Glulam is a new type of material that is made of sheet metal or small-sized material, which is long in size, widened and laminated. It has the characteristics of stable size, non-deformation, and easy cracking. It has the mechanical properties of uniformity and solid wood. The strength is 1.5 times that of sawn timber and can be used in construction, furniture, vehicles, ships, etc. The processing process is as follows: material→dry→double-sided planing→multi-slice saw→defective→finger joint→four-sided planing→integration→sanding→intercepting→factory laminated material started late in China and developed rapidly in recent years There are also more production companies. However, there are many problems in the production of enterprises, which are characterized by low product quality, low yield, single product and narrow application range. The reason is mainly the two major aspects of the management mechanism and the technical level. At the same time, it is also the main reason why enterprises cannot make great progress and struggle. Therefore, the author puts forward some suggestions from the following aspects on how to get rid of this dilemma and passive situation and improve product quality and yield.
1 Material
When making materials, it should be processed according to the specifications of the product, leaving the machining allowance and dry shrinkage allowance. The machining allowance is generally 6~8mm; the dry shrinkage allowance depends on the tree species (see table), and its calculation formula is δ= Bk(30-w)
Where δ——drying allowance (mm);
B——sheet size (mm);
K——drying factor (%);
w - final moisture content (%).
Wood shrinkage factor of common tree species Table radial drying shrinkage factor (%) Chordwise dry shrinkage factor (%)
Larch 0.187 0.408
Red pine 0.122 0.321
White birch 0.188 0.258
Ash ash 0.171 0.322
柞木0.181 0.318
Spruce 0.171 0.349
楸木0.104 0.232
There are many companies that purchase boards from outside. When purchasing, the product specifications should be considered in relation to the blanks of the sheets, leaving a margin for processing. Otherwise, regardless of whether the blanks are too thick or too thin, the yield will be reduced and the cost will be increased. It is extremely unfavorable to improve the production efficiency of enterprises.
2 drying
The board should be naturally dried first, and when the water content reaches about 30%, it will enter the artificial drying stage. When drying, the same tree species (or similar density) and the same thickness of the plates are stacked separately; at the same time, the load is pressed on the plate to reduce defects such as deformation and cracking of the plate. In the drying process, the uniformity of the moisture content of the plate should be ensured. The dried plate must be placed in the outdoor slab for more than 20 days, so that the moisture content reaches the local equilibrium moisture content (8% to 15%), and the equilibrium moisture content of the plate is ensured. Uniformity provides a reliable guarantee for stable product quality.
3 Water content control
The water content must be strictly monitored, which directly affects the quality of the product. The water content test should be carried out for each process. The final moisture content of the plate should be determined according to the purpose and location of the product, generally 8% to 15%; The smaller the moisture content deviation of the slats of the material, the better, in principle, the deviation is controlled within 3%. If the moisture content of the wood is too high, the moisture in the wood dilutes and saturates the adhesive into the wood, which not only causes gelation, but also the glued product is easily deformed and cracked; if the moisture content is too low, the coating of the adhesive is affected. However, depending on the adhesive, sometimes even a high water content is easy to obtain a good gluing effect. At present, enterprises generally use a moisture meter to measure. The results measured by this method are not accurate enough, and there is a certain deviation from the actual moisture content. Therefore, it is better to use a dry method to periodically check the moisture meter and compare the two. Deviation, so that the actual moisture content of the wood can be determined, and the phenomenon of deformation and cracking of the product during use can be avoided due to the uneven water content, which not only affects the use effect of the product, but also affects the reputation of the enterprise.
4 sheet processing
In some cases, due to the large width specifications of the sheet, many high-quality materials are wasted due to insufficient size during longitudinal sectioning. Therefore, when the material is made, the sheet that meets the product size requirements should be processed. In addition, when processing the sheet, the plate with large curvature is firstly cross-section, so that the full-length of the sheet is less than 2 mm, which reduces the amount of cutting; the sheet that has been cut by double-sided planing, the transverse cross-section is large, then flat A planing surface is formed on the planing side, and then longitudinally sectioned into a specification sheet. The cross-cutting process is very important. Although it does not require high precision, according to the product quality requirements, the worker should judge the grade of the board and cut off it in an instant. Therefore, it is necessary to configure skilled workers in the process to reduce the wood. waste.
