SLS 3D Printing: Selective Laser Sintering Service
SLS 3D printing produces nylon parts without support structures. Layer resolution 0.1mm, production-grade mechanical properties, and self-supporting complex geometry — ideal for functional prototypes and low-volume production at FIRMFG.
SLS 3D Printing: Selective Laser Sintering Service
Selective Laser Sintering (SLS) uses a CO2 laser to fuse nylon powder layer by layer into solid, functional parts. Unlike FDM and SLA, SLS is self-supporting — the un-sintered powder surrounding each layer holds up overhangs, internal channels, and complex geometry. This eliminates support structures entirely and unlocks design freedom that no other 3D printing technology can match.
At FIRMFG, our SLS service delivers production-grade nylon parts with a layer height of 0.1–0.15 mm, dimensional tolerance of ±0.2 mm, and build volume up to 330 × 330 × 600 mm. We offer four materials — PA12, PA12-GF, PA11, and TPU — covering rigid structural parts, glass-filled stiffness, tough ductile components, and flexible elastomers. Batch nesting lets us run dozens of parts in a single build, making SLS cost-effective for low-volume production runs of 50–500 units.
This guide covers how SLS works, available materials, design guidelines, a comparison with FDM and SLA, post-processing options, and cost factors. Ready to get started? Request a quote and our engineers will help you choose the right material and orientation for your SLS project.
SLS 3D Printing Quick Specifications
Key printing and material parameters for SLS selective laser sintering at FIRMFG.
| Specification | Value |
|---|---|
| Layer Height | 0.1 – 0.15 mm (100 – 150 μm) |
| Dimensional Tolerance | ±0.2 mm (±0.008") |
| Maximum Part Size | 330 × 330 × 600 mm |
| Surface Finish | Ra 5 – 10 μm (grainy) |
| Minimum Wall Thickness | 0.7 mm (0.028") |
| Print Technology | CO2 Laser Sintering (self-supporting) |
How SLS 3D Printing Works
A CO2 laser selectively sinters nylon powder, building parts layer by layer. The un-sintered powder acts as built-in support, enabling complex self-supporting geometry.
Step 1: Powder Bed Preparation
A thin layer of nylon powder (typically 100–150 μm) is spread across the build platform inside a heated chamber. The chamber is held just below the melting point of the polymer, so only a small thermal input is needed to fuse the next layer.
Key detail: Powder layer: 100 – 150 μm, chamber temp near melt point
Step 2: Laser Sintering
A CO2 laser traces the cross-section of the part, selectively fusing (sintering) the powder particles together. The laser energy raises the local temperature just past the melting point, bonding particles into a solid layer without full liquefaction.
Key detail: CO2 laser, scan speed up to 10 m/s, spot size 0.3 – 0.5 mm
Step 3: Layer-by-Layer Build
After each layer is sintered, the build platform lowers by one layer thickness and a fresh powder layer is spread on top. Because un-sintered powder remains in place, it naturally supports overhangs and complex geometry — no separate support structures are required.
Key detail: Self-supporting: un-sintered powder acts as support
Step 4: Cooling & Depowdering
Once the build completes, the entire powder cake cools slowly inside the chamber to relieve internal stress and prevent warping. The part is then extracted and excess powder is removed by brushing and compressed air, ready for post-processing.
Key detail: Cool-down: 6 – 12 hours, then depowder and sieve
Available SLS Materials
Four nylon-based materials cover the full range of mechanical, thermal, and flexible requirements for SLS printing.
PA12 (Nylon 12)
The standard SLS material. Balanced mechanical properties, good chemical resistance, and excellent long-term stability. White in color, dyeable, and suitable for the majority of functional prototypes and end-use parts.
Properties: Tensile 48 MPa, HDT 175°C, elongation 18%
Best for: General functional parts, enclosures, complex geometry
PA12-GF (Glass-Filled)
PA12 reinforced with glass fiber for higher stiffness, dimensional stability, and thermal resistance. Reduced creep and shrinkage make it ideal for load-bearing structural components and tight-tolerance assemblies.
Properties: Tensile 45 MPa, HDT 175°C, stiffness +40%
Best for: Structural brackets, load-bearing parts, jigs
PA11 (Nylon 11)
Tougher and more ductile than PA12, with superior impact resistance and elongation. Bio-sourced from castor oil, offering higher elasticity for living hinges, snap-fits, and parts subjected to repeated flexing.
Properties: Tensile 48 MPa, elongation 30 – 40%, high impact
Best for: Living hinges, snap-fits, impact-resistant parts
TPU (Elastomer)
Thermoplastic polyurethane powder for flexible, rubber-like SLS parts. Combines the design freedom of self-supporting SLS with elastomeric properties for seals, bellows, cushions, and wearable components.
