Class 8

8. 3D Printing & Additive Manufacturing
Fall 2013
Prof. Marc Madou
MSTB 120
3D printing has been in existence for almost three decades, yet
has only recently spread to mass markets. The primary 3D-
Printing techniques were established in the eighties
(StereoLithography, fused deposition modeling, and laser
sintering). These innovations were theoretically groundbreaking,
but most practical applications remained prohibitively expensive.
How we got here
Adrian Bowyer’s RepRap project changed the game forever. The
RepRap project, established in 2004, aimed to make 3d printers
financially accessible to everyone. RepRap printers had the
ability to materialize CAD designs and also to print the essential
parts necessary to assemble a clone printer. The movement
incorporated open-source file sharing, thus allowing users to
share their 3D designs and ideas.
After the growth of the RepRap movement, companies such as BotMill,
MakerBot, and Bits from Bytes began manufacturing consumer-friendly 3D
printers. Now 3D printing has reached a new stage of development: small
businesses, educational institutions and large corporations are pushing the
bounds of the possible. Meanwhile, consumer adoption continues rushing
forward, capturing a broader slice of the population with ever-decreasing
Market Landscape
3D printing is approximately a $600 million-dollar industry. The industry
goliath, 3D Systems Corporation, by itself reported a 2011 net income of $41
The 3D printing industry is comprised of different segments. The primary 3DPrinting users include hobbyists, artists, educational institutions, engineering
firms, and industrial manufacturers. These segments can be further broken
down into three end-uses.
Segment 1
First, there are consumers (designers, inventors) who want their own 3Ddesigns printed, but can’t afford or don’t need to own their own printer. They
will seek out a 3D-Printing service like Shapeways, Imaterialise, or Sculpteo to
get their object printed. The consumer simply uploads his/her 3D file,
chooses the material and build size, and within weeks, the service will print
and deliver their 3d model.
Segment 2
The second category consists of hobbyists or diyers, seeking their own
personal printers; these printers, provided by companies like BotMill,
MakerBot, and BitsFromBytes, range from $800 to $5000. Initially, most
hobbyists were most interested in assembling and constructing the printer
itself –less interested in the final product. Now, as more printers come preassemble (ready-to-print), greater attention is given to the 3d models
Segment 3
Third, there is the high-end educational/industrial segment. Lastly,
educational institutions, engineering firms, and other large corporations that
want to possess their own heavy-duty printers can invest anywhere from
$10,000 to $80,000 per printer.
Fused Deposition Modeling (FDM)
1. A spool of themoplastic wire (typically
acrylonitrile butadiene styrene (ABS)) with a
0.012 in (300 μm) diameter is continuously
supplied to a nozzle
5. The sacrificial support material (if available)
is dissolved in a heated sodium hydroxide
(NaOH) solution with the assistance of
ultrasonic agitation.
2. The nozzle heats up the wire and extrudes a
hot, viscos strand (like squeezing toothpaste
of of a tube).
3. A computer controls the nozzle movement
along the x- and y-axes, and each crosssection of the prototype is produced by
melting the plastic wire that solidifies on
4. In the newest models, a second nozzle
carries a support wax that can easily be
removed afterward, allowing construction
of more complex parts. The most common
support material is marketed by Stratasys
under the name WaterWorks)
3D Printing (3DP)
1. A layer of powder (plaster,
ceramic) is spread across the
build area
2. Inkjet-like printing of binder over
the top layer densifies and
compacts the powder locally
3. The platform is lowered and the
next layer of dry powder is
spread on top of the previous
4. Upon extraction from the
machine, the dry powder is
brushed off and recycled
Selective Laser Sintering (SLS)
1. A continuous layer of powder is
deposited on the fabrication
2. A focused laser beam is used to
fuse/sinter powder particles in a
small volume within the layer
3. The laser beam is scanned to
define a 2D slice of the object
within the layer
4. The fabrication piston is
lowered, the powder delivery
piston is raised and a new layer
is deposited
5. After removal from the machine,
the unsintered dry powder is
brushed off and recycled
EBM (Electron Beam Melting)
This solid freeform fabrication method produces fully dense metal parts directly
from metal powder with characteristics of the target material. The EBM
machine reads data from a 3D CAD model and lays down successive layers of
powdered material. These layers are melted together utilizing a computer
controlled electron beam. In this way it builds up the parts. The process takes
place under vacuum, which makes it suited to manufacture parts in reactive
materials with a high affinity for oxygen, e.g. titanium.
The melted material is from a pure alloy in powder form of the final material to
be fabricated (no filler). For that reason the electron beam technology doesn't
require additional thermal treatment to obtain the full mechanical properties of
the parts. That aspect allows classification of EBM with selective laser melting
(SLM) where competing technologies like SLS and DMLS require thermal
treatment after fabrication. Compared to SLM and DMLS, EBM has a generally
superior build rate because of its higher energy density and scanning method.
The EBM process operates at an elevated temperature, typically between 700
and 1 000 °C, producing parts that are virtually free from residual stress, and
eliminating the need for heat treatment after the build.
PolyJet/Multijet Modeling (MJM)
• Both systems use piezoelectric print heads with thousands of nozzles to jet 16
micron droplets of photopolymer that are immediately cured by UV light. The
model material for the part and the support material that fills the voids come from
different nozzles.
photopolymer as support material;
the support material is designed to
crosslink less than the model material
and is washed away with pressurized
The 3D Systems InVision uses wax
as support material, which can be
melted away.
