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Bad first and/or second layer  

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RickSeiden
(@rickseiden)
Eminent Member
Bad first and/or second layer

Hello,

I'm having trouble printing.  I am using a filament that is only a few months old, and within the past month printed something out just fine.  I'm also seeing the results I'll talk about with more than one filament.  I sliced my model with PrusaSlicer using the default Generic PLA settings. I've cleaned and lubricated the extruder gears, and I've done a cold pull.

It started with a first layer that would start off well, but then go to hell.  It looked like this:

So I reached out to Prusa support via live chat and they said that my first layer was too close.  I did a Live Z Adjust and went from -0.6+ to -0.489.  That seemed to do the trick, as the first layer now printed out fine (although some striping is visible below).  But then the second layer started.

There's some clicking coming from the printer.  I think it's the extruder, but I can't pin it down.  The second layer ends up looking bad, too:

The numbers you see are me playing with the live z adjust.  I started out at -0.498, like I said, and then just dialed in in, going all the way through -0.6, then back up to -0.4+.   It made a difference, but it didn't give me a good second layer.

I've printed a ton of stuf with this printer as a MK3 and an MK3S.  The only difference is that my old flex steel bed was in bad shape, so I replaced it with a brand new one from Prusa (not a 3rd party).

Of course, the first layer was nice and slow, and the second layer sped things up, so maybe it's speed related now?  I just don't know.

Any help you can give me would be greatly appreciated!

 

Thanks

Rick

Posted : 26/10/2019 3:37 pm
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(@)
Illustrious Member
RE: Bad first and/or second layer

Your image looks like you might be a bit low (extrusions too thin).  But it is hard to tell for sure.  Try slicing and printing one of these circles to dial in you Live-Z value.

The ideal is a 0.2 mm thick sheet of plastic that peels off with a stickiness of masking tape, with no strings: it should be a solid sheet all threads welded together as in the photo.  

Cal Circles

 

Posted : 26/10/2019 3:53 pm
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(@)
Illustrious Member
RE: Bad first and/or second layer

Oh -- and FYI - Live-Z only affects the first layer and changing the value after Layer 1 is down is a bad idea.  Layers 2 and higher are set by the slice and are not adjustable after the fact.

Get layer 1 correct, and treat subsequent layer issues separate.   E.g., extruder clicking implies a nozzle jam or under tension on the Bondtech idler gear.  And the second layer requires extruding at quite a bit high flow than layer 1, and that's why problems show up there.

The image of layer 2 looks like under extrusion. This can be from several causes.  The most common is a nozzle jam, and a cold pull usually resolves those. Another common issue is the tension screw on the extruder is too loose. The MK3S requires the screw to be tighter than the two MK3 screws (twice the force is needed).  On new kit printers, a third less common issue is the idler gear axle has slipped off one of the door tabs so the gear is flopping around. After those three are checked off, then temperature and extrusion ratios need to be checked.

 

 

Posted : 26/10/2019 4:57 pm
RickSeiden
(@rickseiden)
Eminent Member
Topic starter answered:
RE: Bad first and/or second layer

@tim-m30

Another common issue is the tension screw on the extruder is too loose.

That was it.  Stupid simple thing I should have tried on my own.

Thanks!

 

 

Posted : 26/10/2019 8:08 pm
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