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First layer issue

Posted by DaSt 
First layer issue
July 05, 2018 01:12PM
Hi,

I'm using a modified ANET A8 with RAMPS 1.4, Marlin 1.1.8 and a BLTouch sensor.

Problem is the first layer is never really clean (seen from both up and down) even though the rest of the print is quite good. I mainly print at 0.16 and .08 but the issue is consistent no matter the layer height.
200°/50° temperatures, using S3D.

Z offset has been setup several times (always finding the same offset) with cold nozzle, the sheet of paper moves quite freely and the nozzle does bend it when moving. What Ithink is a good way to ensure the offset is good.

For my first layer i tried all the range between 0.16 and 0.64 mm :
0.16 to 0.32 : first layer is totally transparent
0.40 to 0.48 : between transparent and overextruded
0.56 to 0.64 : overextruded
I tried setting first layer width to 50 to 150%, no change (weird??). Speed is 50% from 40mm/s

The overextruded first layer make the following ones having the nozzle "sliding" on the previous layer rather that being 0.16mm above it.

I really think i'm missing a simple key element here, but I don't see which one ?

Attached is a picture of what an overextruded first layer looks like from under. Unfortunately i don't have the possibilité for now to post a picture from above, I'll try later today.

Thanks !

Edited 2 time(s). Last edit at 07/06/2018 03:18AM by DaSt.
Attachments:
open | download - IMG_20180705_190643.jpg (751.7 KB)
Re: First layer issue -
July 06, 2018 12:19AM
Did you calibrate the e-steps? You might be lucky and the extruder current is set low enough to skip steps when it actually would overextrude. It shows only when 1st. layer is set very high.
Is your filament dry? Does it look, like it foams up after extruded in free air? Is the extruded diameter bigger than nozzle size?

Edited 1 time(s). Last edit at 07/06/2018 12:20AM by o_lampe.
Re: First layer issue -
July 06, 2018 03:16AM
Hi there

Quote
o_lampe
Did you calibrate the e-steps? You might be lucky and the extruder current is set low enough to skip steps when it actually would overextrude. It shows only when 1st. layer is set very high.
I tried before posting yesterday. Following the process I noticed that extruding 10mm does indeed use up 10mm of filament but extruding 100mm only uses like 40mm of filament o.0. I ended up calculating a new step/mm at 217 instead of 100. When using that new value it clearly began to overextrude on every single layer. I went back to 100 and printed my part. I used those settings : layer 0.16, first layer 0.48, first layer width 50%, 40mm/s, 20mm/s first layer. The first layer was perfect for the outline but the infill was overextruded again. The first few layer slided over the first layer as expected. The print finally came out real good looking, even the bottom has a real mirror finish. Form the outside you can't say i had thoses issues with the first layer.


Quote
o_lampe
Is your filament dry?
I believe it is yes

Quote
o_lampe
Does it look, like it foams up after extruded in free air?
Nope

Quote
o_lampe
Is the extruded diameter bigger than nozzle size?
Nope

Thanks smiling smiley
Re: First layer issue -
July 12, 2018 09:05AM
Hi there,

Reading through forum I saw that S3D increases the flow whenever the first layer height is above 200%. When I use 300 to 600% i guess it may be normal to overextrude, then.

What if I try to reduce the first layer height in S3D while compensating by increasing the distance between nozzle and bed via modifying the Z offset ?

Thx
Re: First layer issue
July 13, 2018 06:21PM
Increasing the Z offset might help. If your nozzle is too close to the bed, one row of filament might pull on the previous row lifting it up and causing artifacts like you are seeing.
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