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NASA 3D prints rocket parts — with steel, not plastic
By John Hewitt on November 15, 2012 at 10:47 am
http://www.extremetech.com/extreme/140084-nasa-3d-prints-rocket-parts-with-steel-not-plastic
NASA’s Marshall Space Flight Center in Huntsville, Alabama, has 3D printed nickel alloy rocket engine parts using a fabrication technique called selective laser melting, or SLM. The part will be used on the J-2x engine for the largest rocket ever built, known simply as the Space Launch System. 3D printing (see: What is 3D printing? [1]) has become popular for fabricating parts from plastic, but using the technique with metals requires equipment that is a bit more extreme. Will 3D printing of hard materials become part of a general, growing trend, or will these exotic fabrication technologies be viable only for elite, niche markets?
SLM evolved from an older method known as selective laser sintering, or SLS. In the traditional sintering process, a part is first molded from ceramic or metal powder and pressed into the desired shape. The “green,” as it is called at this point, is then fired in a oven to bond it. The oven was later replaced with a laser which provides greater precision and eliminates the need to handle the fragile, green part. Since full melting of the powder would destroy the part in the process of fusing it, sintered parts are not as strong as cast or machined parts, but they do retain intrinsically desirable properties like resistance to corrosion and temperature.
It was later discovered that full melting of powdered metal particles could be achieved by a technique called electron beam melting, or EBM. Since electrons tend to scatter off of gas molecules, expensive and inconvenient vacuum chambers are required for this process to work. As more affordable laser systems with higher power, more accurate beamsteering, and better focusing optics were developed, SLM was born. Like EBM, the powder material is fully melted during fusion, but the SLM laser does not require vacuum to function. It only requires that an inert argon or nitrogen atmosphere is used in the work area to prevent oxidation.
A part such as this J-2x manifold would not be milled on a CNC machine because the forces required to remove metal would warp and destroy a part this thin. Before SLM, it would have to be fabricated as a weldment from its component parts. Its curved and flaring nozzles would first be stitched together from sheet metal, than bent, and tacked to the main body. Welding introduces nonuniform stress points or “heat affected zones” at the weld sites, and makes failure modes less predictable. It would be beyond human skill to manually reproduce parts like this to the required tolerances. It would therefore have to be made using automated bending machines and robotic welders, which take considerable time to program and set up.
[2]If one can afford the M2 Cusing SLM machine on which this part was printed (pictured right), the main concern is probably not the price of a few weldments. In many complex governmental projects like the Space Launch System, a majority of efforts are spent setting and revising project timelines. The primary driver for continued funding is demonstrating the ability to get the parts in hand by the time stated in the proposal.
Owning an M2 Cusing SLM machine goes a long way towards meeting deadlines, but with 3D machines that print an ever increasing variety of materials rapidly proliferating, it is important to clearly understand when plastic will suffice for a part and when something different is needed for the job. (See: The world’s first 3D printed gun [3].)
[4]Most plastics are relatively soft materials with low compressive and tensile strengths, low melting points, and poor chemical resistance. Even the more expensive formulations like polyimide or polyether ether ketone (PEEK) give only modest improvements relative to metals. Plastics also become brittle when cold, and are quickly aged by exposure to UV light from the sun. Their lack of hardness also means that fine details cannot be rendered by traditional methods of manufacture since they do not hold up to the forces required to create them. Fine detail is also quickly degraded by repetitive use.
Many of our everyday products depend upon the electric or magnetic properties of metals. Recently, engineered plastics have been made which have conductivity approaching that of steel. Copper, aluminum and precious metals are still in a class by themselves and will remain so for some time. Plastics can, however, be embedded with other materials to yield unique properties in a way not readily done with metals. The high temperature necessary to process metals, and their lack of transparency to many forms of energy, make them incompatible with many materials that be used in plastics for expanding their capabilities. Metals can be made insulating, like plastics, by adding a protective oxide coating through the process of anodization [5]. Metals can also be readily labeled by laser etching, and they stand up to a variety of coatings which expand their range of functions.
