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A case study of XL .6 brass vs .4 ObXidian vs MK3s .4  

Eminent Member
A case study of XL .6 brass vs .4 ObXidian vs MK3s .4

I figured I'd document trying out some new nozzles. There is a lot of chatter about .4 vs .6 regarding stringing & oozing. Hardened nozzles can also be a bit of a pain to tune or use, although the ObXidian is mostly brass, so shouldn't have the issues an all hardened steel nozzle has. This isn't a request for help or anything. I know I need to do some more testing for filament drying & probably some profile tuning. I've printed off a number a temp towers for the MK3 a few years ago, but mostly just stuck with the stock profiles. The temp tower I printed on the XL a few weeks back looked the same at all temps, so I suspect it only printed at stock profile temps, despite having the pre-sliced Gcode.

I'm printing up a ton of Gridfinity boxes for storage & took the time to compare a few different nozzles. Some of the boxes are different sizes, but given their nature they are all equal complexity. I get bed adhesion issues on 5-20% of a square on each corner on most gridfinity boxes over 3x3. Enough to notice, but not enough for me to bother doing anything about given the nature of them being storage boxes with a grid underneath to keep them stable. I could use a brim or make some ears on the corners, but the post processing doesn't seem worth it. The curling only happens on long prints when the cooling contractions start to add up. So I'm pretty sure they had nothing to do with my massive failed print.

I'm only messing with single filament prints at the moment, so this doesn't relate to material or color switching. That will generate more stringing issues from what I've seen. I've been using the stock Prusa PETG profiles for all prints, layer height is set to maximum with draft or structural quality. I want speed of prints & strength for these storage containers, they don't need to be that pretty. .3 layer height for the MK3, .32 layer height for the XL with the .6 nozzle. I don't remember what it is for the XL with a .4mm nozzle at the momentI'm really only printing in PETG on the XL at the moment. there are some PLA prints, mostly from the MK3. I may very have some filament dryness or other issues, but I'll fiddle with that separately. I have a EIBOS Cyclopes I've been using. I may have overheated some of the filament, particularly the white stuff mixing other dryer temps vs what Eibos recommends. It got pretty soft at one point, particularly on the bottom near the heater. The 2nd roll of Overture space grey was not ran through the drier. I've been using Overture, Space grey, White & black, although none of the black stuff got used for testing.

We have a MK3S+ I got us for Christmas a few years ago as a MK3 I think. My wife has well over a thousand hours of print time logged on it so it's not just my toy. I have a .4 NozzleX (hardened steel) for the MK3 I've never been entirely happy with. I got tired enough fiddling with different temperature profiles between brass & NozzleX I gave up & went back to brass. It's probably a E3D nozzle on there now, but not sure.

  1. Printed off numerous Prusa Galaxy Black PLA containers on the MK3 (mostly for reference, not a direct comparison)
  2. Printed 3x4 grey tray among many others with the .6 brass on the XL on head 5
  3. Swapped over to black, printed a bunch more trays, then had one fail catastrophically
  4. Spent half an hour removing the blob of death. Cause unknown. Coincidentally that morning my new .4 brass & ObXidian nozzles showed up. So I installed the .4 ObXidian while I had head 5 off
  5. Printed off the pair of 3x4 trays in Overture Space Grey with the .4 ObXidian on head 5
  6. Removed the roll of Space Grey Overture PETG off the XL & put it on the MK3Printed the 2x4 tray
  7. Printed off the pair of 2x6 trays with white Overture PETG on head 4


Observations from testing & generally comparing a XL to a MK3S+

  • Stringing on the XL with PETG isn't great, I'm seeing a fair bit
  • I'm seeing similar amounts of stringing between the .6 brass & the .4 ObXidian
  • I'm seeing more stringing on the XL than I am with the MK3
  • I get a lot of nozzle buildup on the XL, followed by globs falling off, which have lead to a few head crash detections & possibly the big failure
  • Usually I can use some nippers to remove the glob & recover the print.
  • I haven't been printing that much PETG on the MK3
  • I don't see really any difference in stringing between the .4 ObXidian & the .6 brass
  • I can's see a difference in layer height related to stringing
  • The XL is WAY louder than the MK3. We can hear the XL located in the dining room from our bedroom down the hall. You almost couldn't hear the MK3 on the other side of the dining room before we moved it. I thin it's mostly the Core XY steppers or belts. The cachunk from head swaps isn't quiet, but is nothing compared to the higher pitched whining when printing. There may be a chance the XL gets banished to the basement due to the noise
  • The XL doesn't seem that big & the build plate isn't that impressive, but when I go back to the MK3 the build plate seems tiny. CoreXY definitely makes better use of footprint than a bed slinger. The XL has about the same footprint as the lack table enclosure for the MK3.
  • You can have .4 & .6 nozzles on different heads, but it's a pain. I haven't tried any multi-head prints, but hear you can't do that. PrusaSlicer kept clobbering my PrusaConnect profile for a .6 nozzle when trying to create a .4 nozzle profile. I've got both now, but it has been a bit fiddly. Similar issues trying to get an InputShaper & non-InputShaper profile. Sometimes one profile disappears

My path forward

  • Filament drying testing
  • Temp tower tests & profile tuning
  • At this point I'm not sure what I'm going to do nozzle wise. I was hooping for some reduction in stringing, but I'm not seeing it so far.
  • I should test out a .4 brass as I have a couple now, but lack of difference between 6 brass & .4 ObXidians has me wondering if the effort is worth it.
  • I had planned on putting .4 ObXidians on heads 4 & 5 with .4 brass on 1-3. But I'm wondering if it's worth it
  • I've been eyeing the DiamondBack diamond tip nozzles, for their anti-stick properties almost as much as their hardness & thermal properties. They are claiming they may have some Nextruder compatible ones out in a few months. I'm not going to fiddle with a V6 adapter to put one on, despite having that adapter due to preordering. So any decision there will be a ways off.

Left to right

  1. .6 Brass XL head 4 White
  2. .6 Brass XL head 4 White
  3. .6 Brass XL head 5 Grey
  4. .4 ObXidian XL head 5 Grey
  5. .4 ObXidian XL head 5 Grey
  6. .4 Brass MK3 Grey
  7. .4 Brass MK3 Black PLA.
  8. 4 Brass MK3 Black PLA
  9. Unexplained failure
  10. A small part of my GridFinity goodness (most containers before I started taking notes on stuff)
  11. A small part of my GridFinity goodness (most containers before I started taking notes on stuff) 


Posted : 27/01/2024 5:20 am
Acht and nhand42 liked
Eminent Member
Topic starter answered:
RE: A case study of XL .6 brass vs .4 ObXidian vs MK3s .4

Looks like the forum isn't excited about multiple photos. Higher res ones are in my XL Google Photo album at if you want close ups of the stringing, along with a few fan errors I fought with assembly.

Posted : 27/01/2024 5:25 am
Argent Doom
New Member
RE: A case study of XL .6 brass vs .4 ObXidian vs MK3s .4


Posted by: @fallon

Looks like the forum isn't excited about multiple photos. Higher res ones are in my XL Google Photo album at if you want close ups of the stringing, along with a few fan errors I fought with assembly.


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Posted : 13/05/2024 8:04 pm