As we all know, wood drying is an important part of the production of solid wood furniture, which directly determines and affects the quality of furniture products. The problem of wood drying in the production of furniture is mainly concentrated in the category of real furniture. This problem includes: the supply of dry materials, the drying of warm materials, the quality and cost of drying, the control of moisture content during production, and so on.
The minimum value of the equilibrium moisture content in the three regions is 12 . 4 %, while the high value is much higher than 10 %, so there is a dehumidification problem in the production of wood products in this environment. The equilibrium moisture content depends on the temperature and the humidity. Even in the same area, the temperature and humidity change greatly during the day and night, so the equilibrium moisture content also differs greatly. The actual measurement in a certain area of ​​Jiangsu shows that the minimum moisture content of the area in the day and night in June is 7 . l %, the maximum is 24 . 2 %, the difference is 17 . 1 %, average is 16 . 5%; equilibrium moisture content of less than 10% of the time zone of 11: 30 to 16:30, total 5H; equilibrium moisture content at 10% to 14% of the time, a total for 3.5 h; equilibrium moisture content of 14% to 24 at. 2% of the time, a total of 15.5h; 19 hours a day there is a problem faced by dehumidification. Within a day and night to noon pm (11:30 - 16:30) is the ideal moisture content environment time; the higher nighttime equilibrium moisture content, wood moisture easily, moisture control is very important. In the production process, there is no moisture content control, the final moisture content of the product has a large difference, generally there is a significant difference after 3 days and nights, and the moisture absorption of the ring hole material and soft material is especially obvious, such as the water content of the feed is 6 %. The ash and rubber wood, after 7 days and nights, their final moisture content increased to 15 respectively . 2 % and 15 %. In the production process, the main methods for controlling the moisture content of wood are:
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Supply of dry materials China's current supply of wood is still mainly log, although some plates have been supplied, but it is far from being a major supply method, especially in provinces and regions where the economy is still underdeveloped. China should change the supply mode of wood as soon as possible, and realize “concentration of materials, concentrated drying, and supply of dry materials†as soon as possible. The production methods and supply methods of such dry plates have many advantages, and the main advantage is that it is The socialization and specialized division of labor for wood processing and furniture production provides a basis for the supply of materials. Solid wood furniture production plants hope to have dry plates of various specifications for the commonly used tree species in production, and have a good supply method to ensure timely and stable supply of required materials.2
Drying of wet materials China's solid wood furniture factory has various forms of wood drying equipment to ensure the dry sheet of the factory. Due to the extremely unbalanced development of China's furniture industry, advanced factories and relatively backward factories have far different levels of drying equipment; the more serious problem is the mastery and application of drying process technology due to the gap in the technical level of these factories. There is a world of difference. Therefore, in China's furniture industry, wood drying is a very prominent technical "bottleneck". To solve this problem, we must first fundamentally solve the problem of the supply of wood, which has already been mentioned above. For medium and small-sized furniture enterprises, there is no need for “small but completeâ€. The need for dry materials can be completely solved from the market. There is no need to set up a drying workshop. For large enterprises, due to the wide variety of products, there are also comprehensive utilization. Considering that the demand for materials is also complicated, it is necessary to set up a drying workshop. It is very important to use wood drying equipment and scientific use of wood drying technology. At present, many large-scale solid wood furniture factories in China have a tendency to “seek foreign trade†when purchasing drying equipment. However, little is known about the introduction of advanced foreign drying equipment, and the role of equipment has not been fully utilized. On the other hand, The drying process is not well mastered, or the drying cycle is too long, or the drying is not proper, and the loss of wood is so amazing. The problems of small and medium-sized enterprises in this aspect are even more serious.3
Dry quality and cost Dry quality and cost should be the main criteria for selecting a drying method. Most of the wood used in furniture factories is high-priced hardwood, and the material loss is very large for the factory. Drying is caused by poor handling and poor drying equipment during the drying process. Most drying defects are closely related to the drying speed. Drying too fast is mainly caused by too high drying temperature, too low humidity or too high wind speed. For precious tree species and difficult-to-dry and fragile tree species, the wood before drying is simply cut to eliminate the tiny gaps left during sawing and has a good anti-cracking effect. This tiny gap is also one of the causes of dry cracking, including dry cracking and internal cracking; about 98 % of the internal cracking of wood is caused by deepening of the crack. Research in the United States has shown that for red Oak boards, the possibility of wood cracking is reduced by 18 times, drying speed is increased by 10 %, kiln drying capacity is increased by 10 %, and energy saving is 10 %. These data are difficult for others. The same broadleaf is also suitable. The end of the wood paint also has a good anti-cracking effect. If the end is painted with wood, the wood utilization rate can be increased by