Next page: When plastic just isn’t enough, and the future of 3D printing [6]
When steel is stronger than steel
When something more robust than plastic is needed, you probably think of steel as a suitable choice. It may therefore sound strange to say that steel, at least in its tempered form, is in fact relatively soft. Fortunately, as ancient cave man discovered, it is readily hardened by firing and rapidly quenching in water, into something that is truly hard. But if this “heat treatment” is overdone, the metal becomes brittle like glass. Heat treatment is the reason that it is possible to use a hacksaw or file made of steel to cut through non-hardened steel without dulling the tool. It is true that diamond is polished with diamond in the form of dust or paste, but this is economically achieved only by converting a small volume of the polishing agent into a large surface area of sharp abrasion that can be sacrificially dulled.
Tools, cutlery, and weapons that have been around since long before the industrial revolution are actually examples of what we might today call “smart materials.” They are smart in that their microscopic or grain structure is tightly controlled to yield specifically desired properties in different locations. A hammer or screwdriver is first heat treated in such a way as to optimize tensile strength so that it can be pried upon without brittle fracture. Then the working surfaces are hardened to resist the wear of repeated use by “case hardening” to a desired depth through the introduction of extra carbon with a quick heating and chemical treatment. There are literally hundreds of different kinds of steels available, each one a unique alloy optimized for a particular use. If 3D printed materials are to become competitive with traditionally manufactured materials, they will have to be capable of functioning under the wide range of operating conditions that traditional materials routinely do.
The future of 3D printing
An attractive feature of 3D printing is that, as an additive manufacturing process, it can be more efficient in many ways than traditional machining. There is little doubt that it will come to replace machining for many types of products. It should be realized however, that only a small portion of our everyday products are made from subtractive techniques like CNC milling or turning. Most common articles are made by mass production processes involving various combinations of casting, forging, extruding, stamping, bending, spinning, drawing, or molding. In order to compete with these processes, 3D printing will need to gain efficiency by multiplicity. In other words, pipeline several machine heads in parallel such that one control and one set of motive elements drives the simultaneous creation of many parts. The process would be reminiscent of a pantograph copier [7] but instead of a single copy, many would be made at once.
[8]The recent Maker Faire in New York [9] showcased many new and novel machine geometries including flexible multi-axis or hexapod machines with non-Cartesian geometries. The geometry of the machine can be optimized to the parts it is destined to make. Peculiarly absent from the Maker Faire was the 3D printing equivalent of the basic and universal machine tool, the lathe. Lathes, while in some sense the most primitive machine tool, can be used to easily make threads in metal. Threads are only robust in the hardest of plastics, yet perhaps they will become more dispensable in a world where complex parts can be printed whole rather than pieced together from simpler components. The side effect is that parts will not be easily disassembled, and when they fail, a complete part will need replacement.
Dentistry is one area where 3D printing of hard materials [10] has successfully demonstrated its advantages over milling. Replacement teeth are small parts, yet to produce their complex geometry with subtractive machining, a large 5-axis machine is required. 3D printing will allow the manufacturing technology to be physically closer to the point of end use; in this case, the dentist’s chair.
[11]One new concept ideally suited to 3D printing is brought to us thanks to Omote 3D [12], in Japan. With its new system, patrons are scanned in a booth and a colored replica of them is soon printed in any one of 3 sizes — at a cost of $500. Productions by standard multi-axis mills producing foam props for the entertainment industry come nowhere close to this performance or price point.
There are plans already, to make 3D printing workable in the zero gravity conditions [13] of space. This would present unique challenges and opportunities, and hints at aspirations of forward thinkers at NASA and elsewhere. The structural integrity of 3D printed parts like the J-2x will still need to be fully vetted in the materials testing lab. They will be crushed, stretched, diced, and X-rayed to reveal grain microstructure. Provided the parts hold up to the standards expected, the J-2x will be just the beginning of 3D laser printed parts at NASA and beyond.
