I tried Sport Mode for the 1st time today with 0.6 mm nozzle at 0.42 layer height. It failed within couple of layers, it seems extrusion rate is not fast enough and hotend couldn’t keep up, maybe both.
Anyone else having success printing higher speed with 0.6 and 0.8 mm nozzle?
The hotend is your bottleneck. There is a maximum volume of plastic the hotend can melt at a given temperature per second (known as max flowrate). I haven’t found the official max flowrate of the stock Bambu hotend, but some article said it was about 30 - 35 mm^3/s.
I tried printing PETG at 290C and was able to achieve a flowrate of 31 mm^3/s. This is way over recommended temps, but shows how temperature can relate to flowrate.
So, since the .6mm nozzle at .42mm layer height is pushing out more plastic than the .4mm, you either need to raise the temperature or slow down the print speeds or both.
Basically, higher speeds will always be able to be achieved by using a lower layer height since it’s harder to hit the max flowrate. However, even though you’ll need to slow prints down with the .6mm nozzle, the overall print time can be less if you use larger layer heights, wider line widths, less walls, etc.
If you want to print at the same speeds as the .4mm nozzle at the same temps, you’ll need a high-flow hotend like this one from E3D (not released yet, I think): E3D High Flow ObXidian™ HotEnd for Bambu Lab X1/P1 Series
Even with this high-flow hotend, there is still a max. The Bambu is kinda weird in that the motion system is capable of out-running most hotends. I’ve been having to relearn a lot coming from and Ender 3.