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Faster prints

Famed Member

Hi, Luke:

Any suggestions on how to speed up this print? This is for a .4 nozzle; we have .6 and .8 but haven't played with them yet.  Thoughts? 



Topic starter Posted : 23/05/2021 5:02 pm
Expert Moderator

Hi Susan 🙂

Well, it's a pretty massive print, so by far the best thing you can do is move to a larger nozzle. Instead of 3 perimeters at 0.48mm extrusion width with a 0.4mm nozzle, you can do 2 perimeters with a 0.6mm or 0.8mm nozzle. Layer height should be 50-75% of nozzle diameter.

With a 0.8mm nozzle and 0.5mm layer height (very coarse), 2 perimeters, 3 top/bottom layers you already lower print time from 17 hours to 7 hours.

Other possible refinements are to switch to adaptive cubic infill (faster and uses less material than gyroid), and increasing the print speeds. Here's a tweaked .3mf for a 0.8mm nozzle. An 0.5mm layer height is quite coarse and will have a distinctive appearance and texture - make sure you're OK with this before committing to a full print! (you might print a calibration cube with my settings first).

Be aware of the the volumetric flow rate limit. Your stock hotend is good for about 15mm3/s (source: ). You'll definitely be hitting this limit with an 0.8mm nozzle at 0.5mm layer height - the maximum speed tops out around 40mm/s to keep flowrate below 15mm3/s.

You can set a limit under the print settings:


But there's also an override under the filament settings (which takes priority over the one under print settings):


In this case the Prusa profile already has the 15mm3/s limit pre-set. Setting a volumetric limit is more convenient because if for example you decide to go for 0.3mm layer height or 0.4mm layer height so it doesn't look so coarse, the actual speeds will automatically increase for the rest of the print - I've set an inner perimeter speed of 60mm/s for instance. PrusaSlicer will automatically adjust based on whichever limit it hits first (volumetric flow rate or ordinary speed).

You can visualise all this in the plater by switching between volumetric flow rate view and speed view -


If you have fantastic results with the 0.8mm nozzle with the existing 15mm3/s setting and you want to try and push the envelope a bit, you can try increasing it slightly and check for clicking and skipping of the extruder.

More temperature helps, so I've bumped up the nozzle temps to 220°C.

One last optimisation - because the part has lots of pointy protrusions, and a 0.8mm nozzle is thick, it generates shapes that require gap fill to fill. That's indicated by the white areas (I've marked 4 of them in the pic):


To disable gap fill, you set gap fill speed to "0". That actually eliminates another hour of print time since this part is all gaps, bringing the total time down to 5.5 hours. However you will have some open gaps in the top surface, which isn't the best result cosmetically. If this isn't acceptable, you can revert gap fill speed to 40mm/s to turn it on again, or you can experiment with ironing the top surface to close the gaps (it might need a fair amount of tweaking to get good ironing with a 0.8mm nozzle).

Here's the file with all the updates included. I believe all changes should be marked with the orange arrows in your settings. If you'd like to learn the rationale behind any particular changes feel free to ask 🙂


Posted : 24/05/2021 5:35 pm

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