Feb 8, 2016 | By Benedict
The Raspberry Pi Foundation has released the 3D printing files for its Astro Pi enclosure, as used by British astronaut Tim Peake aboard the International Space Station. The cases sent to space cost £3,000 ($4,300) to produce, but makers can print their own replicas for a fraction of that price.
Back in December, astronaut Tim Peake became the sixth UK-born astronaut to visit the International Space Station. As part of his six-month mission, the astronaut brought two specially augmented Raspberry Pis, called “Astro Pis”, each running experimental Python programs. These programs were written by school-age students, and will have their results sent back to Earth to be published online.
Understandably, the European Space Agency (ESA) and NASA uphold extremely stringent safety requirements for small payloads aboard the ISS. These high standards required the Astro Pi flight unit—a highly reinforced aluminum case for the miniature computer—to be put through a rigorous qualification process, evaluated by a panel of experts at ESA ESTEC in the Netherlands.
When details of this super-strong case were released in May 2015, many Pi users wanted to get their hands on one. However, only eight of the £3,000 units were made. Each was milled from a solid block of aerospace-grade aluminum using a five-axis CNC mill, heat-blasted, anodized with a special coating, and touched up before having the standard Raspberry Pi hardware placed within. Once the markings and logos had been laser-etched onto the case, the devices were ready for space.
Due to the costliness and extreme precision required to produce each Astro Pi, the Raspberry Pi Foundation made it abundantly clear that the cases would not be made available for the general consumer to buy. However, true to its word, the foundation has instead released the object files of the component so that schools with 3D printers can print their own iterations of the cosmic case.
The Raspberry Pi team initially tried to print the original CAD files on a regular 3D printer, but ran into difficulties, with the design requiring an unrealistic amount of scaffolding and rafting. Seeing this problem, the designers modified the CAD model into a simpler and more budget-printer-friendly design. “The first change we agreed on was to slice off the heat sink on the base, so that it could be printed in the opposite orientation,” explained David Honess, Education Resource Engineer at the Raspberry Pi Foundation.
“That way it would have nothing overhanging to cause support structure to be built between the pins,” he continued. “We then sliced off the top of the lid so that it could be printed with the clean side facing upwards, meaning the stringy side would face down. That was a lot nicer looking. So with the lid and heat sink sliced off, it meant the two original middle bits were left as discrete parts.
“We also removed the pillars between the USB and Ethernet ports because these snapped off easily. Finally, for convenience, we changed the corner bolt enclosures from a sunken captive screw to a straight-through M4 nut-and-bolt design. You can use epoxy adhesive (or similar) to join the heat sink to the base and the lid to the middle.”
The Astro Pi enclosure has been divided into four STL files to minimize scaffolding and rafting, and to decrease printing time. The files have been released under the Creative Commons license, so tinkerers are free to modify the design as they see fit. An educational resource written by the Pi team explains how to fit the hardware inside the case. Planet Earth is blue and there’s nothing Pi can’t do!
Posted in 3D Printing Application
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