Dual Extruder Prime Tower topple

Snapmaker Luban
1

I have the latest versions of software and firmware installed.
When I print a PVA/PVB model on a SM2, the Prime Tower and Ooze Shield, the tower always topples.
The Ooze Shield does not appear to have influence on this issue.
I’ve tried different filament temperatures, print speeds, over/under print tower flows, bed temperatures, retraction amounts, and etc…

My sense is that the PVA/PVB adhesion is lacking and that the PVA ooze is adding volume to the Prime Tower such that the PVB nozzle interferes with the tower.

Comparing Luban 4.9.1 to Ultimaker Cura, there appears to have tower parameters missing.
I’m not sure about the expectations of the Generate Interlocking Structure effects.

Perhaps others could share their successes in order to provide insight toward a more successful path.

2

I was able to print a PVB part with PVA support, without having the Prime Tower topple.

There is a 4.9.1 Luban Dual Extruder Helper bug. After selecting the “Prime Tower” then later selecting the “Ooze Shield” or “None”, the printer nozzle G-code Travel path takes the nozzle to the far back-right bed corner for each layer.

The most significant success parameter is the PVA support print speed. It needs to be “very slow”.
The setting used was 15/12/10(tower)/20(travel)mm/s.

In order to provide filament/filament adhesion: 1) high filament temp (212degC, both filaments), 2) no fan, 3) 60degC bed

The PVB line width seems to have a significant impact. It needs to be equal or greater than the nozzle size (0.4mm). After using the calculator, I set the layer height to 0.34mm and line width to 0.41mm.
This rectangle volume (0.340.41) is the same as the .4mm nozzle circle (Pi0.4**2) volume.

Both PVA and PVB filaments are hygroscopic, meaning they need to be dry. Using 55degC for 6 hours seems to do the trick.

Typically either the Prime Tower, Ooze Shield, or None would be selected. The Prime Tower and Ooze Shield basically serve the same purpose to reduce filament whiskers and surface clumps. Minimizing the amount of support filament required is normally a best practice.

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