Properties: Shore 86A – 92A, elongation 300%+
Best for: Seals, bellows, flexible couplings, wearables
Design Guidelines for SLS Printing
SLS design rules leverage self-supporting geometry. Focus on wall thickness, powder removal from enclosed features, and part orientation for optimal results.
| Design Feature | Recommended | Minimum |
|---|---|---|
| Minimum Wall Thickness | 0.8 mm (0.031") | 0.7 mm (0.028") |
| Minimum Hole Diameter | 1.0 mm (0.040") | 0.5 mm (0.020") |
| Minimum Gap (Moving Parts) | 0.5 mm (0.020") | 0.3 mm (0.012") |
| Minimum Engraved Detail | 0.6 mm (0.024") | 0.4 mm (0.016") |
| Internal Channel Diameter | 1.0 mm (0.040") | 0.8 mm (0.031") |
| Living Hinge Thickness | 0.5 mm (0.020") | 0.4 mm (0.016") |
| Threaded Holes | Heat-set inserts | Tapping (M2 and above) |
| Large Flat Surfaces | Add ribs or gussets | Avoid large flat planes |
DFM Tips for SLS Printing
- No supports needed — design freely with overhangs, undercuts, and internal channels that would be impossible in FDM or SLA.
- Add drain or escape holes (at least 3–5 mm) to any fully enclosed cavity so trapped powder can be removed after printing.
- Keep internal channel diameters above 0.8 mm to ensure powder can be cleared. Narrower channels may clog with fused powder.
- Design mating parts with a 0.3–0.5 mm clearance gap to account for surface roughness and prevent parts from binding together.
- Avoid large flat surfaces — they tend to warp during cooling. Add ribs, gussets, or a slight curvature to maintain flatness.
- For threaded connections, use heat-set inserts rather than tapping directly into nylon. Tapped SLS threads are durable but inserts are stronger.
SLS vs FDM vs SLA Comparison
Understanding how SLS compares to FDM and SLA helps you choose the right technology for your geometry, strength, surface, and material requirements.
| Criteria | SLS | FDM | SLA |
|---|---|---|---|
| Support Structures | None (self-supporting) | Required | Required |
| Mechanical Strength | High (isotropic) | Moderate (anisotropic) | Moderate (brittle) |
| Surface Finish | Grainy (Ra 5 – 10 μm) | Visible layer lines | Smooth (Ra 0.5 – 2 μm) |
| Material Range | Nylon, TPU | PLA, ABS, PETG, TPU | Photopolymer resins |
| Complex Geometry | Excellent | Limited (supports) | Moderate (supports) |
| Dimensional Accuracy | ±0.2 mm | ±0.2 mm | ±0.1 mm |
| Cost per Part | Medium | Low | Medium |
SLS occupies a unique position: it is the only mainstream 3D printing technology that combines self-supporting complex geometry with production-grade thermoplastic material properties.
Choose SLS When
You need complex geometry, internal channels, or low-volume production in production-grade nylon without support removal. Best for functional, self-supporting parts.
Choose FDM When
You need low-cost prototypes in standard thermoplastics (PLA, ABS, PETG) and can accept support structures and visible layer lines. Best for budget prototyping.
Choose SLA When
You need maximum surface finish, fine detail, or optical clarity in photopolymer resin. Best for cosmetic models and high-accuracy master patterns.
Post-Processing Options
As-printed SLS parts have a grainy surface. A range of finishing operations transforms them into production-quality components with smooth, colored, or sealed surfaces.
Sandblasting
Glass bead or sand blasting removes the grainy surface texture left by sintered powder, producing a uniform matte finish and improving cosmetic appearance.
Dyeing
Nylon parts can be dyed in black, red, blue, green, and other colors through a hot dye bath. Color penetrates the surface for durable, through-color finish that resists chipping.
Vibratory Smoothing
Tumbling in abrasive media smooths sharp edges and reduces surface roughness. Ideal for batch processing multiple parts to a consistent finish.
Coating & Sealing
Epoxy or polyurethane coating seals the porous SLS surface, improving moisture resistance, chemical barrier properties, and surface hardness.
Machining & Tapping
CNC post-machining of holes, threads, and mating surfaces achieves tighter tolerances than as-printed parts. Heat-set inserts provide durable threaded connections.
Painting
After primer filling of the porous surface, SLS parts accept paint for custom colors, branding, and high-gloss or textured cosmetic finishes.
Need a specific finish for your SLS parts? Explore our complete custom surface finishing services, including sandblasting and bead blasting for uniform matte SLS surfaces.
SLS Cost Factors
SLS cost is driven by material volume and build nesting. Batch nesting multiple parts in a single build significantly reduces per-part cost for low-volume production.
