3D Printing Technologies Explained: FDM, DLP/SLA and SLS

3D Printing Technologies

3D printing is not a single technology, but an umbrella term for various manufacturing methods that each build a product or component layer by layer in their own way. The choice of technology largely determines the material properties, dimensional accuracy, surface quality and cost of a part. Below, we explain the three technologies we use most: FDM, DLP/SLA and SLS.

FDM (Fused Deposition Modeling)

With FDM printing, also known as FFF printing, a thermoplastic filament is fed through a heated nozzle and melted. The print head deposits the molten material layer by layer according to the digital model, often in STL, OBJ or STEP format. Each layer then cools and bonds to the previous one. Commonly used materials include PLA, PETG, ABS, ASA, PC, nylon and flexible TPU, each with its own properties in terms of strength, temperature resistance and chemical resistance.

Various other types of filament can also be used, such as carbon-fiber-reinforced PA6 filament. This provides high stiffness, high strength and good thermal resistance while remaining lightweight.

Filaments reinforced with glass fiber are also available. These provide good chemical resistance and a smoother surface, combined with moderate thermal resistance. They are ideal for robust end products, housings that need to withstand outdoor conditions and small-series production.

DLP/SLA (Resin printing)

DLP and SLA are resin-based or photopolymerization technologies. A liquid, light-sensitive resin is selectively cured with UV light, layer by layer. The difference lies in the light source: SLA uses a laser point to trace the contour, while DLP and related mSLA/LCD technology expose an entire layer at once using a projector or LCD screen. This generally makes DLP faster and more consistent.

This technology provides the highest level of detail and the smoothest surfaces of the three, with fine features and sharp edges. It is therefore widely used for master models, for example for silicone and PU casting, fine prototypes, dental applications and jewelry applications. Points to consider include post-processing: printed parts need to be washed, usually in IPA, and post-cured under UV light. Material properties are another consideration: standard resins are relatively brittle, although tough and temperature-resistant engineering resins are now also available.

SLS (Selective Laser Sintering)

With SLS, a thin layer of polymer powder, usually nylon such as PA12 or PA11, is spread across a heated build bed. A laser then precisely fuses, or sinters, the powder where the part needs to be formed. The bed lowers, a new layer of powder is applied, and the process is repeated. The unprocessed powder surrounding the part acts as a support, eliminating the need for additional support structures and allowing complex shapes, cavities and moving components to be printed in one piece.

This makes SLS printing suitable for functional end products and small-series production, as the parts are strong and have largely direction-independent, or isotropic, properties. The surface has a characteristic, slightly grainy matte texture. Post-processing mainly consists of depowdering; removing support structures is NOT necessary.