Burnt support structure! Any ideas?

[rabbit 0]

Hello everybody,

 

I have some strange issues. I am trying to print some ABS parts. The part itself is looking good but I have some problems with the support structure. As you can see it starts to become brittle and burnt in some areas. The support is crumbling and sometimes it sticks to the printhead which, in the worst case, causes a failed print.

I use Innofil ABS, print at 245/250°C and the heatbed is at 100°C, print speed is 45mm/s, 0.1mm layer and I use a 0.4mm nozzle. the cooling is on.

 

Does anyone of you have an idea how to solve this problem?

Thank you all

[Nicolinux 288]

Hi,

 

if you use Cura, check the print speed at which it prints the support. I assume it prints way too fast and filament strands are dragged around and clump together.

[rabbit 0]

Thank you for your answer Nicolinux,

the supportspeed is 20mm/s. I think that is slow enough. ?

[Nicolinux 288]

Ok, then it must be something else. Looking at the brim for the object, I can see that it is very spotty. The brim should have a tight surface so it could be a sign for underextrusion. I wonder how the main object print quality is like. Do you see signs of underextrusion there too?

[rabbit 0]

I printed with raft. The mainobject looks pretty good except for the burnt crumbles dragged in from the support.

In the first layers there is no brittling at all. It starts somewhere at a hight of 5mm or something.

From there on it is getting more and more.

Material flow is at 108%

retract length 6.5mm

retract speed 30mm/s

 

[Nicolinux 288]

Then I am out if ideas - sorry. I don't print with ABS but maybe @Anders Olsson knows something.

[Anders Olsson 136]

It is a bit difficult to determine what went wrong.

- Burnt ABS generally means that you could/should lower the printing temperature a bit, what brand material did you use?

 

- ABS generally don't like cooling fans, on a model like that you should definitely leave the fans completely off (or issues with brittleness and warping will increase)

 

- What slicing software did you use? My experience is that the sudden speed changes and excessive travel moves of some of the more recent versions of Cura made things much worse, compared to the good old 15.04.06 version.