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First layer ripple

Discussion in 'Troubleshooting' started by Shrey, Feb 4, 2018.

  1. Shrey

    Shrey Active Member

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

    IMG_3574.JPG IMG_3575.JPG


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  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    I'd start by checking the temperature, but if not too hot it is perhaps a bit too high in that area. I assume this is early layers only?
     
  3. Shrey

    Shrey Active Member

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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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    #3 Shrey, Feb 4, 2018
    Last edited: Feb 4, 2018
  4. supercazzola

    supercazzola Active Member

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    Same happens to me on my R2


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  5. Shrey

    Shrey Active Member

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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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  6. supercazzola

    supercazzola Active Member

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    [​IMG]

    Mine still does it



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  7. WheresWaldo

    WheresWaldo Volunteer ( ͠° ͟ʖ ͡°)
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    Crappy auto-leveling (tramming really) and too few probe points. I have suggested on multiple occasions for Robo to at the very least switch to BILINEAR auto-level. You are never going to see a completely flat first layer. Even their newest test firmware has the same sucky leveling. Rant over.

    I would try the same print with a bed temperature about 10°C cooler than whatever you have it set too. It kind of looks like to me the bed is too hot.
     
  8. Shrey

    Shrey Active Member

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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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  9. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Yep. Too hot.
     
  10. supercazzola

    supercazzola Active Member

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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.
     
  11. Shrey

    Shrey Active Member

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


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  12. supercazzola

    supercazzola Active Member

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

    [​IMG]

    [​IMG]


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  13. WheresWaldo

    WheresWaldo Volunteer ( ͠° ͟ʖ ͡°)
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    The second one looks much better than the first and I am pretty sure it is caused by a warped bed, since nearly every consumer grade 3D printer that uses an aluminum bed is using bed cut from sheets there is not a single one out their that isn't experiencing some sort of warp, and heating the bed will induce it. This goes back to the leveling method used in Robo firmware. It is inadequate to compensate for any warp, no matter how small in the bed. One possible way to overcome this, decrease the extrusion overlap at the same time increasing the extrusion multiplier for layer one. That will force more plastic extrude directly under the nozzle and still provide a smooth layer without the little ridges resulting from too much overlap. Another way is to just ignore the minor imperfection.
     
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  14. OutsourcedGuru

    OutsourcedGuru Active Member

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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.
     
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  15. WheresWaldo

    WheresWaldo Volunteer ( ͠° ͟ʖ ͡°)
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    Rafts are dumb and wholly unnecessary when printing on a PEI or BuildTak bed. Rafts were used as a way to gain adequate bed adhesion, not a method to insure a perfectly flat build surface. Don't waste filament on using a RAFT.
     
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  16. Lance Weston

    Lance Weston Active Member

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    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.
     
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  17. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    I agree -- there is exactly one use-case where I will consider a raft and that is if the model is printed up-right and it is very tall and narrow. Nothing else needs it (and the one I do use it on may not if you can reorient it).
     
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  18. tkoco

    tkoco Administrator
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