It is still a mystery for many people how bamboo plywood sheets are produced, which causes difficulties in buying suitable bamboo products. Thus, there are some tips of the production process of bamboo plywood sheets.
1. Raw materials
It should be bamboo grown for five years because it has good toughness and hardness.
2. Preparation of thick bamboo slices with grooves
The large-diameter moso bamboo is cross-sectioned into sections, the outer of which is milled and longitudinally cut into 2-4 pieces, and then the inner of which is milled to soften by steaming. Then, it is heated and pressurized on the upper pressure single-layer flat press to unfold the curved bamboo block into a plane. Finally, it is processed into bamboo slices of equal thickness without bamboo green and bamboo yellow after double-sided planing.
3. Setting and drying
In order to prevent the bamboo pieces from curling and deforming under the action of the transverse elastic restoring force during the drying process, pressure drying technology and equipment must be adopted to heat the wet bamboo pieces under pressure. When the pressure is released, the moisture should be removed with free shrinkage.
4. Bamboo sizing
A four-roll gluing machine is used to roll the bamboo sheet with water-soluble phenolic resin glue, and the glue amount is 300-350g/㎡ (double-sided). 1%-3% of flour, soy flour and so on can be added to the adhesive as a filler which can make the bamboo chip easy to form a glue film on the surface after the glue is applied. It is not easy to cause glue flow during hot pressing, and can improve the brittleness of the glue layer after curing.
The blank is formed by hand in strict accordance with the principle of symmetry, odd number of layers and the principle of perpendicular texture of bamboo slices in adjacent layers. The panel is required to be made of bamboo with good material, and the bamboo with inferior material is used as the back plate. The bamboo green face outwards and the bamboo yellow face inwards. When the core board is formed, the orientation of the adjacent bamboo pieces is required to be arranged alternately according to the bamboo green surface and the bamboo yellow surface.
6. Pre-pressing and hot pressing
(1) Pre-pression. In order to prevent the defects caused by the displacement of the slab to the hot press, the slab should be prepressed at room temperature before the hot pressing after forming the slab, so that it can be bonded into a whole material.
(2) Hot pressing. The hot-pressing temperature is about 140oC, the unit pressure is 2.5-3.0 MPa while the hot-pressing time is calculated according to the thickness of finished bamboo plywood sheets, which is generally 1.1 min/mm.
In order to prevent the occurrence of "bubbling", the three-stage depressurization process is usually adopted in the late period of hot pressing. The first section from the working pressure to "balance pressure", the second section from "balance pressure" to zero, the third section from zero to the hot-pressing plate to complete the opening.
7.Sawing board processing and packaging
The hot-pressed bamboo plywood sheets are sawn into 1.22 meters wide and 2.44 meters long on the saw table, and then stacked neatly, filled with a layer of putty powder. Packing is usually done in the factory with 5 verticals and 2 horizontals. It can also be packed according to customer requirements, with a wooden square underneath to facilitate transportation and turnover without damaging the bamboo plywood sheets.