UM3 Retraction Settings

[BJC 0]

 

Just got my UM3 and did a test print, machine ran smooth but the print could be improve. According the the makers, this test print is all about retraction settings.

I also printed a long large screw, though the print was perfect, during print, I can see similar branches happening inside in the infill.

So my question is, how can I improve so that the spikes are all perfect without the branches appearing? Retraction settings? Temperature/fan speed settings?

 

Some of the settings of the actual print:

Used the Cura 3.1 Fine preset -> 0.1 layer height, print speed 70, infill 20, filament is the metallic silver PLA that came with the UM3

Edited January 3, 2018 by BJC

[yellowshark 152]

OK, well it looks quite small and with those narrowing cones I think you are way too fast. I suggest..

 

30 mm/s

fan 100%

You do not mention extruder temp but cooler will help reduce/remove stringing. At 30 mm/s and .100 layers I would suggest 190 for the extruder.

I do not know if you can manually change the print speed during a print on a UM3 but you can you may want to reduce it to 20 mm/s as you start to get closer to the top of the cones.

Apart from the 1st layer (20 mm/s) set all your other printing speeds to 30mm/s i.e. the same as you main print speed.

 

You do not say what your retraction settings are but yes they may be helping to cause the problem; although if they are standard Cura settings (which I have never used so do not know what they are) one would think they will be OK. I do not have access to mine on this PC; I will try and get them tomorrow

 

[pbackx 11]

I think @yellowshark explained it well.

 

Start by lowering the temperature and speed. There used to be a plugin to change settings based on height. I can only find this one, but I don't think it works with the latest Cura: https://www.youmagine.com/designs/swap-at-z

 

You could increase the retraction distance, but that may create more trouble than it's worth.

 

One more thing: it's normal that there is stringing inside the infill. Because it will not be visible anyway, there's no retraction happening when printing the infill, so that's fine.

 

[yellowshark 152]

My retraction settings, for PLA, up to 18 months ago were

Distance 5.5mm

Speed 50 mm/s

Minimum travel 0.8mm

Maximum count 90

Min. extrusion distance 5.5mm

 

Then I tried the nGen filament and got a lot of stringing. I overcame that by changing

Minimum travel from 0.8mm to 1.0mm

Min extrusion distance from 5.5mm to 0.2 mm

 

And I have used these new settings with PLA ever since (and PLA was fine on the older settings). Which only goes to show that the material in use can affect it, even it is one manufacturers PLA compared with another's PLA and that you may need to experiment a bit to get it right for you. I am not trying to suggest that the above settings are the best and you should use them, just that the settings work for me. The change in the min. extrusion distance is dramatic and I have no memory of what led me to that change.