Veneer quality control Part 9: Thin wood face veneer manufacturing process
Usually, the natural veneer is processed by planing. The process flow is as follows:
Log Truncation Cutting,, Softening (Steaming or Boiling) Planing, Drying (or Not Drying) ,Shearing ,Inspection, Packaging, Storage,
1, section cutting
After entering the factory, the logs should be cut into segments according to the required length first, and then cut into wooden blocks. The sawing scheme must be selected according to the diameter of logs, wood texture and the fixed method of the logs on the planer, so that the width of the planned thin wood is not less than the relevant requirements.
Reasonable plan not only has high yield, but also produces more diameter-cut thin wood and fewer chord-cut thin wood, resulting in high decorative value of products. Different sawing schemes should be adopted for logs of different diameters. The thick solid line in the figure is the sawing line, and the arrow direction is the cutting direction of the planer.
In actual production, sawing scheme B is usually used for logs with diameter less than 400 mm, while sawing scheme D and E are mostly used for logs with diameter between 400 and 800 mm. When using these sawing and cutting schemes to produce thin wood, the board yield is high, the quality of thin wood is good, and the efficiency of planer is high.
The plasticity of wood increases after cooking (i.e. hydrothermal treatment). The most effective way to improve wood plasticity is to adjust the temperature and moisture content simultaneously, that is, to increase the temperature and moisture content of wood at the same time. This is the reason why the wood square is usually boiled with saturated steam or hot water in practical production.
Firstly, when putting the wood into the cooking pool, it should be carried out according to the tree species and the wood specifications respectively; the water temperature should be kept at room temperature, and the temperature should be raised slowly, so as to avoid cracking of the wood due to thermal stress. When the temperature rises above 40 C, the heating rate should be slowed down; excessive cooking will also reduce the quality of thin wood; cooking pools should often remove resin, bark, sediment, and often change water to reduce wood pollution; after cooking, the wood should be placed in the storage tank in time before planing and cutting machine, and kept in the range of 40-50 C (depending on the tree species and thickness of thin wood). The following table lists the cooking benchmarks for several types of wood for reference only.
The moisture content after drying is generally 8%~12%. Thin wood drying equipment includes continuous drum dryer, belt dryer and intermittent drying room. Drying chamber is an old-fashioned drying equipment, which is not economical, but the drying quality is better. The most widely used is drum dryer. Comparing thin wood, especially thin wood with thickness less than 0.4mm, must be dried by belt dryer.