Sapphire Pro - quarter shrunk object

Hey everyone,

First off, I would appreciate any and all help with this issue, as I'm quite at a loss at the moment.

So I'am running a heavily modified Twotrees Sapphire Pro corexy printer, and it produces quite fine prints, almost perfect.
The issue I'm facing is that I've recently purchased a spool of white TPU, and while printing ring objects, it produces these weird artifacts.
Please view the picture for details.

To me it seems like the lower half of the objects has shrunk, or that the layers has shifted, except the issue isn't uniform, turn the object 180 degrees, and that side is OK.
The circles are perfectly uniform.

I've tried tightening the belts, re calibrating everything (e/x/y steps etc). I'm printing at 205 degrees on the hotend, and 50 at the glassbed. The hotend doesn't go lower than 200 without affecting extrusion, and the bed I've tried at 30 degrees, but no difference. Speed is 7mm/s across the board, except travel. The cooling is running at 20%.

Any ideas?

I usually print TPU at 30-50 mm/sec with no cooling and don't have any of that sort of problem.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

I've tried running it without cooling, with no difference.

I honestly have no idea what could be causing it.
If it were loose belts, the circles would be ovals.
If it was shrinkage it would be uniform?

Re calibration did nothing, the issue persist.
I tried running it through a different slicer, with no effect,
which makes me believe it's mechanical?

Any suggestions?

Quick update, I ran the same model with pla, and it came out perfect.

This issue is only visible on the TPU model.
So I guess it's not mechanical. Could it be an issue with cooling somehow?

Temperature?

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

... elasticity?

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Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

I guess it might be ambient temperature related.
I placed the printer in a warmer room, and it kinda came out perfect, moved in back into the garage and it became crooked again.
Could this be an factor with tpu? or maybe a draft or something?

The ambient temperature in the garage is about 19 *C, and the other place 26*C.
Otherwise I ran the same file, and such a different result...

Interesting...

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Does seem that your TPU is shrinking.
Is this an enclosed printer? I noticed some have doors at the front that don't go the full height. That may mean the front of the bed is cooler in a cold environment. More significantly the back is hotter and more likely to shrink. As the bed lowers this becomes less of an effect as it drops inside the doors..
The airflow from the hot end fans can be causing a draught.