Changing colors mid-print

I have a Folger Tech 2020 i3 running their stock Marlin code. I wanted to stop mid-print to change colors so on the LCD screen I selected 'Pause Print' and then manually moved the head to one side using the controls. I changed colors and flushed the head by pushing the new filament through until the color changed. I then selected 'Resume Print' thinking (hoping) that the machine would know enough to go back where it was. No such luck. It just moved back over the print but didn't go back to the height or position where it was.

Has anyone else figured this one out?

Use the front-panel controls to move the head, or issue a 'G28' or 'Home' command before hitting 'Resume Print' if you have manually moved the effector.

Stepper motor systems (like yours) control the stepper by giving it a relative direction - move forward N steps, move backwards M steps.

The motors themselves have no sense of where they are (unlike servos, where the motor is told to move to an absolute position from 0..N).

So when you moved the motor manually, the firmware had no idea that you had moved them, and thought they were still at the last printing position.

Didn't think of the 'home' command! Duh. I'll give it a try. THANKS!

I wouldn´t recommend a home command for a Prusa i3, but G28 XY
Furthermore, there is a" change filament" command in the LCD menu, which lifts and parks the head somewhere and keeps the steppers enabled, no matter how long the change takes. Then push the encoder button and print on.
-Olaf

No 'change filament' command in my reprapdiscount smart controller that I can find. Maybe there is in the other one that's available. That's a good reason to upgrade, if that option is in that one.

It appears in the controller, but is determined/enabled in the firmware . . .

- Tim

Edited 1 time(s). Last edit at 10/02/2015 08:49PM by tadawson.

It´s located in the config_adv.h section, but you can also send "M600" from Pronterface.

// Add support for experimental filament exchange support M600; requires display
#if ENABLED(ULTIPANEL)
  //#define FILAMENTCHANGEENABLE
  #if ENABLED(FILAMENTCHANGEENABLE)
    #define FILAMENTCHANGE_XPOS 3
    #define FILAMENTCHANGE_YPOS 3
    #define FILAMENTCHANGE_ZADD 10
    #define FILAMENTCHANGE_FIRSTRETRACT -2
    #define FILAMENTCHANGE_FINALRETRACT -100
  #endif
#endif

As I suspected, that's for the ultipanel, not the reprapdiscount smart panel.

I'd put the filament change in the gcode anyway, you can do this right before the next layer. When doing this mid print with the controller you may not be able to time it, starting the other color part with the wrong color.

Quote
tjnamtiw
As I suspected, that's for the ultipanel, not the reprapdiscount smart panel.

It worked for my RepRap discount smart LCD. The software for both is the same in marlin ( only difference is encoder and beeper stuff. )
-Olaf

So all you did was uncomment the ultipanel line and comment out the smart controller line? I am away from the printer for a few days so I can't try it.

No, you keep the RRD smart LCD defined.
Somewhere later in the code, all character LCDs will be treated as ultipanel or ultralcd. There are only different pinmappings, but that happens automatically.

Just define "filamentchangeenable" and see what it does in LCD menue.
-Olaf