What do people want in a multi-nozzle-hotend?
I am definitely going to tackle this. Almost certainly a bowden only affair. Should sell on http://www.e3d-online.com for £100-150. Maybe even less.
I am thinking 3 nozzles:
Perimeter.
0.25mm with a short melt zone used for creating super precise perimeters with pricier HQ nicely coloured filament (faberdashery). To give best accuracy and finish.
Infill.
0.7mm with a fast long melt zone used for infil should make printing infill very fast, and also produce very stong objects. Use cheaper filament here too.
Support.
0.Xmm for support material. Best properties for a support material nozzle as yet unknown to me. Suggestions?
The above categories are supported in slic3r for use each with a separate extruder.
Also going from 3 nozzles to 4 nozzles induces problems with levelling and planarity of the nozzles. 3 is much simpler for us, and for the end user.
Hot side would be just like my current E3Dv4 nozzle, but with stated nozzle variations. Only 1 heatsink for all 3 nozzles though - watercooling a very real possibility here. Would probably ship with a whole array of nozzles too, so if you just wanted multicolour prints from RGB 0.4mm nozzles you could do that too.
Don’t forget precise x/y positioning of the nozzles. Screwing them all into a single heatsink will go a long way for this, but you also need to consider machining tolerances with regard to hole positioning, eccentricity, perpendicularity, etc. You want to have simple offsets (say, 20 or 25mm) and be able to disassemble one of the nozzles without having to change all of your offset settings when you put it back together.
Yes. Yes. I’d buy what you’ve described in a heartbeat. What are the bonding properties of PLA and ABS, or other common filament material combinations? If you not only extrude with different size nozzles to aide printing speed / surface accuracy, maybe one could optimize material properties?
I’m not saying the materials would be mixed in the melt zone - but on top of / next to each other on the print.
WRT to supports, I’ve been playing with the slic3r 0.9.9 support feature recently and found that forcing a wall thickness below the nozzle diameter really helps to reduce the adhesion between support and perimeters while still doing the support job. In my case, using a 0.35 J head and forcing 0.15 wall thickness is providing supports that break away easily and leave little surface imperfections. I’m not sure of why this is the case but I suspect it’s a factor of the thin walls cooling more quickly, having a lower density and a lower surface area for adhesion to the part… Were you intending for the support nozzle to be used for dissolvable support material? I guess in that case a wider orifice for speed might be preferable.
Also, might it be worth considering a twin nozzle ‘dualstruder’ version for those of us with a bowden aversion? 
@Anthony_White pretty much any printed object will happily be printed upon in my experience. Probably any thermoplastic object really.
@Nick_Parker We had a lot of trouble getting PLA to stick to PVA supports, and they’re supposed to be even worse for ABS.
that’s odd, i’ve printed PLA on ABS and vice versa tons at least.
@Nick_Parker PVA, not PLA.
Oh, I haven’t tried that stuff yet. I have a sample from ultimachine, but i haven’t tried it yet.
@Whosa_whatsis
Much experience with HIPS? Seems like a better (and proven) alternative to PVA (as long as you can get hold of limonene of course).
I have tested printing with HIPS (though not on a dual-extruder machine yet, so not as support). The limonene I ordered also finally came in but I haven’t opened it yet.
I think you know what group to ask if you need any beta testers…
Another potential dual-strusion use would be nylon on PVA. Seems viable in the one test I did. I printed a thin sheet of PVA on blue tape then swapped in some taulman 618 nylon and printed a test cube. Nylon stuck to the PVA as I’d hoped, but pulled the PVA off the tape. More testing to be done once I’ve got dual extrusion capabilities.
I vote a watercooled version for sure, even if you do a non-watercooled version as well.