Klipper Pressure Advance Line Calibration Macro

pa_cal.cfg

[gcode_macro PA_CAL]
# Klipper pressure advance line calibration macro.
# Usage: PA_CAL BED=100 NOZZLE=240 PA_START=0.0 PA_STOP=0.1 NZL=0.4
# Or you can execute with no parameters, which will use values from printer.cfg and saved_variables.cfg.
# First prints a line with current set PA, then prints 21 additional line segments starting with PA_START, and increasing to PA_STOP.
# Based on http://realdeuce.github.io/Voron/PA/pressure_advance.html
# Cleaned up and moved to using saved_variables.cfg by u/jibbsisme
# Assisted by u/imoftendisgruntled, u/scul86, and thanks to u/beansisfat, u/stray_r

description: Tune Pressure Advance
gcode:
  # saved_variables.cfg
  {% set speed = printer.save_variables.variables.speed %}
  {% set nozzle_temp = printer.save_variables.variables.nozzle_temp %}
  {% set bed_temp = printer.save_variables.variables.bed_temp %}

  # macro parameters
  {% set BED = params.BED|default(bed_temp)|float %}
  {% set NOZZLE = params.NOZZLE|default(nozzle_temp)|float %}
  {% set PA_START = params.PA_START|default(0.0)|float %}
  {% set PA_STOP = params.PA_STOP|default(0.1)|float %}
  {% set NZL = params.NZL|default(printer.configfile.config["extruder"]["nozzle_diameter"])|float %}

  # calculated variables
  {% set PA_STEP = (PA_STOP - PA_START) / 20 |float %}
  {% set E20 = (0.1147475 * NZL) * 20|float %}
  {% set E40 = (0.1147475 * NZL) * 40|float %}
  {% set X_MID = printer.configfile.config["stepper_x"]["position_max"]|float / 2.0 %}
  {% set Y_MID = printer.configfile.config["stepper_y"]["position_max"]|float / 2.0 %}

  START_PRINT BED_TEMP={BED} NOZZLE_TEMP={NOZZLE}

  G21 ; millimeter units
  G90 ; absolute XYZ
  M83 ; relative E
  SET_VELOCITY_LIMIT ACCEL=3000 ACCEL_TO_DECEL=1500
  G92 E0
  M106 S0

  G1 X{(X_MID-40)} Y{(Y_MID-65)} F{speed}        ; move to start position
  G1 Z0.25 F300                                  ; move to layer height
  G1 E0.75 F1800                                 ; un-retract
  G1 X{(X_MID-20)} Y{(Y_MID-65)} E{E20} F300     ; print line part one
  G1 X{(X_MID+20)} Y{(Y_MID-65)} E{E40} F3000    ; print line part two
  G1 X{(X_MID+40)} Y{(Y_MID-65)} E{E20} F300     ; print line part three
  G1 E-0.75 F1800                                ; retract
  G1 Z1 F300                                     ; move above layer height

  {% for i in range(0, 21) %}
      SET_PRESSURE_ADVANCE ADVANCE={PA_START + (i * PA_STEP)} ; set Pressure Advance
      M117 PA={PA_START + (i * PA_STEP)}, STEP={PA_STEP}.
      G1 X{(X_MID-40)} Y{(Y_MID-35)+(5*i)} F30000           ; move to start position
      G1 Z0.25 F300                                         ; move to layer height
      G1 E0.75 F1800                                        ; un-retract
      G1 X{(X_MID-20)} Y{(Y_MID-35)+(5*i)} E{E20} F300      ; print line part one
      G1 X{(X_MID+20)} Y{(Y_MID-35)+(5*i)} E{E40} F3000     ; print line part two
      G1 X{(X_MID+40)} Y{(Y_MID-35)+(5*i)} E{E20} F300      ; print line part three
      G1 E-0.75 F1800                                       ; retract
      G1 Z1 F300                                            ; move above layer height
  {% endfor %}

  END_PRINT

  # these may not work, in which case you will need to count and do the math yourself!
  M117 New PA = ({PA_START} + (bestLine * {PA_STEP}) )
  {action_respond_info ("Find best line and multiply it by (" + PA_START|string + " + (bestLine * " + PA_STEP|string + ") ) to find your PA setting.")}

saved_variables.cfg

[Variables]
speed = 9000
nozzle_temp = 215
bed_temp = 60

{% set E20 = (0.1147475 * NZL) * 20|float %}

What is the number that is being multiplied by the nozzle size? Is it printer specific, or universal?

Thanks for sharing this.

I forked this from @JeremyKennedy so we'd have to ask him.

Here's some more context on that: https://www.reddit.com/r/klippers/comments/tet8jc/pressure_advance_tuning_box_vs_lines/i0vubdd/?context=3

I think I found the math for this a few days ago:

https://github.com/th33xitus/klipper_config/blob/cd6052284861b57bfc51dc5c94824f99ec2dd4df/macros/pa_calibrate.cfg#L61-L69

ksanislo has created a pretty advance macro for this that I'm using. It also is calculating this value dynamically.

I believe that as long as you don't modify the line height, and use 1.75mm filament the hardcoded value should be ok.