Selective Laser Sintering (SLS) is the rapid prototyping technology of choice for a range of functional prototype applications, including those with snap fits, living hinges and other mechanical joints. The ability of SLS to produce several pieces at one time also makes the process a good choice for Direct Digital Manufacturing (DDM) of products requiring strength and heat resistance.
WHAT IS LASER SINTERING?
SLS technology uses a laser to harden and bond small grains of plastic, ceramic, glass, metal (we talk in a different article about direct metal sintering), or other materials into layers in a 3D dimensional structure. The laser traces the pattern of each cross section of the 3D design onto a bed of powder. After one layer is built, the bed lowers and another layer is built on top of the existing layers. The bed then continues to lower until every layer is built and the part is complete.
One of the major benefits of SLS is that it doesn’t require the support structures that many other AM technologies use to prevent the design from collapsing during production. Since the product lies in a bed of powder, no supports are necessary. This characteristic alone, while also conserving materials, means that SLS is capable of producing geometries that no other technology can. In addition, we don’t have to worry about damaging the part while removing supports and we can build complex interior components and complete parts. As a result, we can save time on assembly. As with other AM technologies, there’s no need to account for the problem of tool clearance—and thus the need for joints—that subtractive methods often encounter. So we can make previously impossible geometries, cut down on assembly time and alleviate weak joints.
SLS really shines when you need plastic parts that will last. SLS is capable of producing highly durable parts for real-world testing and mold making, while other additive manufacturing methods may become brittle over time. Because SLS parts are so robust, they rival those produced in traditional manufacturing methods like injection molding and are already used in a variety of end-use applications, like automotive and aerospace.
Considering its robustness and capability to produce complex whole parts, SLS can bring major time and cost benefits for small-run parts that would usually require some assembly with traditional manufacturing. It’s a perfect marriage of functionality, strength and complexity. We can produce parts faster and cut down on the time required to put them together. But we can also produce fewer parts, as SLS parts tend to stand up better to wear and environmental conditions. Especially for mass customization for certain low-volume end-use parts, SLS blows traditional manufacturing out of the water because there is no expensive and inefficient retooling to worry about. One of the other big things with SLS, as we’ll see with many other additive manufacturing technologies, is it allows us to store and reproduce parts and molds, using data that will never corrode, get lost in transportation or require expensive storage. The designs are always available and ready to be produced when we need them, even if the original is unavailable.
One way we can think about the uses for SLS parts is in terms of the materials it uses. Styrene-based materials are great for making castings—in plaster, titanium, aluminum and more—and are compatible with most standard foundry processes. SLS also can create impact-resistant engineering plastic that’s great for low- to mid-volume end-use parts, like enclosures, snap-fit parts, automotive moldings and thin-walled ducting. Engineering plastic can also be made with flame retardant material, to fit aircraft and consumer product requirements, or gas-filled material for greater stiffness and heat resistance. There’s even fiber reinforced plastic for ultimate stiffness, and, on the other end of the spectrum, rubber-like material for flexible parts, like hoses, gaskets, grip padding and more.