No retraction on travel

[kazzaqov 0]

Hello everyone,

I have a following problem: retraction itself is fine, but when printer finishes the layer, it travels through whole model to start printing the next one (to another corner of the bed) with no retraction and this creates horrible strings.

Anyone knows how to solve this? Maybe somehow set different travel route that will not affect the model?

 

[illuminarti 18]

Are you printing with no infill, just loops? I've seen this behavior with the new Cura engine - it seems to consider that anything 'internal' to the model where there is (or could be) infill is fair game for stringing, and it doesn't retract. I too wish there was a way to tell it to not do this (or that it had more smarts - particularly in a zero infill, open top/bottom print), but it doesn't seem to be the possible yet.

 

[kazzaqov 0]

I am printing thin (2.5mm) and tall (10 cm) object, but with 100% infill. Did previous Cura's engine also had this issue? Or trying to use older version (which one?) could help?

 

[illuminarti 18]

So is the head only moving 'within' the model (over the infilled part) during the troublesome move? And you are still getting stringing?

 

[kazzaqov 0]

Head moves only within the model. But the model is an engraved image ( a lithophane), so it leaves strings on edges of the engraving.

 

[kazzaqov 0]

 

[illuminarti 18]

You're printing it laid flat on the bed, right? So it's just a few layers of print. And you do have retraction turned on for this print, and set to reasonable speeds and distance?

You might try using an older version of Cura that still used Skeinforge - try 13.04, and see how that behaves. Or you might try another slicer like Kisslicer.

 

[kazzaqov 0]

I tried printing both flat and upright. The one at the photo was printed upright, so its a lot of layers. Printing flat makes quality much worse. I am using the following retraction settings: speed 70mm/s; distance 9mm

Thank you, I will try slicing in 13.04

 

[illuminarti 18]

That seems like a lot of retraction - and too fast. There's a bug in older versions of Marlin (which you will have unless you compiled your own) that makes retraction happen slower than it should. In any case, it can't happen faster than about 48mm/s on an Ultimaker, as there's a limit of 40,000 steps per second for any one axis. I'd try reducing your speed down to about 40mm/s, and most people use a distance of 4.5mm or so. Not that that will affect your problem here, if the retraction isn't triggering at all.

You might also check your infill overlap percentage as that can potentially cause messy edges in the latest Cura.

 

[kazzaqov 0]

Thanks a lot, illuminarti!

I tried different retraction settings, but I actually see no difference.

But using Cura 13.04 helped. Now it has a normal travel route and I don't have any strings at all!

 

[gr5 2,005]

Retracting 9mm is too much as you will get air in the nozzle and then you will get other problems later. But this isn't your current problem.

In the lithograph picture, the edges look like that because the tool you used (and I used) has a bug/feature where it leaves you with very rough edges. When it prints those edges the UM makes a horrible sound as it weaves in and out of all those bumps.

I don't see the stringing issue you mentioned in the pictures but if you say you see no retraction then I believe you. The older cura (13.04) had a checkbox:

"retract on jumps only" which defaulted checked but which I liked to uncheck for certain prints. If you uncheck this then cura retracts on all moves. You could try that. There was a major change in Cura I think version 13.05 - completely rewritten slicing algorithm.

 

[gr5 2,005]

Oh. You printed upright. Now I see it. I understand now - it's during the infill stage - causing strings from island to island. The older Cura might fix that as I mentioned in previous post.

Another possible solution is to try "skin" infill only. Set the skin setting to something huge like 20mm. Not sure what will happen - look at the gcode view carefully before you decide to print.

 

[kazzaqov 0]

Guys, using Cura 13.04 fixed the stringing issue, but now weird holes appear. Need your advise again on what might have caused them.

layer height 0,2

wall thickness 0.4

bottom/top thickness 0,4

fill 100%

speed: 100mm/s

temp: 220

These settings worked fine with Cura 13.06

 

[illuminarti 18]

If you look at the gcode, are the holes visible there? In other words, are the holes areas that it simply isn't trying to print - or are they areas that there should be printing, but for some reason it doesn't happen?

Earlier (Skeinforge-based) versions of Cura had problems filling in small spaces sometimes. It might be that. Generally, setting wall thickness = nozzle width so that you just get a single perimeter seemed to make that a lot better, but it looks like you already did that.

 

[gr5 2,005]

That's a good theory and makes sense. Easily checked in gcode view. You might be able to fix by making the minimum thickness of your lithograph .8mm thick. Less than .8mm and Cura will have trouble. Or print it flat side down.

Or it could be underextrusion. Maybe tighten the extruder spring a few turns or slow down the printing speed to 50mm/sec to see if that makes a difference.

 

[kazzaqov 0]

If I understood you correctly, the gcode looks like this:

 

[illuminarti 18]

Oh, you're printing it vertically still... I thought the problem was the little tiny dot at the top of her head... but now it looks like the more fundamental problem is that a bunch of layers aren't printing at all. As George said, if you print it vertically, then the minimum thickness needs to be at least wide enough for the nozzle to pass along the back, and the front, of the STL without an overlap (the newer slicer is a bit less picky, but it causes other problems).

If it determines that it can't print both sides, it will simply print nothing.

I think another problem you may run into when printing vertically - especially with the old slicer - is that the shade variations are based on the thickness of the plastic. Since the old slicer is particularly poor at filling in narrow gaps, you will often get a gap between the walls that doesn't get filled. So while the object is physically thicker, there's not any extra plastic, just an air gap. So I think you will lose a lot of subtlety in the shading compared to printing it laid down, where you can vary the thickness of plastic in each place in tiny amounts, based on the layer thickness.

 

[kazzaqov 0]

I would print it horizontally, but it makes no sence. Because the picture on a lithophane becomes barely visible. Ill try 0.8 wall thickness and 0.6 bottom/top now

 

[gr5 2,005]

Here's something I printed myself laid down flat:

http://www.thingiverse.com/make:40709

 

[gr5 2,005]

If you print it sideways you must make the minimum thickness (in the lithopane software - not in cura) be .8mm. If you make it thinner than .8mm then Cura will mess up.

If you print the part flat you can make the minimum thickness one layer (for example .1mm).