Obxidian first impressions
So I swapped all my 0.4 brass nozzles for 0.4 Obxidian this weekend and thought I'd share my findings.
Nozzle swap procedure:
Very straightforward. Heat up, clean nozzle, cool down. Switch printer off. Put filament box on bed, remove tool from dock by hand and lay on box. Unscrew the center screw between alignment knobs with Torx driver, pull nozzle down a cm or two. Wires can stay connected. Grab heaterblock with two fingers, unscrew nozzle with printed tool from printables (some of mine could be unscrewed with fingers only). Pull old nozzle out, put new nozzle in and guide directly into the hole while/during screwing. I screwed them in all the way with fingers only to make sure they're properly threaded in, then tightened lightly with the printed tool. Then push up the nozzle/block all the way and hand-tighten the central screw. About two minutes each, three if you remove the sock (which I did to check heaterblocks for gunk, but it's not necessary).
I found the whole procedure very well designed, HOWEVER:
I am 100% certain I used the same force to tighten the lock screw, but still one of my tools dropped down during the test print and ruined my sheet. The sheet has a temp-tower shaped hole now, thanks to collision checks turned off by default in the current firmware. I stopped the print, heated up and pulled the filament out manually with the idler door open, then reseated the nozzle. It had also killed the sock by running it into the print. I don't know how this happened, I tested the force required to move the nozzle after the incident and it was very substantial with the screw still locked in place (it didn't drop due to gravity, the filament must have pushed it down). Maybe I missed the locking ridge by a mm. The nozzle survived, as shown by a comparison of benchies between all tools. No difference.
Also: 3 of my brass nozzles unscrewed awkwardly. It felt as if there were chipping or dirt in the threads or something, but the threads looked clean. After blowing out the heaterblock side and screwing them back in to test it was a bit better. Nothing like that when screwing in the Obxidians, maybe the brass nozzle threads were not properly cut or cleaned. One of my brass nozzles refused to come out of the toolhead, I have no idea why. It needed significant force with pliers to get it out. Unfortunately I forgot to try putting it back in to check if something was stuck there or if it was the nozzle itself (it doesn't look bent though). The Obxidian just slid in smoothly.
Print quality:
I made before/after prints on all tools. They are 100% identical between tools, including a tiny bit of underextrusion in one specific spot on the benchy, which I also had with the copper nozzle, and which only occurs on T1. But it's tiny and you would never spot it without comparing the other tools. I think it's just idler tension or a bit more friction in the PTFE. Comparing the Obxidian with the copper nozzles, the quality is a tiny bit better. Artifacts appear in exactly the same places but are a bit less pronounced. I had stellar quality with the copper nozzles already, so I guess not much to improve there. Stringing (with dialed in filament and nozzle brushes) is now 100% gone. I had some tiny wisps before, and even those are eliminated now. These were not real stringing, but came from deposits on the copper nozzle sides.
Settings:
No changes. I printed a few temp towers with different PLA and PETG brands to double-check.
Multicolor:
There is about 80-90% less filament buildup on the nozzle. I did a couple of two-color 10h prints in (crappy and undried) PETG with many fine details: no stringing, no colour contamination, nothing. It was almost perfect before, now it's flawless. There is definitely some remaining build-up, but it doesn't creep up the nozzle and it all comes off with one pass over the brush when docking. I'm using these brushes:
https://www.printables.com/model/678695-nozzle-wiper-brush-pre-leveling-prusa-xl
and
https://www.printables.com/model/678703-prusa-xl-tool-change-wiper-brush
I think the levelling brush isn't really necessary. But it's definitely a quality of life addon and you have to buy at least 6 of the brushes anyway (they come in packs of 2).
My resumee is that Obxidian should just be standard at this price point. It's definitely an upgrade I would recommend, if you want to run multimaterial / multicolor prints.
RE:
A follow-up:
So far I've used PLA, ASA, PETG, TPU 98A and ABS from various brands (all dialed in with temp towers and stringing tests) and ran a few kg of filament through all nozzles combined. Both single and multicolor, but not multimaterial yet (except some initial testing of which sticks to which). Zero issues, perfect fist layer EVERY SINGLE TIME.
TPU 98A sticks to the Obxidian coating just as badly as it sticks to brass nozzles, and that produces stringing when the deposits attach to the print. Also it globs like crazy after toolchanges, because the retract on park cannot be set to 20mm like other filaments. 20mm will induce heat creap/clogging eventually, until the extruder skips. So you cannot retract out of the melt zone, and it will drip while cooling down and heating up again. My theory is that this retraction move leaves some residual filament in the melt zone that transfers heat further up, it's obviously not as stiff as regular filament. I have no clue how to address this problem. Using a wipe tower for these prints improves it quite a bit but there is some underextrusion and stringing remains. But the same happens with brass nozzles, so even in this case the Obxidian performs at least not worse than brass.
I removed the probing brush, I found it's not necessary anymore and the additional gcode/moves were annoying.
RE: Obxidian first impressions
Interesting! Thanks! Where can I get those silicone brushes from?
RE: Obxidian first impressions
From the company that should not be mentioned, they are spare parts for the A1 mini - "Heatbed Nozzle Wiper" (2 per pack, so you need 3 packs). Or you wait until PR comes up with an XL+ upgrade, I'm 100% sure something like this will be retrofitted.
RE: Obxidian first impressions
Got it! Thanks! 🙂 No, I might need it before XL+ comes it 😉 My XL is just a few days young and did not do more than the traditional Benchy and a banding test. The results are better than I though. On the same level with mk4 or even lightly better. In the banding tests with 5 colors I also saw quite some stringing 😉 I also got one Obxidian nozzle for my MK4, but I think, I will try it in XL and see how it works. This is how I came to this post. Thanks for the quick reply and the above report!
Greetings!
RE: Obxidian first impressions
are you using a silicone sock as well with the Obxidian nozzle?
RE: Obxidian first impressions
Yes and I would recommend it especially with TPU. Sometimes you just drag a string and while most will not stick to the Obxidian, they definitely will stick on the heater block 😜