Retraction on infill

[veedee 4]

Hello people,

I'm using my ultimaker for quitte a while now, but i've expected some issues with retraction.

Retraction allways happens on the outsides of a layer (I think), but retraction takes a moment to happen. So when te retraction takes place, the hot end stays still for a while creating a little blob on the outside of the layer. This is very ugly when you create stuff like iphone cases and so on.

Is it possible to let the retraction happen somewhere on the infill of a layer? And create a better print this way? Or is this already tested without good results..?

Grtz, Sven

 

[illuminarti 18]

Hi Sven, welcome to the forum.

Yes, it's a recurring issue - how to ensure that retraction happens as quickly as possible, and preferably in a more convenient place. :-)

The first can be addressed by tuning the retraction speed and also ensuring you have the most recent firmware (more recent than what is supplied in Cura), as older versions had a bug.

Regarding the second, it used to be possible to tweak the print order in Cura, to adjust whether internal loops, the outer perimeter, or infill got printed first. That could sometimes help in putting the jumps (and hence the retractions) in a better spot in the sequence. But that option is currently missing from the newer, re-engineered version of Cura - and I'm not sure if it is ever coming back.

It's a difficult problem, because even just moving an oozing head over already printed loops and infill can cause print quality problems of its own.

 

[Daid 306]

Actually, Cura moves the head slightly inwards of the model before retraction (in the 13.06.4 release). But not all the way into the infill. You might just want to lower your temperature a bit so the nozzle doesn't meld the outside walls as much. Could make all the difference.

 

[veedee 4]

On projects with retraction like phone cases, I lower the temperature to about 200 degrees. I normaly use between 210 and 220 because (I always think) it makes stronger prints.

Is there some kind of a golden rule for retraction speeds and distances? Or does it vary a lot with the material that is used?