Gathering ideas how to solve wavy walls..

I’m fighting wavy walls after corners, see this picture for a worst case szenario. I printed dozens of this samples with different settings in the last days:

I know, first thing everyone would think about is corner ringing. This would be due to the “shock” that’s created during the direction change and the axis is swinging after this. But that’s not the case. If anyone has an idea, especialy if he uses a simmilar setup and has no wavy walls, I would be very glad if you would read the following and comment!

I’m printing with PLA at 205° nozzle temperature, Openrail Mod on X and Y axis (no play!).
I did following tests to gather some informations:

  1. Print at 0.2mm layer height at different perimeter speeds (20-40-60-80): nearly 0 wavy walls at 20mm/s, increasing with speed. Maybe a little bit better at 80mm/s than 60mm/s. So 60mm/s is worst.
  2. Reorientate the part along the other axis: No change.
  3. Print at different accelerations (500, 800 and 1100mm/s²): Aprox. linear increase of the waves, as they also did in 1)
  4. Reducing current to the x and y steppers: No significant change.
  5. Add a flywheel with different mass to the Y stepper, printing the part in X and Y orientation: No changes between 0g to 50g.
  6. Printing at same speeds as in 1) but at 0.1mm layer height: Much better!
  7. Disable my advance feature (which leads to higher extrusion speeds during acceleration): Better.
  8. Braking the belt idlers during printing with my fingers: No change.
  9. Apply pressure (weight) to the print bed or the print head at different angles during the print: No change.

As a last test, I printed a single perimeter wall to see if the waves are due to swinging print head 90° to the print head or if the waves are changes in line width in reality:

As you can see, as suspected, the width is changing, creating the waves. So it should be due to inconsistent extruder flow or inconsistent x/y axis stepper speed.

My conclusion: I don’t believe it’s some kind of resonance, vibration or speed inconsitences of the x or y stepper because nothing from my tries that should change the vibration or speed behavior changed anything to the print. But there are significant changes in my experiments when the flow rate was changed as in 1, 6 and 7.
That’s why I think it might be some kind of flow rate pulses due to friction in the hot end, likely in the area of the heat brake, melt chamber and nozzle. The bad thing: If that’s right, the only way to prove this would be to buy another hot and, maybe an e3d one…

What’s your opinion, do you find a mistake in my tries or conclusion? Any other ideas what could be tested? Realy, any hint is much appreciated!

It looks like you may be running into the PLA fan cool solidification heat pulse issue. You may want to see about finding or casting a high temper silicon jacket for the Hotend of the Hexagon, which will mitigate that issue and allow for full fan flow with PLA.

Or you can switch to a different extruder.

PLA fan cool solidification heat pulse issue. Sounds very :sunglasses:
So you say it might be due to the fan. I will print another sample with fan off and see what’s happening :slight_smile: But I guess it will not change something, as I see the ripples also on big parts where the fan will only run at 20%. We will see…

No change. The surface is a little bit more shiny, but waves are identical…

How consistent is the diameter of your filament?

My eSun is very precise. All my rols are 2.89mm except two colors with 2.9 and 2.93mm.
I think it’s also very unlikely that the diameter of the filament varies always in the moment of accel. after a corner, never in long straight parts.