What is Selective Laser Sintering –
Advantages and Disadvantages
Introduction to Selective Laser Sintering :
Additive manufacturing, or 3D printing, is the process of turning digital designs
into three-dimensional objects. It is a convenient and affordable way to make
prototypes as well as finished products, making it popular with businesses, hobbyists
and inventors.
One of the technologies used by today’s 3D printers is called selective laser sintering
(SLS). During SLS, tiny particles of plastic, ceramic or glass are fused together by
heat from a high-power laser to form a solid, three-dimensional object.
The SLS process was developed and patented in the 1980s by Carl Deckard — then
an undergraduate student at the University of Texas — and his mechanical
engineering professor, Joe Beaman.
Selective laser sintering (SLS) is an additive manufacturing (AM) technique that
uses a laser as the power source to sinter powdered material (typically metal),
aiming the laser automatically at points in space defined by a 3D model, binding the
material together to create a solid structure. It is similar to direct metal laser sintering
(DMLS); the two are instantiations of the same concept but differ in technical details.
Selective laser melting (SLM) uses a comparable concept, but in SLM the material is
fully melted rather than sintered, allowing different properties (crystal structure,
porosity, and so on). SLS (as well as the other mentioned AM techniques) is a
relatively new technology that so far has mainly been used for rapid prototyping and
for low-volume production of component parts. Production roles are expanding as
the commercialization of AM technology improves.
Working of SLS – Selective Laser Sintering
In this method, a thin layer of powder is applied using a roller. The SLS uses a laser
beam to selectively fuse powdered materials, such as nylon, elastomers and metals
into a solid object as shown in the Fig.
selective laser sintering process
The CO2 laser is often used to sinter successive layers of powder instead of liquid
resin. Parts are built upon a platform which sits just below the surface in a bin of the
heat-fusible powder. A beam of laser then traces the pattern on the very first layer
thereby sintering it together. The platform is further lowered by the height of the
second layer and powder is again applied. This process is continued until the part is
completed. The excess amount of powder at each layer helps to support the part
during its build-up.
Advantages of SLS
• A distinct advantage of the SLS process is that because it is fully self-
supporting, it allows for parts to be built within other parts in a process
called nesting – with highly complex geometry that simply could not be
constructed any other way.
• Parts possess high strength and stiffness
• Good chemical resistance
• Various finishing possibilities (e.g., metallization, stove enameling, vibratory
grinding, tub coloring, bonding, powder, coating, flocking)
• Bio compatible according to EN ISO 10993-1 and USP/level VI/121 °C
• Complex parts with interior components, channels, can be built without
trapping the material inside and altering the surface from support removal.
• Fastest additive manufacturing process for printing functional, durable,
prototypes or end user parts.
• Vast variety of materials and characteristics of Strength, durability, and
functionality, SLS offers Nylon based materials as a solution depending on
the application.
• Due to the excellent mechanical properties the material is often used to
substitute typical injection molding plastics.
Disadvantages
SLS printed parts have a porous surface. This can be sealed by applying a coating
such as cyanoacrylate.
Indirect selective laser sintering (SLS) is a promising
additive manufacturing technique to produce ceramic parts with complex
shapes in a two-step process. In the first step, the polymer phase in a
deposited polymer/alumina composite microsphere layer is locally molten
by a scanning laser beam, resulting in local ceramic particle bonding.
LASER ENGINEERED NET SHAPING PROCESS
Laser engineered net shaping
From Wikipedia, the free encyclopedia
(Redirected from Laser Engineered Net Shaping)
Laser powder forming, also known by the proprietary name (laser engineered net
shaping) is an additive manufacturing technology developed for fabricating metal
parts directly from a computer-aided design (CAD) solid model by using a metal
powder injected into a molten pool created by a focused, high-powered laser beam.
This technique is also equivalent to several trademarked techniques that have the
monikers direct metal deposition (DMD), and laser consolidation (LC). Compared to
processes that use powder beds, such as selective laser melting (SLM) objects
created with this technology can be substantially larger, even up to several feet
long.[1]
Method[edit]
A high power laser is used to melt metal powder supplied coaxially to the focus of the laser beam
through a deposition head. The laser beam typically travels through the center of the head and is
focused to a small spot by one or more lenses. The X-Y table is moved in raster fashion to
fabricate each layer of the object. The head is moved up vertically after each layer is completed.
Metal powders are delivered and distributed around the circumference of the head either by
gravity, or by using a pressurized carrier gas. An inert shroud gas is often used to shield the melt
pool from atmospheric oxygen for better control of properties, and to promote layer to layer
adhesion by providing better surface wetting.
Other techniques[edit]
This process is similar to other 3D fabrication technologies in its approach in that it forms a solid
component by the layer additive method. The LENS process can go from metal and metal oxide
powder to metal parts, in many cases without any secondary operations. LENS is similar
to selective laser sintering, but the metal powder is applied only where material is being added to
the part at that moment. It can produce parts in a wide range of alloys,
including titanium, stainless steel, aluminum, and other specialty materials; as well as composite
and functionally graded materials. Primary applications for LENS technology include repair and
overhaul, rapid prototyping, rapid manufacturing, and limited-run manufacturing for aerospace,
defense, and medical markets. Microscopy studies show the LENS parts to be fully dense with
no compositional degradation. Mechanical testing reveals outstanding as-fabricated mechanical
properties.
The process can also make "near" net shape parts when it is not possible to make an item to
exact specifications. In these cases post production process like light machining, surface
finishing, or heat treatment may be applied to achieve end compliance. It is used as finishing
operations.
