Other
terms that have been used as synonyms or hypernyms have included desktop
manufacturing, rapid manufacturing (as the logical production-level
successor to rapid prototyping), and on-demand manufacturing (which
echoes on-demand printing in the 2D sense of printing). That such
application of the adjectives rapid and on-demand to the noun
manufacturing was novel in the 2000s reveals the prevailing mental model
of the long industrial era in which almost all production manufacturing
involved long lead times for laborious tooling development. Today, the
term subtractive has not replaced the term machining, instead
complementing it when a term that covers any removal method is needed.
Agile tooling is the use of modular means to design tooling that is
produced by additive manufacturing or 3D printing methods to enable
quick prototyping and responses to tooling and fixture needs. Agile
tooling uses a cost effective and high quality method to quickly respond
to customer and market needs, and it can be used in hydro-forming,
stamping, injection molding and other manufacturing processes.
History
1981
Early additive manufacturing equipment and materials were developed
in the 1980s. In 1981, Hideo Kodama of Nagoya Municipal Industrial
Research Institute invented two additive methods for fabricating
three-dimensional plastic models with photo-hardening thermoset polymer,
where the UV exposure area is controlled by a mask pattern or a scanning
fiber transmitter.
1984
On 16 July 1984, Alain Le Méhauté, Olivier de
Witte, and Jean Claude André filed their patent for the
stereolithography process. The application of the French inventors was
abandoned by the French General Electric Company (now Alcatel-Alsthom)
and CILAS (The Laser Consortium). The claimed reason was “for lack of
business perspective”.
Three weeks later in 1984, Chuck Hull of 3D
Systems Corporation filed his own patent for a stereolithography
fabrication system, in which layers are added by curing photopolymers
with ultraviolet light lasers. Hull defined the process as a “system
for generating three-dimensional objects by creating a cross-sectional
pattern of the object to be formed,”. Hull’s contribution was the STL
(Stereolithography) file format and the digital slicing and infill
strategies common to many processes today.
1988
The technology used by
most 3D printers to date—especially hobbyist and consumer-oriented
models—is fused deposition modeling, a special application of plastic
extrusion, developed in 1988 by S. Scott Crump and commercialized by his
company Stratasys, which marketed its first FDM machine in 1992.
AM
processes for metal sintering or melting (such as selective laser
sintering, direct metal laser sintering, and selective laser melting)
usually went by their own individual names in the 1980s and 1990s. At
the time, all metalworking was done by processes that we now call
non-additive (casting, fabrication, stamping, and machining); although
plenty of automation was applied to those technologies (such as by robot
welding and CNC), the idea of a tool or head moving through a 3D work
envelope transforming a mass of raw material into a desired shape with a
toolpath was associated in metalworking only with processes that removed
metal (rather than adding it), such as CNC milling, CNC EDM, and many
others. But the automated techniques that added metal, which would later
be called additive manufacturing, were beginning to challenge that
assumption. By the mid-1990s, new techniques for material deposition
were developed at Stanford and Carnegie Mellon University, including
microcasting and sprayed materials. Sacrificial and support materials
had also become more common, enabling new object geometries.
1993
The
term 3D printing originally referred to a powder bed process employing
standard and custom inkjet print heads, developed at MIT in 1993 and
commercialized by Soligen Technologies, Extrude Hone
Corporation, and Z
Corporation.
The year 1993 also saw the start of a company called
Solidscape, introducing a high-precision polymer jet fabrication system
with soluble support structures, (categorized as a “dot-on-dot”
technique).
1995
In 1995 the Fraunhofer Institute developed the
selective laser melting process.
2009
Fused Deposition Modeling (FDM)
printing process patents expired in 2009. As the various additive
processes matured, it became clear that soon metal removal would no
longer be the only metalworking process done through a tool or head
moving through a 3D work envelope transforming a mass of raw material
into a desired shape layer by layer. The 2010s were the first decade in
which metal end use parts such as engine brackets and large nuts would
be grown (either before or instead of machining) in job production
rather than obligately being machined from bar stock or plate. It is
still the case that casting, fabrication, stamping, and machining are
more prevalent than additive manufacturing in metalworking, but AM is
now beginning to make significant inroads, and with the advantages of
design for additive manufacturing, it is clear to engineers that much
more is to come.
As technology matured, several authors had begun to
speculate that 3D printing could aid in sustainable development in the
developing world.
2013
NASA employees Samantha Snabes and Matthew
Fiedler create first prototype of large-format, affordable 3D printer,
Gigabot, and launch 3D printing company re:3D.
