My multi-color/-material printers

[spegelius]

And another shot at getting the PVA printing properly. Actually looking pretty good so far, only one failed filament swap and even that was easily corrected by the MMU by using the filament cutter so pretty neat compared to the manual labor I had to put in for the previous prints. Took a couple of tries to get some settings dialed in, but this latest run has been going very well.
IMG_20210126_125744.jpg

The changes I've made so far:
- swapped the E3Dv6 heatbreak to Trianglelabs bi-metal part I bought as it looked interesting. I did polish it with Dremel, drill bit, steel wool and toothpaste. Not sure if this matters much, although I've heard that this should reduce heatcreep so maybe?
- applied some Boron Nitrate paste the hotend heatsink and heatbreak. Also should reduce heatcreep
- swapped the hotend PTFE tube from Prusa's special 1.85mm id tube to Capricorn tube. The Prusa tube was malformed, most likely while I cleared the infernal clog that happenend during the first PVA experiments (had to ram a hex key in with quite a lot of force...). It seems that the clog happened because this PVA is actually ~1.85mm in diameter, should have measured that in the beginning. So if I use the spare Prusa PTFE tube I got with the MMU, I can't print this PVA. Luckily the Capricorn seems to work nicely and it should be ~1.9mm id.
IMG_20210123_191456.jpg

On sw side, following changes were made for the PVA filament profile:
- max flow rate restricted to 1.5mm^3/s, which is around 20mm/s head speed, seems to help getting better support structures
- z-hop 0.6mm -> 0.1mm
- retraction 1.2mm
- printing temp 222 C, way over the manufacturers max, but seems to be required to get the PVA to bond to PLA properly. Wonder if this because the PVA is quite old...
- enlarged the support area, wastes material but for now it seems to make the PVA structure more stable
- support interface gap to zero in xy-direction, it has been 0 on z-direction

Looking good so far, I'm happy if I get the PVA used and don't have to throw it in trash.