UM2(+) Pause for Filament Change with M600 - What position for printhead?

[reibuehl 41]

When pausing a print for a filament change via the front button on the UM2, the head automatically moves to a park position in the front left corner and lowers the build plate. However if  the pause for filament change is initiated via the M600 command in G-code, the head stays over the part and makes it impossible to extrude the filament during the filament change.

I use the @TinkerGnome firmware. In the firmware source it seems M600 can take optional parameters for the head parking position:

// M600 - Pause for filament change X[pos] Y[pos] Z[relative lift] E[initial retract] L[later retract distance for removal]

But what values should be used to get a similar behaviour like a pause from the front panel knob? And do I have to add a manual move back over the part or will this be done automatically? I use Prusa Slicer 2.5 to generate the g-code.

[reibuehl 41]

Digging further in the @tinkergnome Firmware source, I found this in UltiLCD2_menu_print.cpp that seems to be responsible for the move:

 

void lcd_print_pause()
{
    if (!card.pause())
    {
        card.pauseSDPrint();

        // move z up according to the current height - but minimum to z=70mm (above the gantry height)
        uint16_t zdiff = 0;
        if (current_position[Z_AXIS] < 70)
            zdiff = max(70 - floor(current_position[Z_AXIS]), 20);
        else if (current_position[Z_AXIS] < max_pos[Z_AXIS] - 60)
        {
            zdiff = 20;
        }
        else if (current_position[Z_AXIS] < max_pos[Z_AXIS] - 30)
        {
            zdiff = 2;
        }

        char buffer[32] = {0};
        #if (EXTRUDERS > 1)
            uint16_t x = max(5, int(min_pos[X_AXIS]) + 5 + extruder_offset[X_AXIS][active_extruder]);
        #else
            uint8_t x = max(int(min_pos[X_AXIS]), 0) + 5;
        #endif
        uint8_t y = max(int(min_pos[Y_AXIS]), 0) + 5;

        sprintf_P(buffer, PSTR("M601 X%u Y%u Z%u L%u"), x, y, zdiff, uint8_t(end_of_print_retraction));
        process_command(buffer, false);
        primed = false;
    }
}

 

I don't fully understand the code though. Does this mean that the head moves to absolute X=5 and Y=5 and relative Z = +70?

 

Would it be possible to execute this function instead of whatever M600 does?

 

Edited December 30, 2022 by reibuehl

[tinkergnome 926]

On 12/30/2022 at 10:56 AM, reibuehl said:

I don't fully understand the code though. Does this mean that the head moves to absolute X=5 and Y=5 and relative Z = +70?

 

Would it be possible to execute this function instead of whatever M600 does?

 

Besides the fact that M600 is ignored by the UM2 🙂... you're right.

That's what i used with Octoprint:

 

;M601 Pause in UltiLCD2, X[pos] Y[pos] Z[relative lift] L[additional retract distance in mm]
M601 Z10 X10 Y200 L8

 

You have to consider the maximum z-height (there are no limit checks if you use the gcode).

The extra retract distance may play a role if you manually change the material during the pause.

 

All parameters are optional (as usual).