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In the past we had printers with poor mechanics and with primitive software algorithms, therefore we used to print inner perimeters faster than the outermost one. See for example (generic, found online):

enter image description here

However now we have pressure/linear advance which reduces extra oozing/extrusion in corners or areas with variable speed, and in Klipper we also have resonance compensation which takes care of imperfect mechanics allowing printers to be pushed to higher acceleration without visible artifacts (in my case from 2000 to 6000 mm/s^2), see (generic) photo:

enter image description here

However printing slower has a clear disadvantage: E steps calibration is speed dependent with more filament being pushed out at lower speed, see

Is there any reason left to print outer perimeters at a lower speed? Using one speed only except for specific areas (small perimeters, bridges, support) seems to make more sense to me to improve quality and reduce printing times.

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    $\begingroup$ Thank you for this question and all provided insight. I started experimenting with higher speeds after trying to answer question: Ideas to tune for 300 % speed. I observed big drops on start after long track's pressure-then-retraction, and had almost the same conclusion as a great explanation in the video. I manipulated flow rate to compensate, and slowed on last layers for nice finish. Actually the answer I proposed there reflects your way of thinking. So I upvote your question, curions to read from others. $\endgroup$
    – octopus8
    Jan 25 at 21:36
  • $\begingroup$ @octopus8 the implications of that video are quite far reaching... it is known for a while, but it has been forgotten. extrudable.me/2013/04/18/… and forum.duet3d.com/topic/5588/non-linear-extrusion/6 $\endgroup$
    – FarO
    Jan 26 at 9:57
  • $\begingroup$ @octopus8 I replied to that question as well $\endgroup$
    – FarO
    Jan 26 at 10:30
  • $\begingroup$ The claim that E steps calibration is speed dependent is false unless your extruder is skipping, in which case you just can't print at that speed without increasing temperature or upgrading your extruder and/or hotend. $\endgroup$ Mar 8 at 14:23
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    $\begingroup$ @octopus8: Sounds like you don't have linear advance dialed in right. $\endgroup$ Mar 8 at 14:27
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Lowering speed on outer perimeter has always been mostly wrong, but possibly useful. Usually, it's a poor approximation for what you really want to do, which is lowering acceleration on the outer perimeter, to avoid surface quality and dimensional accuracy errors due to ringing and backlash. However, on bowden printers without compensation for pressure ("linear advance" in Marlin, aka "pressure advance" in some other firmware), slow acceleration and high speeds give really bad error in extrusion consistency, so you're better off just lowering the max speed too whenever you lower acceleration.

It's also possible that you may want to print at extremely high speeds for inner walls and infill - speeds so high that you get a lot of extrusion consistency problems. If so, it would make sense to retain a sensible max speed on the outer wall. This won't avoid the part strength problems from printing too fast, but if your models are just decorative, it might be worth it.

Generally, though, I'd recommend solving these problems right (using linear advance if your printer needs it, lowering outer perimeter acceleration to get rid of artifacts, printing at a speed your hotend can handle, etc.) and deem "slower outer perimeter" an idea whose time has passed.

Also, note that if you're using a bowden printer without linear advance, sticking to the same speed for all extrusion will largely paper over the problem. This is probably the source of your observation that it "improves print quality" for you.

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Thanks to Input Shaper, you can print faster, sometimes to the point of reaching your speed limit on the max nozzle flow speed. At that point, if all speeds are hitting that threshold without any changes in quality, you could print every part at the same maximum speed.

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    $\begingroup$ Hi and welcome. What is Input Shaper? Is this an additional product (software/hardware?)? Could you edit your answer, and explain a bit more? As it stands, your answer, looks a little bit like spam (although I'm sure that you posted with good intentions). If it is a third-party product, are you affiliated to the company at all? If you are you must disclose this fact. Or is it something that you yourself use and have found to be useful? Thanks $\endgroup$
    – Greenonline
    Mar 9 at 1:53
  • $\begingroup$ Victor, check the question asked: "Is there any reason left to print outer perimeters at a lower speed? ". Your answer is not answering it... this website works strictly as question/answer approach. $\endgroup$
    – FarO
    Mar 9 at 9:07

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