Laser Sintering (LS) / Selective Laser Sintering (SLS) systems usually use
a CO₂-Laser as an energy source. The laser is directed by a scanner system.
This scanner is an arrangement of two mirrors in XY-configuration to direct
the laser beam in the XY-plane on the powder bed. To compensate the focal
height in the z axis a special flat field/ f-theta lens is used.
The build material is in powder form. A hopper or rollers is used to apply the
material in thin layers. The build chamber is filled Nitrogen as a shielding gas.
The laser power is compared to metal powder bed fusion systems, with
max. 50 Watts, significantly lower. The reason for this is that the whole build
chamber is heated up. The material temperature is just under its melting
temperature when the lase scans it. The laser is contributing only the missing
five degrees Celsius to melt and fuse the material. Further the materials have
a higher absorption rate compared to metals. This allows significantly higher
scan/processing speeds of polymer systems compared to metal systems.
Professional SLS/LS machines
Prices for pro machines are starting at about 200 000 dollars
but they can easily reach up to a one million dollars.
Prosumer SLS/LS systems
Patents for LS/SLS technology expired in 2014.
Several start-up companies announced to release
prosumer systems at a fraction of the cost of pro machines.
One of those companies, called Norge LTD, got acquired through the French Groupe Gorgé
in March 2015 [link to press release]
The Swiss startup SINTRATEC GmbH raised funding on the INDIGOGO crowdfunding platform.
Certainly something to keep an eye on.
Build space sizes
Small systems have build envelopes of about 250 mm x 200 mm x 330 mm
Medium size systems have build envelopes of about 350 mm x 350 mm x 600 mm
Large size systems have build envelopes of about 600 mm x 600 mm x 1200 mm
The machine with by far the largest build envelopes is the Binhu SLS 1400 with
build space dimensions of about1400 x 700 x 500 mm.
As SLS does not require support structures the build space can be fully utilised.
Nesting software allows to position up to hundreds of parts the most efficient way.
Materials typically used are Polyamides (PA11, PA12), Polystyrene
but also PEEK & PEEEK can be processed on special machines.
The powder not fused in the process can be recycled to a certain percentage.
An exception are PEEK and PEEEK materials as theses materials cannot be recycled.
The ration of virgin and recycled material affects material properties of the parts build.
Filled materials: Materials can be filled or mixed with other materials to improve thermal
and thermal properties. Glas beats, glas and carbon fibres are usually used for this.
The layer thickness can vary typically from 0,04 mm – 0,15 mm.
Due to the high position accuracy of the XY-laser scan systems used the
geometrical accuracy of the parts is more affected by warpage of the parts.
Experienced machine operators know how to prevent and mitigate this issues.
SL/SLS has been used for prototyping and part production since decades.
Material properties and geometrical accuracy are a good trade off to create
robust parts which can be sanded, died, glued or welded and coated.
Higher machine capacities and more competition in the material market
has made this technologies economical for more and more applications.
Here some examples from different industries:
Prototyping for 0 series, custom parts for luxury vehicles
Anatomical models, drill guides and cutting jigs for surgeries.
Implants in PEEK&PEEEK to replace bone structure
On platforms like Shapeways.com end consumers
can upload and share designs and get theses manufactured
with LS/SLS technology. From student projects to jewellery to
spare parts and improvements for commercial products.
This are still niche applications but LS/SLS is used for low batch
production from sunglasses to 3D printed bikinis made 3D fabrics.
(Please note: We are currently working on our website.
We are updating our content to provide you with more information soon)