 washers (to protect the clear plastic window from cracking), and 2 M3 nuts.  It would be good to use some threadlocker on these screws and nuts.
11. Before you install the enclosure top, remove the old PTFE Tubes from the heads, and pull them completely off the printer.  This is also the time to replace the tube/harness clips on each head.  Replace the three furthest from the head for each print head, leaving 2 of the existing clips - these will later hold the shortened PTFE tubes.
12. Reinstall the enclosure top onto the printer.
13. Make some extended filament sensor cables if you cannot find any that are long enough.  You can use the existing cables by cutting and splicing some lengths of wire in them.  You can estimate how long you need your cables to be by using some string - tape it to the control board, and then route it to the installed filament sensors. Measure that string and that will tell you how long your cables need to be.  For good measure, try to make them a little longer than you think you need.  Note that the original cables are wired differently from what you might expect.  Pin 1 maps to pin 5, 2 to 4, 3 to 3, 4 to 2, and 5 to 1.  When you splice the cables, you'll need to preserve that pinout or you'll get some odd and seemingly unrelated errors when you turn on the printer after this (don't ask me how I know. :-))
14. Route and install the new filament sensor cables.  Make sure that you're plugging in the sensors to the right sockets on the board.
15. Install the PTFE Tubing.  To get the correct lengths, I installed a tube that I removed earlier, moved the head to the corner farthest from the manifold, and trimmed the tube to be about 50mm longer than it looked like I needed.  I did this for each head.  If the tubes are too short, they won't reach the corners and cause binding.  If they are too long, they could tangle with each other or with the head wire bundle.  They do need to be long enough that at the farthest extent, they don't have any tight bends - the filament path needs to be smooth.  Once they are trimmed, plug them into the manifold, and clip them into the two PTFE clips that remain on the harnesses (see step 11)
16. On top of the printer, use the leftover lengths of tube to connect the filament sensors to the manifold.  You'll probably want to trim these a bit, but again, make sure that they aren't too short - you need the filament path to be smooth with no tight bends.  Make sure that you map these correctly - that the sensor for head 1 actually feeds into head 1.
17. Make sure everything is reassembled and that all the screws are tight, and start printing!