Apologies about the delay in this post. Went on vacation then came back and got distracted by shiny VR stuff. Ended up getting motivated to get Tombstone finished, but got an ear infection and still can't hear out of my left ear. I'll try to keep on-task keeping this post organized despite all the actual work being spread out.
Shes finally awake. After finishing up the wiring and getting marlin 2.0 installed, its able to do basic functions like movement, homing and heating. Getting the bed and extruder heated allows for enclosure temperature testing. Also allowed me to test the maximum power draw of the setup so I can properly size the AC fuse. Printed in ASA for the first time as well, but ended up melting the PETG print head parts in the process.
Wiring
All that was really left to finish for wiring was getting the everything from the printer that connects to the DB25 and DB9 connectors routed onto the SKR V1.4 Turbo board. This was a little involved, but straight forward.
I did end up wiring the dual Z motors separately to independent stepper motor drivers. This lets me take advantage of a new Marlin 2.0 feature that lets the printer align the two Z steppers by probing the bed and making adjustments. On a printer where the bed drops fairly easily, its good having this automated so I don't have to waste time making sure these are aligned before each print.
Firmware Configuration
I have configured Marlin 2.0.x before, but had a bit of an issue the first time around trying to get it to compile. They are trying to push people towards the platformIO plugin in Visual Studio Code for Arduino marlin builds, which was throwing all sorts of errors for me, even though I had it configured and was using it before.
I eventually found out that I had to delete the platformIO plugin and remove its install directory. I also fiddled with file permissions in my documents project location which seemed to get me to finally compile.
I have never setup sensor-less homing (XY), dual Z motors, or apparently configured the BL touch homing boundaries properly before. This printer also has its bed drop as the Z height of the print increases, which really messed with my head for a bit. I eventually figured out that the printer will have a max build volume of 340Y 370X 415Z. I also took the time to setup the Raspberry Pi 4 with Octoprint witch allowed me to manage the printer from my computer in the other room.
Enclosure Temperature and Power
With the printer now able to heat the extruder and more importantly the bed, I am finally able to test ambient air temperatures as a complete system. It works surprisingly well. The ambient air temperature can maintain 57C (135F) while the bed is over 95C (203F) even with the HEPA filters pulling room air into the enclosure.
This is at the maximum I wanted to push the temperatures inside the enclosure, as the 100W heater I am using is only rated for 60C. This heater performs its function well and cycles on-off to maintain 57C as intended. I could see adding more insulation to the front of the enclosure so that less heat is lost due to thermal conduction and saving the heater from having to run as often.
In a desktop 3d printer, the cooling of the cold end of the extruder would be done with ambient air. Because I am using a liquid cooling loop to extract the heat and cool it external to the enclosure, I am not too concerned about this having much effect on ambient air temps inside. I did however have an issue with the direction of the tubes and visual feedback on the liquid cooling loop working.
Initially there were problems with air working its way into the pipes if the printer sat for a while without being used. This I think is fine, because all that happens if that the cooling fluid works its way down and settles into the reservoir. Whats not okay is that when starting things up, a lot of the air would get trapped inside the radiator and would not make its way into the reservoir and escape the loop. This would make the radiator much less effective, so I ended up changing in-out on the pump so that air traveling down from the printer would hit it and its built in reservoir first which worked perfect.
The other issue I had was flow. The printer only turns on the cooling for the hot-end if its over 50C and cannot be turned on/off by hand. With no bubbles in the loop, there is really no way to see if the fluid is moving or not. So I ordered a flow meter and hooked it up. The crappy thing is that due to the restricted flow of the smaller diameter tube at the print head, it doesn't flow well at all unless in a vertical position. I plan on changing the liquid cooling mount to allow for the flow meter to be fixed properly.
Luckily its super easy to see what AC current the whole setup is drawing from the wall at a glance with the meters on the front panel. With everything running I have only ever seen it draw 10A. Rule of thumb is to put an fuse rated for twice as much as the power you are drawing... but I am a little nervous of the house wiring I am using. I will probably put a 15A fuse in and see if its good enough.
First Prints - Part Cooling
I bought a couple of spools of Prusament ASA when this project was getting closer to being finished. They have been sitting on a shelf looking at me funny for a month or so now. So of course I did the sane thing and jump right into printing ASA without even tuning prints for PLA or PETG. Which I guess was for the best considering I ended up having to re-design the part cooling setup.
I probably should have seen this one coming because I made the same mistake before in the last enclosure. PETG melts when it too close to a 285C extruder. These are really the only times I have had issues with PETG's temperature resistance. So during my first ASA tuning prints for calibrating wall thickness, I noticed that the cooling fan ducts I needed were melting.
This is a real chicken before the egg situation. You can only really print ASA well with slow speed part cooling or it can get pretty melty, but you need ASA printed part cooling fan ducts to make sure they don't melt next to the hot extruder. I did end up printing some pretty crappy fan ducts with no cooling as a stepping stone to print more ASA parts properly.
It turned out that the PETG mount that keeps the head on the Y carriage was also melting, albeit slower than the part cooling fan ducts. After some work; all three parts are ASA now, and the part cooling fans are about 7mm further from the extruder. ASA also needs some distance from the extruder even though its temp resistance is higher but still seems to work well enough.
Also turns out that ASA reeks as bad as ABS in my opinion. The HEPA and active carbon fans keep it at bay, but I will likely be moving the printer into a different room once its finished even with the filters for health reasons.
First Prints - Large ASA Object
I had been using a .4 mm nozzle for re-printing the extruder parts in ASA. For larger prints this is not very practical especially where you don't need amazing surface quality. Also larger parts warp more and need to stick to the surface more than smaller ones.
I purchased a few larger nozzles. The one I am going to use for now is .5mm will allow me to print at .29mm layer height instead of the .2 mm I would have on my other printers. This will also allow for less perimeters to be used for the same wall thickness also increasing the speed of the print.
Instead of using AquaNet hairspray like I had for small parts, I ended up making a slurry of ASA and acetone I had lying around from when I printed in ABS a few years ago. This is best applied on a cold bed and left to evaporate at room temp and away from where it can be breathed in. What is super fortunate is that I ordered a second glass print bed by accident, so I can service once bed and get it prepped while the other is being used. Its sooo convenient.
As far as I can tell the prints have minimal warping. They are noticeably lighter as well. It took a bit of tuning, but my prints are coming out really great. I could have never gotten these results in the old passive printer enclosure with ABS.
Up Next
The list keeps getting smaller and smaller, but the thing I am tackling now is a filament run-out sensor. This is probably the last bit I need to wire and configure in firmware. For a spool holder I went with a Polymaker PolyBox Edition Ⅱ which will keep the filament from collecting moisture. I would have printed something custom, but at this point I kind of want to wrap things up.
I also need to set up the cooling fans for printing low temp plastics. Having the enclosure too hot for these is not optimal for the part cooling fans, and being able to maintain a constant warmish temp is preferred for consistency. I have decided to use magnetic covers to keep the fans completely closed when doing high temp filaments. This will prevent the hot air from escaping the enclosure through the fans when not in use.
The other thing is filament configuration. I should take the time and tune a bunch of profiles for printing PLA, PETG, ABS, and TPU properly for the brands I usually use at .4 and .5 mm nozzles. Having these done will help make the printer usable as a tool when printed on demand for other up coming projects.