Scanning and Curing in SLA

In SLA, a UV laser scans each layer's cross-section on the liquid resin surface; the exposed resin cures (solidifies) and bonds to the layer below.

Scanning techniques

• Vector (point) scanning: the laser spot is steered by two galvanometer mirrors along the outline (contour) and then fills the interior, in lines (hatch).
• Raster scanning: the beam sweeps line by line over the whole layer area, switching on only where needed.
• Scan patterns: contour, hatch, cross-hatch, spiral. Spacing between lines and scan speed control the exposure.
• Newer systems project a whole layer (DLP/LCD) rather than scanning.

Curing

1. Green curing: during scanning, the resin is only partly polymerized (green strength) so that the layer bonds to the previous one. The cure depth depends on exposure: $C_d = D_p \ln(E/E_c)$.
2. Layer recoating: platform dips, a blade levels the resin.
3. Post-curing: after cleaning, the part is exposed to UV (and sometimes heat) in a chamber to complete polymerization, raising strength and stability.

Key parameters

Laser power, scan speed, spot size, hatch spacing, layer thickness and resin sensitivity.

Exam tip

Draw the laser, galvo mirrors, vat and platform, then explain scanning (contour and hatch) and post-curing.