Dual extrusion weirdness

[jens3 12]

I am trying to sort out dual filament printing.

For reasons that are a mystery to me, no matter what I do and what settings are, the printer will always prime the first extruder even though no material will be printed for several layers. The sequence will be as follows: Extruder 2 is heated to operating temperature, Extruder 1 is heated to standby temperature. The printer then prints brims (if configured) for the model (in this case overridden to extruder2), prints the brim of the prime tower even though it is specifically not configured. (this also prints with extruder 2). After that, the bottom of the model is printed (with extruder 2). So far, everything is as expected (other than that the brim for the tower was specifically left unchecked). Next, Cura heats up extruder 1 (nothing is supposed to be printed with extruder 1 for a while) and proceeds to print a line around the outside of both brims. Then, it fills the prime tower bottom with extruder 1.

All of this extruder one stuff produces contamination of the print that is actually meant to print 😞

In addition, extruder 1 starts to heat up at the very beginning of the bottom layer of the model which results in a fully heated extruder 1 which drools all over the material that was printed with extruder 2.

Also of note, I have tried adjusting the heat up and cool down settings for the extruders but that seems to not affect the first layer at all and subsequent layers either start heating at the beginning of the previous layer or at the end of the current layer. I was trying to start the heatup just prior to the layer finishing so the next extruder is heated up just in time for when it is needed but not before (in which case it drools on the previous layer)

 

So, am I missing something here or is the dual extrusion 'smarts' not fully developed in Cura 4.4.1 yet ?

[HanSense 0]

I'm pretty sure this is exactly what's happening for me. I, however, am using PVA (soluble filament) with my second extruder (this is a shared nozzle machine - Sovol SV02). So, the print begins with the PLA (extruder 1), and then switches to the PVA to print ONE line around the brim of the model and the prime tower (extruder 2 is not needed until layer 74 and is not utilized again before layer 74)...this is annoying because for some reason, the purge after the ONE line of PVA just bunches up instead of sticking to the prime tower (PLA), causing the nozzle to drag the purged PVA into the printed PLA of the model and mess up EVERY SINGLE PRINT. I can't figure out how to disable this, as it doesn't seem to be a setting. All of the bed adhesion is set to print with extruder 1 (PLA), so this is very confusing. I remember a setting like "prime all extruders at start of print" or something, but always made sure to disable that, and I can't find it now...so, not sure if that's related. If anyone knows a solution, please help!