Testing method for water boiling resistance of plywood
Improvement measures: Firstly, replace the adhesive, choose a formula with low water content, or add flour and soybean powder appropriately to absorb water; The second is to improve the quality of veneer and strictly control the moisture content of veneer; The third is to adjust the hot pressing process, increase the hot pressing temperature, extend the hot pressing time, and appropriately increase the pressure; The fourth is to regularly inspect the equipment to ensure the accuracy of the rotary cutting machine, and check the steam path and supply situation of the hot pressing plate.
โก Bubbling and local degumming
The main reasons are: the pressure reduction speed is too fast; the moisture content of the veneer is too high; Insufficient hot pressing time or low local temperature of the pressing plate; There are blank spots, inclusions, or sticky stains when applying glue; Pine veneer has poor breathability, high hot pressing temperature, and resin vaporization, resulting in glue opening.
Improvement measures: Firstly, adopt a multi-stage depressurization process and strictly control the depressurization speed; Secondly, reduce the moisture content of the veneer; Thirdly, increase the adhesive concentration or reduce the amount of adhesive applied; Fourthly, for tree species such as pine with poor air permeability, a hot pressing temperature below 110 โ should be used; Fifth, appropriately extend the hot pressing time; Sixth, check the steam path and supply condition of the hot pressing plate.
โข Corner detachment
The main reasons are: the aging time is too long, and the edge glue has dried up; Lack of adhesive at the edges and corners; Large area press presses small area panels with missing adhesive at the edges and corners; When the large face press presses the small face plate, the loading positions of each layer shift, resulting in uneven pressure; Warping deformation of hot pressed plate; The temperature at the corners of the pressing plate is too low.
Improvement measures: Firstly, shorten the aging time; Secondly, pay attention to the gluing operation; The third is that the large press does not press the small plate, and even if the small plate is pressed, the compression positions of each layer should be aligned; Fourthly, when the pressure plate is warped and deformed, it can be repaired by planing the hot pressed plate; When the deformation is large, the pressing plate needs to be replaced; Fifth, check the steam path and supply condition of the hot pressing plate.
โฃ Core plate stacking and separation seam
The main reasons are: manual core arrangement, inaccurate grasp of the expansion gap between zero pieces of single boards; When installing or moving the board, the core board is misaligned; The preloading effect is not good, and the bonding between the veneers is not good; The edge of the core board is uneven; The edge of the core board has ruffles and cracks.
Improvement measures: Firstly, achieve the whole core board or adopt a secondary adhesive coating process; Secondly, the aging time of the opening of the coated core board should be appropriate; The third is to implement pre pressing before loading the slab, and maintain stability when moving the slab; Fourth, grasp the timing of preloading; Fifth, the core board adopts a leveling process, and the core board that is cut first and then dried should be aligned with the edges after drying; Six is to improve the quality of core plate rotary cutting and drying.
โค Board surface adhesive penetration
The main reasons are: the glue is too thin and there is too much water; Excessive glue application; The crack on the back of the veneer is too deep; The moisture content of the veneer is too high; Insufficient aging time of slab; Excessive pressure during hot pressing.
Improvement measures: Firstly, check the quality of the glue, increase the resin content of the glue, and select a formula with low water content; Secondly, reduce the amount of glue applied and replace worn glue rollers; The third is to improve the quality of veneer rotary cutting, adjust the position of the pressure gauge, and increase the rotary cutting and pressing rate; Fourth, reduce the moisture content of the veneer; Fifth, increase the aging time to evaporate a portion of the moisture in the adhesive solution; Sixth, reduce the hot pressing pressure and check the pressure gauge of the hot pressing machine.
โฅ Plywood warping
The main reasons are: the symmetry principle is not followed during the assembly of billets; The front and back directions of the blank assembly are incorrect; The veneer is made from stressed wood segments; Warping deformation of hot pressed plate; Plywood stacked unevenly.
