IT

SLS – Selective Laser Sintering

Selective Laser Sintering (SLS) is a 3D printing technology that uses a laser to selectively fuse polyamide powder layer by layer; the unsintered powder acts as support, allowing complex geometries without additional structures.

SLS – Selective Laser Sintering

What SLS technology is

SLS (Selective Laser Sintering) is a powder-bed fusion additive technology: a laser selectively fuses a thermoplastic powder layer by layer, almost always polyamide — PA12 (Nylon 12) or PA11, sometimes filled with glass or aluminium. It changes the paradigm completely compared with FDM and DLP, because it neither deposits nor cures material: it sinters it from a powder.

The cycle is always the same. A recoater — a blade or a roller — spreads a thin layer of powder over the build platform. A CO₂ laser scans the cross-section of the part, heating the powder just below its melting point until it coalesces, i.e. sinters. The platform lowers by one layer, the recoater spreads new powder and the cycle repeats. Everything happens in a chamber kept at a high temperature, just below the polymer’s melting threshold, so the laser only has to supply the residual energy needed to complete sintering.

Why choose it

What radically distinguishes SLS is self-support: the unsintered powder surrounding the part holds it throughout the build, so no support structures are needed. This brings three advantages that FDM and SLA do not offer as easily.

The first is complex and internal geometries — channels, undercuts, parts printed pre-assembled — achievable without worrying about overhangs or having to remove supports from inaccessible cavities. The second is three-dimensional nesting: you fill the entire chamber volume by packing parts in height as well, not just on the plane, which makes SLS very efficient for small and medium series, with dozens or hundreds of parts in a single cycle. The third is the mechanical properties: sintered PA12 gives robust, near-isotropic parts, resistant to impact and fatigue, suitable for real end-use components and not just aesthetic prototypes.

The trade-off is the finish. The surface is grainy and slightly porous — the typical “sandblasted” look of SLS nylon — with a grey/white base colour; for better aesthetics it requires post-processing such as dyeing, tumbling or smoothing. But when function matters more than appearance, it remains one of the most versatile processes available.

Typical applications

SLS is at its best where functional, robust parts in complex geometries are needed, rather than flawless aesthetic surfaces. Its natural fields are end-use component production in small and medium series, technical brackets and housings, ducts and manifolds with internal channels, spare and custom parts, and functional prototypes destined for real mechanical testing. Volume nesting also makes it particularly cost-effective when printing many parts together, driving down the unit cost. In general, any context where strength, geometric freedom and chamber-fill efficiency matter more than a mirror finish.

Printable materials

TPU
TPUTPU is a flexible, elastic material for MJF and SLS printing, ideal for components that require strength, elasticity and durability: gaskets, dampers, protective parts, footwear and ergonomic parts.
PA12
PA12PA12 is a high-performance powder thermoplastic for SLS printing: an excellent balance of mechanical strength, flexibility and dimensional stability, for prototypes and finished products across many industrial sectors.
PA12 GF
PA12 GFPA12 GF is a glass-fibre-reinforced PA12 for SLS printing: rigidity and mechanical strength higher than standard PA12, ideal for structural technical components with high load capacity.
TPE
TPETPE is an elastic material for SLS printing that combines the convenience of plastic with the softness of rubber: resistant to wear, chemicals and repeated stress, for flexible, ergonomic parts.
ALUFORM
ALUFORMALUFORM is a composite of polymer and metal powders for SLS printing: an aluminium-like aesthetic finish and good strength, for light yet robust components and presentation models.

FAQ

Does SLS require support structures?

No: the unsintered powder surrounding the part acts as support, so complex geometries, undercuts and nested parts can be produced without dedicated supports.

What finish does an SLS part have and how is it improved?

The surface is grainy and slightly porous, with the typical 'sandblasted' look of nylon and a grey/white base colour. For better aesthetics, post-processing such as dyeing, tumbling or smoothing is used, but for many functional parts the raw finish is already enough.

Which materials are used in SLS?

Mainly polyamides: PA12 (Nylon 12), the most common, and PA11, tougher and bio-based. There are also glass- or aluminium-filled grades for greater rigidity and thermal stability, and elastomeric powders (TPU) for flexible parts.

Are SLS parts functional or only aesthetic?

They are functional. Sintered PA12 gives robust parts with near-isotropic mechanical properties, resistant to impact and fatigue: suitable for real end-use components, not just aesthetic prototypes. It is one of the main reasons SLS is chosen.

What accuracy and minimum thicknesses can you expect?

Typical tolerances are in the order of ±0.3 mm (or ±0.3% on larger dimensions), with minimum wall thicknesses roughly around 0.7–1 mm. Exact values depend on the machine, material and part geometry.

Can the unsintered powder be reused?

Partly. Powder that has been through the thermal cycle degrades slightly, so it is not reused as is: for each print a share of fresh powder (roughly 30–50%) is mixed with the recovered powder. It is a factor to consider in the cost of SLS parts.

SLS or FDM?

It depends on the goal. FDM is cheaper for single parts and simple prototypes, but needs supports on overhangs and has anisotropic properties between layers. SLS uses no supports, allows complex internal geometries and volume nesting, and gives more robust, homogeneous parts: it is preferable for complex geometries, functional parts and small/medium series.

Last updated: 10/06/2026