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Extrusion Rate Smoothing Calculator

The Extrusion Rate Smoothing Calculator returns the correct ERS value for your machine from three inputs: external perimeter acceleration, line width, and layer height.

Free, runs in your browser, no registration.

What extrusion rate smoothing does

Section titled “What extrusion rate smoothing does”

Extrusion Rate Smoothing caps how fast the rate of extrusion is allowed to change — it is a limit on extruder acceleration, not on extruder speed.

On a fast machine, pressure advance asks the extruder to make very large, very sudden corrections at every corner and every speed change. The extruder motor physically cannot deliver them. What you see instead is:

  • Bulging or thin patches immediately after corners
  • Audible clicking or grinding from the extruder during direction changes
  • Pressure advance that tunes perfectly on a test print and then misbehaves on real geometry
  • Visible banding on curved walls

ERS smooths those demands into changes the extruder can actually execute.

Who needs it

Section titled “Who needs it”

ERS matters when acceleration is high enough that pressure advance corrections exceed what the extruder can physically do.

  • Below ~5,000 mm/s² — usually unnecessary. Leave it off and tune pressure advance normally.
  • 5,000–10,000 mm/s² — often helpful. Worth testing.
  • Above 10,000 mm/s² — effectively required. Voron, Rat Rig, K2 Plus, SV08 and similar CoreXY machines running aggressive input shaper profiles fall here.

If you are running a stock Ender at 500 mm/s², this setting is not your problem.

Using the calculator

Section titled “Using the calculator”

You need three values, all of which come from your slicer profile:

  1. External perimeter acceleration (mm/s²) — use the external perimeter figure specifically, not your global or travel acceleration. External perimeters are where the artifacts show.
  2. Line width (mm) — your external perimeter line width, typically 0.42 mm on a 0.4 mm nozzle.
  3. Layer height (mm) — typically 0.2 mm.

The calculator returns your ERS value in mm/s².

Where the value goes

Section titled “Where the value goes”

In OrcaSlicer: Printer Settings → Extruder → Extrusion rate smoothing. Requires expert mode to be visible.

In Klipper: the equivalent lives in your [extruder] section as part of pressure advance smoothing. OrcaSlicer’s ERS and Klipper’s pressure_advance_smooth_time address the same problem at different layers of the stack — set one or the other, not both aggressively, or you will double-damp and get soft corners.

Tuning order matters

Section titled “Tuning order matters”

ERS is meaningless if the layers beneath it are wrong:

  1. Rotation distance — the extruder moves the distance it claims
  2. Flow rate — the right volume comes out
  3. Pressure advance — the volume arrives at the right time
  4. Extrusion rate smoothing — pressure advance stays stable under acceleration

Setting ERS before pressure advance is tuned hides the symptom you were trying to measure, and you will end up tuning against your own damping.

Common mistakes

Section titled “Common mistakes”
  • Using global acceleration instead of external perimeter acceleration. These are usually different numbers, and the external perimeter value is the one that matters.
  • Setting ERS too low. Over-damping produces rounded corners and a soft, mushy look — the opposite failure mode, and easy to mistake for under-extrusion.
  • Applying it on a slow printer. At low acceleration ERS does nothing useful and can only hurt.
  • Stacking it with Klipper smooth time. Pick one damping mechanism.
  • Tuning it before pressure advance. See above.
Section titled “Related tools”

Verified profiles

Section titled “Verified profiles”

The OrcaSlicer profiles I actually run, including tuned ERS values for high-acceleration machines, are documented in the Minimal 3DP config packs. My raw Klipper configurations remain free and public in the klipper repository.