.4 vs .6 nozzles - Can I run both.  

As a rough guide the smaller the nozzle the prettier the print but larger nozzles make stronger parts - one of the many 3D printing trade-offs.  As the XL was never really meant for dainty work the 0.6mm nozzles made sense but because so many users were making cosmetic assessments Prusa switched to 0.4mm nozzles as standard.

I currently have two brass and one Obxidian 0.6 nozzles fitted and two brass 0.4mm nozzles.  The smaller nozzles are used for multicolour work - mostly labels and graticules while the larger are used for multimaterial jobs.  Mixing nozzle sizes in a single print is currently ... tricky ... you will find threads on here showing how it is done; I understand Prusa are working on incorporating it into slicer but don't hold your breath.

Cheerio,

RE: .4 vs .6 nozzles - Can I run both.

Thank you!  Yeah I could see where I wouldn't mix during the same print. The nozzle swapping around could be annoying but thats a given/fine.

The printer has been doing amazing prints at .6 and like you said the prints are large and structural for the most part.  I had the printer at my friends place and would go there to use it (and he used it) for all kinds of prints.  But now that its back at my house I have my MK3 here and how I ended up seeing those images above is my MK3 was already in the middle of a 3.5 hour print and I thought "hey i'll run the XL on the other pieces"  and when I flipped the board to XL .6 I noticed the slicing was quite different.  Its definitely a specific case though as those pieces are really small and printing upright like that is also odd.   

Perhaps at some point I'll switch Nozzle 5 over to .4 for some finer prints. Otherwise try to use my MK3.....  Its just so tempting to run both machines at the same time, hehe.

I'm printing a lot in PETG these days. Some PLA for specific jobs but PETG is very common for me now. Supports are funky to remove. I often set the Contact Z Distance to .3.  

I too run a Mk3 as well as the XL, it's mostly used for TPU which I could do on the XL but it means slowing the XL to near MK3 speeds so I let the MK3 chug along while the XL does other things.

Cheerio,

RE: .4 vs .6 nozzles - Can I run both.

If you want to experiment with mixing nozzle sizes you can read through this thread. It's not difficult to do but there are some big and small limitations, some more apparent than others.

One thing you can officially do is mix materials in one print. So zero contact distance PLA supports for your PETG prints can work out very nicely if you find spools that play nicely.