TPU outer perimeter not adhering to inner perimeter

[LVNeptune]

I've mucked about with everything and am unable to resolve this. The strange thing is this only recently happened. Same process same filament, tried a different filament and same thing. The print itself comes out fine except for the outer perimeter not fully connecting with the inner one. I have ran 2 perimeters since I started printing a few years ago and am running another one now with 3 to see if it makes any difference. Anyone have ideas? Changed extrusion multiplier, temperatures, and messed with the extrusion width, nothing seems to help.

[kabali16]

Closeup picture ?? Another thing you may want to look into is the Outline speed multiplier. Keep is low, I believe the extruder is not able to push through enough plastic at the speed you are printing

[LVNeptune]

I have dropped printing speed down from 70mm/s (which mind you I have been printing at on TPU for nearly a year now) down to 30mm/s which is ridiculously slow. The outer perimeter was not affected AT ALL.

Unfortunately it's green and it doesn't show up well at all under any kind of light so a picture would be pointless here.

[kabali16]

I have dropped printing speed down from 70mm/s (which mind you I have been printing at on TPU for nearly a year now) down to 30mm/s which is ridiculously slow. The outer perimeter was not affected AT ALL.

Unfortunately it's green and it doesn't show up well at all under any kind of light so a picture would be pointless here.

thats crazy fast. I am surprised you are not getting any kinks. What kind of an extruder do you have ? Also, the outline speed in the Other tab will reduce the print speed by 50% by default. If this is not helping. The only other thing I can think of is the extrusion multiplier.

If you are having gaps in general on prints, you can try doing a cold pull.

[LVNeptune]

I kept upping the extrusion multiplier. I was at 1.09 then just said screw it and went to 1.3 expecting it to be bulging all over the place...it fixed my issue completely ...? Why 1.3 that makes no sense to me. The filament measures about 1.70-1.71

[dkightley]

The filament measures about 1.70-1.71

And the filament diameter setting in your profile is...?? 1.75 ??? Which might explain why you have you wind up the extrusion multiplier to compensate.

[LVNeptune]

Yea but 1.70 to 1.75 is a 3% difference. I am upping the extrusion rate to 1.30 which is 30%. That's 10x more.

[kabali16]

Yea but 1.70 to 1.75 is a 3% difference. I am upping the extrusion rate to 1.30 which is 30%. That's 10x more.

I think there is more than just Math involved here. Printing with TPU might introduce new variables in the eqn. You may want to study about Non newtonian fluid flow to start with.

But it looks like you have found the right settings to prevent the gaps