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nick-foley

Retraction in Cura 13.11 and 13.12

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What's going on here? If I'm try to describe the behavior, it is:

Printing an island,

Stopping in the middle of that island and retracting,

Moving a tiny amount (<1mm) within that same island,

Un-retracting while still on that same island,

Then jumping over to the next island.

Is this the way it is supposed to be? Is this the way it always was?

It seems like it should retract, move to the next island, and then un-retract. I'm getting some pretty crappy results with stringing and blobbing. Will try moving back a few versions in Cura, but anyone else seeing this?

 

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Certainly doesn't sound like the way it's supposed to be. I know there was a bug where everything under 10mm got treated as a within-island combing move, and there was no retraction, but that's supposed to be fixed in the new version.

Is it that you have a non-zero minimum extrusion setting? In that case, the head might retract to move within the first island, to add some extra fill or something, and then choose not to retract on the big move, because it hasn't extruded enough since the last retraction.

I'm still not sure about the 'combing' behavior in general. I can see why you'd want to move within an island wherever possible, rather than cutting across the walls. But it seems that when you enable that, you also are electing to not have retraction happen on those moves. And that seems like a bad idea to me, as it causes oozing and scars on the print. I'd prefer to always have retraction, except for the very shortest moves (e.g., between adjacent infill line) - especially on the UM2, where retraction seems rock solid reliable.

 

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Yeah, I'm printing the star ornament as a test since I just switched my hotend up. Lots of retraction and tiny printed areas.

Anyway, I can confirm that 13.06.4 isn't moving in this illogical fashion - it is printing an island, retracting, and then moving to the next island while simultaneously un-retracting. Makes a huge improvement in print quality.

I will play around with the minimum extrusion before retraction setting and see if it makes any difference in 13.12. It was previously at the default 0.1mm

 

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I will play around with the minimum extrusion before retraction setting and see if it makes any difference in 13.12. It was previously at the default 0.1mm

 

That's way too much. .1mm of 2.85mm filament covers 2.85^2 / .4^2 or 50X the area of a .4mm by .1mm cylinder which is about 50*.4 or about 20mm of printing in a line. So if you set minimum extrusion before travel and then print less than 20mm it will skip a retraction. I recommend something more like .01mm or 0mm.

 

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Anyway, I can confirm that 13.06.4 isn't moving in this illogical fashion - it is printing an island, retracting, and then moving to the next island while simultaneously un-retracting. Makes a huge improvement in print quality.

 

That should be impossible, even in 13.06 the code for retraction is always "in place". Simultaneous unretract with move is never commanded by Cura.

Are you running on an Ultimaker or another printer?

 

What's going on here? If I'm try to describe the behavior, it is:

Printing an island,

Stopping in the middle of that island and retracting,

Moving a tiny amount (<1mm) within that same island,

Un-retracting while still on that same island,

Then jumping over to the next island.

Is this the way it is supposed to be? Is this the way it always was?

It seems like it should retract, move to the next island, and then un-retract. I'm getting some pretty crappy results with stringing and blobbing. Will try moving back a few versions in Cura, but anyone else seeing this?

 

Are you getting this in both 13.11.2 and 13.12-test ? And which with exact model?

I have been making changes in the retraction code, it's tricky to get exactly what I want, but in my tests it works as intended...

The "tiny move" is as intended, what it should do, is moving inwards of the print, retract, move to the new position, but inside the print area, push forwards, and move to the final position for printing. This does the retracts/pushes inside the print instead on the edge, preventing blobs on the outer skin.

 

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Daid - you might also take a look at this thread...

http://umforum.ultimaker.com/index.php?/topic/3724-need-help-fine-tuning-multiple-object-print/?p=29145

This user is seeing the print head jump off-island before retracting, when combing is enabled.

 

Yes, that's a bug, I fixed it, but I'm not 100% sure if I fixed it before the 13.12-test from http://software.ultimaker.com/Cura_closed_beta/

 

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