Print time goes down when print speed decreases?

[nritch 0]

Hi everyone,

I have been messing around with settings on Cura to see what kind of effects occur in an attempt to find optimal print settings. However, I noticed something unusual when changing the outer and inner shell speeds that I have been unable to find an explanation for. When lowering these settings below their default values, print time actually decreases instead of increasing.

For example, when the outer shell at 30 mm/s the estimated print time is ~9 minutes. But when the print speed is lowered to 10 mm/s, the print time decreases to ~6 minutes without changing any other settings. These predicted times are matched by my observations of the printers speed- it seems to print noticeably faster on 10 mm/s than on 30 mm/s.

As I said, I have been unable to find an explanation for this phenomena elsewhere on the net. The best explanation I can think of is that the this a glitch; perhaps a decimal point is being added to low numbers (i.e. 10 mm/s actually translates to 100 mm/s etc.). I would greatly appreciate if anyone can lend some insight to this!

[DaHai8 74]

What version on Cura?

Can you post an image of the model you're printing?

Things like acceleration, jerk speeds as well as minimum layer times can affect the time to print a model - as well as it's size.

[nritch 0]

Sorry for the late reply- the version we're using is Cura 21.03 (for Lulzbot mini). Here is a link to the model we were using: http://www.thingiverse.com/thing:213860

[DaHai8 74]

That is strange. I tried it with Cura 15.x and got logical results: 5min for 30mm/s and 11mins for 10mm/s

Unless the 'Cool -> Minimum Layer' time is set to something really large (or small), I can't explain it other than there is something wrong with Lulzbot's version of Cura.