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How to Control moisture content in making solid Wood Furniture
Dec 08, 2018

The moisture content problem of solid wood furniture is more prominent in the solid wood furniture production problem. We take the export of wooden antique furniture from the United States as an example. Generally speaking, the moisture content of furniture exported to the United States should be controlled within 8%. This is mainly due to the following reasons: first, Export to the United States requires a long period of container transportation, the temperature in the container can reach 50 ℃ ~ 70 ℃, or even higher, such temperature is higher than the desiccant drying temperature; Secondly, in general, the relative humidity of the American indoor air is lower than that of the air in China, and they use the humidity of the environment in which the furniture is used. The degree is generally about 7% or 9%. So furniture used in such temperature and humidity, if the moisture content does not meet the requirements, the furniture will produce cracking, bending, loose structure and paint bubble damage.

In our country, because of the humidity difference between north and south, the requirement of wood moisture content is different. For example, the average annual moisture content of wood in southern Guangzhou is 15.6cm, the highest is 18cm; In the north, for example, the average wood moisture content in Beijing is 11.8a year, and the lowest is 9.3%. Therefore, if the furniture produced in the south wants to be transported to the north for sale and use, attention should be paid to the control of the moisture content of the furniture.

However, in the process of furniture production, wood is exposed to the atmosphere, so how to control the moisture content in the range we need? Take the example of antique furniture exported to the United States with a moisture content of 8%. The basic process of this furniture production is: Wood drying, wood processing, carpentry assembly, paint packaging, and integration of the whole process. Water content can be controlled in the following ways:

Strictly control the final moisture content of wood drying

Wood drying is the source of moisture content control. Only when the final moisture content of wood is up to the requirement, can it be effectively controlled in the process of processing. There are three main ways to remove moisture in wood during drying: free water, washed water and combined water (chemical water). When the wood is dry below 30% free water has been completely discharged, and then the water discharged is washed water from the wood. Nowadays, wood processing plants generally use desiccant drying kiln to dry wood. The moisture content of wood obtained by this drying method is more uniform, but the drying time is longer. If the furniture company itself does not have the conditions for wood drying, so that the wood dry The dry final moisture content is more strictly controlled, and the final water content is better lower, because these wood have to go through transportation and other links.

Control of moisture content in Machining process

The moisture content of wood in the process of processing is difficult to control. The most effective way is to minimize wood in the machining phase of stay. In rainy weather, it is best to close doors and windows processing, and in sunny days, it is best to open doors and windows for ventilation, ventilation. In this way, the humidity of the air in the processing workshop can be reduced, thus slowing down the moisture absorption rate of wood. Some parts of furniture that require secondary processing (that is, furniture parts have to be assembled by carpentry and returned to the motor vehicle room for dimension modification, sanding, or other processing techniques) are required to enable the parts to be matched to the woodworking workshop. Don't cause one part to make the other Eight percent of the parts were stuck in the workshop for a long time. Such as antique furniture door frame door cap and door straight, when entering the carpentry workshop should be a complete set. This carpentry assembly, immediately can be taken back to the motor vehicle for a second processing.

Another way to solve the moisture problem is to install dehumidification equipment in the transfer buffer warehouse between machining workshop and woodworking workshop, which can also reduce the moisture absorption rate of wood parts.

Moisture content control in woodworking assembly stage is mainly to assemble parts and components. Some parts that can not be machined (such as engraving parts curved surface curves) must be sanded by hand and carried out in woodworking workshop. Therefore, the woodworking workshop to a product that needs secondary processing of parts to be processed first. Some furniture that uses glue is best placed where heating facilities are in place to increase the speed of glue curing and to reduce wood moisture absorption. When all the parts are ready, the woodworking finished product assembly speed is generally faster. But in order to ensure the quality of the product, we still have to control the air in the assembly plant. Relative humidity, open windows on sunny days, close windows on rainy days to control wood moisture content.

Control of moisture content in paint stage

The relative humidity of the air is generally higher in the paint workshop because the paint itself contains moisture, which sprays on the furniture surface and reacts with the paint to form a paint film, but some of it is absorbed by the furniture. Now paint production lines are using water screen (curtain) spray table, so the evaporation of water curtain moisture increased the air humidity in the workshop. The solvents used in paint are generally flammable, explosive organic solvents, and the paint itself is a flammable substance that floats in the air with paint particles, if the mixture reaches a certain concentration. If you don't notice, there will be a combustion, an explosion, so in order to reduce this With the concentration of the mixture, the paint shop itself needs a slightly higher relative humidity. In order to ensure the quality of the paint film, the paint workshop needs a relative production environment, so the floor of the paint shop needs to be cleaned frequently, the most common of which is to use wet mop to clean the floor. In this way, the evaporation of 9 moisture on the ground will also increase the humidity in the workshop. For these reasons the primer should be sprayed immediately when the product enters the paint shop so that the film will form a protective film between the furniture and the atmosphere and reduce the absorption of air moisture by wood. Doors and windows should be opened on sunny days so that the air in the workshop can be ventilated so as to reduce the The concentration of the gas mixture in the workshop can also reduce the relative humidity of the air in the workshop.

Many furniture factories now use assembly lines to paint, so they can install far-infrared drying devices or other heating devices on a certain section of the assembly line, the main function of which is to speed up the drying of the paint film. But at the same time the control of moisture content of furniture is also greatly beneficial.

The control of moisture content is not only an important part in the process of furniture production, but also difficult to control. However, as long as reasonable production arrangements and appropriate measures are taken, satisfactory results can be achieved.

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