Ben Reytblat has some useful (and I assume accurate, though I can’t vouch) info in comments at this previous post today:

The vomit comet ride was to see that it worked in microgravity. The environmental testing is for safety.

There are a couple of challenges for Filament Deposition-style printers (FDM) in microgravity:

– Outgassing: the printer works by melting the filament inside the extruder, so there WILL be some outgassing. The question is how much and of what gases. And that depends heavily on what material they use and in what thermal regimes. If they want strongest and toughest results, they’ll use ABS, which stinks to high heaven when printed. If they want least environmental impact, they’ll use PLA, which is easy on the nose and eye and produces parts that are strong but somewhat more brittle than ABS. Nylon, Polycarbonate, HIPS and PEI have their own tradeoffs. The environmental testing will help sort that out.

– Layer adhesion: the printer works by depositing one layer at a time on top of each other. The parabolic flights demonstrated that this challenge can be solved – that’s a really important result. I would be interested in hearing more about the materials tested and see the pictures of the results. For example, if they used ABS, were there delamination problems that are common in 1g? What about warping? How was the build platform adhesion?

– Thermal environment: FDM printers require tight control of the thermal environment during the process. There are several sources of heat (extrdurs, linear motion control motors, control electronics), and several areas that need constant steady temperature control (extruder, electronics, frame). Prints may take a long time (it’s not unusual for a large complex print to take 24 hours or longer), so heat buildup is a significant issue in the absense of convection cooling. I’ve been following MiS with great interest since their original announcement, and I haven’t seen any discussion of how they plan to address this issue yet. But I would not be at all surprised if this is a major challenge and requires solutions that are not common in the 1g environment.

– Scaling – Power consumption and weight: most desktop printers today can only produce small parts: .25 – .5 cubic foot is common – and because of this don’t comsume much power and are light. It’s not clear to me, though, that such a small build volume will be worth the effort of all this testing and then hauling the machine up and teaching the astros to maintain what is likely to be a temperamental and finicky machine. When we scaled our machine to 1 cu. ft., we discovered the hard way that the square-cube law really does work against you 🙂 both in terms of power needed to run the machine fast enough to make large format prints practical and in terms of raw weight of structures needed to make the machine robust enough. Our big machine (8 cu. ft. build volume) is even more challenging. I’d love to hear how MiS is addressing these issues as well.

– Impact on the station: an FDM printer has a couple of parts that are moving all over the place (the extruder heads and some parts of the frame) at a fairly good clip (100-200 mm/sec). An extruder might mass 1kg. Is that enough momentum to disturb the micro-g environment for the other users of the station? I don’t know, but I haven’t yet heard anyone do the numbers.

Net-net: there are a few of challenges in this, but none of them look to be insurmountable. And all of them need both analytical and experimental answers – which is exactly what NASA is doing with MiS’s help. Props and best wishes to them both.

Indeed.