27
3.3.2 Veneer quality 3.3.2.1 Measurements of thickness variation
Veneer sheets produced from each segmented rings were collected and clipped to 10x60 cm veneer specimens. Three test specimens were used for the
measurements of thickness variation. Six points of thickness measurements were marked on the side of each test specimen. see Figure 11
Figure 11 Schematic diagrams of samples for veneer thickness variation, contact angle, surface roughness and LVL production
3.3.2.2 Measurements of lathe check frequency
The test specimens were kept in the green condition. In order to be able to observe lathe checks clearly improve contrast, red ink was stained on loose side
of veneer samples. The loose side by the dimension of 20x100x3 mm Figure 12 was set up on the table of digital video microscope under 30X magnification.
Then a digital video microscope was used to capture images from the surface of veneers loose side. The images then were analyzed using motic image 2.0
version software to count the lathe checks frequency, length and depth Figure 12.
60 cm Veneer sheet
for LVL production
6 - 24 cm 16 - 34 cm
60 cm The width of
veneer sheet from pith to bark varied
from 16 to 34 cm Veneer sheet
60 cm
10 cm 2 cm in length for
lathe check
2 cm in length for contact angle and
surface roughness 1
2
1
1 2
2 The points for
measuring thickness variation
28 Frequency of lathe check was presented as the number of lathe check per cm
length of veneer.
Figure 12 Veneer thickness 1, depth of lathe check 2 and length of lathe check 3 of poplar veneers’ loose side
3.3.2.3 Surface roughness measurement
A portable surface roughness tester TR200 was used for roughness evaluation of the samples. A total of 10 roughness measurements were conducted
according to JIS standard 2001 by using the roughness tester. Measurements were performed on each surface roughness test specimen across the grain orientation of
the veneer. Tracing speed, diamond tip radius, and tip angle were 0.5 mms
-1
, 5 μm and 90
o
, respectively. The length of tracing line was 15 mm and cut-off was 2.5 mm. The measuring force of the scanning arm on the surfaces was 4mN 0.4 g,
which did not put any significant damage on the surface. Measurements were repeated whenever the stylus tip fell into the pores. The calibration of the
instruments was checked in every 100 measurements by using a standard
reference plate with Ra values of 7 μm. Average roughness Ra values were recorded to evaluate surface roughness.
Figure 13 Contact angle of water a and PVAc as adhesive b on jabon veneers’
loose side 3.3.2.4 Measurements of contact angle
Water and PVAc were dropped by using pipette on loose side of veneer Figure 13. Video images were taken starting from initial drop up to 180 seconds
wetting. Then pictures were consecutively collected at every 10 seconds from the video images. Those single pictures were analyzed by motic image software to
measure their contact angles. Then, equilibrium contact angle was determined by segmented regression analysis using PROC NLIN on SAS software.
a b
1 3
2
