Wall ends not joining with 0.7mm layers - asking for hints

[danielkschneider 0]

Hi, I am printing 0.7mm and 0.6mm layers with a 0.7mm nozzle. Some outer wall ends do not join well, typically small circles that you would find underneath duplo compatible pieces. Right now, I got retraction = off, skin overlap percentage = 20 (0.14mm) and extrusion = 100%. The walls themselves and walls with infill context nicely and I print rather slowly, i.e. about 33 mm/s.

 

Any ideas what I should do, e.g. define negative extrusion ? I am aware that this is a problem influenced by how much (little) plastic the printer can push through and I am just asking if someone has a good "trick" for my problem. Also, the previews look just fine, lines are joined.

 

Cura version 4.8.0 on Ubuntu 18, Felix Pro 2 printer

 

PS: In case you wonder why I print Lego and Duplo compatible pieces so coarsely: I just want to create lots of pieces in reasonable time and the ones I do fit nicely and are functional.

[gr5 2,230]

Cura has a bit of trouble on thin walls like that that are slightly wider than line widthX2.  I assume your line width is 0.7 and so if those internal duplo walls are 1.5mm then there is a .1mm gap.  There is a new alpha version of Cura that supposedly does better with this sort of thing here - called arachne:

https://github.com/Ultimaker/Cura/tags

 

It has lots of buts but might do better.  But a better solution is to use this tried and tested version of Cura from one of our community members which does MUCH better on thin walls like this.  I use his versions of cura much more often than the Ultimaker version.  It's quite safe.  I met the guy in person:

https://github.com/smartavionics/Cura/releases

[danielkschneider 0]

Hi, thanx much for the help, but this is not my problem (I should have explained better !). The walls do join, but the ends of the walls do not. I attach a new picture that shows the problem better.

Actually (after posting) I now have the hypothesis that the pressure in the nozzle may not be enough and that there is a short lapse before the printer starts extruding after a jump.

[Smithy 1,146]

Check if you have "Coasting" enabled in your Cura settings. If so, disable it.

[danielkschneider 0]

Hi, thanx. I think it's off (unless I checked it by mistake) !  I will see on Monday, since the printer is at work.

- greetings !

[gr5 2,230]

I was going to say the same thing.  It looks like you have coasting enabled.

[danielkschneider 0]

Hi thanx again.

 

No, coasting was not enabled. So, my conclusion is that this has to do with extruder mechanics.

For example, the extruder could lack sufficient pressure to push out the plastic in time when it starts a line or there is some unwanted retraction (by the plastic itself and not the extruder) when traveling.

 

Heating more (e.g. 230 for PLA) should help a bit, I have "heard" some folks printing PLA at 240^C when printing with large nozzles and will try that too. I don't want to add more extrusion since it leads to messy knobs.

 

Other than printing with smaller layers (e.g. 0.56mm for a 0.7mm nozzle) I don't have a solution, yet 🙂