Now read: 3D printing: a replicator and teleporter in every home [14]
Endnotes
What is 3D printing?: http://www.extremetech.com/extreme/115503-what-is-3d-printing
: http://www.extremetech.com/wp-content/uploads/2012/11/mr-cusing.jpg
The world’s first 3D printed gun: http://www.extremetech.com/extreme/133514-the-worlds-first-3d-printed-gun
: http://www.extremetech.com/wp-content/uploads/2012/10/3D-Globe.jpg
the process of anodization: http://www.extremetech.com/electronics/136835-apple-responds-to-iphone-5-scuffgate-scratches-and-chips-are-normal" title="Apple responds to iPhone 5 scuffs, says scratches and chips are ‘normal’
When plastic just isn’t enough, and the future of 3D printing: http://www.extremetech.com/extreme/140084-nasa-3d-prints-rocket-parts-with-steel-not-plastic/2
pantograph copier: http://en.wikipedia.org/wiki/Pantograph
: http://www.extremetech.com/wp-content/uploads/2012/11/wooden-lathe.jpg
Maker Faire in New York: http://www.extremetech.com/electronics/137098-3d-printer-safari-maker-faire-ny
3D printing of hard materials: http://dentallabnetwork.com/forums/f33/why-3d-printing-will-replace-milling-6860/
: http://www.extremetech.com/wp-content/uploads/2012/11/otome-3d-photo-booth.jpg
Omote 3D: http://www.gizmag.com/worlds-first-3d-printing-photo-booth/24965/
zero gravity conditions: http://2012.spaceappschallenge.org/challenge/space-based-3d-printing-platform/solution/157
3D printing: a replicator and teleporter in every home: http://www.extremetech.com/extreme/92042-3d-printing-a-replicator-and-teleporter-in-every-home
By John Hewitt on November 15, 2012 at 10:47 am
http://www.extremetech.com/extreme/140084-nasa-3d-prints-rocket-parts-with-steel-not-plastic
NASA’s Marshall Space Flight Center in Huntsville, Alabama, has 3D printed nickel alloy rocket engine parts using a fabrication technique called selective laser melting, or SLM. The part will be used on the J-2x engine for the largest rocket ever built, known simply as the Space Launch System. 3D printing (see: What is 3D printing? [1]) has become popular for fabricating parts from plastic, but using the technique with metals requires equipment that is a bit more extreme. Will 3D printing of hard materials become part of a general, growing trend, or will these exotic fabrication technologies be viable only for elite, niche markets?
SLM evolved from an older method known as selective laser sintering, or SLS. In the traditional sintering process, a part is first molded from ceramic or metal powder and pressed into the desired shape. The “green,” as it is called at this point, is then fired in a oven to bond it. The oven was later replaced with a laser which provides greater precision and eliminates the need to handle the fragile, green part. Since full melting of the powder would destroy the part in the process of fusing it, sintered parts are not as strong as cast or machined parts, but they do retain intrinsically desirable properties like resistance to corrosion and temperature.
It was later discovered that full melting of powdered metal particles could be achieved by a technique called electron beam melting, or EBM. Since electrons tend to scatter off of gas molecules, expensive and inconvenient vacuum chambers are required for this process to work. As more affordable laser systems with higher power, more accurate beamsteering, and better focusing optics were developed, SLM was born. Like EBM, the powder material is fully melted during fusion, but the SLM laser does not require vacuum to function. It only requires that an inert argon or nitrogen atmosphere is used in the work area to prevent oxidation.
