First layer ripple

Any idea the reason behind this, I get his on all large prints right around the middle area of the bed.




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Yeah it’s always the first layer but I will try testing with lower temperature once the print is finished and see if that makes difference


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Same happens to me on my R2


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I’ve been messing with the manual z offset when the print starts and little by little I’m getting to the point no more ripple I think it’s more or less finding that perfect balance


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Mine still does it



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I use to print at 55 I lowered t to around 40-42 as for the first layer I haven’t had chance to print big para yet and I’m leaving for vacation tomorrow so I’ll be gone for a week but after I come back I will give mine a try and show the first layer


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This is a virgin R2, with the bed temp at 60, hotend 190 for PLA. I will drop the bed down to 50 and see... It’s a v2 bed.

 

Drop it to 42 you should be able to adhere well without any issues


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This is at 45 on two different R2.
One is more problematic than the other






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On my C2, I get this on all large parts on the first layer. The C2 has an unheated bed of course.

[fairly technical discussion]

Assuming that you've got the bed temperature dialed in, I'd suggest that this is an artifact caused by not managing static electricity. In a rotomolding factory I once worked in, the static electricity from the process would generate around 50K volts, enough to statically pull dirt from a distance of about ten feet—we had to work on solutions to electrically ground things eventually. Here, I would guess that the process of friction-loading the filament through the extruder assembly as well as heating the plastic is producing a fair amount of charge. The bed material doesn't conduct electricity so the result is that a negatively-charged bed and a negatively-charged filament repel each other, or so I would hypothesize. It manifests itself in the next run of plastic nicely adhering to its neighbor and yet wanting to repel from the bed, causing it to want to hover like that.

Eventually, though, the next cross layer in my experience somewhat "irons out" the problems in the first. And yet, that first layer is the bottom of the part and doesn't look great, to be honest.

One solution would be to print three layers of PVA onto the bed as a makeshift raft as an initial print job. Then change filament and print the second print job on top of all. In theory, the third layer of PVA would be a smooth surface to begin the job and would wash away to reveal a smooth part bottom for everything else. PVA isn't really cheap but you'd think that three layers wouldn't consume too much of the stuff.

Otherwise, I would guess that switching to a conductive print bed covering, combined with grounding it would negate the problems that I'm seeing (which happen to be your problem as well). In fact, positively charging the print bed would allow one to programmatically adjust the adhesion, in theory anyway.

 

I have the same problem and this is what I have found so far:

First I am printing on a 3/16" tempered glass surface that is very flat. I have run the bed temperature up and down and the hotend offset up and down. I do not use auto leveling but I manually level very accurately. I have played flow rates up and down.

The rippling is very dependent on material. Most of the brands I use do not ripple, some do. The ones that ripple have no adjustment that I have found to stop the rippling. It is an ongoing effort on my part and will update if I ever find something that works.

 

I have done testing and verified that the problem is caused by a bed that is not flat. I floated a 3/16" thick 12"x12" piece of hardened glass on my bed with high temp RTV glue in only 4 places so the drying glue would not distort the glass. I then clamped a piece of 3/32" thick piece of glass on top. I do not use auto leveling, I manually leveled the bed. I printed a 7" square and got no rippling. I then took a grain of sand and put it under the 3/32" glass and clamped to the 3/16" piece of glass. I could feel a very slight gap as I clamped the thin piece of glass. I reprinted the 7" square and got the rippling.
I had been chasing this problem for awhile and replaced all of the rods and gears in pursuit of a fix. Now I know what the problem is.