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The title says it all. 

Juaquin Anderson's profile photoSamuel Smith's profile photoRichard Hoefer's profile photoDavid Fuchs's profile photo
It does say it all, but I'll add this excerpt anyway, because I haven't understood what the elemental composition is of 3D-printed objects.

"... Laser sintering is capable of producing all kinds of metal parts, including components made from aerospace-grade titanium. One of the attractions of printing parts is that it saves material. Instead of machining components from solid billets of metal, in which much of it may be cut away, only the material that is needed to shape the part is used. Printed parts can also be made lighter than forged parts, which promises fuel savings. Many manufacturers already use 3D printing to make prototypes of parts, because it is cheaper and more flexible than tooling up to produce just one or two items. But the technology is now good enough for it to be used to make production items too..."

That's damn impressive. Still, I wonder about the reality and the perception of strength of parts 3D-printed by the purchasing public, whether that's a company, or a consumer... If I'm buying a car that's been made from 3D-printed parts, I know I am going to have a perception that there's no way those parts are going to be as durable and as reliable as "real parts" ... There's going to have to be a huge amount of proving to the public about all of this... If our jet is grounded in Denver due to unexpected maintenance, and word travels "I heard they are printing a 3D-part and using it instead of a regular fan-blade." "What?? I am getting off this plane. Let me out of here now"...

I'm simply saying that whether the things manufactured by 3D printing are, in reality, of equal quality or better than conventionally manufactured parts isn't going to matter as much as how people perceive their strength and durability to be. In my opinion...
Its unclear if They are printing compressor or turbine blades, but this reminds me of one of the stories from the 90's of GE application of genetic algorithms to pushing limits of jet engine performance.

Conventional jet compressor and turbine design relies on the engineers understanding of reliable designs.
usually genetic algorithms are applied to design problems where modeling can predict performance. A population of design parameters is produced at every generation and the fittest survive. the next generation of offspring is created with combinations and mutations. Eventually the design evolves to an optimal one by evolution. This sometimes presents surprises as it works even when the design problem isn't well understood.
This can improve on the engineers first guess but is limited by the accuracy of the modeling. GE sought to improve performance further with a massive process of actually building a population of jet compressors with cnc one off manufacturing of compressor parts and testing each compressor to keep the fittest of the population for the next generation. Supposedly this allowed ge to produce the best jet engines in the world.

This was part of GE previous work and this article reminds me of that. I wonder if They are making compressor blades.
That's very interesting +Juaquin Anderson. If I follow you, this would be a very thrifty way to make one-offs which could then be tested and logged, while an optimization algorithm is run to attempt to produce the best possible part properties for a compressor blade.. Is that what you are saying, more or less? That's fascinating to me as part of the R&D process, where I would see this whole 3D-printing capability transforming production in the same way robotics has changed part assembly.

I wish, +David Fuchs, that your article posting attracted more mechanical engineer's eyes, as well as supply chain logistics managers, because I was hoping several people would have come back to educate me, especially if it was "you don't even know what you're talking about" (and I don't). I was really hoping for subject matter experts to argue the pros and cons, of which I imagine there are thousands.
No problem, David!  I just had curiosity, that's all. I didn't mean my reply in that way. I meant those in your circle, not you.
I wonder what is the mechanical properties of the materials of 3d printed parts... also what's the surface finish like? and what's the tolerances on thickness of parts. Does the process have artifacts, like ailiasing in digital graphics. That sort of thing could present a problem in thin high stress thin parts with vibration.

Also I wonder if parts need heat treating or are They hardened as They form.

Are the quality of materials inferior to quality alloys, or better as is the case with some powdered metals. the unusual way the metal is formed may allow creation of unusual alloys as is the case in powdered metal.

If the metal is hardened as it grows it could have qualities superior to conventional metals that depend on heat treating. With heat treating, heat penetrates differently over the shape of the part, making strength non-uniform over the part.

Anyhow it would be interesting to know these things..
+Juaquin Anderson Truth be told I do not know enough about laser sintering to tell you the mechanical qualities of the material. I really do like where this technology is going at this point. 
Probably few people know. Probably why GE bought this company that developed the tech.
I am not the one to convene such a thing but... it would be great if there is a mechanical engineering Community that would do a Hangout on Air to take up just these kinds of questions. That's what we have G+ for ! :)
As I understand it, FDM (plastic) parts have ~90% the strength of injection molded parts. Laser sintering may be similar, but the deficiencies in material strength can certainly be worked around by design, especially as the 3D printing process can create parts that can be made no other way. I'd love to see a breakdown of which parts  are still made traditionally and which are being replaced by printing.
So, +Samuel Smith, though I know you did not say this precisely, it sounds to me like you have faith in this evolving manufacturing methodology that it will be able to produce parts, let's say for cars and Boeing jets, as quick examples that will be equal to or stronger than those parts made by other methods used currently. Is that right? ...