Because of its 600x600 dpi
resolution, MJM is a relatively fast
process. The resolution is not as
good as for SLA.
Stereo-lithography (SLA)
• The liquid resin is kept either in the fixed surface mode or in the free
surface mode.
– In the case of free surface, solidification occurs at the resin/air interface, and care
needs to be taken to avoid waves or a slant of the liquid surface.
– In the fixed surface mode, the resin is stored in a container with a transparent window
plate for exposure. The solidification happens at the stable window/resin interface. An
elevator is pulled up over the thickness of one additional layer above the window for
each new exposure.
Stereo-lithography (SLA)
• The two major types of stereolithography
stereolithography and projection stereolithography.
– The scanning stereolithography parts are constructed in a point-by-point and line-byline fashion, with the sliced shapes written directly from a computerized design of the
cross-sectional shapes by a beam in the liquid.
– Projection stereolithography is a parallel fabrication process that enables sets of truly
3D solid structures made of a UV polymer by exposing the polymer with a set of 2D
cross-sectional shapes (masks) of the final structures. These 2D shapes are either a
set of real photomasks used to subsequently expose the work, or they involve a
dynamic mask projection system instead of a physical mask.
Stereo-lithography (SLA)
Two-photon lithography provides a further enhancement of the SLA resolution. If an
entangled photon pair comes out from a point of the object plane, it undergoes twophoton diffraction, resulting in a very narrow point spread function on the image
plane. The result is extremely local polymerization, with resolutions in the tens of
nanometers range.
Polylactic acid (PLA)
PLA, or polylactic acid, is an ideal material to use in 3D printers. It is pleasant to work
with, available in optically clear forms, and produces no noxious fumes when extruded;
the odor has been likened to candy floss and it is made from the natural acid present in
yogurt. The Natural filament has no additives and is quite safe to use with foodstuffs –
the material is used to make soluble sutures for surgery and it doesn’t affect the
lactose intolerant.
Mechanically, it fuses together well when molten and will shatter rather than bend. Its
melting point is relatively low at 180C and it softens in boiling water. When molten, the
clear forms have very low viscosity and so extrude rapidly. Opaque colorants stiffen the
plastic, lessening its tendency to shatter and preventing it from flowing away. It also
has a very low resistance on steel bars and is used for printing sliding bearings.
Generally extruded at between 180C (320F) and 190C (340F). Clear PLA is suitable as
the core for investment castings, as the plastic vaporizes leaving little ash. It will not
biodegrade unless properly composted.
Acrylonitrile butadiene styrene (ABS)
Acrylonitrile butadiene styrene is a common plastic, used to make such things as Lego
bricks and monitor cases. It is recyclable but does produce styrene fumes and other
gasses when heated that some find unpleasant, and good ventilation is recommended.
It is tougher than PLA and withstands 60C with ease. It flexes rather than shatters, but
abrades away when pressed on by axles etc. Extrusion is done at anywhere between
220C and 270C, and any blockages should be cleared with acetone while cool as ABS
will turn to ash if you try to burn it out.
3mm ABS Filament
3mm PLA Filament
Stratasys ABS+ Plus Filament
Stratasys SST Filament
1.75mm ABS Raft Detail
Dimension ABS Build Detail
UP 1.75mm ABS Build Detail
Dimension SST Build Detail
UP Edge Build Detail
UP Edge Build Detail
Dimension SST Edge Detail .020
2 Photon Lithography
2 Photon Lithography
2 Photon Lithography
2 Photon Lithography
2 Photon Lithography
2 Photon Lithography
Drop on demand cell Printer
Heart Valve Printer
Cartilage Tissue Printer
Captive Shell Cell Tissue Printer
Muscle Tissue Printer
Cell Scaffold Printer
Cartilage Tissue Printer
3D Printed Ear with Electronics
3D Printed Droplet Network of Cells
3D Printed Hearing Aid Shell
10,000,000 3D printed hearing aids in circulation worldwide
CandyFab 4000
Sugar drop on demand 3D Printer
Large Format 3D Concrete Printer
Large Format 3D Concrete Printer
Large Format 3D Concrete Printer
Tennessee Ball Clay
Large Format 3D Concrete Printer
Large Format FDM
Free form 3D Printer
Free form 3D Printer
Cell Printer
Prototype Delta 3D Printer
3D Food Printer
Food Printer
3D Solar Powered Sand Printer
Ceramic Printing Orbital Re-entry
3D printed alumina/silica
architected sandwich panel
after bisque firing and sintering.
(a) Isometric view; (b) Front
view. The external vertical
columns were printed to
support the face
sheet during sintering and
preserve the shape of the part.
They were removed prior to
and testing
Ceramic Printing Orbital Re-entry
(a) Sintered ceramic cylinder embedded in epoxy resin. Notice that the resin partially wicks through the
cylinder (coloring was added to emphasize the gradient in composition). (b) Optical micrograph of a crosssection of the cylinder in (a), showing a gradient in resin volume fraction; (c) Digital thresholding of the image
in (b), clearly showing a gradient in porosity. Notice that the infiltrated (hybrid) regions are nearly fully dense,
whereas ~50% porosity remains in the ceramic regions.
Material Properties as they exist now
Randal Schubert, HRL Laboratories @ 2013
A Vision for Additive Manufacturing
Model Manufacturing Platforms (MMP)
Open Source & Creative Commons
Pwdr (3D Powder Printer)
3D Bioprinter
3D Laser Sintering
Thank You !
Ed Tackett, Director
[email protected]
Facebook ~ RapidTech

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