5 finger joint
Due to the different texture and softness of the wood, in order to prevent chipping (defects in milling teeth), the thickness of the wooden strip on the left side of the moving table should be the same when milling the teeth, otherwise the layer after the finger joint is easily bent into an arch. shape. The finger joint pressure should not be too high, otherwise the rebound will easily occur after the pressure is released, resulting in poor glue and affecting the quality of the glue. The finger joint pressure is generally 6 to 10 MPa for softwood and soft hardwood, and 8 to 10 MPa for hardwood. The finished material after finger jointing should be placed for more than 24 hours.
6 finger joint planing
The finger-joining process is very important. At present, many companies have many problems in the processing of this process. This process must use a four-sided planer to ensure that the adjacent faces of the processed plates are perpendicular to each other. When the glued surface and the non-glued surface are subjected to four-sided planing, the cutting allowance of each surface is more than 2 mm, and a large amount of high-quality wood which has been strictly selected is wasted. If it is improved on the four-sided planer, reduce the pressure of the feed roller and reduce the laminate indentation, the shaving allowance of each glued surface can be adjusted to 1mm (the above processes must be strictly controlled and managed), which reduces the cost of the laminated timber. . It is important to note that the finger-joined material after planing should be finished in 24 hours.
7 integration
It is required that the upper and lower sides of the finger slats are perpendicular to the two sides, the waviness of the glued surface is less than 1.5 mm, and the thickness tolerance of the laminate is within ±0.2 mm. The laminates should be symmetrically configured to reduce distortion. To get good gluing performance, uniform gluing is very important. There are two methods of single-sided gluing and double-sided gluing. The glue amount of each rubber layer is 200-300g/m2, and the prepared adhesive is prepared. It must be used during the active period, so that it can be used as needed, otherwise it will cause waste of adhesive or poor bonding. The glued laminate shall be immediately fitted with a blank, and pressure shall be applied before the adhesive is uncured. The purpose of the pressurization is to make the adhesive surface tightly glued, and the adhesive forms a thin and uniform film; with the curing of the adhesive, there is also a subsidized volume shrinkage. effect. The conditions of pressurization are: applying appropriate pressure, the pressure of each part is balanced, and the head spacing is about 40 cm. When the pressure is insufficient, the formed rubber layer is thick and the bonding performance is low; on the contrary, if the pressure is excessive, the lack of glue may result in poor bonding. Therefore, the pressure applied generally is 0.5 to 1 MPa for softwood and soft hardwood, and 1 to 1.5 MPa for hardwood. The temperature is 20 to 30 ° C, and the time depends on the type of rubber. The integrated sheet (or square) should be aged for more than 3 days to allow the adhesive to fully cure and then proceed to the next step.
8 adhesive
At present, the domestically produced laminated materials mostly use imported rubber, the performance of the glue is good, the bonding quality of the laminated materials is high, but the price is expensive; while the domestic rubber is more and more mixed, some adhesives with poor water resistance and aging resistance flood the market, and its products The performance is extremely unstable, and there are many quality problems in the use process, which seriously affects the use range of the laminated materials. Therefore, it is necessary to develop adhesives with stable gluing performance and multi-purpose integrated materials to meet the requirements of use, get rid of imported rubber, and revitalize the rubber industry. When adjusting the glue, the viscosity of the adhesive should be moderate. If the viscosity is too high, the adhesive does not flow in the wood tissue, and a uniform and strong adhesive layer cannot be formed. On the contrary, if the viscosity is too low, too much glue penetrates into the wood, which may occur. Lack of glue. Therefore, the viscosity of the adhesive should be adjusted within an appropriate range according to the adhesive application method of the adhesive and the gluing device, thereby obtaining a higher gluing quality and quality of the finished product.
