Normal Exposure Time

Theoretical Background & Photopolymerization Kinetics

In Vat Photopolymerization processes (such as SLA, DLP, and MSLA/LCD), the Normal Exposure Time is the duration for which the UV light source is active to cure a single normal (non-bottom) layer of liquid photo-reactive resin. This setting lies at the core of print quality, defining the chemical and physical properties of the printed green part.

The Chemical Mechanism of Curing

Liquid resin is a mixture of monomers (low molecular weight reactive molecules), oligomers (partially polymerized structures that define the mechanical base), photoinitiators, and additives (pigments, stabilizers, UV blockers). The curing process occurs through three primary steps:

In-Depth Quality & Strength Analysis

Choosing the correct normal exposure time is a delicate balance. Even small deviations (like $0.2\text{ s}$) can significantly affect the mechanical properties and dimensional quality of the parts.

Calibration Methods & Tools

Relying on the resin manufacturer's defaults is not enough because light intensity decays over time as LCD screens age, and temperature drastically affects reaction speed. The following calibration models are industry standards:

1. ChiTuBox Resin Calibration Matrix / XP Finder

A flat, thin model (usually $1.5\text{–}2\text{ mm}$ thick) printed directly on the build plate (without supports) to check X/Y resolution.