NASA Announces New Trials For In-Space Laser Welding

November 13, 2024 by Maya Posch 20 Comments

In-space manufacturing is a big challenge, even with many of the same manufacturing methods being available as on the ground. These methods include rivets, bolts, but also welding, the latter of which was first attempted fifty years ago by Soviet cosmonauts. In-space welding is the subject of a recently announced NASA collaboration. The main aspects to investigate are the effects of reduced gravity and varying amounts of atmosphere on welds.

The Soviets took the lead in space welding when they first performed the feat during the Soyuz-6 mission in 1969. NASA conducted their own welding experiments aboard Skylab in 1973, and in 1984, the first (and last) welds were made in open space during an EVA on the Salyut-7 mission. This time around, NASA wants to investigate fiber laser-based welding, as laid out in these presentation slides. The first set of tests during parabolic flight maneuvers were performed in August of 2024 already, with further testing in space to follow.

Back in 1996 NASA collaborated with the E.O. Paton Welding Institute in Kyiv, Ukraine, on in-space welding as part of the ISWE project which would have been tested on the Mir space station, but manifesting issues ended up killing this project. Most recently ESA has tested in-space welding using the same electron-beam welding (EBW) approach used by the 1969 Soyuz-6 experiment. Electron beam welding has the advantage of providing great control over the weld in a high-vacuum environment such as found in space.

So why use laser beam welding (LBW) rather than EBW? EBW obviously doesn’t work too well when there is some level of atmosphere, is more limited with materials and has as only major advantage that it uses less power than LBW. As these LBW trials move to space, they may offer new ways to create structure and habitats not only in space, but also on the lunar and Martian surface.

Featured image: comparing laser beam welding with electron beam welding in space. (Source: E. Choi et al., OSU, NASA)

The Metal 3D Printing Hack Chat Brings The Heat

March 11, 2022 by Tom Nardi 8 Comments

At this point, it’s safe to say the novelty of desktop 3D printing has worn off. The community has largely come to terms with the limitations of extruded plastics, and while we still vehemently believe that it’s a transformative technology, we’ll admit there aren’t too many applications where a $200 USD printer squirting out PLA is truly the best tool for the job.

But rather than looking at today’s consumer 3D printer market as the end of the line, what if it’s just the beginning? With the problems of slicing, motion control, and extrusion more or less solved when it comes to machines that print in plastic, is it finally time to turn our attention to the unique problems inherent in building affordable metal printers? Agustin Cruz certainly thinks so, which is why he took to the Hack Chat this week to talk about his personal vision for an open source 3D printer that can turn powdered metals into solid objects by way of a carefully controlled electron beam.

To be clear, Agustin isn’t suggesting you toss out your Creality anytime soon. Metal 3D printing will always be a niche within a niche, but for applications where even advanced engineering plastics like PEI and PEEK simply won’t do, he argues the community needs to have a cheap and accessible option. Especially for developing and low income countries where traditional manufacturing may be difficult. The machine he’s been working on wouldn’t be outside the capabilities of an individual to build and operate, but at least for right now the primary target is hospitals, colleges, and small companies.

The Chat was full of technical questions about Agustin’s design, and he wasn’t shy about tackling them. Some wondered why he decided to sinter the metal powder with an electron gun when solid-state lasers are cheap, easily available, and relatively straightforward to work with. But while the laser might seem like the easier solution on the surface, Agustin points out that using a magnetically focused electron beam gives his printer some unique capabilities.

For example, he can easily defocus the beam and pass it over the entire build plate to pre-heat the powder. The steerable beam doesn’t require mirrors either, which not only reduces the weight and complexity of the machine, but in theory should allow for faster print speeds. The beam can be moved in the X/Y dimensions with an accuracy of 0.01 mm, and while the beam diameter is currently a respectable 0.5 mm, Agustin says he’s working on bringing that down to 0.1 mm for high detail work. The temperature at the focal point of the beam is between 1,400 and 1,500 °C, which he notes is not only hot enough to melt the powdered metal, but can also weld stainless steel.

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The March Toward A DIY Metal 3D Printer

July 26, 2019 by Sharon Lin 20 Comments

[Hyna] has spent seven years working with electron microscopes and five years with 3D printers. Now the goal is to combine expertise from both realms into a metal 3D printer based on electron-beam melting (EBM). The concept is something of an all-in-one device that combines traits of an electron beam welder, an FDM 3D printer, and an electron microscope. While under high vacuum, an electron beam will be used to fuse metal (either a wire or a powder) to build up objects layer by layer. That end goal is still in the future, but [Hyna] has made significant progress on the vacuum chamber and the high voltage system.

The device is built around a structure made of 80/20 extruded aluminum framing. The main platform showcases an electron gun, encased within a glass jar that is further encased within a metal mesh to prevent the glass from spreading too far in the event of an implosion.

Vacuum chamber enclosed in mesh (new gasket shown)

Mold for making silicone gasket

The design of the home-brewed high-voltage power supply involves an isolation transformer (designed to 60kV), using a half-bridge topology to prevent high leakage inductance. The transformer is connected to a buck converter for filament heating and a step up. The mains of the system are also connected to a voltage converter, which can be current-fed or voltage-fed to operate as either an electron beam welder or scanning electron microscope (SEM). During operation, the power supply connects to a 24V input and delivers the beam through a Wehnelt cylinder, an electrode opposite an anode that focuses and controls the electron beam. The entire system is currently being driven by an FPGA and STM32.

The vacuum enclosure itself is quite far along. [Hyna] milled a board with two outputs for a solid state relay (SSR) to a 230V pre-vacuum pump and a 230V pre-vacuum pump valve, two outputs for vent valves, and inputs from a Piranni gauge and a Cold Cathode Gauge, as well as a port for a TMP controller. After demoing the project at Maker Faire Prague, [Hyna] went back and milled a mold for a silicone gasket, a better vacuum seal for the electron beam.

While we’ve heard a lot about different metal 3D printing methods, this is the first time we’ve seen an EBM project outside of industry. And this may be the first to attempt to combine three separate uses for an HV electron beam into the same build.