MMU2s with PETG (5 Colour Benchy = 20hrs & 540 Changes) - Results  

MMU2s with PETG (5 Colour Benchy = 20hrs & 540 Changes) - Results

So my MK3s/MMU2s is working pretty well in with single colour prints using PLA, PETG, even some ASA - the prints looks great.  But I'd only been printing PLA in Multi-Colour and while these too look great and I've had little issues (recently) I thought I'd give a 5 Colour, 20hr, 540 change Print (Benchy/Boaty) a go.  I even setup a video camera to see what it was up to overnight (which turned out boring... which is good 🙂 )

Interventions:  After a few hours I started seeing the printer try to load a filament twice, then 30min later it asked for intervention.  Looking closely at the Sensor Screen I could see that the IR Sensor was toggling between 1 and 0 when even the filament was loaded.  I loosened the chimney bolt, pressed the chimney hard over the the right and tightened it.  Now the IR Sensor was just 0 or 1 depending when the filament was loaded or not.  Earlier that day I had removed the chimney for some maintenance so maybe I'd not set it correctly back up but about the same time I got that grinding/clicking noise on the Bondtec when there is no filament in the teeth (it seems to happen after a lot of loads and unloads or maybe when it gets hot....).

Crud Build Up & Filament Tips:  You can see from the pic, a lot of fine PETG Tip Strings build up in the MMU2s, even wrapping around the spindle and getting into nooks and crannies.  While this did not cause me any issues, I'm sure it could at some point especially if it fouled the Finda / Ball Bearing  (I have the mod so you can see the ball bearing and will be adding the magnet next maintenance as they have now arrived).  I've also include a pic of the Filament tips so you can see the strings.

Print Quality:  Not to shabbie.  No stringing to speak of on the Benchy.  No Colour bleed (I'd increased it from stock for when moving to white).  The biggest issue with quality, is on this model a colour change may be made to just put the tiniest amount of filament down, sometimes it is more of a Dot than a Line and you can see the impact of this on the White of the Gunnel Top.  Apart from that it was pretty good.

Speed:  Not surprisingly, with 540 changes on a model with only 320 lines it is sloowww.  Each change adds about 2mins to the print time (which they could get this down as some if it does not seem necessary), and some lines have multiple changes.  Even where there is no filament change, just adding a layer to the purge block adds 15sec for each line.

Conclusions:

- IR Sensor:  You may have it calibrated and working fine, but after a few hours the machine heats up and possible things move just a bit and all of a sudden the IR Sensor is not reliable.  After i'd set it during the print, it then worked without issue for the rest (I even put a camcorder on the screen to keep an eye on it overnight).  That said, I think it and the PINDA are a poor design choice due to their fine operating tolerances.  When they work they are fine but it is easy for them to drift out of tolerance mid way through a print due to heat, vibration, or the build up of crud. 

- Tweaking Profiles:  I've tweaked my PETG profile how I like it for my single colour prints but it seems that when you select MMU2s it grabs a different profile.  I need to check on this as it was obvious that both Boaties Infill and that of the purge block was poor yet earlier in the day was perfect on a PETG single colour print.