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Increasing infill speed not reducing print time  

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Oliver
(@oliver-9)
New Member
Increasing infill speed not reducing print time

I'm slicing a model for printing using PrusaSlicer and the estimated printing time doesn't seem to be affected by greatly increasing the infill speed. What am I missing?

I'm using the default settings for PLA on an original Prusa i3 Mk3 and a 0.4mm nozzle. The estimated printing time for my model is 4h 20min. When I increase the "infill" and "solid infill" speeds to 160 (their default is 80), the estimated printing time is still 4h 20min.

Looking at the slices in the plater, I can see that all the infill is set to print at 160 and that the infill's volumetric flow rate has gone up greatly (but is still below the maximum 11.5mm3/s). Why isn't the estimated printing time decreasing?

I'm sure I've missed something obvious - thanks for any help!

Posted : 19/02/2021 2:46 pm
bobstro
(@bobstro)
Illustrious Member
RE: Increasing infill speed not reducing print time

Depending on the size of the model, and specifically the infill areas, the nozzle may not be getting up to anywhere near your specified speeds during the actual print. Acceleration and jerk affect how quickly the nozzle speeds up and slows down. Set too high, you'll get poor quality due to ringing and possible under extrusion. There are a number of other infill techniques you can try.

  • If your layer height is low enough, you can set Print Settings->Infill->Reducing print time->Combine infill every to combine multiple layers of infill into a single extrusion. Note that the total number of combined layers should still be below 80% of your nozzle size (e.g., 3 layers at 0.15mm high total 0.45mm, which is too high for a 0.4mm nozzle but fine for a 0.6mm nozzle).
  • Enabling Print Settings->Infill->Reducing print time->Only infill where needed will only print infill where it will support top surfaces. Note that you want sufficient perimeters to provide part strength rather than relying on infill.
  • If the infill area is large enough to benefit, try one of the Support or Adaptive Cubic patterns that vary infill density.
  • Use wider extrusion widths for infill (Print Settings->Advanced->Extrusion width->Infill). This will print fewer, wider lines of infill. 

I've written some notes here that might be helpful. 

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 19/02/2021 3:33 pm
Oliver
(@oliver-9)
New Member
Topic starter answered:
RE: Increasing infill speed not reducing print time

Thanks!

Does that mean that even though the volumetric flow rate preview is showing nearly all of the infill as dark red, the actual volumetric flow rate will be much lower due to acceleration and jerk? I.e. the preview doesn't account for speeding up and slowing down between regions of different flow, but just assumes that it instantly switches into its new ideal speed without needing to accelerate?

Posted : 28/02/2021 6:37 pm
bobstro
(@bobstro)
Illustrious Member
RE: Increasing infill speed not reducing print time
Posted by: @oliver-9

Does that mean that even though the volumetric flow rate preview is showing nearly all of the infill as dark red, the actual volumetric flow rate will be much lower due to acceleration and jerk? I.e. the preview doesn't account for speeding up and slowing down between regions of different flow, but just assumes that it instantly switches into its new ideal speed without needing to accelerate?

I believe the preview shows the flow average for each layer. I don't know how that is derived internally. You should see all layers printing at a MVS at or below your specified maximum in either filament or print settings.

 

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 28/02/2021 10:02 pm
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