Sudden ripples on my first layer

Bambu Lab H2 Series
1

So, out of nowhere. I went ahead and did some maintenance (and am currently down to printing only on the left side) but now my left side printing is looking like this on the first layer.

As you can see, we’ve got the ripples there. If it tells anyone anything useful, I’m doing monotonic, and if I rotate the print 45 degrees my ripples now run horizontally along the print. The location on the9

I’ve recalibrated multiple times, I’ve tried adjusting my Z-offset, and honestly, at that point BL support seems to have no more suggestions (I’ve removed the 3 screws at the front of the bed on the bottom) and…that’s about it.

If I change to, say, Archimedian Chords, and the effect becomes less noticeable, but if I pause after the first layer I see a very rough surface.

This is on a model I’ve literally printed over a thousand copies of, the filament is plenty dry. Happens with multiple filaments.

So….I’m looking for help from anyone who can make a suggestion.

(what you’re seeing below is the bottom)

IMG_20260425_152804655_AE
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2

Usually caused by infill telegraphing into the top and bottom layers. Try increasing by one.

3

Just a couple of suggestions:

You might want to change the nozzle. Try setting your first layer flow rate to 0.9 and see if that helps.

4

I’ve changed the nozzle to a brand new one that arrived the day before as that had been on my list of suspects.

Lacking ideas, I’ve just downgraded firmware from the latest to one step back as that newer one came out around the time of my problem, but I was dealing with hardware issue and figured they were the cause. Still nothing better.

I’ve just done a total reset and calibration and this is what I’m seeing (top is straight up print, bottom is removing to show the bottom, which I realize is kind of pointless on a 1 layer print, but wanted to show it):

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Top and bottom of a .2mm print.

I’ll give it a shot on the .9 first layer flow and updated.

5

OK, so, I changed the initial layer to .9, and here’s what I got. I cancelled pretty early as you can see.

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The printing starts at the bottom right corner, and as you can see, it actually looks about right at the start before getting progressively worse.

As a test I’m now trying to work with my Z-offset, figuring maybe the nozzle is pushing some filament ahead of it. However, the interesting thing is if I go and modify this second value:

{if curr_bed_type=="Textured PEI Plate"}
    {if nozzle_diameter[initial_no_support_extruder] == 0.2}
        G29.1 Z{+0.01} ; for Textured PEI Plate
    {else}
        G29.1 Z{-0.02} ; for Textured PEI Plate

and then save it as a new preset, my slicer is changing the plate type to engineering plate (from textured PEI) so I’m genuinely not entirely sure if when I tell it to raise the Z, it’s actually doing it or not.I do swap it back to textured PEI, but I’m not sure I can truly tell.

6

So, after some poking around, what I’ve arrived at is a very good smooth surface at an initial layer ratio of 0.9 and a Z for textured PEI at +0.06.

That seems like two fairly extreme numbers in those values. Are they extreme? Any long term headaches that’ll be coming from using these values if there’s no other way around them?

7

default Z offsets are good. your extrusion has issues I would start to inspect nozzle temperature readings during any print job, to see if they are constant or not

8

Sure, but I did have to go so far as disassembling most of the hot end recently. So I’m figuring that maybe things got shifted a bit.

9

Too much heat maybe. Maybe a tiny bit too much flow. Try lowering build plate temp by 15º and extrusion temp by 10º and see if that improves things.

10

Well, I’m running at a ratio of .9 and a z of 0.06 which seems kind of nuts to me.

11

Could just be a dirty print bed. Have you tried cleaning it with dish detergent?

12

If you mean your layer height is 0.06mm, that’s probably your first problem. Compounded by a flow of 0.90. Less plastic comes out of the nozzle than it necessary to “keep up” with the nozzle’s movement, so the plastic being extruded drags along the previously extruded adjacent plastic as it passes by. And the really thin first layer doesn’t have enough strength to resist that pulling.

Go back to defaults and see how that works, and assuming the problem is addressed (or mostly so), then make your layer and flow changes one at a time to see what change causes the problem to come back.

13

It’s not the plate, it’s something with the extrusion. If I change values to a Z-offset of +0.06 and reduce initial layer ratio to 0.9, it prints almost perfectly.

14

No, not layer height, the layer height is a default .2mm. It is Z-offset.

If I run default, I get the garbage you see above. If I run with the initial layer ratio of 0.9, it prints basically smooth as glass.

I thought I’d mentioned in the first post, but obviously did not, that I had to do some big disassembly on the print head. I am pretty certain I’ve screwed something up in there, but I have no idea how to figure out what.

15

Ah. OK. Then at a guess, the bed probing for Z homing is not working right.

Reduce the flow, it gets better because your layer height is lower than you think it is, and if you don’t reduce flow, the nozzle is squirting out too much plastic for the spacing between the nozzle and build plate, and you end up with the crummy results you get.

I’d check to make sure all the screws are tight in the print head. Especially the extruder mounting screws.

16

Yeah, once my filament guide replacements are in (There’s a small divot keeping the right side from feeding correctly) I’ll take the entire thing apart again and…I don’t know, be more careful, I guess? Maybe I’ll get lucky.