I. Core Definition and Industrial Value of the Spraying Process

, is a technology that evenly applies paint to product surfaces with professional equipment. Suitable for plastic, metal, ceramics and other materials, it aims to meet key quality requirements such as high temperature resistance, friction resistance, UV protection and corrosion resistance. For glasses, spraying enhances appearance and extends service life. Unsprayed frames are prone to oxidation, scratching and have a single color. Professional spraying provides diverse colors (e.g., matte black, gradient blue, metallic silver) to meet aesthetic needs, while forming a dense protective film to resist daily friction, sweat corrosion and outdoor UV radiation, keeping glasses in good condition long-term.

In the glasses industry, it is also known as "color spraying" or "lacquer spraying" (transliterated from English "lacquer", meaning varnish). Despite different names, its core logic is consistent: unifying aesthetics and protection by precisely controlling paint adhesion and uniformity.

II. Core Spraying Equipment: Upgrade from Manual to Numerical Control

The choice of spraying equipment directly affects coating quality and efficiency. The industry has a "manual-semi-automatic-full automatic" gradient configuration to meet diverse capacity and precision needs.

Manual machines are for small-batch production, samples or complex frames. With a simple structure of spray gun, air pressure adjuster and workbench, operators adjust angle, distance (15-25cm) and speed. They offer flexibility for precise thickness control but need skilled operators to avoid defects like missing spray and sagging, suitable for customization due to low efficiency.

Semi-automatic machines are mainstream, balancing flexibility and efficiency. With a rotatable workbench, frames are fixed by fixtures. Operators use a foot switch for 360℃ uniform spraying, and gun rails reduce human errors. A closed chamber with exhaust system discharges paint mist, protecting health and environment, suitable for medium-batch standardized production.

Automatic oil mixing + numerical control equipment is advanced for large-scale mass production. It features precision and automation: the mixing system follows preset formulas to avoid color deviation, while numerical control sets gun parameters for automatic spraying without manual intervention. It achieves ±0.01mm thickness error, 5-8 times higher efficiency than manual machines, and 85%+ paint utilization. High-end models have online detection to ensure qualification rate.

III. Paint Selection: Balance Between Formula and Effect

Paint selection balances appearance, protection and material adaptability, mainly divided into toner-solvent mixed paint and finished paint, each with pros and cons.

Toner-solvent mixed paint is common, composed of toner, solvents (e.g., ethyl acetate) and resin. Precise mixing avoids color spots. It has flexible formulas, low cost, fits most frames, and its matte texture resists scratches, ideal for mass-market glasses.

Finished paint is ready-to-use with high pigment concentration. Its high viscosity requires precise parameter control to avoid defects. It has high color saturation for metallic/bright colors and better wear resistance, protecting metal frames from oxidation.

Paint must match materials: plastic frame paint needs flexibility to avoid cracking; metal frame paint needs strong adhesion, usually with a primer to enhance bonding.

IV. Drying Process: Temperature Control is the Key

Drying is crucial for coating curing, following "material adaptation and precise temperature control" to ensure quality.

Plastic frames (TR90, PC) have poor heat resistance, dried at 60-80℃ for 20-30 minutes. Overheating causes deformation; insufficient drying leads to peeling. Hot air ovens ensure uniformity, and high-end models use segmented drying to avoid blistering.

are heat-resistant, dried at 120-180℃ for 30-45 minutes. High temperature strengthens the protective film. Infrared ovens enable deep curing, shorter time and higher efficiency.

V. Environmental Upgrade: Wide Application of Water-Based Paint

Driven by environmental policies, water-based paint becomes mainstream. Traditional oil-based paint emits VOCs, harming environment and health. Water-based paint uses water as solvent, with almost no VOCs and no odor, solving pollution problems.

It maintains environmental friendliness and performance, with flexible color mixing and equivalent protection to oil-based paint. Tests confirm its durability, and mainstream brands have adopted it, achieving economic and social benefits.

VI. Quality Inspection: Ensuring Final Compliance of the Spraying Process

Strict inspection is required before assembly, focusing on appearance and performance.

Appearance inspection: Visual and 10x magnifying glass checks ensure uniform coating without defects, color matching (ΔE <= 1.5) and no paint accumulation on hidden parts.

Performance inspection includes friction, sweat resistance, high-temperature and UV tests. Only qualified products enter subsequent processes to meet long-term use needs.