I'm still trying to determine the best settings.
I ran a gradient test from 210, 220, to 230°C nozzle temperature (left to right).
I noticed the following:
At the bottom and the top, the Ninjaflex doesn't cool down fast enough and is still liquid when the next layer is applied. This leads to the bigger molten blob at the top of the 230 getting smaller via 220 to 210. It also leads to bulges of material being pushed around by the nozzle at 230° but not at 220°.
I won't use 210°C because the material is too crumbly at this low temperature. You can see this in that the 210 print is much less transparent and more milky white. Also, the fill walls inside are very irregular.
The fill walls are thinnest at 230°. This is hard to see in the photo. They nevertheless are still quite irregular.
So, I'm between 220 and 230°, leaning towards 220 or maybe 225°C. 230° is what the filament producer recommends but I can occasionally already see browning at these temperatures.
I had huge problems switching from printing one sphere to several at a time. Most prints failed towards the top because of a build up of irregularities. This may be a retraction problem, since if you print many, the travel distances are larger requiring more retraction. So, a no retraction that worked fine for one atom caused errors when printing several copies at the same time. I'm testing a longer no retraction distance of 5mm now (1.5 was the default).
I'm using no oil. Retraction was on default for the single prints. Also, printing at normal speed worked. I test with this filament.
What are you printing with?