NASA test-fires 3D printed rocket parts: low cost, high power innovation

Propulsion engineers focus on R&D and pushing new tech into private industry.

Read the whole story

 

[Smeghead]

Boskone[/url]"qn9ifyp]I wonder how much small-scale testing NASA does. I mean, there's bound to be things you can learn about an injector design without actually attaching it to a rocket and firing it to the tune of a gazillion gallons of fuel per second.

I'd imagine that in their terms, a rocket that generates 20,000lbs of thrust is a small-scale test.

 

[SBD]

crash13[/url]":3pgg953z]

charleski[/url]":3pgg953z]NASA also devloped a different 3D-printing method called EBF3. It would be interesting to know what the trade-offs are between the two processes.

I'll preface this reply with the fact that I'm one of the two developers of the process at NASA Langley Research Center and have been working with it for the last 12 years.

The basic diferences between the two processes are that DMLS is done in a powder bed, while EBF3 uses a wire feedstock. There are several implications to this:
1) The powder bed size (and associated inert gas shielding chamber) puts a limit on part size. While it is possible to build a larger powder bed, you start to run in to diminishing returns - the bed needs to be filled (lots of expensive powder) and leveled and each layer needs to be a precise thickness.
2) EBF3 is done in a vacuum chamber with a wire feedstock. All of the feedstock is incorporated in the final build. Our current laboratory system has a vacuum chamber 7 feet by 9 feet by 9 feet with a build volume of 4 feet by 4 feet by 6 feet. Pumpdown time to working vacuum is ~25 minutes.
3) Deposition rates are hugely different: DMLS is several cubic inches per hour; the one production application for EBF3 is 150 cubic inches per hour.

Any aerospace components produced by any of the metal additive manufacturing processes will require heat treatment. Our experience with aluminum and titanium alloys is that the tensile, fatigue and fracture properties are comparable to wrought properties.

Is any of your titanium fatigue data public? I've heard the claim over and over again, and tested it over and over again, always with significant knockdown in high cycle fatigue. I suppose definitions and baseline targets differ from application to application.

Another advantage of working in a vacuum is that porosity created can sometimes be healed with subsequent thermomechanical processes - that's a big deal for a lot of applications.

To boot, if anybody wants to see the kind of system he's talking about work in titanium, Sciaky posts some videos (complete with sweet marketing graphcis) of their process: http://www.youtube.com/watch?v=A10XEZvkgbY

Could anyone elaborate on rough comparative costs of additive manufacturing using DMLS versus machining?

This is very alloy and part-specific. Aluminums cut like butter and pretty much as fast as you can run the machine is as fast as you can cut it. High strength steels or nickel-based super alloys that you would find in gnarly, hot-section rocketry parts would be orders of magnitude more expensive to machine, especially in one-off quantities. The machine time is expensive for high-stiffness CNC machines that cut hard metals, the cutters are expensive, and you remove material relatively slowly. Without divulging too much, by the time you shape, machine and process a part in titanium for example, you could very easily be talking about 150x-200x $/lbs for an installable part versus the ingot you started with, assuming you're producing that part in reasonable quantity.

 

[jthill]

Nice job arranging the article so

could potentially decrease its build costs by orders of magnitude

is the bottom line.

 

[crash13]

SBD[/url]":1sq9b6c0]

crash13[/url]":1sq9b6c0]

charleski[/url]":1sq9b6c0]NASA also devloped a different 3D-printing method called EBF3. It would be interesting to know what the trade-offs are between the two processes.

I'll preface this reply with the fact that I'm one of the two developers of the process at NASA Langley Research Center and have been working with it for the last 12 years.

The basic diferences between the two processes are that DMLS is done in a powder bed, while EBF3 uses a wire feedstock. There are several implications to this:
1) The powder bed size (and associated inert gas shielding chamber) puts a limit on part size. While it is possible to build a larger powder bed, you start to run in to diminishing returns - the bed needs to be filled (lots of expensive powder) and leveled and each layer needs to be a precise thickness.
2) EBF3 is done in a vacuum chamber with a wire feedstock. All of the feedstock is incorporated in the final build. Our current laboratory system has a vacuum chamber 7 feet by 9 feet by 9 feet with a build volume of 4 feet by 4 feet by 6 feet. Pumpdown time to working vacuum is ~25 minutes.
3) Deposition rates are hugely different: DMLS is several cubic inches per hour; the one production application for EBF3 is 150 cubic inches per hour.