about 8 % for Zm long plates . Of course, the end painting should be carried out immediately after the sawing of the wood, as soon as possible. Only in the coating after sawing l ~ 3d, will achieve such an effect; after 3d, you can only receive half the effect. The cost of drying depends on many factors, and has a lot to do with equipment and process. It is also closely related to the management of drying. I won't go into details here. It is worth noting that the impact of drying and lowering on drying costs cannot be underestimated. Especially for furniture factories, because the wood used is mostly high-quality hardwood, the price of the wood is expensive, and the drying and lowering have a greater impact on the drying cost. At present, domestic drying costs (excluding losses such as drying and lowering) vary from about 100 to 200 yuan per cubic meter, but the price of dried wood in furniture factories is always above 1,000 yuan per cubic meter, such as red glutinous rice and up to 800 yuan per cubic meter. Meters, such as 10 % loss of wood due to falling . The amount should be above 100 yuan / cubic meter, and even as high as several hundred yuan per cubic meter, much higher than the drying cost. Therefore, in the wood drying problem of furniture factories, the quality of drying should be emphasized, and the drying cost cannot be reduced at the expense of dry quality. In the future, in the calculation of the drying cost, whether the drying and lowering can be included, in order to improve the rationality of economic accounting.4
Moisture control during production In China's export furniture, the actual proportion of furniture accounts for a large proportion. The foreign customers have high requirements on the moisture content of this product. Generally, the polished wood products require the moisture content of the surface to be no more than 8 %. Solid wood furniture products require that the moisture content of the board surface is not more than 10 %, which is significantly more difficult than the national standard water content ( about 15 %) required by the national standard . From the quality requirements of wood products, if the water content exceeds 10 %, once the product reaches the high temperature and low humidity environment, the phenomenon of warpage, deformation and cracking of the board surface will occur, which will affect the product quality and lead to customer rejection and claim. . It is not difficult to achieve the above requirements in the drying kiln; and in the production of furniture to ensure that the wood is in the low moisture content range, corresponding measures are needed. China has a vast territory with an average annual average moisture content of around 15 %. For example, Qingdao, Shanghai and Guangzhou are examples:The range of variation of equilibrium moisture content in Qingdao, Shanghai and Guangzhou
area | Moisture maximum value% | Moisture content minimum % | Average moisture content% |
Qingdao | 20.0 | 12.8 | 14.4 |
Shanghai | 17.6 | 12.4 | 15.1 |
Guangzhou | 17.9 | 14.7 | 16.0 |
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. 1 control the initial moisture content after drying wood Generally, the initial moisture content of the polished solid wood furniture material is controlled within 6 %, and the initial moisture content of the non-polished solid wood furniture material is controlled within 8 %; the wood cannot be immediately put into production after drying. It should be stored in the dry storage for 2 to 3 days . The temperature in the dry storage is controlled at 35 to 40 °C, and the relative humidity is controlled at 40 % to 50 %. In this way, the wood can eliminate the dry stress in the dry stock and smooth the moisture content gradient.4
. 2 try to shorten the production cycle The length of the production cycle directly affects the moisture content of wood products. Therefore, it is necessary to organize the production reasonably so that the moisture content of each component is simultaneously balanced. At present, in many enterprises in Taiwan, the production cycle is generally controlled at 2 to 3 days , while most enterprises in the mainland generally have a production cycle of 10 to 15 days . This is an urgent need for improvement.4
. 3 Create a low moisture content environment, allowing wood products to be stored in low moisture content without processing Wood products in the natural environment, obviously want to absorb moisture. Therefore, it is necessary to establish a low water content environment to control the water content in the environment below 8 %. There are two ways to create this environment: ( 1 ) The wet room is created and equipped with a dehumidifier to control the equilibrium moisture content of the indoor air; ( 2 ) In the dry material warehouse, using the principle of wood drying, equipped with a fan and a heat sink to control the equilibrium moisture content of the indoor air; ( 3 ) Distinguish the primary and secondary, different requirements for the use of different dehumidification methods, such as the use of dehumidification rooms for demanding polishing furniture parts; and for secondary parts such as dental plates, only plastic cloth or canvas, etc. cover; ( 4 ) Strictly control the moisture content of the white blank before the paint, and the moisture content of the white blank of the polished furniture parts should be controlled within 8 %; and the moisture content of the white blank of the non-polished furniture parts should be controlled within 10 %. Can only be painted. For parts and components whose water content has been out of control, remedial measures should be taken resolutely. The drying or surface dehumidification treatment must make the water content meet the requirements; ( 5 ) Improve the process to prevent the moisture content from rising, such as strengthening the white of wood productsClosure of the blank, strengthening the sealing of the non-painted surface, controlling the moisture content of the packaging carton (the moisture content of the packaging carton is generally
14 % ~ 18 %, generally should be dehumidified to about 10 % is appropriate).Accept Small order!!
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