What is SLA and SLS?

Quick Answer

SLA (Stereolithography) and SLS (Selective Laser Sintering) are two leading 3D printing technologies. SLA cures liquid photopolymer resin layer by layer using a UV laser, producing parts with exceptional surface finish and detail. SLS fuses nylon powder using a laser, creating durable, functional parts that require no support structures. Each technology serves different applications and budgets.

SLA - Stereolithography

SLA was the first 3D printing technology commercialized, invented in 1986. It uses a UV laser to selectively cure liquid photopolymer resin in a vat. The build platform lowers incrementally as each layer is cured. SLA is known for producing parts with the smoothest surface finish and highest detail resolution among all 3D printing technologies, with layer resolutions as fine as 25 microns. It is ideal for concept models, investment casting patterns, dental and medical models, and visual prototypes.

SLS - Selective Laser Sintering

SLS uses a high-power laser to fuse nylon powder particles into solid structures. The unsintered powder surrounding each part acts as natural support, eliminating the need for dedicated support structures. This allows complex geometries and interlocking assemblies to be printed in a single build. SLS parts are durable, impact-resistant, and suitable for functional testing and end-use applications. Typical layer thickness is 100-120 microns.

Key Differences

Surface Finish: SLA produces smoother surfaces (typically 0.5-1.5 Ra) while SLS has a matte, slightly grainy texture (3-6 Ra). Material Properties: SLA resins are available in various formulations but are generally more brittle. SLS nylon parts are tough, flexible, and impact-resistant. Support Structures: SLA requires supports, SLS does not. Post-Processing: SLA needs washing and UV curing; SLS requires bead blasting to remove excess powder.

Why Choose SOMI Custom Parts

At SOMI Custom Parts, we offer both SLA and SLS 3D printing services alongside our CNC machining capabilities. Our engineering team helps you choose the right technology for your specific application -- whether you need the fine detail of SLA for presentation models or the functional strength of SLS for testing prototypes. Combining 3D printing with CNC machining, we provide the most cost-effective path from prototype to production.

Case Study

A medical device company needed highly detailed anatomical models for surgical planning. SLA printing was the clear choice -- SOMI produced 3D-printed resin models with 50-micron layers, capturing fine anatomical features including blood vessels and nerves. The surgeon used the models for pre-surgical planning, reducing operating time by 25%.

Industry Data

The global 3D printing market was valued at $20.4 billion in 2025 and is expected to reach $55.8 billion by 2030 (Wohlers Report, 2025). SLA and SLS together account for approximately 40% of all industrial 3D printing applications, making them the most widely used technologies for professional prototyping.

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