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Strange "M82; absolute extruder mode" being added to start gcode


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Posted · Strange "M82; absolute extruder mode" being added to start gcode

Hi, All. 


I've started experiencing strange filament volumes on Octoprint. I've figured out that since I upgraded to Cura 4.8.0, Cura is adding a "M82; absolute extruder mode" to my start gcode. I checked my printer settings and its not inserted by me to add to start gcode. I do have stuff added to my start gcode for Octolapse and ABL. The start Gcode I added myself starts with "; Script based on an original..." and ends with "G1 X5 Y20 Z0.3 F5000.0 ; Move over to prevent blob squish". I also tried using one of the default profiles in case this was a setting I adjusted but I get the same inclusion of the strange M82 regardless of which profile settings I use.


If I comment out the strange M82 then Octoprint correctly see the right filament volume. 


See extract below with issue line bolded and entire gcode file attached. 


;Filament used: 3.4782m
;Layer height: 0.2
;Generated with Cura_SteamEngine 4.8.0
M82 ;absolute extrusion mode
; Script based on an original created by tjjfvi (https://github.com/tjjfvi)
; An up-to-date version of the tjjfvi's original script can be found
; here: https://csi.t6.fyi/
; Note - This script will only work in Cura V4.2 and above!
; --- Global Settings
; layer_height = 0.2
; smooth_spiralized_contours = True
; magic_mesh_surface_mode = normal
; machine_extruder_count = 1
; --- Single Extruder Settings
; speed_z_hop = 5
; retraction_amount = 5
; retraction_hop = 0.2
; retraction_hop_enabled = False
; retraction_enable = True
; retraction_speed = 30
; retraction_retract_speed = 30
; retraction_prime_speed = 30
; speed_travel = 175.0

; Ender 3 Custom Start G-code


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    Posted · Strange "M82; absolute extruder mode" being added to start gcode

    There are 3 ways for Cura to calculate the extrusion E numbers.  Absolute, Relative, and Volumetric.  There needs to be synchronicity between the various components so they understand each other.


    That file is sliced in "Absolute" mode and so there is an M82 line to inform the printer of that.  Since you have Octoprint between the printer and the slicer, you may need to change a setting in Octoprint.


    Under "Special Modes" you will find "Relative Extrusion".  When selected it will add an "M83" after your start up gcode.  That will negate the M82, but as I say, that file is sliced in Absolute Mode so telling the printer to reset to 0 after every line of Gcode (that's what Relative does) will make a mess.


    In addition you have the standard lines that are included with the Ender 3 definition file:

    G1 Z2.0 F3000 ; Move Z Axis up little to prevent scratching of Heat Bed
    G1 X0.1 Y20 Z0.3 F5000.0 ; Move to start position
    G1 X0.1 Y200.0 Z0.3 F1500.0 E15 ; Draw the first line
    G1 X0.4 Y200.0 Z0.3 F5000.0 ; Move to side a little
    G1 X0.4 Y20 Z0.3 F1500.0 E30 ; Draw the second line
    G92 E0 ; Reset Extruder
    G1 Z2.0 F3000 ; Move Z Axis up little to prevent scratching of Heat Bed
    G1 X5 Y20 Z0.3 F5000.0 ; Move over to prevent blob squish
    G92 E0
    G92 E0
    G1 F1800 E-5


    Those extrusions are in Absolute mode and so there is an M82 before them.

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