Effectively solve the warpage and deformation of panel!

Effectively solve the warpage and deformation of panel!

In recent years, in the manufacturing of solid wood furniture, large-scale components are often made of solid wood panel made of solid wood narrow panel and small material glue, which can not only alleviate the shortage of supply and demand of high-quality solid wood resources, but also meet the growing market demand of solid wood and its products.

Solid wood mosaic process

Quality problems such as warping, deformation and cracking are easy to appear in solid wood panel. In this paper, by analyzing the main factors that affect the quality instability of solid wood panel, the methods to improve the stability of panel are summarized, so as to solve the quality problems such as warpage and deformation of solid wood panel.

I. common quality problems of solid wood panel

At present, there is no corresponding standard for solid wood panel in China. Most enterprises and users pay more attention to the appearance of solid wood panel, but lack of inspection standards and management methods for quality problems such as surface warpage, glue layer cracking, finger tenon falling off and fracture. Many enterprises often use simple repair methods to cover up, which to a certain extent affects the development of solid wood panel industry. Therefore, how to ensure the shape stability and reduce the deformation is the key to improve the quality of solid wood panel.

II. Factors affecting the dimensional stability of solid wood panel

1. Wood factor

Wood will crack and deform without external stress, which is mainly caused by internal stress in wood. In addition to the internal stress of the wood unit itself, the internal stress of the solid wood panel also exists between the wood units – the internal stress produced in the process of panel splicing. These are related to the density, moisture content, surface roughness, splicing method, glue type, glue application amount, glue pressure and air temperature and humidity.

2. Glue application amount

When the amount of adhesive is too low, there will be lack of adhesive and uneven distribution of adhesive; when the amount of adhesive is too high, the adhesive layer is too thick, and the volume shrinkage of the adhesive layer will produce internal stress and destroy the cohesion of the adhesive, reducing the bonding strength.

3. Gluing pressure

Pressurization is beneficial to the full penetration of glue liquid and the combination of glue liquid and wood active molecules to form a uniform glue film. However, the unsuitable pressure is easy to extrude the glue liquid, resulting in the phenomenon of lack of glue and penetration. At the same time, the larger pressure will make the material deform seriously and form greater stress.

It can be seen that to eliminate the internal stress of the material and improve the dimensional stability of the solid wood panel can start from the aspects of raw materials and technology.

III. methods to improve the dimensional stability of solid wood panel

Based on the above reasons, corresponding measures can be taken to improve the quality of solid wood panel according to the actual situation in the aspects of batching, moisture content control, gluing amount and gluing pressure. Through the previous research, we found that we can improve it from the following aspects:

1. Reasonable ingredients

When making solid wood panel, try to use the same tree species or wood with air dry density difference of no more than 0.2g/cm3, and try to avoid the wood with large difference in density and shrinkage, so as to reduce the internal stress of the board. Because wood is an anisotropic material, and the radial moisture absorption deformation is smaller than the chord direction, the chord and radial texture of adjacent narrow strips should be reasonably matched during splicing to avoid excessive chord direction wood.

2. Control water content

The final moisture content of the solid narrow board should be controlled according to the moisture content of the land where the product is used. Some studies have shown that when the moisture content of wood is controlled between 5% and 10%, the bonding strength is the highest. At the same time, special attention should be paid to that the moisture content difference between adjacent panel narrow strips should not be too large. Generally speaking, controlling the moisture content deviation within 2% can effectively reduce the shrinkage stress of wood.

3. Use appropriate glue application amount

During the curing process of adhesive, the adhesive layer will produce shrinkage and internal stress, which will lead to the decrease of adhesive strength, and the greater the amount of coating, the more obvious the internal stress. Generally speaking, the amount of single-sided glue can be controlled within 180-300g / ㎡, while the amount of double-sided glue can be controlled within 140-220g / ㎡.

4. Adopt reasonable glue pressure

Some studies have shown that the bonding pressure of hard wood should be controlled at about 10 ~ 15kg / C ㎡, while that of soft wood should be controlled at about 5 ~ 10kg / C ㎡. At the same time, in order to prevent the solid narrow board from warping or bulging during gluing, the pressure of 0.1 ~ 0.2MPa is often applied on the side of gluing direction.

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