Classification of 3D PRINTING:
1. Liquid Polymer Systems
The first commercial system was the 3D Systems Stereolithography process based on liquid
photopolymers. A large portion of systems in use today are, in fact, not just liquid polymer
systems but more specifically liquid photopolymer systems. However, this classification
should not be restricted to just photopolymers, since a number of experimental systems are
using hydrogels that would also fit into this category. Droplet deposition of polymers using
an array of 1D channels can simplify the curing process to a floodlight (for photopolymers) or
similar method. Controlling the area to be exposed using digital micro-mirror devices (DMD)
or other high-resolution display technology obviates the need for any scanning at all, thus
increasing throughput and reducing the number of moving parts.
2. Discrete Particle Systems
Discrete particles are normally powders that are generally graded into a relatively uniform
size and shape and narrow distribution. The finer the particles the better, but there will be
problems if the dimensions get too small in terms of controlling the distribution and
dispersion. Again, the conventional 1D channel approach is to use a laser, this time to
produce thermal energy in a controlled manner and, therefore, raise the temperature
sufficiently to melt the powder. Polymer powders must therefore exhibit thermoplastic
behavior so that they can be melted and re-melted to permit bonding of one layer to
another. There are a wide variety of such systems that generally differ in terms of the
material that can be processed. The two main polymer-based systems commercially
available are the Selective Laser Sintering (SLS) technology marketed by 3D Systems. Printing
technology is used to print a binder, or glue, onto a powder bed. The glue sticks the powder
particles together to form a 3D structure. This basic technique has been developed for
different applications dependent on the type of powder and binder combination.
3. Molten Material Systems
Molten material systems are characterized by a pre-heating chamber that raises the
material temperature to melting point so that it can flow through a delivery system. The
most well-known method for doing this is the Fused Deposition Modeling system. Two
extrusion heads are often used so that support structures can be fabricated from a different
material to facilitate part cleanup and removal. Supports are removed by inserting the
complete part into a temperature-controlled bath that melts the support material away,
leaving the part material intact.
4. Solid Sheet Systems
One of the earliest AM technologies was the Laminated Object Manufacturing (LOM)
system. This technology used a laser to cut out profiles from sheet paper, supplied from a
continuous roll, which formed the layers of the final part. Layers were bonded together
using a heat-activated resin that was coated on one surface of the paper. Once all the layers
were bonded together the result was very like a wooden block. A hatch pattern cut into the
excess material allowed the user to separate away waste material and reveal the part.
3D PRINTING PROCESS CHAIN (or) The Generic 3d printing process:
1. CAD Model
2. STL convert
3. File transfer to machine
4. Machine setup
5. Build
6. Remove
7. Post-process
8. Application
Distinction between AM and Conventional Machining:
Sl.
No. AM Conventional Machining
AM technology was
Conventional Machining can
originally developed around
be used for soft materials,
polymeric materials, waxes
like medium- density
1 Material and paper laminates.
fiberboard (MDF),
Subsequently, there has
machineable foams,
been introduction of
machineable waxes, and
composites, metals, and
even some polymers
ceramics.
To make a part in an AM High speed Conventional
2 Speed machine, it may take a Machining can generally
few remove material
hours much faster than AM
machines
3 Complexity AM can build the part all at If Conventional Machining is
once. being used to create a
part directly in a single
piece, then there are some
geometric features that
cannot be
fabricated.
The accuracy of
Conventional Machines on
Accuracy AM machines
the other hand is mainly
generally operate with a
4 Accuracy determined by a similar
resolution of a few tens
positioning resolution along
of microns.
all three orthogonal axes
and by the diameter of the
rotary
cutting tools
AM machines essentially
Perfect geometry can
break up a complex, 3D
become extremely difficult to
5 Geometry problem into a series of
produce with Conventional
simple 2D cross- sections
Machining, even with 5-axis
with a nominal
control or greater
thickness
Determining the program
sequence for a Conventional
Machine can be very
6 Programmin AM don’t require involved, including tool
g programming selection, machine speed
settings, approach position,
and angle, etc
