Klipper macros for drying filament using the heated build plate of a 3D printer

filament_dryer.cfg

; An idea for using the heated bed of a 3D printer as a filament dryer.
; Adds GCODE command: START_DRYER TIME=T TEMPERATURE=C
; (T is time in seconds, C is bed temperature in Celsuis)
; To stop drying early, use STOP_DRYER.
; Also defined some utility macros: DRY_PLA, DRY_PETG and DRY_ABS.
; Edit these with your own preferred defaults.

[gcode_macro START_DRYER]
description: Start the heated bed filament dryer.
gcode:
    {% set ChamberTemperature = params.CHAMBER | default(25.0) | float %}
    {% set BedTemperature = params.TEMPERATURE | default(50.0) | float %}
    {% set DryTime = params.TIME | default(14400) | int %}
    ; turn the heaters on, however you do that.
    M140 S{BedTemperature}      ; Sets the print bed temperature without waiting.
    M141 S{ChamberTemperature}  ; [OPTIONAL] Sets the enclosure temperature.
    ; then finally,
    SET_GCODE_VARIABLE MACRO=DRYER_STATUS VARIABLE=time_remaining VALUE={DryTime}
    SET_GCODE_VARIABLE MACRO=DRYER_STATUS VARIABLE=bed_temperature VALUE={BedTemperature}
    SET_GCODE_VARIABLE MACRO=DRYER_STATUS VARIABLE=chamber_temperature VALUE={ChamberTemperature}
    UPDATE_DELAYED_GCODE ID=DRYER_TIMER DURATION=1

[gcode_macro STOP_DRYER]
gcode:
    ; Turn off heaters etc. here
    M140 S0 ; Disable bed heater
    M141 S0 ; [OPTIONAL] Disable enclosure heater/fan
    SET_GCODE_VARIABLE MACRO=DRYER_STATUS VARIABLE=time_remaining VALUE=0
    UPDATE_DELAYED_GCODE ID=DRYER_TIMER DURATION=0    ; Stop the timer.
    M117 Drying Stopped

[gcode_macro DRYER_STATUS]
variable_time_remaining: 0
variable_bed_temperature: 0
variable_chamber_temperature: 0
gcode:
    {% if time_remaining > 0 %}
        M140 S{bed_temperature} ; Reset bed temperature (prevents timeout)
        SET_GCODE_VARIABLE MACRO=DRYER_STATUS VARIABLE=time_remaining VALUE={time_remaining - 1}
        M117 Drying {time_remaining}
    {% else %}
        STOP_DRYER
    {% endif %}

[delayed_gcode DRYER_TIMER]
gcode:
    UPDATE_DELAYED_GCODE ID=DRYER_TIMER DURATION=1
    DRYER_STATUS

[gcode_macro DRY_PLA]
gcode:
    START_DRYER TEMPERATURE=50 CHAMBER=25 TIME=14400

[gcode_macro DRY_PETG]
gcode:
    START_DRYER TEMPERATURE=55  CHAMBER=30 TIME=18000

[gcode_macro DRY_ABS]
gcode:
    START_DRYER TEMPERATURE=65 CHAMBER=40 TIME=14400

Another addition, to avoid too "many" logs if you're using a modified M117 that logs on klipper console, it's possible to add a "if" to only log in certain scenarios

    {% if time_remaining > 0 %}
        M140 S{bed_temperature} ; Reset bed temperature (prevents timeout)
        M141 S{chamber_temperature} ; [OPTIONAL] reset chamber temperature
        SET_GCODE_VARIABLE MACRO=DRYER_STATUS VARIABLE=time_remaining VALUE={time_remaining - 1}

        {% if (time_remaining % 600 == 0) or (300 <= time_remaining <= 1800 and time_remaining % 300 == 0) or time_remaining < 60 %}
            M117 Remaining drying time {time_remaining|int}
        {% endif %}
    {% else %}
        STOP_DRYER
    {% endif %}
  

@RealSpyKitty indent the lines beneath gcode:

Parameters changed with new updates. The two under are ok, but anyone got one for TIME?

{% set bed_temp = params.BED_TEMP|default(60) %}
{% set extruder_temp = params.EXTRUDER_TEMP|default(200) %}

This is working for me:

; An idea for using the heated bed of a 3D printer as a filament dryer.
; Adds GCODE command: START_DRYER TIME=T TEMPERATURE=C CHAMBER=C
; (T is time in seconds, C is temperature in Celsuis)
; To stop drying early, use STOP_DRYER.
; Also defined some utility macros: DRY_PLA, DRY_PETG and DRY_ABS.
; Edit these with your own preferred defaults.