I'm not an engineer... But I think in an interdisciplinary way. If the answer is yes, then do you think this 3D-printing process will still only be used for rapid prototyping and after-market spare parts?.. or do you think factories will employ them in the actual production line of hundreds of thousands of automobiles, or by the various suppliers of component parts? I'm trying to get a handle on whether this becomes economical for mass production, or perhaps just way economical for prototyping and replacement parts.  Any opinion would help!
I do have quite a bit of faith in this technology, but don't think it will replace mass production. Its weakness is the slow build time, several hours for even moderately sized pieces. The main strengths of additive manufacturing are infinite customization, and certain geometries that cannot be created otherwise. It will be used in niche consumer markets, and to shorten development cycles from weeks or months to just hours or days. (Likely other uses I haven't thought of as well. Did you see the TED video of the boy who got a printed kidney?)
One use for it could be to shrink certain inventories. Instead of having a warehouse full of parts, some of which are only called for rarely, you could have a supply of plastic, a printer, and an electronic catalog. Have you ever eaten at Sub Zero? They are an ice cream parlor with no stock of ice cream. They have cream, flavorings, and LN2. Customers order whichever flavors they want in any combination and the ice cream is made on the spot! This is my vision of 3D printing; build orders on the spot, factories and distribution centers not required.
+Samuel Smith That's fascinating - the boy getting a 3d-printed kidney! (Didn't see that TED talk; will look for it). ... No I have never eaten at subzero, but that is fascinating as well, and smart. On-demand creation sounds like it would have many possibilities. Your example of auto parts is perfect. ... Extending that thought further, I imagine as the technology progresses and costs reduce to a level where consumers can afford some basic versions, perhaps certain gadget parts replacements, maybe for a vacuum cleaner or refrigerator shelf part, could be printed at home based on some QR code searched for online... Or perhaps Radio Shacks could include parts-on-demand for all sorts of product lines, where they just process the 3d output.. and consumers have contacted brands obtaining part-codes, which get fed to city distribution points like radio shacks. I don't know, I am just thinking based on what you're saying.
But back to the kidney, that's a huge category in itself, human body parts that have organic functions. Wow, how in the world they pulled that off, I have got to see. ... but I do know my mom had knee replacement surgery, and later a shoulder joint replacement, and I would imagine the medical applications here are bountiful.
Thanks for sharing your thoughts!
+Samuel Smith I think the speeds will get faster, and they will become main stream for manufacturing in less than 15 years. Most people picture one print head. What will happen is hundreds of print heads working at the same time. 

Eventually it will match mold, pour, mill, finish. in one step, and it will match the speed of a CNC. 
So +David Fuchs, is this a total transformation in manufacturing? I'm trying to see on what order of magnitude this is a whole re-engineering of process, tools, out-with-the-old devices, in with all new systems, and how this plays out in a national and international economy?
+Richard Hoefer I do not know how this will play out. It is a disruptive technology the government will try to control or ban under the guise of  "for the children", "guns", "drugs", "we need to protect you from the harm this can do", or "terrorism". No idea which.

This and nanotechnology are game changers, every large and century old business will fight against the use of these devices as they evolve. It empowers people not corporations. 
+Richard Hoefer We have an ever accelerating rate of change in technology. Like all things,it will not happen over night. You will see press releases more and more about 3D printing.

The old school stuff, I like so much

will always be there. Tools are never lost. Name a tool and you can find someone using it online or IRL today. 

I will do the national and international economy part in the next comment. 
It may work out that manufacturing is done by fedex. Cad it up at the shop, send the shape by email. Receive the parts by fedex. 
+Juaquin Anderson short term maybe but long term it will all go local manufacture, eventually home manufacture. 
+Samuel Smith  Thanks for the link! ... Ah yes, copyright law and patent law. Heaven forbid I try to create a rectangular shape with soft curved corners andd 5 rows of 4 across soft-curved squares inside the perimeter. ... But I don't want to derail the thruline of thought here, because in a fairly compact thread, it seems like the core issues have surfaced. And +David Fuchs's comment last night about how this is a disruptive technology more likely to produce benefits for people vs large corporate operations, that still has to be unpacked for me. ... Because it's there that entrepreneurship in creating completely new product designs will blossom, and also there where the patent wars will more readily erupt, I imagine. ??
+Juaquin Anderson I saw this in a video the other day. It seems that one way to strengthen the materials is to put them under extremely high pressure. I am guessing they use oil in a tank under high pressure to compress the object after printing. It wasn't explained.
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