Saturday, September 1, 2018

Prusa Mk3 Hot Extruder Fix

This is a gcode only fix for the hot extruder motor problem afflicting the Prusa i3 MK2 and MK3 (and both s models). The extruder current setting is obviously ridiculously high. My machine has over 13,000 hours on it, and I saw no reason to suddenly up the current so high on a proven setup. Published on 7/29/19, date of post adjusted for archival purposes.

Just thinking about how bad the web forums have gotten with 3D Printing related advice fatigues my mind, so I won't be posting this there. 

Set current on Mk3/s in the custom gcode section of PrusaSlicer:

M912 E28   M910-M918 have been disabled, ref issue #1277
M907 E475

Set current on Mk2/s in the custom gcode section of PrusaSlicer:

M907 E475

Note: E475 is half-way between old firmware values and new firmware values. Tune as required

Below is some additional information about the change, when and where it was made, and there are plenty of reference links at the end of the post.

Firmware v 3.7.2 current setting, variants/1_75mm_MK3-EINSy10a-E3Dv6full.h   (Mk3s identical).

260 #define TMC2130_CURRENTS_H {16, 20, 35, 30}  // default holding currents for all axes
261 #define TMC2130_CURRENTS_R {16, 20, 35, 30}  // default running currents for all axes
262 #define TMC2130_UNLOAD_CURRENT_R 12 // lowe current for M600 to protect filament sensor 

Commit for this change:

Firmware v 3.7.2 current setting, variants/1_75mm_MK25S-RAMBo13a-E3Dv6full.h

(Same lines for all MK2, note which board you have).

274 // Motor Current setting for BIG RAMBo

#define DIGIPOT_MOTOR_CURRENT {135,135,135,135,135} // Values 0-255 (RAMBO 135 = ~0.75A, 185 = ~1A)
#define DIGIPOT_MOTOR_CURRENT_LOUD {135,135,135,135,135}

278 // Motor Current settings for RAMBo mini PWM value = MotorCurrentSetting * 255 / range

#define DEFAULT_PWM_MOTOR_CURRENT  {270, 830, 450} // {XY,Z,E}
#define DEFAULT_PWM_MOTOR_CURRENT_LOUD  {540, 830, 500} // {XY,Z,E}
#define Z_SILENT 0
#define Z_HIGH_POWER 200


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