Retraction

[johan 0]

Hi,

I am using Cura on both my Ultimaker, and my Reprap, and am very pleased.

At the moment I am printing on the Reprap at high speed, and it is coming out nicely. The only thing is that I get a little blob where the z lifts. I use a retraction speed of 35mm/s, distance 12mm and extra lenght on start 0mm. The Reprap have a Bowden extruder.

I can see that it purges out about 7mm before it starts to move the head. I guess this happens because of preassure beeing build up in the Bowden tube. In SF you set both the lenght of retraction, and how much you push back after the move if I remember right? Is it possible to do this in Cura?

Johan

[Daid 297]

Yes, you can configure both the retraction, and the extra length after pushing back in the advanced tab.

[johan 0]

I found that, but can I set the pushing back to less than the retraction lenght? for example retract 10mm, and push back 5mm instead of 10mm?

Johan

[Daid 297]

Uh, try a negative extra start. Even if the GUI says it's wrong, you can still try. Not sure if it works, you'll have to try.

However, I do not see how that would make sense.

[johan 0]

Thank you. I'll test!

Johan

[yzorg 2]

i have the same smal blob issue on my ultimaker.

what is suggested to change first?

[Daid 297]

I highly doubt you have the exact same issue, blobbing can be caused by many different things. What settings are you printing at yzorg?

[yzorg 2]

I got you some screenshots..

[Daid 297]

0.28mm layers at 80mm/s? That's a lot of filament you are extruding per time, most likely you have a very high pressure build up, most likely some of this pressure is still escaping as filament during the retraction. You could try retracting less, this will give slightly more strings but makes the head stop shorter causing less blobbing.