Strange Wave Patterns

[pyronaught]

Anyone ever see this or know the cause? I've tried different Z heights and different print speeds and nothing effects it. It's not a z stop issue because the same waves occur on every layer and not just the first one, and they always run perpendicular to the direction of the layer lines. I've seen a similar thing when the z height is too low, but it only occurs on the first layer and is more random than this. If I run the same .g file on another printer the problem doesn't happen, so that rules out any kind of software settings. It has to be something with the print head-- either clogged nozzle or something stuck in the gears, except I would expect a more random flaw from that. Also the filament extrudes straight down from the nozzle without any kind of hooking to the side. You can actually see the filament jumping up and down as it scans across the plate though. I can't find anything like this in the pictorial printing flaw websites. It's not a ringing issue, it's happening on a big flat part. I'm just totally baffled by this!

[Jules]

Yep! Frequently.......

Sometimes it was caused when the adhesive was too light in a couple of spots on the plate, or there was an oily spot on the plate, and the print was not sticking....(once those waves start, they just keep going, and they do carry forward into subsequent layers, and across the flat part of the print).

Other times it was because the the gap was not set correctly (generally it was off by only 0.02-0.04 mm (too large) and a slight adjustment fixed it.)

But if I had to guess....that's white filament.....and those are always fiddly, flow-wise. The color might also have something to do with it - try upping the temp by about 5 degrees, to get a more liquid flow.

[pyronaught]

Temp is already at 265, so that's not it. I've done multiple attempts, wiping the plate with a new layer of ABS slurry each time, and the wave pattern is always the same. The waves appear in the same place at the same frequency every time. When the wave pattern goes to the next layer, it is not just the wave from the previous layer telegraphing through, but rather an entirely new set of waves that are perpendicular to the new direction the layer lines are running. So the next set of waves can be crossing the previous set at a 90 degree angle. It seems mechanically related to the direction of travel, but I can't imagine what the phenomenon is that causes it. The extruder gear is clear and the nozzle is not jammed. The waves do not appear on short travels of 2" or less, they appear to require long runs. That's why you don't see any waves in the areas behind the holes on the corners.

[Raddiver]

I'm just spit-balling here as I'm new to all of this, but maybe change print speed?
Resonance issue possibly?
Is the printer on a steady surface?

[pyronaught]

I'm just spit-balling here as I'm new to all of this, but maybe change print speed?
Resonance issue possibly?
Is the printer on a steady surface?

The waves do diminish as speed is decreased, but even at 4000 I still get them and normally I print this part at 6000 or even 8000. I just printed this same part on the same printer with the same filament two days ago and didn't have this problem.

[jsc]

My experience has been that happens when you are over extruding. Print a thin wall calibration cube to make sure your extrusion multiplier is correct, or if you're more the freewheeling type, dial down the extrusion multiplier using S3D during a print until the waves go away.

[jimc]

your printing your first layer too close to the bed. the gap is too tight. to test, print the same thing again and while your nozzle is off to the side doing the purge give the knob 1 click counterclockwise to drop the bed a hair.

[pyronaught]

your printing your first layer too close to the bed. the gap is too tight. to test, print the same thing again and while your nozzle is off to the side doing the purge give the knob 1 click counterclockwise to drop the bed a hair.

That's an interesting trick with the knob, I never thought of modifying the z-stop during a print like that.

Usually when I print too close to the bed I get a different defect I like to call "astro turf". It's a much finer wave pattern and can even have little bits of plastic flick up like blades of grass. This print here is not close though, there is not even any flattening out of the filament as it goes on the plate.

[Jules]

.........there is not even any flattening out of the filament as it goes on the plate.

It needs to flatten just a little, or you might have trouble with adhesion. Ed's got a great diagram that shows the ideal....(and of course I can't find it now..... .)

Try closing the gap by 0.04 mm. It's not much, but it might make a difference in the wavies.

[ednisley]

diagram that shows the ideal....

viewtopic.php?f=3&t=3047&p=19578#p19578

The key part is realizing why ±0.05 mm makes the difference between a good first layer and crappy adhesion: getting the initial gap set properly is that critical.