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I am a consulting electrical engineer (consulting EE) and this is part two in my series on 3D printing. Today I will be discussing the possibility of 3D printing making its way into space, and why I believe it is possible based on my experience with 3D printing.
3D Printer Headed to Space
3D printing seems to be everywhere these days from people’s living rooms to Office Depot, and now it seems space is the next stop. According to NASA they are planning on sending a 3D printer to the International Space Station (ISS). They have already done some preliminary experiments on the “vomit comet” airplane, which gave enough success to let them move into the next phase of experiments. Missions 41/42 and 43/44 will be starting in September 2014 and proceeding into 2015.
3D Printing Process
I believe that there is no reason that 3D printing would not work in zero-G. The process does not depend on gravity-Raw material (filament) is mechanically pushed into a heated chamber which terminates in a nozzle. It is then extruded in a thin bead and the extruder is moved to lay down the pattern on each layer. Each successive layer melts into the preceding one and thus sticks where it is placed.
The first layer is the tricky part. It has to adhere to a bed and this is a universal problem for all 3D printers to solve. The extruded material has to stick to the bed just enough to hold it in place both during the printing process and also while it cools. The adhesion has to resist the tendency of the material to shrink as it cools. Not enough “stick” and the first layer shrinks unevenly on its long axis and curls away from the bed. Too much “stick” and the unfinished piece cannot be removed from the bed without damage to the piece or bed.
Lots of experimentation is going on to try and achieve a reliable, repeatable bed surface. There are many hobby solutions and some serious materials science is also happening to find just the right coating for the perfect stick/release surface.
For more information about a kick starter-funded group that is making some inroads into the solving the problem see the URL:
Benefits of 3D Printing in Space
However it is achieved, the first layer is extruded onto a bed surface and adheres temporarily, without bonding. There is a ponteintal advantage to printing in a zero-G environment because the issue of bridging large gaps with molten filament is not a problem.
The traditional issue with gaps is that the extruded material is hanging unsupported as the nozzle travels over a gap. Imagine a rope suspended over a chasm. Gravitational forces may cause the viscous material to droop. The resultant droop in the hot filament material comes about from its viscous state when it leaves the extruder nozzle. It solidifies as it cools but by then the damage is done and you no longer have straight lines of material over gaps. In space, this problem goes away, at least in theory. Perhaps it will be replaced by another problem as the extruder material has some inertia when it leaves the nozzle. That is something we can learn when the printer gets up there.