Quad extruder

What is the opinion on being able to extrude four different materials on the same print?

I feel like the opportunity to print different objects different colors or have more tips sizes for different detail or any combinations could be useful. This of course would need to be done in an efficient manner where bed space isn't hogged and in a way where there wasn't a ton of tolerances to calibrate so prints can be repeatable.

Another key point to shoot for is an extruder that is durable by design that isn't built from plastic. I guess what I am getting after is the need for a quality multi-extruding device that makes the experience of printing more seamless and precise.

I have been working on this design that I am currently prototyping and should be printing this week with the newest version. I have been through a number of variations and after facing a list of complications I am confident I have a fully functional part.

So I am here to promote it a little and see what end users see as requirements for a good print head. I know from my experience, which has been frustrating, that constant calibrations is the biggest pain and I want something that works and works perfect 9 out of 10 times I use it, not 4 out of 10. So I am intrigued to here what this community has to say.

D3D

i have seen a few ideas like this come up over time, but i dont think you could switch materals. if they are all coming throught the same tip.

if you got it up to 5 you would be on the way to full color printing.

Plastibot (local company based on reprap) has quad extrusion that works, saw it at Maker Faire NC.

Biggest problem that hinders this is lack of hardware+firmware support....