4 ms·

To further explain my point but also support the root comment. Aluminium/steel/titanium airframe parts are usualy machined or forged. It is not possible to rep

To further explain my point but also support the root comment. Aluminium/steel/titanium airframe parts are usualy machined or forged. It is not possible to replace them with 3D printed parts just yet. But! All of jet engine turbine blades are cast, not machined. Those parts can be safely 3D printed, as various metal sintering/remelting methods produce similar or better structural quality. Same goes for those magnesium castings used in aircraft landing gear - can be replaced with 3D printed ones. Parts that only under hydrostatic load like fuel nozzles can be 3D printed. Fatigue is not an issue there. Parts that do not experience significant structural loads, but high thermal loads (combustors) can be also 3D printed. I believe that's a better answer to the topmost comment.

systemvoltage 6y ago
I also worked on Turbine blades. Specifically did studies on trailing edge dump and pressure side bleeding holes, the air is bled from 7-10th compressor stage for cooling. 3D printing would massively benefit it because more than structural loads, the part is at its thermal limits and structurally it becomes weak as a result. If they can just cool it by 200 degrees, it would be groundbreaking. The trailing edge of the blade is by far the most critical - thicker and aerodynamic efficiency will take a toll; make it razor sharp and it will just melt away.
- d_silin 6y ago
  I think industry is moving to CMC materials for first stage blades, because nickel superalloys hit the limit of performance. Not sure if those can be 3D printed reliably.
  - systemvoltage 6y ago
    That's insane. During my tenure in the industry, we had ceramic coatings on the first stage. We were hitting some 1250 C temperatures with these things and they were barely holding up. There was a huge push for efficiency in that era and we would shorten the life of the blades in favor of efficiency, there would be regular inspections and coatings were such a pain in the ass.
  - yodelshady 6y ago
    A lecturer and later colleague of mine did CMC blade research as a postgraduate. Taught some of it to me as an undergraduate, alas I forget most of it. He's retiring now. Not sure what to make of that. I do hope the idea finally has its day.
- throwaway_pdp09 6y ago
  "make [the trailing edge of the blade] razor sharp and it will just melt away" Why would this happen on the trailing edge?
  - systemvoltage 6y ago
    Not enough cooling. A turbine blade has a web of channels and internal cavity for cooling. Here is a good diagram: https://www.semanticscholar.org/paper/Numerical-study-of-trailing-edge-cooling-in-a-gas-Thongsanit-Mookum/b31a28df1144f133cc0eeed19a84cbb0b8f2aae6/figure/0 https://www.semanticscholar.org/paper/Numerical-study-of-tra...
yodelshady 6y ago
> Those parts can be safely 3D printed, as various metal sintering/remelting methods produce similar or better structural quality. Wait, really? If that's true, colour me impressed. I would have put getting the creep resistance, fracture resistance, and tolerances necessary for turbine blades from 3D printing as just about impossible. I'm conflicted by agreeing with systemvoltage's point, that it's overhyped, with knowing it is empirically wrong. Still, turbine blades? Wow.
dTal 6y ago
I would like to add that additive manufacturing is still in its infancy, and that there are structures that pay large strength dividends which are impossible to manufacture any other way, such as 3-dimensional honeycombs, which haven't made their way into standard engineering practice yet. But there may come a point where the available design space is so much better that it's worth sacrificing some strength in the material itself.

systemvoltage 6y ago

I also worked on Turbine blades. Specifically did studies on trailing edge dump and pressure side bleeding holes, the air is bled from 7-10th compressor stage for cooling. 3D printing would massively benefit it because more than structural loads, the part is at its thermal limits and structurally it becomes weak as a result. If they can just cool it by 200 degrees, it would be groundbreaking. The trailing edge of the blade is by far the most critical - thicker and aerodynamic efficiency will take a toll; make it razor sharp and it will just melt away.

d_silin 6y ago
I think industry is moving to CMC materials for first stage blades, because nickel superalloys hit the limit of performance. Not sure if those can be 3D printed reliably.
- systemvoltage 6y ago
  That's insane. During my tenure in the industry, we had ceramic coatings on the first stage. We were hitting some 1250 C temperatures with these things and they were barely holding up. There was a huge push for efficiency in that era and we would shorten the life of the blades in favor of efficiency, there would be regular inspections and coatings were such a pain in the ass.
- yodelshady 6y ago
  A lecturer and later colleague of mine did CMC blade research as a postgraduate. Taught some of it to me as an undergraduate, alas I forget most of it. He's retiring now. Not sure what to make of that. I do hope the idea finally has its day.
throwaway_pdp09 6y ago
"make [the trailing edge of the blade] razor sharp and it will just melt away" Why would this happen on the trailing edge?
- systemvoltage 6y ago
  Not enough cooling. A turbine blade has a web of channels and internal cavity for cooling. Here is a good diagram: https://www.semanticscholar.org/paper/Numerical-study-of-trailing-edge-cooling-in-a-gas-Thongsanit-Mookum/b31a28df1144f133cc0eeed19a84cbb0b8f2aae6/figure/0 https://www.semanticscholar.org/paper/Numerical-study-of-tra...

yodelshady 6y ago

> Those parts can be safely 3D printed, as various metal sintering/remelting methods produce similar or better structural quality. Wait, really? If that's true, colour me impressed. I would have put getting the creep resistance, fracture resistance, and tolerances necessary for turbine blades from 3D printing as just about impossible. I'm conflicted by agreeing with systemvoltage's point, that it's overhyped, with knowing it is empirically wrong. Still, turbine blades? Wow.

dTal 6y ago

I would like to add that additive manufacturing is still in its infancy, and that there are structures that pay large strength dividends which are impossible to manufacture any other way, such as 3-dimensional honeycombs, which haven't made their way into standard engineering practice yet. But there may come a point where the available design space is so much better that it's worth sacrificing some strength in the material itself.