9 standard
Glulam is still a new type of material in China and has developed rapidly in recent years. However, at present, most enterprises do not have complete production standards, and some have no specific standards at all. The export products of individual enterprises are organized according to the requirements of foreign companies. This state is extremely unfavorable for the development and quality management of laminated materials. Therefore, in order to get rid of the status of being controlled by people, it is necessary to formulate a unified standard for the production and quality of laminated materials suitable for China's national conditions in light of the specific conditions of China. This standard must ensure that the products have good performance and that the wood is fully and reasonably considered. Utilization, production enterprises have higher economic benefits. There are unified standards throughout the country, which is also convenient for enterprises to organize production and management departments to conduct quality supervision, thereby promoting the improvement of product quality and promoting the steady development of integrated production.
1 Material
When making materials, it should be processed according to the specifications of the product, leaving the machining allowance and dry shrinkage allowance. The machining allowance is generally 6~8mm; the dry shrinkage allowance depends on the tree species (see table), and its calculation formula is δ= Bk(30-w)
Where δ——drying allowance (mm);
B——sheet size (mm);
K——drying factor (%);
w - final moisture content (%).
Wood shrinkage factor of common tree species Table radial drying shrinkage factor (%) Chordwise dry shrinkage factor (%)
Larch 0.187 0.408
Red pine 0.122 0.321
White birch 0.188 0.258
Ash ash 0.171 0.322
柞木0.181 0.318
Spruce 0.171 0.349
楸木0.104 0.232
There are many companies that purchase boards from outside. When purchasing, the product specifications should be considered in relation to the blanks of the sheets, leaving a margin for processing. Otherwise, regardless of whether the blanks are too thick or too thin, the yield will be reduced and the cost will be increased. It is extremely unfavorable to improve the production efficiency of enterprises.
2 drying
The board should be naturally dried first, and when the water content reaches about 30%, it will enter the artificial drying stage. When drying, the same tree species (or similar density) and the same thickness of the plates are stacked separately; at the same time, the load is pressed on the plate to reduce defects such as deformation and cracking of the plate. In the drying process, the uniformity of the moisture content of the plate should be ensured. The dried plate must be placed in the outdoor slab for more than 20 days, so that the moisture content reaches the local equilibrium moisture content (8% to 15%), and the equilibrium moisture content of the plate is ensured. Uniformity provides a reliable guarantee for stable product quality.
3 Water content control
The water content must be strictly monitored, which directly affects the quality of the product. The water content test should be carried out for each process. The final moisture content of the plate should be determined according to the purpose and location of the product, generally 8% to 15%; The smaller the moisture content deviation of the slats of the material, the better, in principle, the deviation is controlled within 3%. If the moisture content of the wood is too high, the moisture in the wood dilutes and saturates the adhesive into the wood, which not only causes gelation, but also the glued product is easily deformed and cracked; if the moisture content is too low, the coating of the adhesive is affected. However, depending on the adhesive, sometimes even a high water content is easy to obtain a good gluing effect. At present, enterprises generally use a moisture meter to measure. The results measured by this method are not accurate enough, and there is a certain deviation from the actual moisture content. Therefore, it is better to use a dry method to periodically check the moisture meter and compare the two. Deviation, so that the actual moisture content of the wood can be determined, and the phenomenon of deformation and cracking of the product during use can be avoided due to the uneven water content, which not only affects the use effect of the product, but also affects the reputation of the enterprise.
4 sheet processing
In some cases, due to the large width specifications of the sheet, many high-quality materials are wasted due to insufficient size during longitudinal sectioning. Therefore, when the material is made, the sheet that meets the product size requirements should be processed. In addition, when processing the sheet, the plate with large curvature is firstly cross-section, so that the full-length of the sheet is less than 2 mm, which reduces the amount of cutting; the sheet that has been cut by double-sided planing, the transverse cross-section is large, then flat A planing surface is formed on the planing side, and then longitudinally sectioned into a specification sheet. The cross-cutting process is very important. Although it does not require high precision, according to the product quality requirements, the worker should judge the grade of the board and cut off it in an instant. Therefore, it is necessary to configure skilled workers in the process to reduce the wood. waste.
5 finger joint
Due to the different texture and softness of the wood, in order to prevent chipping (defects in milling teeth), the thickness of the wooden strip on the left side of the moving table should be the same when milling the teeth, otherwise the layer after the finger joint is easily bent into an arch. shape. The finger joint pressure should not be too high, otherwise the rebound will easily occur after the pressure is released, resulting in poor glue and affecting the quality of the glue. The finger joint pressure is generally 6 to 10 MPa for softwood and soft hardwood, and 8 to 10 MPa for hardwood. The finished material after finger jointing should be placed for more than 24 hours.
