(solved) MMU layer shift from nozzle getting stuck in wipe tower
For discussion (and "note to self" if running into it again):
I'm printing ASA at 275 degrees, which is the upper limit printed on the spools, in other words quite far above the melting point (/glass transition temperature).
When the MMU changes filament, it hesitates several seconds over the wipe tower with minimum (if any) gap. This (possibly in combination with some material dripping from the nozzle) results in an uneven wipe tower surface that eventually catches the nozzle, leading to layer shift. Settings may work on testprints with small objects but fail when the printing time per layer goes up.
The solution was to insert a custom "Tool change" G-code (Printers/custom G-code/Tool change G-code):
G1 Z+10 F10000; avoid melting into wipe tower (-mn)
This raises the head by 1 cm for the color change.
RE: (solved) MMU layer shift from nozzle getting stuck in wipe tower
I found that this helped me as well, thanks! The only issue I subsequently discovered is that the print head is only lifting to Z=10mm, not a relative lift of +10 on Z. This whole thing works as well as it does because the printer is set to absolute, rather than relative coordinates (so that it goes back to what it was doing after the filament change), but will lead to crashes for wipe towers taller than 10mm. I tried wrapping this with a switch to relative coordinates:
G91;G1 Z+10 F10000;G90
But for some reason this causes my print to fail to even make the base of the wipe tower properly. Perhaps there's some important value getting wiped out in the G91/G90 transition. Have you any thoughts on this?
RE: (solved) MMU layer shift from nozzle getting stuck in wipe tower
Hello!
Printing ASA at 275°C caused nozzle drag on the wipe tower during MMU filament changes, leading to layer shifts. The fix was adding a custom tool‑change G‑code (G1 Z+10 F10000) to lift the nozzle 1 cm during color swaps, preventing it from melting into or catching on the tower.
RE: (solved) MMU layer shift from nozzle getting stuck in wipe tower
Hello!
Printing ASA at 275°C caused nozzle drag on the wipe tower during MMU filament changes, leading to layer shifts. The fix was adding a custom tool‑change G‑code (G1 Z+10 F10000) to lift the nozzle 1 cm during color swaps, preventing it from melting into or catching on the tower.
Did you ever print anything that required a wipe tower more than 10mm high? The problem I ran into is that putting that command into the tool change gcode only moved my extruder to z=10mm, and started crashing into the wipe tower once the tower exceeded 10mm. Was this not a problem for you?