Date: January 17th, 2023 By: Ken Xiong
Bamboo’s uniquely fast growth, moisture-wicking fibers, and ease of cultivation have made it a popular choice for people looking for a more sustainable option.
We will have a look at the process that bamboo goes through before it becomes a finished and polished product ready to be used in your daily life.
The newly harvested bamboo stems are cut into strips (panels), those bamboo panels are available in 4-by-8-foot sheets or narrower 16-by-72-inch panels, with thickness ranges from 2 to 19 millimeters.
The bamboo panels need to go through a few steps before lamination:
The time and temperature requirements for preserving will vary according to bamboo species and desired heat penetration. Most manufacturers boil strips at a temperature of 100°C for at least 24 hours. In addition, boiling also increases the moisture content of the core of the sections, which is beneficial for further air-drying and kiln drying. Also, internal stress in the strip will be released while boiling.
Some customers prefer bamboo products with light to deep brown coloration. These colors can be produced by steaming the strips in a pressure tank, which is heated by steam. At certain temperatures, some chemical components (e.g. lignin) will deepen their color. The higher the temperature and the longer they are steamed, the deeper the color they take on. Usually, the section will take on a chestnut color at a pressure of 3-5 kg/cm2 for 90-105 minutes.
The moisture content of boiled or steamed strips is about 100%. It is generally desirable to dry the bamboo before use because dry bamboo is stronger and less susceptible to degradation (biological, thermal, or chemical) than wet bamboo. Sections are either air-dried, kiln-dried, or both.
The sections have excellent dimensional stability after drying. At this time, they can be planned to the required thicknesses and widths. A precision planer is an ideal machine for this. It is equipped with four blades, two horizontal and two vertical, and can plane all four surfaces of each strip at the same time to predetermined dimensions. It also smoothes the surface.
The bamboo strips are now ready for the lamination process:
(Lamination by definition is the process of manufacturing a material in multiple layers so that the composite material achieves improved strength and stability )
The adhesive is spread on the plane and edge surfaces of the graded and classified sections. The most common adhesive in the laminated bamboo industry is urea-formaldehyde resin. The glue is applied to the sections using a variety of techniques including roller spreaders, spray lines, curtain coaters, and brushes. Each of these techniques has its advantages and disadvantages, depending upon the type of manufacturing operation under consideration. Roller glue spreaders are employed in most factories because of their low price, efficiency, and stability.
Sections are assembled (laid up) into laminated blanks immediately after the application of adhesive. This must be done rapidly and carefully. Speed in assembly is necessary because the glued sections must be placed under pressure within certain time limits or they will dry out and become ineffective. Careful workmanship is required to lay up the face, core, and back strips correctly.
Assembled units are loaded into the hot press, where hydraulic rams press the assembled units in two directions, horizontal and vertical, exerting a pressure of 1.2-1.4 MPa. The temperature of the hot press is usually set in the range of 200°C-300°C.
After hot pressing, many mills post-press the units. This is performed in a cold press which consists of one stationary platform and one connected to hydraulic rams. The load is held under pressure for several hours to maintain the shape and dimensions of the unit.
After all those steps bamboo is almost done and we are ready to make your favorite furniture, the laminated bamboo need just to be shaped and polished.