Mini dual extruder

I just got my mini a couple days ago, and I’m realizing fast that for what I want to print I really need to be able to use a support material…

Is there any plans to add an offal dual extruder upgrade for the mini?
Is there any good way to mod it myself?

Take a look at You might find something in there you could use to mod one yourself. The tricky part with a mini would be adding the second extruder run. I’m not sure if the mini control board does or does not have the necessary connection. It might but you would want to check. If it does, its certanly possible. You would have a fair amount of electrical cable running and firmware modification to get it to work though. It would be much easier to get working on a TAZ.

yeah the TAZ would be an easier way to go but the size is just so… massively unnecessary and hard to deal with for me.
The only thing I would get from it would be a massive headache because of it’s size and a vastly higher bill. To tell the truth I think if I had to deal with the size I would probably go with the FlashForge Pro since it comes standard dual and doesn’t need any upgrade kits to do it.

Though really if the DEVs have any realistic plans for an official dual for the mini (So I could avoid the firmware aspect) I would rather stay with the Lulzbot camp.

The hardware aspect I’m sure I could handle given my background the firmware modding… is pretty far out of my comfort zone though.

The modifications would be fairly significant. On the electronics side, you’d have to swap out the Mini Rambo with a full-sized Rambo (or similar) board to be able to control multiple extruders, and that board is larger so you’d have to move the ferrite cores for the motor wiring out of the way. The mounting holes would probably be different, but some adhesive PCB standoffs should work for this.

Adding the wiring for the additional extruder/fan(s)/temperature sensor wouldn’t be too difficult. I’m not sure whether the Taz dual-extruder head would mount on the Mini’s X-axis carrier… I need to look at the schematics.

And then of course there is the issue of Firmware. I’m guessing you could fairly easily modify the Taz 5 firmware.

I’ve been thinking about doing all this myself, but with total cost of an upgrade approaching $700, I’ve been holding off for now.

Yeah the more I got looking into it the more I realized the mini will just never bee a dual extruding machine… By the time you mod it enough to be one it would hardly be the same machine. XD

I have really enjoyed it as a single filament machine though so I’ll definitely be keeping it.
I’ve pretty much decided that I’ll keep the Mini as a pure play around / learning machine than later when the next wave of printers hit pick up one built specifically for dual extruding. I like Lulzbot so here’s hopping they make a native dual printer sometime in the next year!

Don’t give up yet.

I just got the mini for Xmas and it is a great little machine.
The controller board is missing the outputs for the second extruder but perhaps there is a way to use the GPIO’s to control a second mini-rambo board in “slave” mode. Or ideally a second board that is dedicated to a second extruder, which could be made cheaper than a rambo since it needs less stepper drives and mosfets.

This would then be a plug and play option. Then it is just another hot end and extruder (I would go with a bowden type, since you do not have much room)

Hopefully Aleph is already working on this…if not, get to it. you will be selling lots of these minis.

of course, switching the controller to the full rambo may be a faster and easier solution, but the add on board could theoretically be cheaper.

Just brainstorming…

What kinds of pins are available on the Mini control board? Do we have serial/I2C/SPI available? If it’s just digital GPIO, how many?

To run an extruder, you need to be able to control the heater, heat block fan, part cooling fan, and stepper. The heat block fan could be connected to the heater, so 1 PWM line for the part fan, one digital pin for the heater and its fan, and one digital for the stepper driver. It would probably be fine to run the part fan from the existing fan line, saving one pin if needed. Forgot about the thermistor, so we need an analog input as well.

If I’m right about the requirements, the PCB to add on wouldn’t cost much. It’s a couple FETs and a stepper driver. The existing controller could probably do the work. I suspect the code needed is already available, just disabled via #ifdef.

This also assumes the power supply is up to the task. I have no idea what the current requirements are for the heater and such or what the power supply in the mini is rated for. A quick Google says the Hexagon is 12V 30W, I think Lulz uses a 24V setup. So if the wattage is the same, <1.5A, adding a little in for misc losses. Not bad.

Physically, one would need to design a dual mount that fits the mini setup and is rather compact. It needs to be reasonably light too, or deflection on the rails can become a problem. Most of the weight is in the steppers, so I’m not sure how much could be done about it.

It might be tricky to handle the auto-leveling with dual nozzles as well. Probe twice for dual prints, one for each nozzle?

Going to a bowden style for the support material nozzle is the only way I see to physically fit it into the mini. you mount the motor and extruder to the frame and have a tube going down to the hot end (like most deltas do).

I do not know what GPIO’s the mini has, I have not taken mine apart yet. I know there are version 1.0 and 1.3 boards, and the 1.0 do not have the header for the IO’s soldered in, but I think they are still there.

as for the fans…you could just parallel those. Since only one extruder is extruding at a time, it should not matter if the fans are running on the inactive extruder. Or just use a relay to switch the signals between the 2 sets of fans. In fact I was thinking of using a relay to switch the connection to the stepper motors too, that way you do not need a separate drive circuit.

all you would actually need is a microcontroller to handle the heating of the nozzle and switch several relays when the command from the main RAMBO board is sent to change extruders. It would have to send temperature signals to the RAMBO board so it knows when it is up to temperature so some sort of serial connection would be best. Maybe a separate power supply would be needed for this add-on extruder controller too (as you mentioned). I was just searching for extruder controllers and there are a few out there that might be able to be modified to work.

Ideally this add-on extruder controller would have built in drives for the fan motors and a stepper motor drive (it would simplify connections), but it is not really necessary with the use of relays to switch between the 2. there is no need to control both motors at the same time after all.

you could theoretically also use a relay to switch between the thermistor signal too, but that would probably cause some firmware modification nightmares.

auto leveling would only be needed on one nozzle. the height of the add-on nozzle would be physically adjustable to match the height of the probed nozzle. but there would have to be some firmware tweaks to offset the leveling matrix when the program switches between nozzles.

Just throwing this on the table. If there are no outputs available one thing I have done in the past on a horizontal CNC milling machine is put some micro switches at the ends of the table travel for the X and Y axes. Position the Y axis for the switch you wanted to hit and use the X axis to hit it.
Similar to what 1013 wrote you could use a latching relay to switch the step signal from one controller to the other, the direction signal could be just connected to both controllers and not need to be switched.