A CO₂ laser sinters polymer powder in a heated build chamber — producing support-free, isotropic parts with geometries impossible in any other AM process.
SLS doesn't require support structures — unsintered powder supports the part throughout the build. This enables geometries completely impossible in FDM or SLA: interlocking parts, lattice structures, and complex internal channels in a single print.
How a CO₂ laser sinters polymer powder, why no supports are needed, and the complete SLS build cycle from powder bed to finished part.
Why SLS produces near-isotropic parts: Unlike FDM where polymer chains align with the extrusion direction, SLS melting and re-solidification of powder creates a largely random molecular orientation in all three axes. Z-axis strength typically reaches 85–95% of XY for PA12 — far exceeding FDM's 55–70%. This isotropy is the fundamental reason SLS dominates production polymer AM.
The laser delivers energy to the powder bed in two modes: absorption (heating) and conductance (spreading to adjacent particles). The energy balance determines melt pool geometry and penetration depth.
| Parameter | Measurement | Target (PA12) |
|---|---|---|
| Particle Size D50 | Laser diffraction | 50–80 µm |
| Flowability (Hausner) | Tap/bulk ratio | <1.25 |
| Sphericity | SEM / image analysis | >0.90 |
| MFI (Melt Flow Index) | ISO 1133 | Tracks age-degradation |
| Moisture Content | Karl Fischer | <0.1% |
| Material | UTS | Elongation | Specialty |
|---|---|---|---|
| PA12 (standard) | ~50 MPa | ~15% | General production |
| PA11 (bio-based) | ~48 MPa | ~40% | Impact toughness |
| TPU (Shore 88A) | ~30 MPa | ~200% | Elastic, wearables |
| PEBA 2301 | ~35 MPa | ~300% | Footwear, sports |
| PA12-CF | ~70 MPa | ~5% | High stiffness structural |