17 thoughts on “Metal 3-D Printing”

  1. I also like the implications for space exploitation. The processes for forming conventional metal inputs (casting, forging, rolling, etc.) involve heavy machinery. But with 3D printing, the feedstock is a metal powder. It should be possible to make metal powders with less massive equipment, and on a smaller scale.

          1. One of the solutions to the powder/gravity problem is to avoid it. the present plastic 3d printer on the ISS is using plastic thread as the raw material. Metal wire can be made very thin, and the accuracy of shapes is not too badly affected. On spools, it takes up no more volume than powders. The “Spider-fab” concepts at Tethers Unlimited are a more immediate demonstration of how this can work on a larger scale of trusses, and will probably use 3d-printed parts made in orbit as spacing and compression members once the technology gets moving.

            In addition, there is now being worked down here on Earth what is called “Cold Spray”, as 3d printing. It was invented in the USSR during the 1970s without the 3d printing aspect. It uses fast gas sprays to accelerate metal powders to high enough velocities that when the powder particles impact the substrate, they self-forge as flattened deposits on that surface, and begin building up the part needed. The US Army is currently using this to repair magnesium housings in UH-60 helicopters rather successfully.

            In Space, we won’t use gas for acceleration. Instead, we will use electrostatic force in the vacuum so conveniently provided. Like an old TV display tube, electrostatic forces will move and focus the ionized particles, placing them rather well, and do it outside in vacuum. The costs of using pressurized interior volume are thus avoided, and the size of components built can be far larger, perhaps including entire spaceship hulls. This technology should leave little excess powder compared to “Cold Spray” and other techniques, as well as being adaptable in freefall conditions. It also has the advantage that the particle velocities can be higher and particle flow denser, without inducing problems from shock waves in a supersonic flowing gas.

  2. The usual trend for enabling technologies is that we overestimate the short-term impact (because of switching costs) and underestimate the long-term impact (because we imagine it will be used to do the same things better rather than new things).

    1. At least for the near term, traditional fabrication has huge advantages in cost for large scale production of items that work well within their limits. The immediate advantages of 3D printing are complex shapes and short runs.

      1. In aviation, every kilogram you can save on a component is a kilogram your aircraft doesn’t have to carry for millions of miles through its life, and a kilogram more air cargo it can carry over those millions of miles. A small reduction in weight could easily justify using a more expensive production method.

      2. When you’re talking about aircraft, a large production run is in the thousands. There are fewer than 9,000 Boeing 737s in all variants, the most popular series of airliners. On the other end of the market, there are fewer than 200 Airbus A380s and fewer than 400 Boeing 787s.

  4. Ceramic 3-D printing is even more impressive. I wonder how they handle shrinkage? Many metal parts are improved by replacing them with ceramics.

  5. How about putting the powdered metal in a sealed container? If you are mining the metal on the Moon, you put iron in one container, aluminium in another, and so on. You then ship the metal to LEO.

    1. It isn’t transporting it that is the problem. Using powdered metal in freefall is going to be tricky. When SpaceX 3D prints their Super Draco thrusters, they absolutely rely on gravity: a layer of powder goes down, then a laser sinters in the appropriate spots, then another layer of powder. That technique is impossible without gravity.

  6. I’m glad to see the aircraft side of aerospace is starting to catch up; 3D printing offers a lot of advantages, especially on the design side.

    I did find it odd, though, that the article didn’t mention that some fairly large and complex rocket engines were designed to be 3D printed, are 3D printed, and have been for years. (SuperDraco).

  7. There are still issues I have seen over the last few years with using laser-scintered metal for flight parts.

    1.  At present they don’t have good geometric tolerancing, they come out of the printer coarse.  Still need to do a machined pass to finish.

    2.  Mechanical properties are poor.  Strength is lower than equivalent cast parts.

    3.  It takes work to establish strength allowables with statistical certainty.  Need to develop at least B-basis allowables. At present people are printing a test coupon with each batch of parts, and testing the coupon.

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