What is SLS? Complete Guide to Selective Laser Sintering
Selective Laser Sintering (SLS) is an industrial 3D printing technology that uses a laser to fuse powdered material layer by layer. This comprehensive guide explains how SLS works, its advantages, materials, applications, and why it's the preferred technology for functional prototyping and low-volume manufacturing.
SLS Technology Overview
Selective Laser Sintering (SLS) is a powder bed fusion additive manufacturing process invented in the mid-1980s. Unlike FDM printing that extrudes melted plastic or SLA that cures liquid resin, SLS uses a high-powered laser to selectively fuse powdered material into solid structures.
The technology enables the production of functional parts with mechanical properties approaching injection-molded components, making it ideal for engineering applications, functional prototyping, and production parts. SLS is widely used in aerospace, automotive, medical, and consumer products industries.
How Does SLS 3D Printing Work?
Step 1: Powder Preparation
Fine powdered material (typically PA12 nylon with 60-micron particle size) is loaded into the build chamber. The entire chamber is heated to just below the powder's melting point (typically 170-180°C for PA12). This pre-heating minimizes the energy required for the laser to fuse particles and reduces thermal stress in parts.
Step 2: Layer Spreading
A recoater blade spreads a thin layer of powder (typically 0.1-0.15mm) uniformly across the build platform. The powder is distributed from a reservoir on one side to a collection bin on the other side, ensuring consistent layer thickness across the entire build area.
Step 3: Laser Scanning
A CO2 laser (typically 30-100W) is directed by high-speed galvanometer mirrors to trace the part's cross-section for that layer. The laser's energy heats particles above their melting point, fusing them together and bonding to the previous layer. Scan speeds reach 5-10 m/s for rapid processing.
Step 4: Layer Repetition
After each layer is sintered, the build platform lowers by one layer height (0.1mm), and fresh powder is spread across the surface. This process repeats hundreds or thousands of times, building the part from bottom to top. Build times range from 12-48 hours depending on total height.
Step 5: Cooling and Part Extraction
Once printing completes, the build chamber must cool gradually over 6-12 hours to prevent warping and thermal stress. After cooling to handling temperature (40-50°C), parts are extracted from unsintered powder using compressed air or bead blasting. Excess powder is recovered and reused for future builds.
Key Advantages of SLS Technology
No Support Structures Required
Unsintered powder acts as self-supporting material during printing. This enables complex overhangs, undercuts, and internal channels without dedicated supports, reducing post-processing time by 70% compared to FDM.
Isotropic Mechanical Properties
Parts have uniform strength in all directions because powder particles fuse completely. Unlike FDM with weak layer adhesion, SLS parts achieve 48 MPa tensile strength in X, Y, and Z axes.
Design Freedom
Create geometries impossible with traditional manufacturing: lattice structures, conformal cooling channels, organic shapes, and assemblies with moving parts printed in place.
Production-Grade Materials
PA12 nylon offers excellent chemical resistance, UV stability, and long-term durability. Parts can withstand harsh environments and demanding applications.
Batch Production Efficiency
Build time depends only on total height, not part count. Print 1 part or 100 parts in the same time by nesting components vertically and horizontally, maximizing throughput.
Material Reusability
Up to 90% of unsintered powder can be recovered, sieved, and reused. When mixed with 30-50% fresh powder, material costs per part are 60% lower than with non-reusable materials.
Common SLS Materials
PA12 (Nylon 12)
The most widely used SLS material, accounting for 85% of all applications. PA12 offers an ideal balance of mechanical properties, processability, and cost. Tensile strength of 48 MPa, elongation at break of 18%, and heat deflection temperature of 180°C make it suitable for most engineering applications.
PA11 (Nylon 11)
Bio-based polyamide derived from castor oil. PA11 provides superior impact resistance (2.5x higher than PA12), lower moisture absorption, and better flexibility. Ideal for living hinges, snap fits, and applications requiring elongation.
TPU (Thermoplastic Polyurethane)
Flexible, rubber-like material with Shore 92A hardness. TPU enables gaskets, seals, soft-touch grips, and wearable applications. Excellent abrasion resistance and elastic recovery up to 450% elongation.
Experience Industrial SLS Technology
The SinterX industrial SLS 3D printer brings professional laser sintering to your workspace. Request a demo to see the technology in action.