Print Gaps between inner and outer wall lines- What settings affect this

[athollis89 0]

I am having gaps appear on my prints on layers 2 and 3 between the inner and outer walls (I believe). I am printing TPU 95A at 225 with a bed temp of 60 with a print speed of 35mm/sec. I have calibrated flow. I cannot seem to find which settings would affect this. I have messed with line width, flow, unchecked flow compensation. Nothing really seems to affect this gap. Any advice would be helpful. 

 

Note: It happens on multiple printers, I believe it is a setting in Cura I am missing.

 

I have a DD dual gear, extruder that I recently upgraded to (on a few printers). I have checked for partial clogs, changed nozzles, calibrated x, y, z steps and E-steps. Also, I am using Cura 4.13.1. 

 

 

[gr5 2,334]

That's classic underextrusion.  If I had to guess one setting it would be the fan settings.  The fan comes on starting layer 2.  Some printers have the fans pointing too much at the nozzle and the PID controller takes a few layers to catch up.  also the air tends to bounce off the print bed and as you get higher from the print bed it's less of a problem.

 

I think you can get a "sock" for your nozzle.  A silicone cover.  These are cheap.  Less than $1 or 1 euro each.  Or you might have poorly designed fan shrouds.

 

I'd try by experimenting with fan speeds manually.  when it starts the second layer, play with a fan speed percentage that is at around 1/10th full power.  Now that's probably not going to be 10% because fans are weird.  Do it by sound (10X quieter).

 

Anyway by default the fan comes on at the second layer and then gradually increases over 5 layers.  You can change that in the settings.

[athollis89 0]

I am not convinced it is under extrusion. I have calibrated e-steps, and even increased flow and e-steps to close this gap. It only occurs on all layers of these feet (3 layers). I have also messed with the fan and even turned it off.  I have also increased line width and spend the better part of 2 weeks troubleshooting.

 

One additional note: I have reverted back to cura 4.7.1 and did not have this issue, but the prints were not nearly as clean. Also, I use all the same settings in PrusaSlicer and not only got cleaner prints, but also much faster print completion. No holes for either of these. I have read quite a bit on this and it appears to be a known issue with the later versions of Cura. Disappointed that many  people have reverted to "work arounds" instead of it being addressed.