cura printing bottom and top layers thicker than walls longitudinally

[zqk 0]

Hello, this is an issue I've been battling for some time. Cura seems to be printing the bottom and top layers way thicker than the walls, causing the nozzle to scratch on the print and lose steps. The infill and walls are at the perfect thickness, so I've had to resort to printing the least top and bottom layers possible, which introduces sagging artifacts on the top layer because the infill isn't 100%. I can physically confirm it isn't the printer (ender 3), I can see the printer extruding more on the top and bottom layers. 

[burtoogle 515]

Hi @zqk, please save the project file (File -> Save) and then attach the .3mf file to this thread so we can see your model and settings. Thanks.

[zqk 0]

2 minutes ago, burtoogle said:

Hi @zqk, please save the project file (File -> Save) and then attach the .3mf file to this thread so we can see your model and settings. Thanks.

CE3_flexi_75_funnel.3mfhere you go mate

[burtoogle 515]

Sorry, that's not a project file, please do File->Save, not export. Thanks.

[zqk 0]

4 minutes ago, burtoogle said:

Sorry, that's not a project file, please do File->Save, not export. Thanks.

CE3_flexi_75_funnel.3mffixed 

[burtoogle 515]

Thanks for the project file. One possibility is that because the top/bottom speed is lower than the wall speed, it will tend to overextrude compared to the walls. That is because unless your printer has non-linear extrusion rate compensation (most don't I believe) then as the extrusion rate increases, you get more and more under-extrusion. So, you could try an experiment and use the same print speed for walls, infill and top-bottom layers and see if you get more consistent thickness. Hope this helps!

[zqk 0]

19 hours ago, burtoogle said:

Thanks for the project file. One possibility is that because the top/bottom speed is lower than the wall speed, it will tend to overextrude compared to the walls. That is because unless your printer has non-linear extrusion rate compensation (most don't I believe) then as the extrusion rate increases, you get more and more under-extrusion. So, you could try an experiment and use the same print speed for walls, infill and top-bottom layers and see if you get more consistent thickness. Hope this helps!

 

Thank you for your reply burtoogle, This didn't work unfortunately. I printed 2 calibration cubes, and they had exactly the  same artifacts. 

 

 

Edited May 15, 2020 by zqk
readability

[zqk 0]

I've researched the issue you've brought upon me, and most people note a 2% change from 40mm/s to 60mm/s, it gets exponential at higher speeds. A 2% change wouldn't cause this, so I'll do some other stuff I haven't tried, and log it here if it works for the users here. 

[3llled 0]

hi! i am having the same issue...

 

my top/bottom lines are printing at a thicker height (taller) than the walls.

 

i noticed this when i switched to a .6 nozzle, and tried to print at higher layers ie .4

 

i have tried to reduce this by:

 

-matching all speeds

-reducing top/bottom flow

  -this worked a little, but resulted in air gaps when i went below 60%

-increased wall flow, in order not to decrease top/bottom flow less than 75%

  -i went to 140% but the wall lines were just too bloated

-temperature higher/lower

 

what seemed to work the best was reducing the layer heights down to .2

   i am still able to print at .6 wide to save a little time

 

seems as if the top/bottom is still thicker and does scratch, but is not as bad as when the initial layer is .4

 

you can set the infill layer thickness independently, but can you set the top/bottom height and/or perimeter wall height independent?

 

i will try to set up all layers as infill and adjust the height to see if it has any effect...

 

would be great to have some other options to try to match all line heights, i would like to try .8 nozzles next!