Any aerospace components produced by any of the metal additive manufacturing processes will require heat treatment. Our experience with aluminum and titanium alloys is that the tensile, fatigue and fracture properties are comparable to wrought properties.

Is any of your titanium fatigue data public? I've heard the claim over and over again, and tested it over and over again, always with significant knockdown in high cycle fatigue. I suppose definitions and baseline targets differ from application to application.

Another advantage of working in a vacuum is that porosity created can sometimes be healed with subsequent thermomechanical processes - that's a big deal for a lot of applications.

To boot, if anybody wants to see the kind of system he's talking about work in titanium, Sciaky posts some videos (complete with sweet marketing graphcis) of their process: http://www.youtube.com/watch?v=A10XEZvkgbY

Could anyone elaborate on rough comparative costs of additive manufacturing using DMLS versus machining?

This is very alloy and part-specific. Aluminums cut like butter and pretty much as fast as you can run the machine is as fast as you can cut it. High strength steels or nickel-based super alloys that you would find in gnarly, hot-section rocketry parts would be orders of magnitude more expensive to machine, especially in one-off quantities. The machine time is expensive for high-stiffness CNC machines that cut hard metals, the cutters are expensive, and you remove material relatively slowly. Without divulging too much, by the time you shape, machine and process a part in titanium for example, you could very easily be talking about 150x-200x $/lbs for an installable part versus the ingot you started with, assuming you're producing that part in reasonable quantity.

The fatigue work (da/dN, along with tensile and fracture data) was presented at Aeromat a few years ago. Unfortunately, due to a recent incident with a Chinese national, our documents are no longer publicly accessible. I could, however, email you the presentation.

BTW, working with wire feedstock we typically don't see an issue with porosity.

As you alluded to, machining of aerospace components is one of the real drivers for these technologies. I recently came across an expendable Ti-6-4 component that started as a 7500 lb billet and ended as a 250 lb part - over 2000 hours of milling time plus other processing.

 

[lamarcheb]

I think it's pretty funny that you're writing about printed rockets while experiencing the gaseous effects of Solyent Green.

 

[SBD]

The fatigue work (da/dN, along with tensile and fracture data) was presented at Aeromat a few years ago. Unfortunately, due to a recent incident with a Chinese national, our documents are no longer publicly accessible. I could, however, email you the presentation.

Would you, please? My email is in the profile, just take out the spam trap. I'm sure I was at that Aeromat, but as I'm sure you're aware, you never get to see all the talks to plan on

 

[rdamiani]

Dilbert[/url]":3gly2p7f]

carldjennings[/url]":3gly2p7f]Can they 3D print a 3D printer? Change the scale, make a 3D printer a mile high, and print out whole rockets!

Someday that will be the norm. And kids will laugh at our factories with robots soldering and welding and riveting and bolting subassemblies into larger products, just like we laugh at someone carving a wagon wheel out of a piece of timber. Manufacture as we understand it today will probably be a hobby or possibly an art form, just like woodcarving today.

But that day is still in the future.

Edit: delta V = Ve * ln (m0 / m1) BITCHES! I will fly a rover to Duna in honor of this tonight.

The very, very, very far future. One that contains nanobots. An FTL drive seems more likely.

 

[taswyn]

A huge thank you to everyone who weighed in with strong knowledge on costs, it helped a great deal in arriving at a stronger picture of the comparative cost network and the related constraints/considerations. I realized that machining probably wouldn't be cheap, and would increase in cost based on the shape(s) being machined, along with the inability to machine certain shapes in a single piece, but I'd overlooked the issue of harder metal types.

 

[stevenkan]

crash13[/url]":1ayyshg7]I recently came across an expendable Ti-6-4 component that started as a 7500 lb billet and ended as a 250 lb part - over 2000 hours of milling time plus other processing.

Mickey would be proud.