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New S3, very strange first layer behaviour


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Posted · New S3, very strange first layer behaviour

Howdy folks,

 

I'm just starting to get a feel for a brand new Ultimaker S3, with only about 15 prints on the board. I had some very successful test prints (Calicats, Benchies) last week, so this morning I threw together a super-quick design in TinkerCAD (no other software on this computer!) just to test something a little more technical. And the printer is producing some very, very odd results, on the first layer, and I'm not sure why.

 

As you can see from the photos, there is a very strange banding/layering on certain areas of the print. Far worse than the other thread that was recently posted here: https://community.ultimaker.com/topic/31283-first-layer-being-printed-with-blemishes/ . They are not just cosmetic blemishes, because running fingers over it you can feel large divots and ridges. The first time I printed the design, the pattern was *almost exactly* the same. This second time was with a brand new print core, the material re-loaded, exact same result, so I don't think it is just a mechanical gremlin.

 

The material is Innofil/BASF PET (transparent). I am printing using the Cura Generic CPE profile, with minor tweaks to wall count, top/bottom thickness, retraction, and temperature, but nothing that should affect the initial layer like this. On-the-fly alteration of flow ±10% didn't seem to fix anything.

 

I have attached the STL, profile, gcode and images. The STL doesn't seem to have any weird mesh errors. The gcode seems like it has lots of acceleration changes at the start and and of line segements, but is otherwise really clean - nothing that seems like it should create this patterning. The only thing I can think of, is that the printer is getting its auto bed leveling completely wrong, and introducing up-and-downs as part of its levelling compensation. The z-axis screw doesn't seem to be twitching though, so maybe not.

 

Of course, maybe I'm an idiot, missing something simple, and am really bad at this whole 3D printing thing......?

 

Would love to hear some thoughts!

20200302_133804.jpg

20200302_133842.jpg

Spectacular Elzing.stl UMS3_Spectacular Elzing.gcode

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    Posted · New S3, very strange first layer behaviour

    note to others - It was when I clicked the 3rd time on the photo that I could really zoom in quite a bit.

     

    Like I think I said in the other post - it looks kind of normal.  It looks like maybe some oils got on the printer or maybe you used glue stick and the glue is thicker or thinner in those areas.

     

    It would be more interesting to see a photo of the bottom of the finished print but this looks pretty typical/normal to me for 3d printing.

     

     

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    Posted · New S3, very strange first layer behaviour
    1 minute ago, gr5 said:

    note to others - It was when I clicked the 4th time on the photo that I could really zoom in quite a bit.

     

    Like I think I said in the other post - it looks kind of normal.  It looks like maybe some oils got on the printer or maybe you used glue stick and the glue is thicker or thinner in those areas.

     

    It would be more interesting to see a photo of the bottom of the finished print but this looks pretty typical/normal to me for 3d printing.

     

     

     

    Thanks for the feedback.

     

    I'm genuinely surprised that this might be normal. Running fingers over it, there really is a *lot* of height variation, and I find it so odd that the effect is so localised, so well patterned, and so consistent between prints. After months cutting my teeth on an Ender 3, I've never seen anything like this, unless I had something very wrong - plate height completely, poorly calibrated flow, gross over-extrusion, that sort of thing.

     

    I do use glue stick, but I dissolve it in a spritz of DDH2O then smooth it down with Kimwipes to get a super-thin super-flat layer of residual glue. Glass plate was freshly cleaned with DDH2O then 99.9% isopropanol before both prints.

     

    Maybe I'm TOO GOOD at 3D printing, and don't know anything other than perfection? Yeah, I don't think this is the problem either......

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    Posted · New S3, very strange first layer behaviour

    Just as a point of comparison, I printed the same STL using my Ender 3, eSUN PLA+, a CURA profile matched as closely as possible, on a battered and bruised magnetic sheet bed. The results from the Ender are baby-bum-smooth in comparison. You can still feel the slight roughness on the edges of each line, but it has none of the extreme banding and up-and-down undulation perpendicular to the lines. 

     

    I am sure there is something fishy with the results from the S3.

    20200302_180440.jpg

    20200302_180632.jpg

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    Posted · New S3, very strange first layer behaviour

    I think the Ultimaker S line is leveling the bed very close, as a precaution, to make sure the bed adhesion is very good. Effectively deliberately over extruding on the first layer.

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    Posted · New S3, very strange first layer behaviour

    If you level a bit too close and if you have a powerful extruder you can get this pattern.  It's "good" to level "too close" as that way it squishes really well the first layer and the part is less likely to "warp" or lift off the bed.

     

    I think this is on purpose as it should be invisible once you put down the next layer.  Right?

     

    I mean we care how the part looks *after* the print is done, right?  Not while it is incomplete?  Or am I missing something?

     

    It could be that your other printer, because it has that really nice adhesion plate, doesn't need so much squishing so it levels by default with larger nozzle/bed separation.

     

    Those photos look to me like over extrusion - the nozzle is plowing through too much filament and making furrows.  But I'm not certain as bottom-layer-overextrusion looks similar to other issues.  Such as chipped glass, too much glue stick, underextrusion (I know, paradoxical, right?). 

     

    Overextrusion makes an interesting pattern on the bottom layer that is related to the slowdown/speed up at each corner, how much the filament slips in the extruder, and cyclic patterns where the previous line affects the next line put down.

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    Posted · New S3, very strange first layer behaviour

    Note that the most recent 3 printers from Ultimaker (UM3, S5, S3) have a disastrous issue if the part comes loose on the bed - if that happens when the part is wider than tall it can slide around the bed like a hockey puck.  The head keeps extruding onto one spot on the print and you get a growing molten blob of filament.  After a few minutes it goes up inside the print head and builds up inside the print head - a massive molten blob.  Eventually the pressure slowly pushes open the head and then all the extruding is inside the head.  It makes a massive mess.  it's called "head flood".

     

    Because of "head flood" I think Ultimaker takes "making parts stick really really well" more serious than other manufacturers and so maybe they are more aggressive with first layer squishing.  I really don't know.  Just a theory.

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    Posted · New S3, very strange first layer behaviour

    Just another update on this......

     

    I'm going through lots of different print settings, learning the new machine, trying to optimise speed vs print quality. One thing that was really confusing me was that Cura was setting the line width so narrow in the default profiles. For example, the Generic CPE profile I started with for AA 0.4 print core has line widths set at 0.35mm for outer walls and top/bottom, and 0.3mm for inner walls. Cura, and all other advice, has always set the line width as equal to or greater than the nozzle size.

     

    So I just started a print with all line widths set to 0.4, matching the nozzle size, and the first layer finish is VASTLY improved, both in terms of feel and visibility. It is definitely still smooshed down.

     

    Now, I'm sure this has been done to death at some point in the history of these good forums. But is there a good reason why the default Cura profiles for Ultimaker printers use such incredibly narrow line widths?

    20200305_174607.jpg

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    Posted (edited) · New S3, very strange first layer behaviour

    Because each line of printed filament is not prefectly rectangular but more a rectangular with round edges, the line width is reduced to really fill the gap between lines. The main issue is not the smaller line width but the auto leveling height of the first layer. The distance is too close for all materials. There is a z offset plugin in the cura marketplace. Try using this and increase the gap size. 

    The waves that you have at your first layer are typical for overextrusion with PETG. When I see them printing with PETG I always change the z offset.

     

    Edited by mkaj2019
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