Perimeters - blobs and waves

K8200 3D Printer K8200 - Issues while printing
1

Hi,

I know the first question was raised before (at least I think it was, the description seemed very similar), but that thread switched over to the z-axis wobble without a solution for the initial problem.

My printer produces small blobs on the external perimeters (see first image). They appear always at the point where the extruder starts to print the perimeter. The blobs are most noticable when printing circular objects, and are a bit more pronounced on holes (i.e. on concave surfaces) than on outer perimeters (convex surfaces).
I already tried the following changes in Slic3r’s settings:

  • ‘External perimeters first’: no visible effect;
  • retraction, disabled ‘only retract when crossing perimeters’: no effect, since there is no retraction before the extruder moves to the point where the blob forms. Just in case it matters anyhow: ‘extra length on restart’ is set to zero and ‘wipe before retract’ had no effect, either.
  • ‘Randomize starting points’ doesn’t reduce the blobs, just spreads them out over the whole surface (and produces additional travel moves).
  • Acceleration is set, but different values (see description below) don’t change the blobs either.

What else could I try?
I was thinking about DEFAULT_XYJERK, maybe increase it in order to get a faster transition between the perimeters? Or decrease for smoother movement? Not quite sure whether that’s the way to go at all. Setting is the default, 20 mm/s, at the moment.

Another issue are waves visible on the external perimeters in certain directions (see second image), most likely due to vibrations in the carriage. They are more pronounced when the object has a sharp edge (>=90°). The location of the waves is always at the “beginning” of the wall, i.e. at the edge where the extruder starts the corresponding path.
I set different accelerations for the perimeters in the print shown in the picture, decreasing from 200 mm/s² at the botton to 50 mm/s² at the top, three layers each. As you can see, the waves are reduced at low accelerations, but they are (although not well visible in the photo) never completely gone. In addition, I would like to set the acceleration higher than 50 if possible, so if you have a suggestion …

Could perhaps XYJERK affect this as well?

Cheers,
kuraasu

2

Did you test with other colors? I’ve noticed I don’t get the same result with different colors.
And each color seems to have a different ideal temperature setting for the extruder.
And I get my worst prints with low speeds.

3

I had the same problem with the waves at the perimeters.
In the next days i will test to change the stepper power at the stepper drivers.

4

Hi,

@raby: yes, the issue is present with other materials, too. Tested so far: Velleman’s white PLA, yellow PLA, blue PLA, and black ABS, plus Ultimaker’s black FlexPLA.

@eytec: thought about that, too, but saw no reason to do so for the time being, since I don’t have locked bearings, chatter marks, skew, or lost steps (any more). Let me know if you see a difference, please!

Cheers,
kuraasu

5

hi,

I have the same problem. Waves appear at the beginning of the X movement. They are most visible at a 90 degrees corner when movement goes from Y to X and phase out as X moves further. The effect is visible in all layers.

I first thought is was because of not enough tension on the Y belt. I installed a belt tensioner but the problem remained.

The waves appear on both sides of a calibration cube but are not identical.

Did anyone manage to solve this?

koke

6

Bonjour j’ai le même problème , avez vous trouver la solution ?