2018
re:3D develops a
system that uses plastic pellets that can be made by grinding up waste
plastic.
General principles
Modeling 3D
printable models may be created
with a computer-aided design (CAD) package, via a 3D scanner, or by a
plain digital camera and photogrammetry software. 3D printed models
created with CAD result in reduced errors and can be corrected before
printing, allowing verification in the design of the object before it is
printed. The manual modeling process of preparing geometric data for 3D
computer graphics is similar to plastic arts such as sculpting. 3D
scanning is a process of collecting digital data on the shape and
appearance of a real object, creating a digital model based on it.
Printing
Before printing a 3D model from an STL file, it must first be
examined for errors. Most CAD applications produce errors in output STL
files of the following types:
holes,
- faces normal,
- self-intersections,
- noise shells,
- manifold errors.
A step in the STL generation known as
“repair” fixes such problems in the original model. Generally STLs
that have been produced from a model obtained through 3D scanning often
have more of these errors. This is due to how 3D scanning works-as it is
often by point to point acquisition, reconstruction will include errors
in most cases.
Once completed, the STL file needs to be processed by a
piece of software called a “slicer,” which converts the model into a
series of thin layers and produces a G-code file containing instructions
tailored to a specific type of 3D printer (FDM printers). This G-code
file can then be printed with 3D printing client software (which loads
the G-code, and uses it to instruct the 3D printer during the 3D
printing process).
Printer resolution describes layer thickness and X–Y
resolution in dots per inch (dpi) or micrometers (µm). Typical layer
thickness is around 100 µm (250 DPI), although some machines can print
layers as thin as 16 µm (1,600 DPI). X–Y resolution is comparable to
that of laser printers. The particles (3D dots) are around 50 to 100 µm
(510 to 250 DPI) in diameter. For that printer resolution, specifying a
mesh resolution of 0.01–0.03 mm and a chord length ? 0.016 mm generate
an optimal STL output file for a given model input file. Specifying
higher resolution results in larger files without increase in print
quality.
Construction of a model with contemporary methods can take
anywhere from several hours to several days, depending on the method
used and the size and complexity of the model. Additive systems can
typically reduce this time to a few hours, although it varies widely
depending on the type of machine used and the size and number of models
being produced simultaneously.
Traditional techniques like injection
moulding can be less expensive for manufacturing polymer products in
high quantities, but additive manufacturing can be faster, more flexible
and less expensive when producing relatively small quantities of parts.
3D printers give designers and concept development teams the ability to
produce parts and concept models using a desktop size printer.
Seemingly
paradoxic, more complex objects can be cheaper for 3D printing
production than less complex objects.
Finishing
Though the
printer-produced resolution is sufficient for many applications,
printing a slightly oversized version of the desired object in standard
resolution and then removing material with a higher-resolution
subtractive process can achieve greater precision.
The layered structure
of all Additive Manufacturing processes leads inevitably to a
strain-stepping effect on part surfaces which are curved or tilted in
respect to the building platform. The effects strongly depend on the
orientation of a part surface inside the building process.
Some
printable polymers such as ABS, allow the surface finish to be smoothed
and improved using chemical vapor processes based on acetone or similar
solvents.
Some additive manufacturing techniques are capable of using
multiple materials in the course of constructing parts. These techniques
are able to print in multiple colors and color combinations
simultaneously, and would not necessarily require painting.
Some
printing techniques require internal supports to be built for
overhanging features during construction. These supports must be
mechanically removed or dissolved upon completion of the print.
All of
the commercialized metal 3D printers involve cutting the metal component
off the metal substrate after deposition. A new process for the GMAW 3D
printing allows for substrate surface modifications to remove aluminum
or steel.
Processes and printers
A large number of additive processes
are available. The main differences between processes are in the way
layers are deposited to create parts and in the materials that are used.
Each method has its own advantages and drawbacks, which is why some
companies offer a choice of powder and polymer for the material used to
build the object. Others sometimes use standard, off-the-shelf business
paper as the build material to produce a durable prototype. The main
considerations in choosing a machine are generally speed, costs of the
3D printer, of the printed prototype, choice and cost of the materials,
and color capabilities. Printers that work directly with metals are
generally expensive. However less expensive printers can be used to make
a mold, which is then used to make metal parts.
ISO/ASTM52900-15 defines
seven categories of Additive Manufacturing (AM) processes within its
meaning: binder jetting, directed energy deposition, material extrusion,
material jetting, powder bed fusion, sheet lamination, and vat
photopolymerization.
