Negative cliff angle (overhang ?) lift and over-extrusion ?

[prevostc 0]

Hi guys,

I'm trying to fine tune the print quality of an ultimaker 2+ and I'm having an issue with cliffs and overhangs. It seems lie the printer is extruding too much material.

See the photos here: Photo album of failed prints

You can see the ear of the ultimaker robot is completely jammed at the bottom and the orange piece, a failed e-nable hand :(, has some sort of extra-material attached to it.

Settings: Cura 2.1.2, nozzle 0.4, fast print preset, light density, no brim, no-support.

I'm re-trying the e-nable hand with the cura normal print preset but any explanation/guess is welcome

Best!

[DidierKlein 729]

Hi and welcome to the forum

As i see you come from France, just to let you know there's also a french part in the community

You can read more about ugly overhangs here

[SandervG 1,521]

Hi, welcome to the forums!

I don't think your overhangs are thát bad. There are several things you can do, like print cooler, make sure the angle is aimed towards the fan or print in thinner layers.

Not turning on your heated bed can also help, because heat makes filament softer / saggy and therefore the radiation from the bed can also negatively influence overhangse which are relatively low on your print.

Printing thinner layers is not always better. A thick layer is heavy and will sag easier, but a thin layer may curl up instead, also leaving its trade on the surface quality.

The ear on your robot is probably due to cooling. The cooling is not entirely symmetrical, cause the nozzle is on the left, and therefore the cooling is slightly better on the left.

[gr5 2,167]

Slow and cold. 35mm/sec, 200C, .1mm layer (optional) and LOTS OF FAN. 100% fan isn't really quite enough - adding another fan helps. Done with *only* 100% fan:

[neotko 1,417]

Slow and cold.  35mm/sec, 200C, .1mm layer (optional) and LOTS OF FAN.  100% fan isn't really quite enough - adding another fan helps.  Done with *only* 100% fan:

 

I don't think you can actually repeat that quality on a um2, maybe a um2 with a bondtech feeder. And probably with a more powerful fans.

That was long ago on a umo right? I mean, umo has a larger hotzone and a overpowered feeder, that probably allowed you to push that filament with less heat. Have you tried to repeat that ever with a um2? Or maybe with the new flame hotends?, I forgot the name, the ones that has the flame nozzle symbol from 3dsolex. Maybe with that and the um2+ feeder + gudo fan system.

[Labern 774]

Yes you can repeat that on a stock UM2 as it was my bench mark when I first started 3D printing

[neotko 1,417]

Yes you can repeat that on a stock UM2 as it was my bench mark when I first started 3D printing

 

With lots of infill to cooldown each layer?

Btw @prevostc that's a good trick. Print stuff with big infills, like 50% or more, so each layer has more time to cold-down. Also, since the normal print order it's outside-inside, all that extra time 'inside' will help push air on the print, so everything get's to the 'ok' temp to avoid overhangs.

So my tips. Fans, ok, as much as posible after layer 1. Then print more than one at the same time, or print each part with larger infills. Ofc, you can print slower. It just that I prefer to print fast and use more powerful fans so I don't waste time or filament.

Edited July 20, 2016 by Guest

[Labern 774]

30% infill.

Even if you use more powerful fans, when you print fast it pulls in more so the curling is more then when you print slower.

There is a point when your printing temp is two low then it will start to curl as the material starts sticking to the cold tip of the nozzle and dragging it.

Also there is a point where having a hot nozzle touching a model with more infill keeps the layer soft like chewing gum.

But all this depends on how picky you are. For normal prints you don't want to have that much experimentation to get it right so you need to be a little less worried about some inperfections.

But it you want that one perfect print then just the your time to learn how the settings effect your print.

[neotko 1,417]

I agree but also disagree. The viscosity of the material used changes that 'pull' effect. Faber for example it's less viscous than colorfabb that it's more prone to get dragged. So the brand/material used changes the approach for each print.

Also I think that it's important to cool the material as fast as possible and because the hotend it's always moving (unless you print small objects) you need not only air on the nozzle but around it. That's why I use 13cfm fans and they actually push much more air than um2 fans. Ofc they add more vibrations at high speeds. So there's always a downside on most sollutions.

[SandervG 1,521]

Ive never had to purposely up the infill for a better surface quality. Dunno if I was blind to improvement but it seemed fine when I found that low sweet spot for printing.

Another factor in play could also be material. For example ABS hides irregularities better than PLA. Does anyone have a preferred PLA brand for smoothest surfaces? (could also be just color related..)

[gr5 2,167]

As neotko suggested - I printed two UMO robots at the same time. This gave one time to cool down while printing the other. Both robots came out just as good. Mainly I needed to do that for the 2 antennas on top of the head.

You don't need a powerful feeder (like bondtech) if you print at 25mm/sec and .1mm layer. That's nice and slow (1mm^3/sec).