[gcode_macro START_DRYER]
variable_time: 14400
variable_temprature: 50.0
variable_chamber: 25.0
gcode:
    ; turn the heaters on, however you do that.
    M140 S{temprature} ; Sets the print bed temperature without waiting.
    #M141 S{CHAMBER}     ; [OPTIONAL] Sets the enclosure temperature.
    ; then finally,
    SET_GCODE_VARIABLE MACRO=DRYER_STATUS VARIABLE=time_remaining VALUE={time}
    SET_GCODE_VARIABLE MACRO=DRYER_STATUS VARIABLE=bed_temperature VALUE={temprature}
    #SET_GCODE_VARIABLE MACRO=DRYER_STATUS VARIABLE=chamber_temperature VALUE={CHAMBER}
    UPDATE_DELAYED_GCODE ID=DRYER_TIMER DURATION=1
    SET_IDLE_TIMEOUT 

[gcode_macro STOP_DRYER]
gcode:
    ; Turn off heaters etc. here
    M140 S0 ; Disable bed heater
    #M141 S0 ; [OPTIONAL] Disable enclosure heater/fan
    SET_GCODE_VARIABLE MACRO=DRYER_STATUS VARIABLE=time_remaining VALUE=0
    UPDATE_DELAYED_GCODE ID=DRYER_TIMER DURATION=0    ; Stop the timer.
    M117 Drying Stopped

[gcode_macro DRYER_STATUS]
variable_time_remaining: 0
variable_bed_temperature: 0
variable_chamber_temperature: 0
gcode:
    {% if time_remaining > 0 %}
        M140 S{bed_temperature} ; Reset bed temperature (prevents timeout)
        #M141 S{chamber_temperature} ; [OPTIONAL] reset chamber temperature
        SET_GCODE_VARIABLE MACRO=DRYER_STATUS VARIABLE=time_remaining VALUE={time_remaining - 1}
        M117 Drying {time_remaining}
    {% else %}
        STOP_DRYER
    {% endif %}

[delayed_gcode DRYER_TIMER]
gcode:
    UPDATE_DELAYED_GCODE ID=DRYER_TIMER DURATION=1
    DRYER_STATUS

[gcode_macro DRY_PLA]
gcode:
    START_DRYER TEMPERATURE=50 CHAMBER=25 TIME=14400

[gcode_macro DRY_PETG]
gcode:
    START_DRYER TEMPERATURE=55  CHAMBER=30 TIME=18000

[gcode_macro DRY_ABS]
gcode:
    START_DRYER TEMPERATURE=65 CHAMBER=40 TIME=14400

the one above doesn't have working parameter, this one's fixed.
also, add [respond] to your printer.cfg, or M118 isn't gonna work.

[respond]
#default_type: echo
# Sets the default prefix of the "M118" and "RESPOND" output to one
# of the following:
# echo: "echo: " (This is the default)
# command: "// "
# error: "!! "
#default_prefix: echo:
# Directly sets the default prefix. If present, this value will
# override the "default_type".

[gcode_macro START_DRYER]
gcode:
{% set TIME_PARAM = params.TIME|default(3)|float %}
{% set TEMP_PARAM = params.TEMP|default(50)|float %}
M140 S{TEMP_PARAM} ; non blocking bed temp
SET_GCODE_VARIABLE MACRO=DRYER_STATE VARIABLE=time_remain_var VALUE={TIME_PARAM}
SET_GCODE_VARIABLE MACRO=DRYER_STATE VARIABLE=bed_temp_var VALUE={TEMP_PARAM}
UPDATE_DELAYED_GCODE ID=DRYER_TIMER DURATION=1
;SET_IDLE_TIMEOUT ;called w/o param and dont even need? cause timer tick reset temp anyway?

[gcode_macro STOP_DRYER]
gcode:
; Turn off heaters etc. here
M140 S0 ; Disable bed heater
SET_GCODE_VARIABLE MACRO=DRYER_STATE VARIABLE=time_remain_var VALUE=0
UPDATE_DELAYED_GCODE ID=DRYER_TIMER DURATION=0 ; Stop the timer.
M118 Drying Stopped

[gcode_macro DRYER_STATE]
variable_time_remain_var: 0
variable_bed_temp_var: 0
gcode:
{% if time_remain_var > 0 %}
M140 S{bed_temp_var} ; Reset bed temp (prevents timeout)
SET_GCODE_VARIABLE MACRO=DRYER_STATE VARIABLE=time_remain_var VALUE={time_remain_var - 1}
M118 Drying {time_remain_var}
{% else %}
STOP_DRYER
{% endif %}

[delayed_gcode DRYER_TIMER]
gcode:
UPDATE_DELAYED_GCODE ID=DRYER_TIMER DURATION=1
DRYER_STATE

;flip filament every 6h
[gcode_macro DRY_PLA]
gcode:
START_DRYER temp=55 time=43200
[gcode_macro DRY_PETG]
gcode:
START_DRYER temp=65 time=43200
[gcode_macro DRY_ABS]
gcode:
START_DRYER temp=80 time=43200
[gcode_macro DRY_WarmRoom]
gcode:
START_DRYER temp=100 time=43200

Thanks for posting the update. I think Klipper changed the syntax for accessing parameter values some time back, which accounts for the errors. I've just updated the Gist with my current working version which should work now. It's interesting to see other people's variations and additions though.