Hi there, I have an issue I can't get rid of.

(Paul Arnold) #1

Hi there,

I have an issue I can’t get rid of.
When the printhead travels from the inner perimeters to the outer perimeter, there is a blob / zit generated because the next layer pushes the excess filament over the edge of the object.
As it’s happening when changing perimeters, I can exclude any retraction issue.
Extruder is calibrated, extrusion multiplier and width is tuned.

Any ideas?

(Kevon Daines) #2

Though it may not coincide with your issue. In the CNC machining world, when this particular error occurs. It is usually due to a program glitch or mechanical error. Suggestion would be to check your axis rods or printing program. If not the case then perhaps the extruder should be the problem.

(Ulrich Baer) #3

is that “random” for z- seam alignment? What slicer do you use? - and did this happens if you use only one perimeter/wall?

(Neil Darlow) #4

Could be ooze occurring when the nozzle decelerates. You could try reducing the extrusion temperature a little.

(George Novtekov) #5

I have absolutely same problem. I manage to improve it alot with presure advance. But it is still there just not as visible as yours. I use E3D v6 extruder and Duet Wifi for control board. My slicer is S3D. My printer use ball screw on all axis and thus for I use low jerk settings 300mm/min. And also low acceleration 450mm/s2. Acceleration and jerk in Marlin/reprap i poorly implemented for rigid non elastic assemblies. Can you share more information about your build so I can mach similarities between your and mine settings. What I think maybe the problem with my build is the slow direction change that allows blob to be created.

(Wes Cherry) #6

Kisslicer has some features which greatly eliminate these blobs. https://m.youtube.com/watch?v=C-AtA_DGiBk&feature=youtu.be

(MidnightVisions) #7

There was an old trick in slicer that you could change you outside fineness resolution level to 99999, which almost eliminated that, but I have not seen that issue for a long time.

(Ulrich Baer) #8

there is also coasting to release pressure towards layer end and a hide seam function which overlap nozzle path which can cause this. Also you could print outer perimeter first which would put those defects inwards

(Mano Biletsky (Open MAKER)) #9

You might be able to reduce this issue by printing at a higher speed. Wich leaves the nozzle with less time to ooze when it reaches the end of a line.

(Kevin Danger Powers) #10

@Paul_Arnold I fixed this issue by turning on coasting and then tweaking extra prime amount to make up for the loss of pressure after coasting. Seems to work pretty well.

(Whosawhatsis) #11

Are you running the inner perimeter faster than the outer one? If so, the nozzle will have excess pressure when it makes the transition, and will push out a little too much plastic (especially if you have a bowden extruder). Pressure advance can help, but I prefer to just run things at a constant speed.

(Kevin Danger Powers) #12

@Whosa_whatsis I never thought of that one. I’ll have to look into it just for a little extra precision.

(Mano Biletsky (Open MAKER)) #13

@Whosa_whatsis where do you change that variable speed setting? I’m using simplify3d.

(Whosawhatsis) #14

It’s under the speeds tab. Set the ones that say “underspeed” to 100% to avoid speed changes (and thus pressure changes).

(René Schmidts) #15

Hi guys, I do have more a question than a solution to this issue, I guess. Would it be helpfull in this case to print the outer perimeter first ?

(Arnulf Mittelstädt) #16

I have the same problem.
Tried everything. But still not very happy with the outcome.

  • outer perimeters first
  • pressure advance at 0.1
  • retract acceleration change in marlin

It’s getting better, but still not perfect. Printing on a Dolly i3 with a v6 chinese clone and Slic3r 1.3.

(ThantiK) #17

@Wes_Cherry holy crap, KISSlicer still exists?!

(Mark Wheadon) #18

Do you have some Z hop during retraction? If so, try setting that to zero – sometimes even a small amount of Z hop slows the retraction process down enough to cause problems.