A part such as this J-2x manifold would not be milled on a CNC machine because the forces required to remove metal would warp and destroy a part this thin. Before SLM, it would have to be fabricated as a weldment from its component parts. Its curved and flaring nozzles would first be stitched together from sheet metal, than bent, and tacked to the main body. Welding introduces nonuniform stress points or “heat affected zones” at the weld sites, and makes failure modes less predictable. It would be beyond human skill to manually reproduce parts like this to the required tolerances. It would therefore have to be made using automated bending machines and robotic welders, which take considerable time to program and set up.
[2]If one can afford the M2 Cusing SLM machine on which this part was printed (pictured right), the main concern is probably not the price of a few weldments. In many complex governmental projects like the Space Launch System, a majority of efforts are spent setting and revising project timelines. The primary driver for continued funding is demonstrating the ability to get the parts in hand by the time stated in the proposal.
Owning an M2 Cusing SLM machine goes a long way towards meeting deadlines, but with 3D machines that print an ever increasing variety of materials rapidly proliferating, it is important to clearly understand when plastic will suffice for a part and when something different is needed for the job. (See: The world’s first 3D printed gun [3].)
[4]Most plastics are relatively soft materials with low compressive and tensile strengths, low melting points, and poor chemical resistance. Even the more expensive formulations like polyimide or polyether ether ketone (PEEK) give only modest improvements relative to metals. Plastics also become brittle when cold, and are quickly aged by exposure to UV light from the sun. Their lack of hardness also means that fine details cannot be rendered by traditional methods of manufacture since they do not hold up to the forces required to create them. Fine detail is also quickly degraded by repetitive use.
Many of our everyday products depend upon the electric or magnetic properties of metals. Recently, engineered plastics have been made which have conductivity approaching that of steel. Copper, aluminum and precious metals are still in a class by themselves and will remain so for some time. Plastics can, however, be embedded with other materials to yield unique properties in a way not readily done with metals. The high temperature necessary to process metals, and their lack of transparency to many forms of energy, make them incompatible with many materials that be used in plastics for expanding their capabilities. Metals can be made insulating, like plastics, by adding a protective oxide coating through the process of anodization [5]. Metals can also be readily labeled by laser etching, and they stand up to a variety of coatings which expand their range of functions.
Next page: When plastic just isn’t enough, and the future of 3D printing [6]
When steel is stronger than steel
When something more robust than plastic is needed, you probably think of steel as a suitable choice. It may therefore sound strange to say that steel, at least in its tempered form, is in fact relatively soft. Fortunately, as ancient cave man discovered, it is readily hardened by firing and rapidly quenching in water, into something that is truly hard. But if this “heat treatment” is overdone, the metal becomes brittle like glass. Heat treatment is the reason that it is possible to use a hacksaw or file made of steel to cut through non-hardened steel without dulling the tool. It is true that diamond is polished with diamond in the form of dust or paste, but this is economically achieved only by converting a small volume of the polishing agent into a large surface area of sharp abrasion that can be sacrificially dulled.
Tools, cutlery, and weapons that have been around since long before the industrial revolution are actually examples of what we might today call “smart materials.” They are smart in that their microscopic or grain structure is tightly controlled to yield specifically desired properties in different locations. A hammer or screwdriver is first heat treated in such a way as to optimize tensile strength so that it can be pried upon without brittle fracture. Then the working surfaces are hardened to resist the wear of repeated use by “case hardening” to a desired depth through the introduction of extra carbon with a quick heating and chemical treatment. There are literally hundreds of different kinds of steels available, each one a unique alloy optimized for a particular use. If 3D printed materials are to become competitive with traditionally manufactured materials, they will have to be capable of functioning under the wide range of operating conditions that traditional materials routinely do.
The future of 3D printing
An attractive feature of 3D printing is that, as an additive manufacturing process, it can be more efficient in many ways than traditional machining. There is little doubt that it will come to replace machining for many types of products. It should be realized however, that only a small portion of our everyday products are made from subtractive techniques like CNC milling or turning. Most common articles are made by mass production processes involving various combinations of casting, forging, extruding, stamping, bending, spinning, drawing, or molding. In order to compete with these processes, 3D printing will need to gain efficiency by multiplicity. In other words, pipeline several machine heads in parallel such that one control and one set of motive elements drives the simultaneous creation of many parts. The process would be reminiscent of a pantograph copier [7] but instead of a single copy, many would be made at once.