PA12 (Nylon 12)
$0.50 – $1.00 / g
Standard material, widest application range
PA12-GF (Glass-Filled)
$0.60 – $1.20 / g
Reinforced, higher stiffness
PA11 (Nylon 11)
$0.70 – $1.30 / g
Tougher, bio-sourced, premium
TPU (Elastomer)
$0.80 – $1.50 / g
Flexible elastomer, specialty
Cost Example: Single Part vs Batch Nesting
| Order Scenario | PA12 | PA11 | Notes |
|---|---|---|---|
| 1 unit (small part, 15 g) | $25 | $35 | Single part, minimum build charge |
| 1 unit (large part, 150 g) | $150 | $200 | Material-dominant cost |
| 20 units (batch nested) | $18 / part | $26 / part | Batch nesting cuts per-part cost by 30 – 50% |
SLS pricing is based on material volume consumed and build time, not part count. Nesting 20 parts in one build shares the fixed machine time and reduces per-part cost by 30–50% versus printing individually. Actual quotes vary with geometry, material, and post-processing.
SLS 3D Printing FAQ
Answers to the most common questions about SLS selective laser sintering at FIRMFG.
QDoes SLS 3D printing require support structures?
No. SLS is self-supporting — the un-sintered nylon powder surrounding each layer holds up overhangs, bridges, and complex internal geometry. This eliminates the need for separate support structures and the associated removal and surface marking. It is the key advantage of SLS over FDM and SLA, enabling parts with deep undercuts, internal channels, and fully enclosed cavities that would be impossible or extremely difficult to print with other technologies.
QWhat accuracy and tolerance can SLS achieve?
SLS parts achieve a dimensional tolerance of ±0.2 mm (±0.008") for features up to 100 mm, and ±0.2% for larger dimensions. Layer height ranges from 0.1 to 0.15 mm. Accuracy is influenced by part geometry, material shrinkage during cooling, and orientation in the build. For features requiring tighter tolerances — such as bearing fits, threaded holes, or mating surfaces — CNC post-machining brings tolerances down to ±0.05 mm.
QWhat is the surface quality of SLS parts?
As-printed SLS parts have a grainy, matte surface with a roughness of Ra 5–10 μm, caused by the sintered powder particles. This texture is uniform and acceptable for many functional applications. For improved cosmetics, the surface can be refined through sandblasting (which evens the texture), vibratory tumbling (which smooths edges), dyeing (which adds color), or coating and painting. SLS cannot match the smooth as-printed surface of SLA resin without post-processing.
QWhat materials are available for SLS 3D printing?
FIRMFG offers four primary SLS materials: PA12 (standard nylon 12, balanced properties, white and dyeable), PA12-GF (glass-filled for higher stiffness and thermal resistance), PA11 (tougher, more ductile, bio-sourced for living hinges and snap-fits), and TPU (elastomeric polyurethane for flexible, rubber-like parts). PA12 covers the majority of applications. Material choice depends on the required mechanical load, flexibility, temperature exposure, and chemical resistance.
QWhat is the minimum wall thickness for SLS parts?
The recommended minimum wall thickness for SLS is 0.8 mm, with an absolute minimum of 0.7 mm. Walls thinner than 0.7 mm risk being too fragile to survive depowdering and post-processing, and may warp during cooling. For load-bearing or structural walls, 1.0–1.5 mm is recommended. Living hinges can be as thin as 0.4 mm in PA11, but only for limited flex cycles. Minimum hole diameter is 0.5 mm, and internal channels should be at least 0.8 mm to allow powder removal.
QWhat is the lead time for SLS 3D printing?
Standard SLS lead time is 3–5 business days from approved CAD files to finished parts, including printing, cooling, depowdering, and basic post-processing. Single parts in PA12 can ship in 2–3 days with rush service. Larger batches benefit from build nesting — multiple parts share a single build — which keeps lead time stable at 4–6 days even for 20–50 parts. Add 1–2 days for dyeing, coating, or CNC post-machining. Complex assemblies with multiple components typically take 5–7 days.
SLS 3D Printing Applications
From complex functional parts to low-volume production and internal channels, SLS serves applications where self-supporting geometry and production-grade nylon are essential.
Complex Functional Parts
Deep undercuts, internal channels, and enclosed cavities that are impossible with FDM or SLA due to the self-supporting nature of SLS powder.
Low-Volume Production
Production-grade nylon parts for 50–500 unit runs without tooling investment. Batch nesting maximizes build efficiency and reduces per-part cost.
Internal Channels & Conduits
Fluid and air channels, manifolds, and ducting with complex internal routing printed directly — no assembly or joining required.
Snap-Fit & Living Hinge Parts
PA11 and PA12 produce durable snap-fits, clips, and living hinges that flex repeatedly without failing, ideal for housings and enclosures.
Wear-Resistant Components
Nylon gears, bushings, and guides with low friction and high wear resistance for mechanical assemblies and moving parts.
Ductwork & Manifolds
Lightweight, complex ducting for automotive, aerospace, and industrial applications where geometry-driven airflow is critical.
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Learn MoreStart Your 3D Printing Project
Upload your CAD files and get a free SLS 3D printing quote within 24 hours. Our engineers provide material recommendations, DFM feedback, and build nesting optimization at no cost. ISO 9001 certified quality, four nylon materials, and 3–5 day turnaround.