This makes sense for rocket engines, which are mostly rigid objects with a lot of internal plumbing. 3D printing is good at objects with complex internal voids. The rigid parts can be made up as one piece, rather than welding or bolting a large number of parts together. The surface finish of the plumbing usually isn't critical, so there's no need for finish machining. It's the right tool for the job.
Here's Space-X's 3D printed engine.[1] Watch the video of the test firing. The engine is being throttled up and down, at higher and higher rates. Those guys like aggressive control strategies, as seen with the Falcon booster landing, and an engine which can keep up helps.
I hadn't heard that iconel was worse to machine than titanium, but machining titanium was a much bigger pain in the ass. You have to be very careful about your metal chips when machining titanium because they can ignite.
According to the machinability ratings [1], Inconel 700 is rated at 0.09 (less is harder) and Inconel 702 at 0.11, while most of the Titanium alloys are above 0.15. There's a single Titanium alloy family (MST) in the table that is just as hard to machine as Inconel 700.
So, you're technically correct: generally, they are on the same scale. And your argument about ignitability is certainly true.
I really wish that we could replace the phrase "3-D printing" with "additive manufacturing" when referring to metals and/or serious, low-tolerance manufacturing.
"3-D printing" should be used when referring to hobbyists making semi-useless, plastic trinkets. No disrespect to plastics or hobbyists, it's just that the phrase lost some dignity when it became a over-generalizing buzzword.
There is a whole range of machines that can be classed as 3D printers, from a simple reprap like setup all the way to SLS and DMP printers. Yes, they're all 'additive', but additive manufacturing is a concept that is a lot wider than 3D printing. For instance metal vapor deposition is also additive manufacturing and definitely not 3D printing.
One nitpick - metal vapour deposition, when done in-situ through a moveable shadow mask, certainly is 3D printing. One can dynamically "draw" out structures having controlled variable-height profiles inside the vacuum chamber during the evaporation process by altering the position (and thus speed) of the moving shadow mask.
This method is quite different from the "ordinary" metallic vapour deposition process you're referring to that uses a simple fixed-position mask, usually photoresist that is baked right onto the silicon wafer.
Eg, here is my research paper from 8 yrs ago demonstrating nanoscale-level dynamic stencil deposition using a nanopore in a suspended silicon nitride membrane shadow mask. We controlled the mask's position using a piezo actuator inside the deposition chamber during the evaporation process to 3D print nanowires and other nanostructures with programmable height profiles. Eg, we created nanoramps, and nanowires with one or more "valleys" to simulate quantum wells or metallic grains.
http://scitation.aip.org/content/aip/journal/rsi/79/7/10.106...
Arxiv link : http://arxiv.org/pdf/0802.1848.pdf
That's very neat, and yes, you're right, when doing it with a movable shadow mask it is 3D printing. Totally missed that option when I gave the examples.
This is what a colleague of my father told him at work some decades ago with microcomputers.
He felt calling those "toys" computers was some disrespectful for the real thing, the one with 125 MBytes hard drive, instead of the ridiculous amount the toys had at the time.
Of course he wanted all the company to buy an IBM mainframe(under his control of course). My father decided to buy 30 micro computers instead. It was a great decision st the end.
Those hobbyists making semi-useless, plastic trinkets are the same people that will make the serious low tolerance manufacturing in the future.
The only dignity the phrase "3D printing" ever had came from hobbyists, the ones building repraps in their basements. You're confusing hobbyists with popularity - 3D printing became a meaningless buzzword only when media and marketing got wind of it and the concept hit mainstream. Industrial technologies used in the past were not even called "3D printing" before that.
It became popular when some key patents expired, which in turn allowed dozens of companies to start producing cheap printers. Previously, the tech had been confined to a handful of manufacturers who focused on industrial/ profitable customers such as automobile prototyping.
So which 'parts' are actually printed? I cannot believe that the turbopump blades could possibly be printed additively as they would lack proper crystal structure.
Piping can be printed, but given the stresses at attachment points, I cannot see that printing pipes would save many man-hours.
The turbopump casings could certainly be printed, but not in "one piece". Someone needs them open to insert the bearings and blades. So two pieces at best ... exactly as if they had been milled rather than built additively.
So what's left? The combustion chamber and bell might do well. They have some internal voids/plumbing that probably suits such printing. But the stresses?
One cool part about this is that once they prove that current engine designs can be replicated using additive manufacturing, then totally new engine designs, different from anything possible with traditional manufacturing techniques, can be developed. It would likely mean higher thrust per unit fuel and generally more efficient systems.
Higher thrust per unit fuel isn't limited by manufacturing technique. Per-unit cost isn't really a limiting factor for rocket engine development. These things cost tens of millions of dollars and they push things worth perhaps a billion. Governments have been throwing billions, defence billions, at the technology for over a half-century.
The physics of ISP is well-understood and current engines are near what is physically possible, regardless of who/what builds the engines. 3d printing could certainly make engines more affordable and/or lighter, but it isn't going to allow an engine to be any more fuel efficient.
Anyone who builds an engine with significantly increased ISP using standard fuels (ie without going nuclear) will probably win a few nobel prizes. 3d printing is about improved manufacturing, not new physics.
This is bigger news for asteroid mining than it is for Mars (why return the ingredients to earth when you can 3D print end products at the source). But kudos to Elon for getting the world talking about Mars again.
Here's Space-X's 3D printed engine.[1] Watch the video of the test firing. The engine is being throttled up and down, at higher and higher rates. Those guys like aggressive control strategies, as seen with the Falcon booster landing, and an engine which can keep up helps.
[1] http://www.spaceflightinsider.com/organizations/space-explor...