Whether veneer veneer or decorative paper veneer in the process will produce some quality problems, the main reasons are as follows.

1. Base material

The smoothness of the substrate surface, the bonding strength of the inner surface and the uniformity of the thickness all affect the veneer quality.

2. Surface quality of substrate

The appearance quality, physical and chemical properties of wood-based panel used in panel furniture must meet the national standards. The surface of the substrate often has a small area of glue spots, paraffin spots, oil and other impurities, which affect the penetration of the adhesive, so that the material can not bond well, and there are problems such as degumming bubbles.

3. Substrate thickness deviation

According to the national standard of wood-based panel, the thickness deviation is within ± 0.2mm. The thickness of E1 grade plate of a certain brand was tested, and it was found that the thickness deviation of nearly 10 plates exceeded the national standard. This is relatively thin facing materials, will produce a variety of quality problems.

4. Facing materials

Too dry impregnated paper will cause white spots; uneven thickness of impregnated paper will cause discoloration. If the thickness of the veneer is too thin, the conduit is too large due to the wood property structure, and the moisture content is too high, the adhesive surface will be penetrated; if the moisture content of the veneer is too high, the black glue joint, separation joint or lap joint will appear at the joint of the veneer; sometimes the whole board surface will be warped and deformed. If the thickness of the veneer is too thin, it will make the surface of the board transparent.

5. Moisture content of decorative materials

Moisture content is one of the important factors that affect the quality of veneer. It affects the viscosity of adhesive, the wettability of adhesive, and the apparent physical properties of decorative materials. Veneer is a kind of wood veneer material with the characteristics of precious tree species. Usually, its moisture content should be 8 ~ 15. If the moisture content of veneer is low, its heat transfer is slow and easy to break. However, the moisture content of the veneer should not be too high, because the moisture content of the veneer is too high, the drying shrinkage will cause the warping deformation of the board surface. The moisture content of decorative paper also affects the quality of veneer. Usually, the processed paper is stored in the environment of 25 ℃ and 55-65% humidity. If the decorative paper is too dry, it will appear day shift and wrinkle.

6. Thickness of decorative materials

The thickness of veneer usually ranges from 0.3mm to 1.5mm. When the substrate surface is flat, the thickness of veneer can be smaller; when the substrate surface is uneven, the thickness is larger. Usually, the thickness of veneer used in furniture companies ranges from 0.4 mm to 0.6 mm, which can not only meet the requirements of veneering technology, but also meet the decorative requirements of solid wood feeling. If the thickness of veneer is too thin, such as large conduit, it will cause the phenomenon of glue penetration and bottom color penetration. The decorative paper should also have a certain thickness, otherwise it will appear through the bottom, if the thickness is not uniform, there will be discoloration.

7. Veneering technology

Veneering process includes the process method, standardized operation, processing conditions and so on, which is the key to ensure the quality of veneer.

8. Process method

Sanding with fixed thickness is an important process to ensure the uniform thickness of the plate and improve the quality of the plate. If the operation is not good or reduce this process, the veneer defects will be caused, and these defects can not be remedied in the later process. The gluing process is to evenly coat a certain amount of glue on the surface of the substrate. Too much glue will make the adhesive layer hard and brittle; too little glue or uneven gluing will cause local lack of glue, leading to blistering; the surface and back gluing facing materials should be symmetrical during blank preparation, otherwise it will cause uneven stress on the surface of the substrate, leading to plate warping.

9. Processing conditions

In the veneering process, good processing conditions should be ensured, such as clean environment, appropriate humidity, temperature and pressure. Before gluing, the board surface should be clean. After gluing, the dust particles should be prevented from falling on the board surface, otherwise, the board surface will have granular protrusion.

3.3.3 standardized operation

Veneer processing should be operated in strict accordance with the process standards. Especially in the process of base material gluing, the adhesive is prepared according to a certain proportion, stirred evenly, and then added into the gluing machine in a special container. In practical operation, workers will directly add the main agent of adhesive to the cots, and then add modified materials such as lignin powder to stir on the gluing machine. This will produce, on the one hand, uneven mixing of the adhesive, the emergence of large particles; on the other hand, it will damage the gluing machine; after gluing, there will be local lack of glue, granular protrusion and other defects.