Dual Nozzle, Dual Stepper, Servo Actuated Nozzle - Marlin Settings?

Good Day,

I have a printer, with two nozzles, and two steppers (one for each filiment), Nothing unusual so far.

The second nozzle is servo-actuated, i.e it slides vertically to be either above or below the primary nozzle. (thus also requires a Z_HOTEND_OFFSET).

I.e when switching to the second Nozzle, the Z axis should raise by Z_HOTEND_OFFSET, and then the servo should move the second nozzle so it is now below the (fixed) first nozzle.

Note: this is very similar in operation to a "SWITCHING_EXTRUDER" in Marlin (see video below), with the sole difference being a SWITCHING_EXTRUDER has a single stepper motor to drive the two filiments.

Example of a SWITCHING_EXTRUDER: [hackaday.com]


I am seeking how to configure and/or code Marlin for it to work on this configuration. I don't expect it to be too complicated, most of the work appears to be in working out *where* to code. Any pointers appreciated.


Summary: trying to get a printer working, dual nozzle, dual filiment steppers (bowden), and second nozzle is servo-actuated to below/above height of first nozzle. What settings for Marlin?


Thanks.

Edited 1 time(s). Last edit at 03/01/2017 12:06PM by Swift.

Solved it. For anyone else looking to do this:

Problem: How to configure Marlin for a: dual-extruder, extruder E1 height toggled by servo, X / Y / Z Offsets required, individual stepper motor for each extruder/filament.

In this configuration: E0 is fixed in space, with E1 parked above. When E1 is in use, it is lowered by the servo to be below the position of E0 - hence X & Z Offset is required, and Y is good to have for fine tuning.


This configuration could be considered a subset of Marlins "Switching_Extruder". The only difference being we have a seperate stepper for each extruder, instead of a single shared stepper. So we add a new #define SWITCHING_EXTRUDER_WITH_MULTIPLE_STEPPERS


The following solution is not ideal or refined, but it works well, including here in case it helps someone (or I get better guidance) until I have a more permanent solution - such as a recode of Marlin to support a servo (and Z Offset) for every extruder.

Notes: "...." means "include the existing code from Marlin, unchanged"
1)
in Configuration.h, alter the following as follows:

#define EXTRUDERS 2
#define SWITCHING_EXTRUDER
#if ENABLED(SWITCHING_EXTRUDER)  
  ...
  #define SWITCHING_EXTRUDER_WITH_MULTIPLE_STEPPERS
#endif

2)
At the bottom of ConditionalsLCD.h, add the following:

    #if ENABLED(SWITCHING_EXTRUDER_WITH_MULTIPLE_STEPPERS)
    #undef HOTENDS
    #undef E_STEPPERS
    #undef E_MANUAL
    #undef TOOL_E_INDEX
    #define HOTENDS      EXTRUDERS
    #define E_STEPPERS   EXTRUDERS
    #define E_MANUAL     EXTRUDERS
    #define TOOL_E_INDEX current_block->active_extruder
  #endif
#endif //CONDITIONALS_LCD_H

3)
In Indirection.h, find the following block of code:

#if ENABLED(SWITCHING_EXTRUDER)
  #define E_STEP_WRITE(v) E0_STEP_WRITE(v)
  #define NORM_E_DIR() E0_DIR_WRITE(current_block->active_extruder ?  INVERT_E0_DIR : !INVERT_E0_DIR)
  #define  REV_E_DIR() E0_DIR_WRITE(current_block->active_extruder ? !INVERT_E0_DIR :  INVERT_E0_DIR)

and change the #if statement to:

#if ENABLED(SWITCHING_EXTRUDER) && (!ENABLED(SWITCHING_EXTRUDER_WITH_MULTIPLE_STEPPERS))

Thats all. You should now be able to tune your X/Y/Z offset between E0 and E1 with M218
e.g

M218 T1 X20 Z-2

will set the offset of E1 as shown

And then you can test the Nozzle servo activation/offset/toolchange with just "T1" and "T0"

Awesome!
What happens during tool change? Does the planner wait for the servo?

Yep it does, in the existing Marline code, there is forced half second delay.

A hardcoded magic number (delay(500)) on line 6792 of Marlin_main.cpp

I'll post the relevent section from the marlin code below:

void tool_change(const uint8_t tmp_extruder, const float fr_mm_m/*=0.0*/, bool no_move/*=false*/) {
          <...code cut here....>
          #if ENABLED(SWITCHING_EXTRUDER)

            // <0 if the new nozzle is higher, >0 if lower. A bigger raise when lower.
            float z_diff = hotend_offset[Z_AXIS][active_extruder] - hotend_offset[Z_AXIS][tmp_extruder],
                  z_raise = 0.3 + (z_diff > 0.0 ? z_diff : 0.0);

            // Always raise by some amount
            planner.buffer_line(
              current_position[X_AXIS],
              current_position[Y_AXIS],
              current_position[Z_AXIS] + z_raise,
              current_position[E_AXIS],
              planner.max_feedrate_mm_s[Z_AXIS],
              active_extruder
            );
            stepper.synchronize();

            move_extruder_servo(active_extruder);
            delay(500);

            // Move back down, if needed
            if (z_raise != z_diff) {
              planner.buffer_line(
                current_position[X_AXIS],
                current_position[Y_AXIS],
                current_position[Z_AXIS] + z_diff,
                current_position[E_AXIS],
                planner.max_feedrate_mm_s[Z_AXIS],
                active_extruder
              );
              stepper.synchronize();
            }
          #endif

Edited 1 time(s). Last edit at 03/02/2017 02:47PM by Swift.

Thanks a lot mate.
You helped me really a lot with that Code. I had the exactly same problem, but I would have never be able to solve it

Hi Everyone
Thank you very much for the detailed information on switching extruder. Im looking for a version to configure dual extruder for my project. If someone can help me with the actual version of Marlin that can do this job.
Thanks in advance.
Avishek.

I am sure Marlin would do a great job.

Personally, I ended up switching from Marlin to Klipper for my dual extrusion needs: [github.com]

Hi Swift,

Would you be able to provide the enire code (package) that i can upload and test?
Tried to work with change/modifications from marlin 1.1...getting several errors.
I'm using Arduini 2560+Ramps 1.3 +A4988 stepper drivers.

Would be very helpful if you can provide the wroking code.

Thank you very much.

The" Switching Extruder" can use two extruder motors and single motor also ok.