6 finger joint planing
The finger-joining process is very important. At present, many companies have many problems in the processing of this process. This process must use a four-sided planer to ensure that the adjacent faces of the processed plates are perpendicular to each other. When the glued surface and the non-glued surface are subjected to four-sided planing, the cutting allowance of each surface is more than 2 mm, and a large amount of high-quality wood which has been strictly selected is wasted. If it is improved on the four-sided planer, reduce the pressure of the feed roller and reduce the laminate indentation, the shaving allowance of each glued surface can be adjusted to 1mm (the above processes must be strictly controlled and managed), which reduces the cost of the laminated timber. . It is important to note that the finger-joined material after planing should be finished in 24 hours.
7 integration
It is required that the upper and lower sides of the finger slats are perpendicular to the two sides, the waviness of the glued surface is less than 1.5 mm, and the thickness tolerance of the laminate is within ±0.2 mm. The laminates should be symmetrically configured to reduce distortion. To get good gluing performance, uniform gluing is very important. There are two methods of single-sided gluing and double-sided gluing. The glue amount of each rubber layer is 200-300g/m2, and the prepared adhesive is prepared. It must be used during the active period, so that it can be used as needed, otherwise it will cause waste of adhesive or poor bonding. The glued laminate shall be immediately fitted with a blank, and pressure shall be applied before the adhesive is uncured. The purpose of the pressurization is to make the adhesive surface tightly glued, and the adhesive forms a thin and uniform film; with the curing of the adhesive, there is also a subsidized volume shrinkage. effect. The conditions of pressurization are: applying appropriate pressure, the pressure of each part is balanced, and the head spacing is about 40 cm. When the pressure is insufficient, the formed rubber layer is thick and the bonding performance is low; on the contrary, if the pressure is excessive, the lack of glue may result in poor bonding. Therefore, the pressure applied generally is 0.5 to 1 MPa for softwood and soft hardwood, and 1 to 1.5 MPa for hardwood. The temperature is 20 to 30 ° C, and the time depends on the type of rubber. The integrated sheet (or square) should be aged for more than 3 days to allow the adhesive to fully cure and then proceed to the next step.
8 adhesive
At present, the domestically produced laminated materials mostly use imported rubber, the performance of the glue is good, the bonding quality of the laminated materials is high, but the price is expensive; while the domestic rubber is more and more mixed, some adhesives with poor water resistance and aging resistance flood the market, and its products The performance is extremely unstable, and there are many quality problems in the use process, which seriously affects the use range of the laminated materials. Therefore, it is necessary to develop adhesives with stable gluing performance and multi-purpose integrated materials to meet the requirements of use, get rid of imported rubber, and revitalize the rubber industry. When adjusting the glue, the viscosity of the adhesive should be moderate. If the viscosity is too high, the adhesive does not flow in the wood tissue, and a uniform and strong adhesive layer cannot be formed. On the contrary, if the viscosity is too low, too much glue penetrates into the wood, which may occur. Lack of glue. Therefore, the viscosity of the adhesive should be adjusted within an appropriate range according to the adhesive application method of the adhesive and the gluing device, thereby obtaining a higher gluing quality and quality of the finished product.
9 standard
Glulam is still a new type of material in China and has developed rapidly in recent years. However, at present, most enterprises do not have complete production standards, and some have no specific standards at all. The export products of individual enterprises are organized according to the requirements of foreign companies. This state is extremely unfavorable for the development and quality management of laminated materials. Therefore, in order to get rid of the status of being controlled by people, it is necessary to formulate a unified standard for the production and quality of laminated materials suitable for China's national conditions in light of the specific conditions of China. This standard must ensure that the products have good performance and that the wood is fully and reasonably considered. Utilization, production enterprises have higher economic benefits. There are unified standards throughout the country, which is also convenient for enterprises to organize production and management departments to conduct quality supervision, thereby promoting the improvement of product quality and promoting the steady development of integrated production.
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