The Kneeslider

Doers Builders and Positive People

3D Printing Functional Jet Engines

By

3D printed jet engine
3D printed jet engine

If you've been following along as new technologies advance, you already know 3D printing is heavily hyped. Just think of all of the things we'll be able to print on demand, they say, unfortunately, those things usually look ... not very functional often disappoint. Lately, though, the quality has been rising while the variety of the parts and pieces being printed is moving into new territory.

GE has been at the forefront of 3D printing and is using printed parts in medical products and even commercial jet engines, but the engineers at GE decided to take on a little side project and print an entire jet engine to see if it could be done. Of course, if you work at GE, you have all of the best toys to play with and those guys started with a jet engine being used in radio control model airplanes and improved it so it would work with additive manufacturing. They also had access to alloys not available to the hobbyist community.

Printing parts using the DMLM, or Direct Metal Laser Melting process
Printing parts using the DMLM, or Direct Metal Laser Melting process

Using a process called DMLM, or Direct Metal Laser Melting, they printed all of the parts and afterwards did a little machining and polishing before final assembly. Then they set up data acquisition systems to measure exhaust gas temperature, engine speed and thrust. The whole setup was placed in a test cell at GE Aviation. It ran quite nicely and during the test hit speeds of 33,000 rpm.

These printers and alloys may not be found in hobbyist garages, at least not yet, but it shows the potential of the technology is advancing far beyond the plastic trinket stage. As noted by GE and as we've noted before, the geometries possible with 3D printing go beyond what can be achieved with normal machining and the improved alloys make parts possible that could not have been printed before. Every time someone does something like this, it paves the way for something even more complex. This is impressive and makes you wonder what we'll see next.

Link: GE Reports

Comments

  1. We’ve been successfully (sometimes not so much) using 3D printed parts in our rocket engines, turbo pumps, and electric pumps. 3D printing and other additive processes like foil fabrication allow us to quickly iterate and test designs that are otherwise impossible to manufacture. Printing can be done in aluminum, stainless, and inconel.

    -todd

  2. I’ve wondered about the metallurgy of printed items. Are the metal’s characteristics/capabilities similar (or superior) to those of a cast or forged material of the same composition?

    • In most cases, the crystal structure will be closest to a cast item with a fast cooling time. Most cast metals have nearly isotropic crystals in a narrow range of sizes. Forged items have their crystals deformed, sometimes substantially, by the forging process.

      Early methods for 3D printing metal powders were usually variations on selective laser sintering. Sintered metal particles are only partially melted, and there often was a binder that had to be melted out in post-processing. The result was a part with some small internal voids and incomplete contact between metal crystals.

      The technique shown in the GE videos above appears to be fully melting the powder, which should result in better contact at crystal boundaries and minimal porosity. I’m curious how much re-melting of previous layers occurs, and to what degree that improves the bonding between successive layers.

  3. 3D printed prefab trash from PLA might not be useful, but forms for fabricating composite parts sure are – that’s covered in John Wanberg’s excellent book “Composite Materials: Step-by-Step Projects”. Useful metal parts have been cast by hobbyists using a “Lost PLA” process. Then there are PLA patterns made for sandcasting metal parts. Otherwise, yes, the whole reprap thing would bore me to tears.

    Check out what can be done with 3D sand printing…

    I can’t help but wonder if the future isn’t printed metals, but rather printed (Or somehow otherwise grown) materials that are vastly stronger, tougher, stiffer, lighter, heat resistant, and most likely, non metallic.

    • Very interesting, especially this quote:

      Compared with a traditionally cast part, a printed valve body has superior strength, ductility, and fracture resistance, with a lower variability in materials properties. The MOV body was printed in less than two days, compared with a typical castings cycle measured in months.

      So it seems their reasoning is practical, going beyond the question of “can we do it?” As Pushrod asked above, I’ve also wondered about the printed metal’s characteristics and SpaceX feels it’s superior. To me, that’s surprising and fascinating.

      • “The MOV body was printed in less than two days, compared with a typical castings cycle measured in months.”

        Just to clarify this point: they mean that from CAD drawing to finished product it took a couple of days, while setting up the same part to be cast would have required the making of ceramic cores, machining of the die for the wax, setting up the process, trials, etc…
        However once the casting process is defined, several products can be obtained in hours.
        One interesting development in casting that involves a faster approach including additive manufacturing is 3D-printing ceramic cores and shells, so there’s no need for wax and machined die.

        • I think 3D printing is still finding its proper role in the manufacturing process, as you mention and as Bob notes above, printing cores for casting or making the molds for composites looks promising, rapid prototypes of new products, obviously and in some cases directly printing finished parts in specific materials like the alloys used in this jet engine may work, but as the hype dies down, 3D printing has to travel the long hard road to useful applications. It’s getting there, but there’s still a lot of work to do.

  7. Commercially viable manufacturing thru metal-printing is already here. Airbus and Boeing both rely on it as an exclusive means of manufacture for a list of components in their A350 and 787, respectively. Now it has to descend from aerospace to the consumer level before its disruptive effect upon society will be felt.

    I work with printed prototype parts and limited “bridge manufacturing” using same. Typically I use ABS plastic, but I have a vendor that can supply a truly exotic range of printable metals at truly exotic prices.