The next frontier of desktop 3D printing is multi-material and multi-color prints. Right now, you can buy a dual toolhead for a Lulzbot, and dual toolheads from other companies exist, although they are a bit rare. In the next few years, we’re going to see a lot of printers able to print dissolvable supports and full-color 3D printers.
Printing in more than one color is almost here, but that doesn’t mean we’re on the cusp of a complete revolution. Multi-material printing is lagging a little bit behind; you’ll be able to print two colors of PLA next year, but printing an object in PLA and ABS is going to be a bit tricky. Printing something in PLA and nylon will be very hard. Color mixing, likewise, will be tricky. We can do it, the tools are getting there, but think of this year as a preview of what we’ll be doing in five years.
The i3 Quad
Last week, Prusa rolled out a 4-extruder upgrade to the latest iteration of the i3 Mk 2. This weekend at Maker Faire, the world got its first glimpse of this machine in action, printing out multicolor fish.
Here’s how Prusa’s 4-color mod works. A small, SSR-based drive is wired into the controller board, allowing four different stepper drivers to be controlled independently, but not simultaneously. These steppers feed filament through a Bowden tube to a four-way Y adapter just above the hotend. To change colors, the printer backs filament out of the Y-adapter very quickly, pushes the new color in, and squirts the remainder of the previous color of filament out onto a waste tower.
When this mod was first released, there were a few questions about how wasteful this waste tower would be. It’s actually very optimized, with photographic evidence:
The ‘waste tower’ has three ‘slots’ where color changes happen. The printer only wastes filament when it needs to, and the slicer is as smart as it needs to be. There’s very little waste here.
To me, this is how we’re going to do multi-color 3D printing in the near future. Stepper motors are cheap, boards that switch motors on and off are cheap. Hotends are expensive, and dual hotends mean leveling and offset problems. That said, this setup has limitations: there is no color mixing, and printing with two materials of different temperatures (PLA and nylon, for example) is going to be hard or impossible. It’s still awesome.
On the other end of the spectrum is ORD Solutions RoVa4D printer. Your desktop inkjet printer uses cyan, magenta, yellow, and black ink to print any color. The RoVa uses cyan, magenta, yellow, black, and white filament to print objects in any color. There are two more extruders on this printer designed for flexible and support material. It’s a printer with seven extruders feeding into one watercooled mixing hotend. It is a triumph of 3D printer engineering.
Right now, slicing multicolor prints is hard. ORD has a tool that allows you to take a standard .STL file and ‘paint’ an object so it can be printed on their printer. That’s amazing, but it’s closed-source. Software devs interested in 3D printing, there’s a project for you.
As far as print quality goes, the RoVa is in a weird place. Right now, nobody is doing mixing color 3D printers. Having that capability at all deserves a thumbs up. However, there are color artifacts in all the prints. Looking at the printed Einstein bust, I can easily see a streak of pink on the layers where the lips were printed. If I were awarding points, I don’t know if I could knock points off for this. It works, but it is the 3D printed version of a color bitmap print made on a dot matrix Image Writer printer. The quality will go up, but I don’t know if it’s going to happen with this machine.
This is pure speculation, but I don’t know how ORD Solutions can afford to sell this printer. Right now, the seven extruder version, with a watercooled hotend, sells for $3750 USD, with delivery in May, 2017. The general consensus is that it’s too inexpensive.
Dual Multi Extrusion
3D printing is slowly moving towards dual and multi extrusion. Color is a big reason, but not the best. LulzBot’s FlexyDually extruder makes the argument for combining flexible and rigid materials for some metamaterial weirdness. Dissolvable filaments allow any dual-extruder printer to create any object without regard to geometry.
Dissolvable filament has been around for a while, from Makerbot’s water-soluble PVA filament to dissolving ABS in acetone to limonene-soluble HIPS. These filaments, with the possible exception of HIPS, never really caught on as a dissolvable support material. This might be changing. At MRRF last March, E3D announced they were working on Scaffold, a water-soluable support material that has the same base material as the stuff gel caps are made out of. To get rid of Scaffold support material, just put your part in the dishwasher. It’s coming, and soon we’ll have a real use for dual and multi extrusion.
We’re slowly creeping towards a compact, desktop device that’s able to print any object in any orientation, in any color. That’s the goal we’re all working towards, anyway. We’re not there yet, but it’s getting there, and we’re really looking forward to where this tech goes.