<p>That is perfectly viable these days in Marlin firmware, there are options for setting this up using the configuration file, e.g.:</p>
<pre><code>// :[0, 1, 2, 3, 4, 5, 6, 7, 8]
#define EXTRUDERS 1
...
...
...
// A dual extruder that uses a single stepper motor
//#define SWITCHING_EXTRUDER
#if ENABLED(SWITCHING_EXTRUDER)
  #define SWITCHING_EXTRUDER_SERVO_NR 0
  #define SWITCHING_EXTRUDER_SERVO_ANGLES { 0, 90 } // Angles for E0, E1[, E2, E3]
  #if EXTRUDERS &gt; 3
    #define SWITCHING_EXTRUDER_E23_SERVO_NR 1
  #endif
#endif
</code></pre>

CC BY-SA 4.0
2022-01-17T06:49:28.373Z
2022-01-17T06:49:28.373Z
0scar
<p>You'll need a custom firmware.</p>
<p>Yur custom firmware will have to react to the &quot;Change extruder&quot; command differently than a normal firmware: instead of just swapping to a different extruder, you'll need to perform some operations to alter the gearing (possibly a solenoid?), and possibly include some kind of &quot;break&quot; to make sure that the filament is not slipping back without the extruder attached. However, there already is a setup that pretty much does this: the Prusa MMU2 uses something similar. The MMU does use a Bowden setup, but you could use Bowden and direct drive in combination, especially if both motors run in sync.</p>

CC BY-SA 4.0
2020-12-22T23:34:48.720Z
I think you misunderstood me. I would still have two extruder gears that stay with the filament. I would just have a gear shifting system that would connect the stepper to either of the extruders. That way no filament cutting is involved. All it needs is a servo or something to move the stepper's gear to one or the other extruders. Marlin should be able to handle that.
Dakkaron
CC BY-SA 4.0
2020-12-23T01:47:08.523Z
@Dakkaron Solenoid. You want to trigger a solenoid. But in either case: you need to make your own firmware, and you can look into how the MMU2 gets away with doing a "tool swap" without using more than one extruder motor.
Trish
CC BY-SA 4.0
2020-12-23T23:24:15.250Z
Marlin has built-in support for servos etc. to be triggered kn tool change. I am  programmer, so I am not worried about the software side. It's more the hardware side that I am worried about. The solution sounds simple, but I have never seen it implemented, so I am wondering what I am missing.
Dakkaron
CC BY-SA 4.0
2020-12-23T23:26:09.417Z
@Dakkaron hm... how about start with a sketch? one or two hotends?
Trish
CC BY-SA 4.0
2020-12-22T13:05:53.700Z
2020-12-23T01:48:45.240Z
2020-12-23T01:48:45.240Z
Trish
<p>I am planning to upgrade my printer with a second extruder. Since my printer is a Tronxy X8 it's frame is not exactly vibration resistant, so I'd like to keep the print head weight down. At the same time I really don't want a Bowden setup.</p>
<p>I came up with the idea of making a dual extruder driven only by a single stepper with a gear shift setup that switches the stepper between the two extruders.</p>
<p>The idea seems simple, but googleing didn't turn up anything else.</p>
<p>Is there anything I am missing that would would make such a setup unfeasible?</p>
<p>Did anyone else build something like that?</p>
<p>A clarification, because it came up in an answer:</p>
<p>What I imagine is this:</p>
<p>One stepper motor is connected to a gear shift system that is either connected to Extruder A or Extruder B, depending on the gear. When shifting it just connects the stepper motor to the other extruder. So it is still similar to a regular direct driven dual extruder system, except that it only uses a single stepper to drive two extruders, each connected to it's own hotend.</p>

<extruder><dual-nozzle><multi-material><drive-gear>
Dual extruder with gear shifting
Dakkaron
# Dual extruder with gear shifting

(Asked by: username_0 on 2020-12-22)

I am planning to upgrade my printer with a second extruder. Since my printer is a Tronxy X8 it's frame is not exactly vibration resistant, so I'd like to keep the print head weight down. At the same time I really don't want a Bowden setup.

I came up with the idea of making a dual extruder driven only by a single stepper with a gear shift setup that switches the stepper between the two extruders.

The idea seems simple, but googleing didn't turn up anything else.

Is there anything I am missing that would would make such a setup unfeasible?

Did anyone else build something like that?

A clarification, because it came up in an answer:

What I imagine is this:

One stepper motor is connected to a gear shift system that is either connected to Extruder A or Extruder B, depending on the gear. When shifting it just connects the stepper motor to the other extruder. So it is still similar to a regular direct driven dual extruder system, except that it only uses a single stepper to drive two extruders, each connected to it's own hotend.

**Tags:** extruder, dual-nozzle, multi-material, drive-gear

---

## 2 answers

### Answer by username_1 on 2022-01-17. Score: 1

That is perfectly viable these days in Marlin firmware, there are options for setting this up using the configuration file, e.g.:
// :[0, 1, 2, 3, 4, 5, 6, 7, 8]
#define EXTRUDERS 1
...
...
...
// A dual extruder that uses a single stepper motor
//#define SWITCHING_EXTRUDER
#if ENABLED(SWITCHING_EXTRUDER)
  #define SWITCHING_EXTRUDER_SERVO_NR 0
  #define SWITCHING_EXTRUDER_SERVO_ANGLES { 0, 90 } // Angles for E0, E1[, E2, E3]
  #if EXTRUDERS > 3
    #define SWITCHING_EXTRUDER_E23_SERVO_NR 1
  #endif
#endif


---

### Answer by username_2 on 2020-12-22. Score: 0

You'll need a custom firmware.

Yur custom firmware will have to react to the "Change extruder" command differently than a normal firmware: instead of just swapping to a different extruder, you'll need to perform some operations to alter the gearing (possibly a solenoid?), and possibly include some kind of "break" to make sure that the filament is not slipping back without the extruder attached. However, there already is a setup that pretty much does this: the Prusa MMU2 uses something similar. The MMU does use a Bowden setup, but you could use Bowden and direct drive in combination, especially if both motors run in sync.

> **Comments:**
> **username_0**: I think you misunderstood me. I would still have two extruder gears that stay with the filament. I would just have a gear shifting system that would connect the stepper to either of the extruders. That way no filament cutting is involved. All it needs is a servo or something to move the stepper's gear to one or the other extruders. Marlin should be able to handle that.  
> **username_2**: @Dakkaron Solenoid. You want to trigger a solenoid. But in either case: you need to make your own firmware, and you can look into how the MMU2 gets away with doing a "tool swap" without using more than one extruder motor.  
> **username_0**: Marlin has built-in support for servos etc. to be triggered kn tool change. I am  programmer, so I am not worried about the software side. It's more the hardware side that I am worried about. The solution sounds simple, but I have never seen it implemented, so I am wondering what I am missing.  
> **username_2**: @Dakkaron hm... how about start with a sketch? one or two hotends?  

---

