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The harvested bamboo stalk is hollow with a hard outer wall and a softer
inner wall. At the primary processing plant, long rectangular strips are
cut from the stalk then milled to remove the inner and outer skin and
nodes. This milling process also shapes the strip into the rough
rectangular shape and dimensions required by the finishing plant. The
strips that pass a final visual quality control inspection will be used to
construct bamboo flooring, paneling or related items. Quality bamboo
strips are the major factor in assembling a premium bamboo product.
The quality of strips is of the utmost importance since bamboo flooring is
an assembled product consisting of approximately 15 strips for the
horizontal construction and about 19 strips for the vertical construction.
This manufacturing process is one of the major differences when compared
to solid wood flooring.
GreenWood’s bamboo strips are obtained from plants located in the bamboo
forests of the Fujian and Zhejiang provinces in China. There, the bamboo
log is split into the rough strips and then processed into semi-finished
strips and dried to reduce the moisture content to 12%. In GreenWood’s
production process, many of the strips required for production into
carbonized products are immediately steamed under high pressure. This
process, known as carbonization, changes the color throughout the strip
from a blonde, yellow color to a brown, coffee color. Carbonization
reduces the strip hardness approximately 20%. Strips not carbonized at
this point must be boiled to kill pests and remove sugar. If the boiling
process is not done in a timely manner, the strips will begin to rot. The
boiling process reduces the strip’s hardness by 8%. Most mills will first
boil the strip and then carbonize the strip, thereby reducing the hardness
of the carbonized strip by over 26%. Our manufacturer’s process removes
the boiling requirement and preserves the hardness that is lost by the
other method.
At the finishing plant, strips are again inspected for quality and
separated into class “A” or class “B” strips. Only class “A” strips are
used for GreenWood's flooring. “B” quality strips are sold at a discount
to less demanding manufacturers. A major reason for the lower prices
offered by some manufacturers and/or importers is their use of “B” quality
strips.
After boiling or carbonizing, the strips are milled to a uniform size then
kiln dried for three days, reducing the moisture content of the strips to
8-10%. The strips are now milled to a final width and thickness in
preparation for finished plank assembly.
The final phase of bamboo flooring production begins with the gluing
process. Most Chinese glue is high in formaldehyde and low in strength
retention. GreenWood requires our manufacturers to use a high quality,
European (E-1) glue that exceeds most indoor air quality requirements for
formaldehyde emission. Our bamboo, when tested in a climate chamber
according to ENV 717-1, 1998, Part 1, Annex A3, emits only 0.0127 parts
per million of formaldehyde.
During the production process, glued strips are assembled face up for
horizontal flooring and side by side for the vertical construction. Hot
pressing, where heat and pressure of up to 1,200 tons PSI binds the strips
together and allows for complete dispersion of the glue, is the next
process.
A major quality consideration is the molding operation where the side and
end tongue and grooves are milled to exacting tolerances that provides a
uniform straight edge. The multi-step, German molding machine performs all
milling functions in one pass. The diamond-tipped cutting tools assure
close tolerance over long production runs. The manufacturer guarantees
tolerances as follows:
Length: +/- 1mm, Width: +/- 0.1 mm, Thickness: +/- 0.1 mm
GreenWood supplies both square edged unfinished flooring and Micro Beveled
pre-finished flooring. Our manufacturer has two fully equipped finishing
lines that apply 6 coats of Treffert’s High Performance Coating (HPC).
This finish consists of micro or nano particle modified acrylate urethane
resins that combine extreme hardness with high mechanical resistance to
scratch, impact and abrasion.
The boards are finely sanded during the finishing process with a high
precision sanding machine. The sanding eliminates air pockets and pinholes
from the final product and also guarantees the high adhesiveness of the
urethane. Treffert, an internationally known European finish manufacturer,
guarantees the finish for 15 years in a residential setting and 5 years
for commercial use. These planks can be easily re-finished as the
anti-abrasion particles are only added in the 2nd step of the finishing
process.
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