Question first then necessary context: Most Bambu Filaments recommend a print speed of <300mm/s and yet when you choose the ‘extra fine’ preset, the sparse infill speed is 450 mm/s while the outer layer is 350 mm/s. What gives?
Context: I have recently had difficulty getting non-Bambu Matte PLA to print the way I want (I have tried Polyterra and another brand). I think the issue is the nozzle hitting the print and brittle support structures on tall prints which according to this website: Common print quality problems and solutions | Bambu Lab Wiki
may be a flow issue (relating to temperature and speed). They do recommend reducing the sparse infill speed which makes sense. I have calibrated temperature etc. on Orca but my results are still not ideal. Could this be due to a speed issue?
Am I supposed to be capping all of my speeds to the max recommended on the BL website? Why would BambuStudio recommend a speed higher for its filament than what the BL website recommends?
A couple of data points. First of all, a filament profile can limit the volumetric speed/flow (in mm³/s) but not the line speed (in mm/s) other than as an effect of the former. Perhaps a max. speed figure could be added (overriding any faster process setting).
However, I’m not sure what their rationale is with the 300 mm/s figure: Is it for finish (eg. glossy or matte) or strength? A good example is PLA Silk. The profile for it has the temperature as 230°C which is in line with the recommendations (for gloss). The print speed is stated as “< 250 mm/s” but for maximum gloss they recommend “30-60 mm/s”. Again, the filament profiles doesn’t have a speed parameter (other than 12 mm³/s flow) so neither of those figures are set by default: You have to create a process profile which limits it. Since the low speed is for looks and not strength, you only need to decrease speed for outer walls and top/bottom layers. But eg. infill can print at 250 mm/s - this is an important point! It will be a whole lot faster compared to some global max. overriding any process setting.
Also, you could want a profile for “not so shiny” for that antique looking spyglass and another for “as shiny as it gets” for the gold medal. So anyway they do it, you might still want several profiles with different properties.
Yes. In addition, I believe Bambu somehow tweaks their filament profiles to slice different parts of the print at different speeds. For example, with the Bambu PLA filament profile, infill near the top of a model was set at a slower speed than my Generic profile, which just set the infill speed as constant. This is despite the max speed in the slicer being the same for both cases.
The only reason I can find for the speed limitation is flow according to the formula: volumetric flow = speed * line width * layer height
or max speed = volumetric flow/(line width * layer height). Reviewing this formula explains why BambuStudio increases max speed when the ‘extra fine’ profile is selected - it is due to the smaller layer height, presumably. Perhaps, however, certain filaments just don’t flow quickly enough for certain print speeds, causing the nozzle to hit the print, for example. You could turn up the temperature (as per the BL help page) but you would get other issues, like stringing. With Matte PLA, the temperature tends to be lower, in my case, calibrated at 220 deg., so maybe that places a hard limit on print speed?
You´re correct; BL´s filament is appropriately designed for high-speed printing. One critical indicator is the filament Melt flow index, which, in general, BL´s filaments overrun others.
Regarding the effective printing speed, you should also account for the minimum layer time, which can significantly influence “smaller” prints.
Right. It’s not clear to me how BL’s filament differs from other brands so that’s useful information. They don’t say very much about their filament and because it’s more expensive unless you buy 4 rolls (with membership) I’ve avoided it. But I’ve ordered some BL matte PLA and will give it a try.
So I compared the ‘melt flow index’ for Bambu PLA to other major manufacturers including for high speed filaments. I’m shocked! The BL filament MFI is at least double other brands. It is widely regarded (on reddit) that BL is repackaging other manufacturers’ filaments. This would argue against that.
I also don’t know the BL filament origin, nor can I be precise about how they achieve such high MFI.
For the latter, additives are the typical solution. Another interesting fact is the printing temperature, which is higher than other manufacturers and improves flowability.
In each case, it may, and likely will, affect the mechanical properties of the print.
I can conceive that one can outsource filament production and define custom specs. Verifying the repacking claim by printing a complex part using BL filament presets seems easy. I failed to print twice a complex shape at high speed using Polyterra and BL PLA preset.
but did you then test that complex shape with BL filament? I have some BL Matte PLA on the way and I will be testing various sculpture STLs which have been challenging thus far. We will see.