Some methods melt or soften the material to produce
the layers. In Fused filament fabrication, also known as Fused
deposition modeling (FDM), the model or part is produced by extruding
small beads or streams of material which harden immediately to form
layers. A filament of thermoplastic, metal wire, or other material is
fed into an extrusion nozzle head (3D printer extruder), which heats the
material and turns the flow on and off. FDM is somewhat restricted in
the variation of shapes that may be fabricated. Another technique fuses
parts of the layer and then moves upward in the working area, adding
another layer of granules and repeating the process until the piece has
built up. This process uses the unfused media to support overhangs and
thin walls in the part being produced, which reduces the need for
temporary auxiliary supports for the piece.
Laser sintering techniques
include selective laser sintering, with both metals and polymers, and
direct metal laser sintering. Selective laser melting does not use
sintering for the fusion of powder granules but will completely melt the
powder using a high-energy laser to create fully dense materials in a
layer-wise method that has mechanical properties similar to those of
conventional manufactured metals. Electron beam melting is a similar
type of additive manufacturing technology for metal parts (e.g. titanium
alloys). EBM manufactures parts by melting metal powder layer by layer
with an electron beam in a high vacuum. Another method consists of an
inkjet 3D printing system, which creates the model one layer at a time
by spreading a layer of powder (plaster, or resins) and printing a
binder in the cross-section of the part using an inkjet-like process.
With laminated object manufacturing, thin layers are cut to shape and
joined together.
Schematic representation of Stereolithography; a
light-emitting device a) (laser or DLP) selectively illuminate the
transparent bottom c) of a tank b) filled with a liquid
photo-polymerizing resin; the solidified resin d) is progressively
dragged up by a lifting platform e)
Other methods cure liquid materials
using different sophisticated technologies, such as stereolithography.
Photopolymerization is primarily used in stereolithography to produce a
solid part from a liquid. Inkjet printer systems like the Objet PolyJet
system spray photopolymer materials onto a build tray in ultra-thin
layers (between 16 and 30 µm) until the part is completed. Each
photopolymer layer is cured with UV light after it is jetted, producing
fully cured models that can be handled and used immediately, without
post-curing. Ultra-small features can be made with the 3D
micro-fabrication technique used in multiphoton photopolymerisation. Due
to the nonlinear nature of photo excitation, the gel is cured to a solid
only in the places where the laser was focused while the remaining gel
is then washed away. Feature sizes of under 100 nm are easily produced,
as well as complex structures with moving and interlocked parts. Yet
another approach uses a synthetic resin that is solidified using LEDs.
In Mask-image-projection-based stereolithography, a 3D digital model is
sliced by a set of horizontal planes. Each slice is converted into a
two-dimensional mask image. The mask image is then projected onto a
photocurable liquid resin surface and light is projected onto the resin
to cure it in the shape of the layer. Continuous liquid interface
production begins with a pool of liquid photopolymer resin. Part of the
pool bottom is transparent to ultraviolet light (the “window”), which
causes the resin to solidify. The object rises slowly enough to allow
resin to flow under and maintain contact with the bottom of the object.
In powder-fed directed-energy deposition, a high-power laser is used to
melt metal powder supplied to the focus of the laser beam. The powder
fed directed energy process is similar to Selective Laser Sintering, but
the metal powder is applied only where material is being added to the
part at that moment.
As of December 2017, additive manufacturing systems
were on the market that ranged from $99 to $500,000 in price and were
employed in industries including aerospace, architecture, automotive,
defense, and medical replacements, among many others. For example,
General Electric uses the high-end model to build parts for turbines.
Many of these systems are used for rapid prototyping, before mass
production methods are employed. Higher education has proven to be a
major buyer of desktop and professional 3D printers which industry
experts generally view as a positive indicator. Libraries around the
world have also become locations to house smaller 3D printers for
educational and community access. Several projects and companies are
making efforts to develop affordable 3D printers for home desktop use.
Much of this work has been driven by and targeted at
DIY/Maker/enthusiast/early adopter communities, with additional ties to
the academic and hacker communities.
Applications
In the current
scenario, 3D printing or Additive Manufacturing has been used in
manufacturing, medical, industry and sociocultural sectors which
facilitate 3D printing or Additive Manufacturing to become successful
commercial technology. The earliest application of additive
manufacturing was on the toolroom end of the manufacturing spectrum. For
example, rapid prototyping was one of the earliest additive variants,
and its mission was to reduce the lead time and cost of developing
prototypes of new parts and devices, which was earlier only done with
subtractive toolroom methods such as CNC milling, turning, and precision
grinding. In the 2010s, additive manufacturing entered production to a
much greater extent.