Film covering is an important method to protect and beautify printed matter. The application of this method has greatly enhanced the brightness of the printed matter. It has achieved the process effect of anti dirty, waterproof, anti discoloration, heat resistance, sunlight resistance and wear resistance. It not only improves the aesthetic feeling of the product, but also enhances the service life of the product, extends the sampling inspection of the product, and ensures the coating process quality.

During the pre production and production period, the coated products should be sampled and inspected to see if the film is firmly adhered to the printing surface, so as to control the quality of the production process, avoid the generation of defective products, and ensure the stability and qualification of the whole batch of products. According to the experience of production practice, there are only the following inspection methods:

1. Kneading test method

Take a sample sheet with appropriate area and rub it back and forth with both hands like washing clothes. Check whether the plastic film and the printing sheet are separated or blistered. The adhesion is firm without film peeling, which indicates that the product quality is reliable.

2. Tear off test

Remove the plastic film layer on the coated sample sheet by hand to see if the printing ink layer and paper fiber are attached to the film layer in large area. If so, it indicates that the process is normal.

3. Pressure test method

Take the laminating sample sheet to the die-cutting indentation machine, after pressing with the die-cutting knife or relief plate, see if there is any bad condition at the pressure part. No delamination phenomenon indicates that the quality of film mulching is good.

4. Heating test method

Put the coated sample sheet into the drying channel and bake at about 65 temperature. No peeling, no blistering and no wrinkling indicates that the film covering is normal.

5. Immersion test method

After soaking the coated sample sheet in normal temperature water for about 1 hour, the film does not separate from the printing sheet, indicating that the film is firmly bonded. Through sampling inspection, it can not only guide the production correctly, ensure the smooth progress of the process, but also avoid the production of unqualified products, so that the product quality and production efficiency can be improved synchronously.