3DO Nozzle Cam for Prusa XL

Nozzle cams are both very useful and very fun. This uses the 3DO kit, which provides reasonable quality and consistency (as opposed to some random endoscope) and 3DO say it's good with the temperatures too. So far I have no complaints.

The black Obxidian nozzles aren't the easiest to see, but you get the idea.

BOM

1x 3DO Nozzle Cam (adjustable focus)
1x 3DO 50mm FPC w/ leds
1x 3DO Nozzle Cam DSP board
1x 3DO JST SH 5x to USB cable (the 700mm one will get you to the back of the printer, use longer cables if your USB host device is further away)
~50mm thick-walled heatshrink tubing, 8mm ID, e.g. Digikey part 2057-HST-A-080-BK-4-SR41-ND
10x Ruthex M3 Voron (4mm long) heat inserts
2x Ruthex M2 heat inserts
~12 10cm zip ties, e.g. Amazon B01018DB2E
2x M3x12mm cap head screws, e.g. McMaster 91290A117
8x M3x10mm countersunk screws, e.g. McMaster 91294A130
2x M2x6mm countersunk screws, e.g. McMaster 91294A004
some PETG or PA filament for the cable strap (PA might be better but PETG works fine for me)
some ABS, ASA or PC filament for the toolhead parts (your choice)

SOURCING

The 3DO stuff you can get from them directly if you're in Europe. KB3D has them in the US and they ship super fast. Heatshrink tubing - I used the part in the BOM above but you can probably just use something from an assortment box. 

PRINTING

Print one of each of the STLs. Included orientation, no supports. You want something flexible for the strap (PETG has been fine for me), and something hard & strong for the toolhead parts. The jig, if you're printing it at all, can be anything.

You're printing a new XY belt clamp and getting rid of the old parts. It is extremely important that this part comes out with no warping. Prusament PC will probably work; I printed mine from Qidi ABS-GF (it's a fantastic filament, very easy to work with). 0.2mm layer height is fine.

PARTS PREP

Only if using the Prusa Original enclosure for the XL: Install two M3 heat inserts in the “club” at the end of the strap. They go in from the chamfered side:

If not using the enclosure, you don't need the above two inserts. We'll talk about it later. Enclosure or not, most of the further stuff is the same:

Install four M3 heat inserts into the USB cable retaining end. They drop in a couple of millimeters on their own. It's important that they do not protrude on the other side.

Install four M3 heat inserts into the belt clamp. It is VERY important for these to be flush with the carriage mounting plate, so the inserts must be pushed in all the way but also not protrude on the other side. The model is 4.2mm thick, the inserts are 4mm long. 

Install the M2 heat inserts into the carriage cover. 

If you're using one of those soldering-iron-holding contraptions for applying heat inserts, the jig.stl model is meant to hold the carriage cover level while the inserts are installed since that surface has a 10 degree tilt. 

Assemble the camera, FPC and PCB. You will want to hook it up to a computer with the 3DO USB cable at this point, and adjust the focus to 66mm. (Just place down some small objects 66mm from the lens and make sure the focus is correct.) It won't be possible to adjust the focus once the camera is installed in the toolhead cover, so you want to get this right.

Install the camera assembly as shown above. The PCB is friction fit into the cover, it is meant to be pushed in until it clicks into place.

Apply the heat shrink tubing to the JST SH connector side of the 3DO USB cable. (1 below) It's meant to make sure the cable is held in place securely. Leave a 2mm gap between the SH connector and the tube (2 below).

Put on the camera clamp and secure it with the M2 screws. (3 above) The clamp is a tight fit over the camera's lens ring, but do not force it. Use a deburring tool to enlarge the hole slightly (or adjust the model using the provided .step file and print it again) if the fit is a problem.

Plug in the JST SH connector, make sure it's tight, and secure the cable & the carriage cover to the strap using 4 M3 screws. (4 above)

Secure the USB cable with the zip ties to the strap:

Click the “insert.stl” object into place over the PCB. It will hold the JST SH connector and the PCB in place when pressed against the belt clamp:

PREPARING THE PRINTER

Loosen the CoreXY belt tensioners on both sides as much as you can (but do not fully undo the screws):

Unclip the toolhead cover with the Prusa XL logo on it. Undo the four screws below that hold the factory belt clamps in place:

Put away the factory belt clamps and the toolhead cover, you won't need them. 
Thread the belts through the new belt clamp, like so:
 

Do this for all four belt ends. There will be just enough slack to do this. Make sure the belts are as tight as possible; you'll tension them later but there's only so much slack that can be picked up with that.

Install the new belt clamp on the toolhead carriage using the screws you removed in the previous step.
 

If you have a lot of belt peeking out where indicated by the arrows, and they prevent the new toolhead cover with the camera assembly from installing flush, you can use a knife or a scalpel to shave off the excess.

Re-tension the belts as per Prusa's instructions:

https://help.prusa3d.com/article/adjusting-belt-tension-xl_401793

FINISHING UP

If you are using the Original Enclosure, remove two of the nylon rivets that hold the left acrylic panel in place, and use the M3x12 screws to attach the club end of the strap where the rivets had been:

If you are not using the enclosure, you can attach the club end of the strap to roughly the same location on the outside of the printer, to the aluminum profile. Partsbuilt3d sells the M3neS nuts that you need for this, but there are printable models too that work well enough. 

Use the last four M3 screws to secure the toolhead cover to the belt clamps:

If you're using the twist lock wire nozzle scrubbers (that are amazing and you totally should), you will have a problem with the camera mount pushing against the brushes and twisting them out of place. I made a better debris bucket design that alleviates this issue:

https://www.printables.com/model/1054341-improved-bins-for-the-prusa-xl-twist-lock-nozzle-s

RANDOM STUFF

The back of the DSP PCB is uncovered for two reasons: heat management and space. There'd need to be at least a 1mm gap between the surface of the PCB and the inside of the toolhead cover if not for having the cutout to allow for the mounted components. In order to keep the design as slim as possible and allow it to work with the Original Enclosure (and not have the toolhead bump the door while homing), this 1mm is not affordable. Further, the components on the board get pretty hot, and I don't think it's a good idea to tightly enclose them in plastic.

If you're using Linux, this udev rule will at least give you a starting point for the camera setup:

marton@pi5-prusa-xl:~ $ cat /etc/udev/rules.d/99-octoprint.rules
SUBSYSTEM=="video4linux", ATTRS{serial}=="3DO", ATTR{index}=="0", SYMLINK+="cam2_xl", RUN+="/usr/bin/v4l2-ctl -d $env{DEVNAME} \
       --set-ctrl=brightness=-15 \
       --set-ctrl=contrast=4 \
       --set-ctrl=saturation=70 \
       --set-ctrl=hue=0 \
       --set-ctrl=white_balance_automatic=1 \
       --set-ctrl=gamma=130 \
       --set-ctrl=gain=0 \
       --set-ctrl=power_line_frequency=1 \
       --set-ctrl=sharpness=7 \
       --set-ctrl=backlight_compensation=1 \
       --set-ctrl=zoom_absolute=55 \
       --set-ctrl=tilt_absolute=-130000 \
       --set-ctrl=auto_exposure=1 \
       --set-ctrl=exposure_time_absolute=700"

I suck with this so if you manage to coax a better picture from the camera, do leave a comment with your settings.