Wood furniture manufacturing process, the method of dry what?

furniture manufacturing process of wood drying is the guarantee and improvement of wood quality, reducing loss of wood, the wood moisture content is the important link. At present, the artificial drying methods include conventional drying, high temperature drying, dehumidifying drying, solar drying, vacuum drying, high frequency and microwave drying and dry flue gas, etc. Of all the artificial drying method, the conventional drying with a long history and mature technology, ensuring the drying quality, easy to realize the advantages of large industrial drying, wood drying industry both at home and abroad are dominate, it accounted for more than 80% in our country. End of the wood in drying process, wood due to moisture evaporates faster drying first, when the end moisture is below fibre saturation point, end cells began to shrink, when the stress reaches the ultimate strength of lumber drying shrinkage, crack occurs end, namely in the pith or coarse wood ray in or along the outer surface longitudinal cracks. In the wood processing production, are generally put the wet wood drying to conform to the requirements of the moisture content before using, the moisture content value is below fibre saturation point, so how much is the production of dry drop-off of wood must consider the question.

furniture wood drying method

after drying of wet wood, its overall dimensions or volume to shrink, the phenomenon is called the dry shrinkage of the wood. After dried wood by absorbing moisture, its size or shape to increase the volume, this phenomenon is called the wet bilge of lumber. Wood drying shrinkage and bulking is refers to the wood to be at a certain temperature and humidity environment produced by the phenomenon. Wood was soaked in the water produced by the phenomenon is another situation, is not in the scope of this concept to explain.

1, the conventional drying is a normal pressure moisture air as drying medium, for steam, hot water, or hot oil furnace as heat medium, indirect heating air, air by convection heating wood drying to achieve purpose. In conventional drying and steam as heat medium of drying chamber in the majority, commonly referred to as steam drying. High temperature drying and conventional drying is the difference between the drying medium temperature is higher. The drying medium can be wet air, also could be superheated steam. The advantage of high temperature drying is fast drying speed, good dimensional stability, short cycle, high temperature drying but are prone to drying defects, color darker, surface hardening, not easy processing.

3, solar drying is the use of solar radiation heat to heat the air, using hot air circulation between collector and material heap to dry wood. Solar greenhouse and collector drying generally have two kinds, the former will collector and drying chamber into an organic whole, the latter collector is separated from drying room layout. Collector type solar drying room decorate a flexible, collector area can be very big, the corresponding drying chamber capacity also relatively large greenhouse type. Although solar energy is clean and cheap energy, but it is affected by the climate of intermittent energy, dry cycle is long, the unit volume of the investment is bigger, therefore, the promotion of solar energy is limited.

5, high-frequency drying and microwave drying are wet wood as the dielectric, under the action of alternating electromagnetic field, make lumber high-speed rotation, frequently in a molecule of water in the water molecules between the friction and heat production, make lumber from inside to outside and heating dry. The two drying methods is the feature of fast drying speed, uniform temperature field in wood, the residual stress is small, good drying quality. The difference between the high frequency and microwave drying is a low frequency and wavelength of the former is longer, the wood of the penetration depth is deeper, is suitable for drying large cross section of thick wood. The frequency of the microwave drying is higher than high frequency ( Also known as ultra high frequency) But shorter wavelength, the drying efficiency is faster than high frequency, but the wood drying the penetration depth of less than high frequency.

2, dehumidification drying and conventional drying, also with normal pressure moisture air as drying medium, air convection heating. Its energy saving, dry the advantages of good quality, no pollution, but the dehumidification drying cycle is long, low temperature, dry, usually rely on electrical heating, power consumption is high, thus affect its popularization and application. Wood drying shrinkage and bulking phenomenon is when lumber moisture content is below fibre saturation point. When the cell cavity free water to reduce the size of the wood with no change. When the cell walls of absorbed water to reduce the size of the wood with decreasing. Because between the micro fibre inside the cell wall and micelles with after sucking water out and narrow the gap, make the cell wall thickness thinning, so wood drying shrinkage phenomenon. When the moisture content of lumber is low or reach the degree of approximation oven dry wood will absorb moisture from the air, the moisture sorption (basic Adsorption) On the cell wall, cell wall thickening, wood is wet bilge phenomenon.

4, vacuum drying, the dry wood under the condition of atmospheric pressure implementation, the drying medium can be wet air, but most is superheated steam. Vacuum drying, water vapor pressure difference inside and outside of wood, to speed up the moisture migration in wood, so the drying speed significantly higher than the conventional drying, usually 3 - faster than conventional drying Seven times. Because of the low vacuum the boiling point of water at the same time, it can be not high drying temperatures to achieve high drying rate, drying cycle short, drying quality is good, especially suitable for thick hard broadleaf timber drying. Due to the complexity of the vacuum drying system, large investment, high power consumption, and vacuum drying capacity is generally small, otherwise difficult to maintain the vacuum degree.