RAMPS and Multiple Extruders

I have two questions that I need to answer before I select the electronics for my current RepRap build:

1. Is RAMPS the right choice for a machine with 2 extruders? (This is my current design--two extruders, two hotends.)

2. If I want to expand to 3 or 4 extruders, can RAMPS be modified or is there an add-on board that will allow me to do this? Or in that case do I need to switch to another controller board altogether?

I've used RAMPS on my MendelMax 1.5 for over a year and a half and have been very happy with it, so many many many thanks to everyone that helped make RAMPS what it is!

Thanks in advance for any responses.

Best regards,
Daniel

Ramps as currently designed will support 1 or 2 extruders/hot ends. To support 2, you have to use the MOSFET output that you would normally use for a fan, so you need an external circuit in order to drive a fan. I've done exactly this, and the circuit is very simple/easy to build.

To go beyond 2 extruders, you'd need external circuitry, and although there might be some out there, I don't know of any. You would need additional circuitry for both the hot end (a mosfer circuit similar to the fan circuit mentioned above) and a stepper driver for the extruder. You'd also have to consider if an additional heater/stepper would "fit" on the 5 amp rail, or if you'd need a different power source.

You also would need to check the normal firmware to see if there is support in there for the extra steppers and heat servo loops.

I believe marlin can be easily configured for up to 3 extruders. I'm not sure about the others.

Thanks everyone. I see that RepRapPro.com has a tri-color Mendel. Looks like they use a second board altogether though.

For now two extruders will do, and I'm familiar with RAMPS so I think I will stick with that on my new machine.

Daniel

I don't think there is currently a plug and play solution, but there are a number of options emerging for multiple extruders. Both RADDS and RAMPS-FD support 3 extruders, RAMPS-FD should work with a Mega but that has not been tested yet. Decapede supports 4 extruders I think.

RepRapPro have an expansion board for their new Duet controller that provides 4 extruders, which might work with a RAMPS, I think it is just a question of wiring. RAMPS has enough pins to support 4 additional extruders, if you are not using them for LCD controller. I am developing a general purpose extension board which uses less pins, but is a bit more work in the firmware. [reprap.org]

Firmware is also expanding, Repetier will have support for 5 extruders.

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