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Selective Laser Sintering (SLS) is an additive manufacturing technique in which a laser is used sinter powdered material into a solid structure. Unlike3D printing, in which a liquid substrate is deposited layer-by-layer to form the item being produced, laser sintering forms the end-product by using the heat from a precisely-focused laser that coalesces a powder substrate into a solid mass. There are a number of advantages to this technique, which we’ll discuss in this post.
For the initiated, the process of sintering has been in use for literally thousands of years. The earliest sintered items were bricks, which were heated to high temperatures in open fires to strengthen them. Ceramics have also traditionally been sintered –notably in the creation of porcelain. The Incas reportedly used sintering to create gold-platinum jewelry.
In modern times, sintering has been inconstant use since the invention of the tungsten light bulb filament, which was ultimately mass-produced via sintering and still forms the basis of incandescent lighting worldwide. Copper-graphite electrical contacts, spark plugs, electrical insulators, porous bronze bearings, and cemented carbides (used for saw blades and other cutting instruments) – all have been traditionally manufactured using sintering. And the list goes on…
When Did They Add Lasers, and How Does it Work?
Dr. Carl Deckard developed and patentedSelective Laser Sintering (SLS) at the University of Texas at Austin in the mid-1980s, ultimately co-founding a startup to commercialize the technology.The company, DTM, was acquired in 2001 by its largest competitor, 3D Systems, and Deckard’s patent actually expired in 2014.
SLS uses a CAD file or similar computer model to guide a laser, which is precisely aimed at points in space and binds material together to form a solid structure. The substrate is typically a nylon or polyamide, although Direct Metal Laser Sintering (DMLS) – wherein the end product is metal – is becoming more common and cost-effective.
The high power (carbon dioxide, or other)laser used in SLS hardens and bonds the grains of substrate into layers to form the 3D dimensional structure. Each cross section of the design is traced onto the bed of powdered substrate, and then the bed is lowered for the next layer to be built. This continues until all layers are complete and the end product is finished.
Why Laser Sintering?
Within the additive manufacturing space, there are many advantages to laser sintering, most notably:
Laser sintering cost-effectively creates parts that are consolidated (requiring no assembly) – including geometries that other techniques can’t produce like moving parts and living hinges.
Laser sintering doesn’t require support structures that 3D printing uses to prevent design collapse during production.With laser sintering, the end product sits in a bed of powder, and thus no supports are necessary to preserve the structure before completion.
Because there are no supports, laser sintering carries an inherently lower risk of part damage when supports are removed. This enables creation of more complex interior components with no need to take tool clearance or draft angles into account.
Products produced via laser sintering tend to be more robust – withstanding both wear-and-tear and environmental conditions better. For small-run manufacturing, this makes laser sintering especially attractive and cost-effective, since no re-tooling is required between products.