First layer issue

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.

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.

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

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

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.

Hi there,

I know it has been quite a while but after this issue I quit printing for quite some time and had some other issue of my own.


I plugged the printer back recently and began with that very same issue. In fact when i could have a correct first layer I noticed many layers in any print would be very weak. I tried recalibrating the e-steps but it just looked like nothing there would help extruding the correct amount of filament.

My issue was indeed mecanical. The filament was not firmly pushed against the extruder teeth wheel. I added some tension to the spring and extrusion just went back to normal, without the need of recalibrating e-steps.

In case anyone stumbles upon such issue in the future.

Thanks for posting the solution.
Glad you got it sorted.