Hi folks,
I’ve been doing a lot of trial and error to finally come up with a satisfactory result for a tabletop miniature, printed with a 0.2 mm nozzle and PVA support.
A friend of mine asked me to print Rendor Holoam, prince of the Silver Dwarves . This miniature is certainly designed for printing with a resin printer, and if you want it really good, you’d need to go that route. However, I do not like working with hazardous chemistry, so I got myself the 0.2 mm nozzle. It was a bit of a learning curve. I guess I needed about a dozen prints or so to finally have something that I’d call good enough. So meet the prince (the photos look worse than reality, the closeup and light emphazise the shortcomings - it actually looks really nice in reality!):
For reference: What the model looks like:
Here’s my setup with the dual extruder:
- 0.2 mm nozzle for white PLA
- 0.4 mm nozzle for PVA support
- Slicer: Cura
- Layer height: 0.1 mm
- Top/Bottom layers & Wall line count: 4
- Infill: 25% Grid
- Print temperature: 210°C for PLA, 185°C for PVA
- Standby temps: 180°C for PLA, 165°C for PVA
- Print speed: 50 mm/s
- Retraction distance: 1.5 mm for PLA, 8 mm for PVA
- Retraction extra prime amount: 0.05 mm³ for PLA, 0.1 mm³ for PVA
- Maximum retraction count: 25 within 1.5 mm
- Retraction minimum travel: 3 mm
- Z-Hop when retracted and on extruder switch
- Print cooling on
- Support Extruder: PLA
- Support Interface Extruder: PVA
- Overhang angle: 45°
- Support pattern: Gyroid
- Enable Support Interface: Yes
- Interface thickness: 0.3 mm
- Prime tower: yes, far enough away that both nozzles are not over the print when the prime tower is printed
- Nozzle switch extra prime amount: 0.05 mm³
- Sacrifical tower (added as object) to ensure that the sword does not melt while printing
Here’s how it looked right after the print was finished (about 3 hrs printing time):
A few remarks on why I did some things as I did them (aka: My learnings):
- Aggressive PVA retraction settings: PVA is oozing like hell. I lost prints because oozed PVA was “baked in” between the PLA, causing print defects
- Prime tower: Absolutely necessary with PVA - after the oozing, you need to build up nozzle pressure again.
- Weak retraction settings on PLA: The 0.2 mm nozzle tends to temporarily clog and can only deliver so much flux. I’ve had the filament gnawed through by the extruder gear due to too many retractions against too much resistance. Better deal with the stringing than lose a print.
- Print speed: 60 mm/s already visibly deteriorated print quality. Speed does not matter all too much, since the many, many details do not allow the print head to get even close to the max speed. Still, it seems to matter, and if I had to print it again, I’d even go down to 40 mm/s. I guess it also makes extrusion a bit easier through the tiny nozzle.
- Cura as slicer: I’d have preferred Prusa slicer, but Prusa does not allow a prime tower with two different nozzle diameters.
- Gyroid support: Cura has surprisingly strong difficulties creating the support structures for such a complicated model. Several parts of the support printed into thin air, would have needed support for themselves, which is a bit disappointing. With the gyroid pattern I got best coverage. Make sure that you use the preview function and look closely before you run the print!
- Sacrifical tower: The sword is just two wall lines thick. As such, it is extremely prone to overheating if the nozzle stays close to it, laying down the next layers. On one of my first tries, I could see that the sword was nice and cool (you can read the runes!) until the nozzle went above the dwarf’s head. Then it was just a glob of molten plastic. Cura has a few strategies to deal with that, but none worked for me. So I added a cylinder to the print that made sure that the nozzle went away from the sword to let it cool down, while still extruding to keep nozzle pressure.
- 0.2 mm nozzle: Several people on the net claim that a 0.4 is just enough. I beg to differ! The runes on the sword would certainly not have been possible with an 0.4 mm nozzle! It is definitely improving the print!
- PVA support: I started with breakaway PLA (the stuff from Snapmaker that came with the DX). That was an utter failure. That stuff was clinging strongly to the print, and I damaged my print considerably trying to remove the support. I tried “standard” support with PLA itself and a bit of distance, but that turned out similarly disappointing. I did not try what some people claim to work, and that is to use PETG as support. Perhaps worth a try, because PVA is a nasty stuff: wobbly, oozing heavily, a bit tricky to get it stick to the bed…
Using PVA is cool as it is water soluble, and this really works like a charm: Put the finished print into lukewarm water, and after 10 minutes you can remove the support - soak it for another hour and rinse it under running water → Done. - PVA interface support: I tried to do the support in PVA completely - result: Bad surface quality of the PLA! My explanation: PVA is wobbly/not stiff, so when printing it, you lose a lot of precision, which then impacts the PLA print. Switching to interface support means that the support structures are printed with PLA, nice and rigid, and you just have a small layer of PVA to separate support structure and print. With warm water you get the support away without much mechanical force, reducing the danger of breaking something. Nice side effect of interface support: You save money, PVA is much more expensive than PLA.
Here’s an image showing the difference between PVA full support (left) and PVA interface support (right):
- Stringing: This is nasty after all. In the photos you can see I did not fully manage to get it away yet. People suggest using a gas flame and quickly pass it over the print, that will melt the strings away in no time. Tried this on a partly unsuccessful print. Yes, the strings melt away - also does the sword… Not an option here.
- Standby temps: These worked nice enough, perhaps next time I’d tune down PVA even to 150°C.
- 0.2 mm nozzle print temperature: The same PLA I used here with an 0.4 mm nozzle I usually print more at 190-200°C. But with the tiny nozzle I needed to go higher - I assume that the tip cools more down with the smaller nozzle, or that the tiny hole needs softer material. Already at 205°C I had extrusion problems.
- Layer height: I tried 0.08 mm, with 0.04 mm being the “magic number” of SM2 with 8mm lead screws. But quality was actually worse as compared to 0.1 mm. My assumption: Imperfections like backlash and tolerances in movement become more pronounced, as they stay the same while the layer gets smaller.
- The sword: Despite being only two walls thick, it is surprisingly stable! I guess it still can break off really easily, but I was afraid it might be much more brittle.
- Ooze shield: I tried that, but that’s not a good idea. The PVA nozzle needs a lot of time to build up pressure, meaning that lines in the ooze shield are not there - that makes the whole shield useless, since material for the shield is printed into thin air and ends up anywhere. Anyhow, since the passive nozzle of the DX is lifted up, it bypasses the ooze shield anyhow.
So, I’m pretty satisfied - still a few things bother me and I’d appreciate advice:
- With basically all my prints, not only on SM2 but also on my previous printer, I have/had it, that sometimes one layer sticks out - here’s what I mean:
I’d really love to get rid of that, but I fail to understand its origin… With the functional part prints I usually do I don’t really care, but with such a project here it starts to matter. - PVA is nice, but also nasty. Did anybody use other water soluble support materials? How do they compare?
So last words: The Dual Extruder with the new door works reliably, really happy with that device. And, let me emphasize again: The photos bring out the worst of the print - it really looks nice and does not put you to shame when using while roleplaying. Still, it certainly does not achieve the quality you could expect from a resin printer, not by some margin.