I have a TAZ 6 (TAZ 4 and TAZ 5 may be a bit different). On my Dual Extruder V2 I just noticed there is no X-axis right-side stop switch. The purple wires for it in the single extruder v2 as well as the switch are not there in the Dual extruder.
So is there a reason for not having it as a safety? If the problem is a physical space problem (although it doesn’t look like one), I might either try to parallel the wires from the controller and place the switch on the stationary right side, or put a magnetic (reed) switch on the Dual head and wire the pins in there.
On the other hand, if the firmware for the Dual Extruder doesn’t use it (lack of memory space?), maybe it needs to be coded in there.
No the switch is on the standard Taz 6 tool head, and not on the dual one. I do not know if they just figure it will not need it or what. But I am not sure I have ever hit the X Max limit switch anyway.
I hit the X-axis end once with the flexy dually. It causes lots of nice noises. I agree that Lulzbot should have put a limit switch on the dual extruders. If you add one, please let us know how it goes, I’ve been thinking about doing the same.
Based upon my testing of the single extruder V2 switch and examination of the RAMBo board schematic, I can tell you that the sensor pin is held at ground (switch is Normally closed) until when the endstop is hit at which switch opens.
The signal is internally pulled up on the RAMBo board, so this means the default read value for the sensor is 0 until it hits the endstop at which point it is a 1 on the single extruder.
However, on the dual extruder, the read value is always a 1, so if it would be used as a endstop signal, it would always be read that way. That implies that the firmware for dual extruder must ignore this signal. The only possibility of potential use this way is that the firmware reads the initial value after a home, and if 0, uses the sensor, otherwise it ignores it. But this seemed like an odd way. I would have expected the switch to close when it hits the endstop, so that the default was the other way.
So I tested the dual extruder firmware and hooked a normally-open switch to the x endstop limit sensing wires. Sure enough, it moved to the right under a gcode command (G1 X250) until I closed the switch. This indicates that the firmware’s sensing is opposite on the dual extruder from the single extruder (very strange, and a bit unexpected).
The dual extruder, IMHO, is the correct way to do it. Unless you either
Wanted a way to detect a dual extruder from a single extruder (which may be the case, but I have not seen the homing take it into account this readable difference, which it could - the homing misses the home switch when using dual extruder with a single extruder firmware), or
Have a fail-safe mode that if the sensor wire breaks (but this would not allow for an extruder that did not have an end-stop switch, or at least jumpered sensor wire in the extruder connecting wire).
So, the takeaway is
The X axis right endstop limit switch is supported in the firmware for the Dual Extruder V2 (and also for the FlexyDually V2)
An end stop switch should be normally open until it hits the right side for the Dual Extruder V2 (and also for the FlexyDually V2)
The switch can be hooked up to the same pins as the switch of the single extruder V2 (2 purple wires on mine)
Finally a holder for a switch on the Dual Extruder could be made between the screw on the metal plate and the screws of the right-side extruder fan where the single extruder’s X axis stop switch makes contact. The 2 fan screws on the right side are M3 x 20mm, and can be additional 10mm maximum longer for a switch holder. The screw on the metal plate towards the back is an M3 x 25mm screw and can be an additional 25mm longer for the switch holder.