Max Volumetric Flow Calculations for High Flow Nozzle?

pbjwm · June 21, 2025, 5:42am

I’m trying to calibrate the speed of my filaments and I’m using this flow test tower.

Now, for the test, I temporarily set my filament’s profile to have a max volumetric flow of 200mm3/s so that there’s no way there’s a bottle neck.

When I slice the model and look at the Flow Color Scheme in the Preview, I see this:

14 seems kinda low for PLA with a HF nozzle, how is this the max?

I started to do some math:
The last layer on this model has its outer/inner wall set to 476mm/s.
As far as I’m aware, to get the MVF, you would do Speed * Layer Height * Line Width.

In this example, the Layer Height is 0.20mm, and the Line Width is 0.42mm

So: 476 * 0.20 * 0.42
This would result in: 39.984mm3/s

Why does the preview show 14.29?
Am I missing something?

Sidenote: My PLA Silk passed the first test completely, so I changed the line width to 0.6mm (hoping to reach a higher max) and it completed that one completely too? What’s going on?

EnoTheThracian · June 21, 2025, 9:26am

The preview does not show an increased flow with increased height. Most likely, intermitted speed modifiers were removed?
As for finding the root cause of the low speed: Did you compare the layer time preview to the Max fan speed threshold Layer time? That setting is also used by the slicer to slow down a layer.

hotellonely · June 21, 2025, 12:15pm

Add another non bambu printer to generate the test, then switch back to bambu printer

Qjo · June 21, 2025, 2:35pm

I’ve also been trying to figure out how to set one of these tests up. I’m running into something different though. My previews are showing the flow going up to about 43 but about half way up the speed caps out at like 173mm/s. I couldn’t get it to change no matter what settings I changed.

I’ve tried setting it up with a non Bambu printer profile and then switching back, but that didn’t work either.

I’m really surprised Bambu hasn’t given us a MVS and temp tower test in their calibration tab yet.