PA / EM Oddities

:dizzy: This page is compatible with Klipper, Marlin, and RepRapFirmware.

Slight Perimeter Gapping

Some find that after tuning PA and EM, minor perimeter gapping is still present:

Assuming EM is well tuned, this is often caused by a slight :page_facing_up: flow dropoff at higher print speeds — since most people print their perimeters faster than their top layer.

There are a few different things you can try:
(in order of my preference)

  1. Ensure that you are not :page_facing_up: outrunning your hotend and that you do not have a partial nozzle clog.
  2. Take measures to improve your hotend’s max flow rates.
    • Higher flow ceilings allow for better extrusion consistency at lower flow rates, as the :page_facing_up: flow dropoff curve starts later. It is beneficial for extrusion consistency at different speeds, even when you don’t intend to use the full flow rate.
    • Try increasing hotend temperatures a bit.
      • Temperature can have a significant effect on max flow rates.
      • Note: temp changes can have a minor effect on PA values.
    • Use a hotend and/or nozzle with a higher flow ceiling.
      • :page_facing_up: Bondtech CHT and :page_facing_up: Bozzle both provide a sizeable flow rate increase to any hotend that supports V6 nozzles. CHT also has a Volcano variant.
    • These steps can reduce the effect, but may not 100% fix it.
  3. Increase your EM until the gaps disappear. Then, lower your top layer flow (fill_top_flow_ratio in SS) until your top surfaces look perfect again.
  4. Follow my :page_facing_up: “determining maximum volumetric flow rate” instructions, and choose the “conservative” (always-100mm) value to enter into your slicer (PS/SS).
  5. Slow your perimeters down. The faster you print, the greater this flow dropoff becomes.