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I am using PLA and I am looking for ideas on using the Tune option to tune my Prusa i3 MK3 to increase the speed to 300 %.

The 300 % speed works perfectly fine for some of the models.

However, for some of the flat surfaces, the printer cannot handle the speed. The issues are pointed in the image below:

enter image description here

It seems that printer is struggling to supply enough filament.

Can I solve the issue by using the Tune menu by changing settings like temperature or flow?

Answer:

While @dandavis is informative, but this is how I did it:

  • increasing z offset so nuzzle has enough space to dispense.
  • Increase temperature +10

Please note that this degrades the print quality, but I am just printing a few organizer boxes. Quality is not essential and not something I expect from a 300% speed.

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extruder clicking means you're getting backed up, grinding.

  • Make the hotend hotter so you can melt filament 3X faster than expected; most materials have quite a range; aim high.
  • Slow down the cooling fan; a lot of them can cool the hotend.
  • You have a silicone boot on the nozzle? that will help some.
  • Use a larger diameter nozzle to reduce backpressure and allow thicker layers.
  • Try cranking the feed rate

Lastly, consider that you simply might not get acceptable results pushing speed THAT much.

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  • $\begingroup$ I like this list, but can you explain "cranking the feed rate" hint? And I agree, if frame mechanics is OK with the speed, then it's all about temperature and pressure to maintain necessary plastic flow. For "hotter hotend" there are limits: too high temperature may damage components (like PTFE), there are also security consderations (like off-gassing). I would probably start with bigger nozzle to reduce pressure issues (I had many lost steps by extruder's motor). $\endgroup$
    – octopus8
    Commented Jan 24, 2021 at 12:00
  • $\begingroup$ feedrate is how many mm/sec of filament is fed into the hotend. On repetier this is a setting you can adjust while printing, not sure about other software, but they probably have something similar. $\endgroup$
    – dandavis
    Commented Jan 24, 2021 at 12:40
  • $\begingroup$ Thank you! I understand that you mean experimenting in runtime. Without more fluent extrusion, just increasing feedrate wouldn't be helpful of course, but reducing it seems to be the solution for middle part of print. I just added alternative answer which is focused exactly on this point, but from G-Code perspective. Side note: there may be also firmware limits set (e.g. for max E velocity) which in some point will make increasing the speed percantage just ineffective at some point. $\endgroup$
    – octopus8
    Commented Jan 24, 2021 at 13:06
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Changing "Flow" will affect whole print. So even if it helped for the middle part (I doubt), the next it would ruin the print on sides by overextrusion. However: if sides are printed ok, then why the middle couldn't? Because walls are printed slower? Indeed, the under-extrusion may quickly rise along with speed because of plastic deformation between extruder gears under pressure and slight slipping, which actually increases with speed. The video "How fast can your hotend print?" presents experiment on this phenomena and its outcomes.

Then we go into master question: 300% of what? Turning the speed knob during print will override all considerations that slicer took into account during calculations - and defintely override Max volumetric speed, which is key factor to limit pressure in the nozzle (vide clicking noise).

The real limit seems to be this middle part of print, and outer part is just cosmetics (probably calculated to print slower because of quality). So if you ensure, that printing these middle surfaces is planned (in G-Code) with similar speed as walls, then (at least in theory) you may be able to increase overall speed, playing e.g. only with temperature. (I actually mean the speed of extrusion, so this may not be simple as just setting equal speed for perimeters and infill, but this does not change the conclusion below.)

So I say all it starts in the slicer software: increase speed there and re-caclulate. This will ensure to not exceed key limitations. Then you may manipulate maximal values in slicer for further experimentation.

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Provided you find a way to increase the extruder limits, as replied by @dandavis , you will still get underextrusion in the infill if the infill is printed faster than walls.

You need to enable some option in the slicer to label each part of the print, so that you get a comment in the gcode to mark walls, infill, and so on.

Then you need to process the generated gcode, so that when you find the label "infill" you replace it with a flow multiplier to increase flow. How much has to be tuned by try and fail.

You also need to replace every remaining label (walls, ...) with a 100% flowrate setting to bring back the setting to the standard value, obviously.

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