UM3 Dual Extrusion PVA Leaving Overhangs Unsupported

[Hendo 1]

Hi Guys & Gals.

 

I have encountered an interesting "Phenomena" where Cura (4.4.1) almost intentionally leaves certain overhangs unsupported when printing the support material with core 2 (PVA). Printing with an UM3, AA 0.4 and BB 0.4 cores, PLA and PVA. I have played around extensively with the parameters and settings and haven't found any solution yet. For the attached illustrations- I have set everything to default/standard:

 

Model:

Here is the model and the specific area of interest for me with the standard settings visible.

 

Slice Preview:

 

Here the preview SEEMS fine with more than enough PVA support all-round (Yes, I can set the XY ofsets ect to print less PVA blah blah but that's not the point of interest here)

 

Problem:

 

Here you can see that it leaves a big chunk of support out where it really SHOULD be putting support...? (Note here that I kind off despise the "Gradual infill steps" setting but understand how it can be beneficial but i mostly set it to 0). I mostly hope that it is me missing something extremely obvious, but it gets interesting; When I SWAP the extruders.... It supports it correctly.

 

Swapping printing Extruders:

Note that I only instructed cura to use extruder 2 for the model and extruder 1 for the support:

 

I have tried multiple permutations of settings to try and get the PVA in the same manner as the PLA (eg making gradual infill steps 0, grid as support structure, density same as infill density ect ect ect but I am always left with this mysterious gap when trying to support that overhang with PVA.. Even tried putting the PVA BB core in Slot 1, and PLA AA to Slot 2 but the slice will still result in the unforgiving black-hole of "NO-SUPPORTNESNES"

 

So for now I'm left with a dead light-bulb floating over my head until I can figure it out. Anybody maybe know what the obvious solution is that I am missing??

 

Okay love you guys, Cheers! 

 

Edited January 23, 2020 by Hendo

[Priddy 10]

It may be a shot in the dark, but does setting "Support Stair Step Height" to 0mm look to help?

[Hendo 1]

Priddy - You are a magician!! It does solve the problem. Will now investigate WHY it works :). Thank you!