Bambu Studio doesn't use full flowrate / speed

[max2017]

Dear Bambu Community,

when I tried to do a speedrun Benchy, I noticed that Bambu studio does funky stuff with speed and flowrate.

Bassicly, I put every slider to the far right.
Flowrate 50mm/s³
Speed >350mm/s
Accel 20000mm/s²
Layer Hight 0,28mm
Line Width 0,7mm

But the slicer neither gives out full flow or full speed on the Print.

Flow:

Speed:

But in some places it is using higher but not full Flow / Speed

What am I doing wrong?

[alain.vd]

It’s a problem of layer time.
Look in the filament settings, section “Cooling” . if the option “Slow printing down fort better layer cooling” is checked, and the layer time is under “Max Fan Speed threshold - layer time”, the print is slowed down.

[lkraus]

The model shape and dimensions can also limit speed and flow. A Veyron may be capable of 260 mph, but not in a residential area with a stop or turn every hundred yards.

[RocketSled]

Acceleration does not equal speed. The equation for speed is V = A*T. Just like your car needs time to get to 60MPH, the printer needs time to get the printhead to full speed. And just like your car can’t get to 60MPH if the road isn’t long enough, the printhead can’t get to full speed if the distance it has to travel before changing direction isn’t long enough.

The speed you enter is a speed limit, but just like your car on a road that’s too short to get to 60MPH, it doesn’t matter if the speed limit is greater than 60MPH, you’re not going to get to that speed anyway. The speed you enter isn’t how fast it’ll go, it’s the maximum it’s allowed to go.

Scale the model up (make the road longer), it should give you higher speeds.

[vladimir.minkov]

Hi Max,
@alain.vd gave you one of the best hints set the min layer time to 0 seconds , instead of default 8seconds for a try
Also make sure the volumetric speed is set to reasonable value 23mm3/S in the filament most filaments will cope with that generic is set by default to 12mm3/s , but really needs to be tested , try and read orca slicer for calibrations MAX speed, max flow , and etc it is eye opener and relatively simple: Calibration · SoftFever/OrcaSlicer Wiki · GitHub
Apart from that the speed may be reduced due to small perimeters relative to speed acceleration etc , overhangs, bridges there are quite a few perimeters to control
Ignore the volumetric speed it is used only to calculate and restrict actual speed, but is good indicator, to see if you are getting to the maximum volumetric of the nozzle and material depending on the extrusion sizes , the max volumetric speed which is set in the filament settings .
Your problem here looks like that is limited to 12mm3/S Default for any generic PLA/ABS/

Here is example with max speed set to 200mm/s and volumetric set to 19-23mm3/s and 0seconds for the minimum layer time or maximum speed with out changing other parameters:

If i change the speed to 300mm/S this model from 24.37s prints for 24.35s the reason is that infill gets close to 23mm3/S and will not allow higher speeds

Last hint this PLA Benchy 0.2mm std. is 28m’31s , 0.24mm draft is 26m’48s(45s with300) 24m’38s
The actual print time really depends on surfaces, details, supports orientation layer height , walls … can make it worse for not much gain . I did print 17 min Benchy with bad quality , PLA best quality max 200mm/S
if in hurry just increase to 128% the speed usually the default profiles allows it with out too much sacrifice the quality for PLA. ABS/ASA/PETG max speed 140-145mm/S , once tuned the materials at max speed and volumetric the 160% Ludicrous mode useless , 128% sometimes works with small issues

[max2017]

Setting the min Layer Time to 0 did the trick.
Now the Flow over the whole Model looks like I imagined it would.

I only set the other Parameters to ridicoulous high values, because I wanted to rule them of slowing down the print.

I pushed Prusament PETG up to 20mm³/s whith decent Print results.