[8]The recent Maker Faire in New York [9] showcased many new and novel machine geometries including flexible multi-axis or hexapod machines with non-Cartesian geometries. The geometry of the machine can be optimized to the parts it is destined to make. Peculiarly absent from the Maker Faire was the 3D printing equivalent of the basic and universal machine tool, the lathe. Lathes, while in some sense the most primitive machine tool, can be used to easily make threads in metal. Threads are only robust in the hardest of plastics, yet perhaps they will become more dispensable in a world where complex parts can be printed whole rather than pieced together from simpler components. The side effect is that parts will not be easily disassembled, and when they fail, a complete part will need replacement.
Dentistry is one area where 3D printing of hard materials [10] has successfully demonstrated its advantages over milling. Replacement teeth are small parts, yet to produce their complex geometry with subtractive machining, a large 5-axis machine is required. 3D printing will allow the manufacturing technology to be physically closer to the point of end use; in this case, the dentist’s chair.
[11]One new concept ideally suited to 3D printing is brought to us thanks to Omote 3D [12], in Japan. With its new system, patrons are scanned in a booth and a colored replica of them is soon printed in any one of 3 sizes — at a cost of $500. Productions by standard multi-axis mills producing foam props for the entertainment industry come nowhere close to this performance or price point.
There are plans already, to make 3D printing workable in the zero gravity conditions [13] of space. This would present unique challenges and opportunities, and hints at aspirations of forward thinkers at NASA and elsewhere. The structural integrity of 3D printed parts like the J-2x will still need to be fully vetted in the materials testing lab. They will be crushed, stretched, diced, and X-rayed to reveal grain microstructure. Provided the parts hold up to the standards expected, the J-2x will be just the beginning of 3D laser printed parts at NASA and beyond.
Now read: 3D printing: a replicator and teleporter in every home [14]
Endnotes
What is 3D printing?: http://www.extremetech.com/extreme/115503-what-is-3d-printing
: http://www.extremetech.com/wp-content/uploads/2012/11/mr-cusing.jpg
The world’s first 3D printed gun: http://www.extremetech.com/extreme/133514-the-worlds-first-3d-printed-gun
: http://www.extremetech.com/wp-content/uploads/2012/10/3D-Globe.jpg
the process of anodization: http://www.extremetech.com/electronics/136835-apple-responds-to-iphone-5-scuffgate-scratches-and-chips-are-normal" title="Apple responds to iPhone 5 scuffs, says scratches and chips are ‘normal’
When plastic just isn’t enough, and the future of 3D printing: http://www.extremetech.com/extreme/140084-nasa-3d-prints-rocket-parts-with-steel-not-plastic/2
pantograph copier: http://en.wikipedia.org/wiki/Pantograph
: http://www.extremetech.com/wp-content/uploads/2012/11/wooden-lathe.jpg
Maker Faire in New York: http://www.extremetech.com/electronics/137098-3d-printer-safari-maker-faire-ny
3D printing of hard materials: http://dentallabnetwork.com/forums/f33/why-3d-printing-will-replace-milling-6860/
: http://www.extremetech.com/wp-content/uploads/2012/11/otome-3d-photo-booth.jpg
Omote 3D: http://www.gizmag.com/worlds-first-3d-printing-photo-booth/24965/
zero gravity conditions: http://2012.spaceappschallenge.org/challenge/space-based-3d-printing-platform/solution/157
3D printing: a replicator and teleporter in every home: http://www.extremetech.com/extreme/92042-3d-printing-a-replicator-and-teleporter-in-every-home
