I was hoping to have the printer finished physically at this point, but I did not quite make it despite the huge leap forward. Notable items completed are mounting the HEPA/activated carbon filtering system, 100W heater, bed and extruder carriage wiring/mounts, and finished extruder liquid cooling loop. There isn't actually much left to physically put together. Once this is done, the rest is in software. I go on Vacation this coming week and will not have time to finish Tombstone in this time unfortunately.
Filtering System and Heater Mounts
The filtering system I have gone with allows for small roomba filters and activated carbon. Its been mounted to be removed if needed without taking the hood off the printer enclosure. I was going to mount them to the hood, but I ended up deciding it would be easiest to mount them and exhaust through the wooden stand on the sides. The actual amount of air these push isn't crazy, but should be enough to keep negative air pressure inside the enclosure to keep fumes from escaping.
The heater has been placed where it will (hopefully) not create too much airflow or risk melting nearby electronics between the HEPA filters. This might get moved later, but I think it will probably be okay where it is now.
Bed and Extruder Carriage Mount and Wiring
-Extruder-
A harness/bundle was need to get wiring, filament and liquid cooling up to the extruder. The trick was getting all of this to move in a flexible way, but work with the existing printer frame. The idea was to connect a routing fixture to the left side of the XY axis assembly to pass the bundle to the print head.
This ended up being the biggest pain to design for any part on the printer. The oddly restricted space and required curves for the filament/liquid tubes made things very difficult. I believe I went though 5 revisions before coming up with the final parts.
As far as the extruder carriage, the majority of the carriage is mounted to a modified after market plate. A simple part that captures the smaller liquid cooling tubes and provides strain relief for the cables was made. This was super simple and only needed a single revision.
There was also a need for a tube routing fixture on the side of the enclosure base to prevent the tube from kinking. Also pretty straight forward.
-Heated Bed-
With the HEPA filters at the rear of the enclosure, there was little room for the heated bed cable to hang where it originally did stock. The solution was to use a m4 hole that was left in the bed support metal by Creality for no reason to mount a strain relief to the side of the bed.
For all power connectors coming out of the mainboard box, I decided to use RC connectors instead. The originally intended aviation connectors were clearly underrated for the higher current needed for the bed, hotend, and 100W heater. For the heated bed I am re-using the stock one.
Liquid Cooling Loop
With both the extruder carriage and XY mount for routing cables/pipes done, I was able to do a good amount of wiring as well as fill the liquid cooling loop. For this I went with this fluid, as it should last for a while. There are no other components in the design that call for 12V, so running a 5V relay and voltage regulator seemed like a good idea. This is fed 24V from the mainboard (SKR V1.4 Turbo) constant fan pin as well as one of the extra control pins that will enable the cooler pump and fan when the hotend is turned on.
Its also worth noting that the cooling system (aside from extra tubing) was purchased from E3D. The hotend is something a little special and has yet to be tested properly. Time will tell if this works well or not, but it seems pretty solid as installed.
Up Next
My laundry list of things to do gets shorter and shorter. I think that almost all of the part design work is finished, aside from final revisions to the cooling fans as well as a method to mount the filament spool and filament run-out sensor. The PTFE tube for the filament feed exits the enclosure base from the bottom left side.
There has been and will be a bit more wiring to do. The majority of it has to be done inside the mainboard control box itself. For example one of the DB25 and DB9 connectors inside the case still need to be soldered and ends crimped, while the cables that connect to them have been terminated on the outside.
After that, I have a smoke detector to install inside the enclosure. Then its all programming and making final revisions to the cooling system. Marlin 2.0 firmware needs to be configured properly, and the raspberry pi 4 needs to have an Octoprint installed and configured. The cooling system need to be aggressive enough to cool things for lower temp filaments, but also not let hot air escape when printing hot filaments. This will have to be done after the printer is configured and tested properly.