Comment by MayeulC
9 hours ago
Hmm, I am not in the 3D printer space anymore, but I am surprised they went with alternating layer per layer, as that severely limits resolution. It's probably the simplest way to achieve reproducible results, but I can think of a few other ways:
* the simplest is just mixing filaments, like one mixes paint. The article doesn't spell out the reason it doesn't work, I am curious as to why.
* together with alternating layers, colors could be alternated in the same layer. Some purging may be necessary, but I think you could either: accept some mixing (compute its impact to compensate) / take into account the volume in the nozzle (extrusion "latency") / discard the unwanted part in the infill (at the cost of less smooth edges)
Of course, the hard work with any approach, including their current work, is calibration, as the article highlights. I wonder if off-the-shelf monitor calibration sensors could help with measuring the filament you have at hand.
This is a software solution designed to work with existing multi colour printers, so you can’t “just mix” them as this would need additional hardware
>the simplest is just mixing filaments, like one mixes paint. The article doesn't spell out the reason it doesn't work, I am curious as to why.
This requires you to control both filaments independently directly at the extruder. Dual direct drive for a single nozzle sounds like an engineering nightmare. The extruder head is going to be huge.
There is also the obvious problem of how to stirr the filament. Printing temperatures aren't hot enough to turn the plastic liquid, they just make it soft enough to drip out the nozzle. This means you can't just feed the filaments at continuos rates, you will have to use a PWM scheme where you extrude the first filament and then the second filament in extremely small discrete increments. That switching will give you the necessary agitation without building a throwaway nozzle that can't be cleaned after a clog.
All of this sounds like it would take at least a year for a well equipped research department to figure out. It's definitely not the simplest solution.
EDIT: https://www.reddit.com/r/ender3v2/comments/ssuw3i/my_crazy_p...
Just the hot end of this extruder costs $70 alone. This is definitely not going to be cheap to do.
Minuteman on youtube has a four extruder single nozzle setup for speed printing. He occasionally uses multiple colors, and they basically don't mix in the nozzle. The cross section of an extrusion looks like a pie chart
You would need special nozzle geometry that encourages mixing, and likely much higher temperatures. And any such mixing geometry will trap some filament. Switching from dark to light colors might require purging with meters of light filament to get all traces of black filament out
Imagine trying to clean that out if it jams.
> the simplest is just mixing filaments, like one mixes paint. The article doesn't spell out the reason it doesn't work, I am curious as to why.
Plastic flow is laminar, where colour mixing requires turbulence. If you make a turbulent nozzle, it's basically impossible to print reliably with it (the pressure used to push filament out of the nozzle is mostly absorbed/redirect into turbulence).