SLS was among the earliest additive manufacturing processes. It has been adapted for use with a variety of materials from plastics, to metals, to a wide range of composites. SLS is especially well suited for printing complex geometries with mechanical properties that rival molded and milled materials.
Today, SLS is capable of directly producing end-user parts due to process improvements and cost reductions with the release of new products like the Formlabs Fuse 1. Instead of investing in complex tooling and molds, engineers and manufacturers can directly print objects on a per-part basis, cutting down on upfront costs and reducing excess inventory.
How Does Selective Laser Sintering (SLS) Work?
SLS stands for Selective Laser Sintering and makes use of high-powered lasers to ‘sinter’ together powderized composites.
- Powder is encased in a build chamber and the printer heats the material to just below its melting temperature.
- A high-powered laser traces a cross-section of the design, sintering together unfused powder. Pre-heating the powder allows the laser to sinter the material more quickly.
- The build platforms lowers by one layer (layer height varies by machine but is usually between 50 and 200 microns)
- A new layers of powder is distributed atop the sintered material at a height of one layer.
- The next cross-section is sintered and the process repeats.
Unlike most other 3D printing technologies, parts printed using SLS don’t require any support structures. Objects are always surrounded by powder and this supports the geometry as it prints enabling designers and engineers to focus more on the creative process and worry less about printability.
Embedded and interconnected objects are easier to print on SLS compared to other technologies. The self-supporting process allows joints and hinges to be printed in place and used immediately after printing with little to no processing required.
Because parts are always embedded in powder, multiple components can be stacked atop each other to maximize build volume utilization. This allows multiple components or large batches of parts to be produced in a single instance reducing both printing and post-processing times.
After printing, the build chamber is removed from the machine and sintered parts are separated from unfused powder. Compressed air is used to remove excess powder and following this step, parts are ready for use. Nylon, one of the most common SLS materials, has a grainy surface by default (similar to 200 grit sandpaper) but is compatible with a wide variety of finishing techniques including sanding, dyeing, painting, and powder coating.
Depending on the material, additional steps may be needed to recycle unfused powder in the build chamber. The Formlabs Fuse 1 uses Nylon as a printing material and can be purchased with Form Recover which streamlines the process of part removal and powder recycling.
Form Recover provides a perforated build surface that printed powder is poured onto, allowing unfused powder to fall into a holding chamber while keeping printed parts on the surface. An embedded compressed air unit helps to remove excess powder from printed parts and Form Recover contains airborne particles to keep them from your work space. Using Form Recover, up to 50% of used material can be reclaimed for future prints.
Any material capable of being powderized and sintered can be used in an SLS system. This includes metals, ceramics, and common thermoplastics. Metals and Ceramics require industrial grade machines that make use of high-powered Carbon Dioxide lasers. All of the other advantages of SLS can be had in lower-cost machines like the Formlabs Fuse 1 which is capable of printing in several types of Nylon.
Nylon is a classification of a group of similar plastics rather than a single material itself. The Formlabs Fuse 1 makes use of two popular types of Nylon, PA11 and PA12, to cover a wide range of different applications.
PA12 is among the most popular materials used by engineers and product designers today. Its moderate stiffness and high tensile strength makes it suitable for the direct printing of end-user products and realistic engineering prototypes.
PA11 has similar mechanical and thermal properties as compared to PA12 but differs with greater flexibility.
New low-cost machines and process improvements are allowing designers and engineers to transition from traditional manufacturing techniques to more efficient digital techniques. Digital Manufacturing describes the direct production of end-user good through processes like 3D Printing.
SLS specifically, allows manufacturers to directly print end-user objects reducing design constraints, cost of iteration, and wasted inventory. The Formlabs Fuse 1 brings low-cost benchtop SLS to a market previously saturated by costly industrial machines and makes Digital Manufacturing a viable and cost-effective technique for your project.