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I am printing out models with holes, the printer makes circular patterns for each hole(which makes sense) but then it also has a string that attaches between each hole. This is unsightly and results in a non-uniform surface finish at the top/bottom of prints.

I am wondering if the string is supposed to be there? I am using CURA on the coarse setting, my machine is direct drive with a 3mm retraction setting. I tried increasing retraction to 6mm but the same thing happened.

When looking at the g-code with a layer viewer it shows the strings but I am not sure if it is only representing tool path or not.

edit:

I just tried printing a retraction tower test and I haven't had any stringing, does this mean it's an issue with CURA?

edit v2:

I looked at the layer path on CURA and these strings are not shown. I am at a loss as to what is going on since the retraction test showed it worked fine but every print with holes has the same problem. enter image description here

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  • $\begingroup$ a picture is needed to explain this $\endgroup$
    – Trish
    Commented Jan 10, 2021 at 1:11
  • $\begingroup$ I will try another print and post a picture, but basically a line is printed along the tool path between holes even though the line doesn't appear on CURA layer viewer. I assumed it was caused by not enough retraction distance but I use a tower test print and no stringing happened. $\endgroup$
    – FourierFlux
    Commented Jan 10, 2021 at 1:15
  • $\begingroup$ I added a photo $\endgroup$
    – FourierFlux
    Commented Jan 10, 2021 at 1:43
  • $\begingroup$ This is combing, one of Cura's many horribly wrong defaults. Change it to "not in skin" or "off" to fix it. $\endgroup$
    – R.. GitHub STOP HELPING ICE
    Commented Jan 10, 2021 at 1:46
  • $\begingroup$ also, not leveled with too thick a gap $\endgroup$
    – Trish
    Commented Jan 10, 2021 at 2:02

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Consider that the string you are seeing is the nozzle wiping across the surface, especially if you are not getting stringing via your test part. As you suggest, it's not unlikely that the layer viewer is showing movement and not extrusion.

Check your z-hop settings as well as the other references in the linked page. Z-hop will drop the bed by the set amount when traveling with retraction.

z-hop graphic

The other useful reference is combing, which limits the travel of the nozzle to remain within the boundaries of the print and also removes the requirement of retraction. It may leave nozzle traces, although that reference is not in the linked page.

combing graphic image

All images attributed to linked page.

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  • $\begingroup$ thanks, I will try changing these and see what happens. $\endgroup$
    – FourierFlux
    Commented Jan 10, 2021 at 1:45
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    $\begingroup$ Your newly added photo tosses my suggestion to the wind. It's obvious that you're getting stringing. Have you checked the nozzle for "hangers-on?" Blobs of filament that wipe across the build plate that aren't directly coming from the nozzle? $\endgroup$
    – fred_dot_u
    Commented Jan 10, 2021 at 1:57
  • $\begingroup$ Hmm, I thought I fixed it by changing the z hop and combining now I am getting weirder results involving blobs $\endgroup$
    – FourierFlux
    Commented Jan 10, 2021 at 2:02
  • $\begingroup$ It's combing. Turn it off. $\endgroup$
    – R.. GitHub STOP HELPING ICE
    Commented Jan 10, 2021 at 2:53
  • $\begingroup$ Thanks, I think I fixed it. It's a number of issues combined. Z hop, combing and I increased my bed temp to 85C for first layer to prevent bed slipping. The circles are small I think following layers resulted in some of them getting lose. I could print a raft, not sure. $\endgroup$
    – FourierFlux
    Commented Jan 10, 2021 at 3:43

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