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In many industrial production processes, adhesives are used for bonding and processing sheet materials. Conventional adhesives require a long curing time, which is not conducive to assembly line operations. Therefore, most enterprises opt for UV coatings to fix or encapsulate the surface of sheet materials. By irradiating the surface of UV sheet materials with UV light, LEDUV curing machines enable rapid curing of UV adhesives, printing inks and other materials in a very short time, meeting the high-intensity operation requirements of assembly lines. Then what are the causes of incomplete curing of UV adhesive by LEDUV curing machines? Let’s find out below:

I. Energy Intensity of LED UV Light Source
The curing of UV materials requires absorption of a sufficient amount of UV light energy to trigger chemical reactions such as polymerization, thermal polymerization and cross-linking of the components in the adhesive, so as to achieve the curing effect. Insufficient energy output from the LED UV light source during irradiation tends to result in incomplete curing of UV consumables.

II. Thickness of UV Coating Layer
The thickness of the UV coating layer exerts a significant impact on the curing effect of the UV curing machine. A thin coating layer may easily lead to poor surface color fastness of the product. A thick coating layer will prolong the required irradiation time, reducing curing efficiency; meanwhile, it will cause excessive temperature rise on the product surface and result in deformation of the sheet material.

III. Curing Distance of UV Light Source
The optimal distance between the UV light source and the sheet surface is generally adjusted to 5–10 mm. A too-short distance will cause rapid temperature rise on the sheet surface, easily leading to thermal damage of the material surface. A too-long distance will weaken the energy of the received LED UV light, resulting in incomplete curing of the sheet surface.

IV. Irradiation Time of UV Light Source
Different UV coatings vary greatly in their compositions. An excessively fast curing speed will cause the UV coating on the sheet surface to remain sticky or result in surface-dry but inner-wet condition. An excessively slow operation speed will lead to surface aging of the sheet material. Professional calculation and testing are required to determine the optimal irradiation time, and the curing speed of the equipment should be adjusted accordingly.

V. Influence of Working Environment
UV curing is also affected by the environment. The internal viscosity of some UV coatings changes significantly under different temperatures. The working temperature should be adjusted to a suitable range, preferably 18–26℃. Meanwhile, attention should be paid to avoiding direct sunlight exposure of the UV light source during operation.