STUDIES ON CO2 LASER-MALAYSIAN WOODS INTERACTIONS USING ULTRASOUND IMAGING, SEM AND EDX

Presenter	:	IZYANI KARUDIN
E-mail	:	-
Date	:	2 / 7 / 2007
Time	:	3.00 PM
Venue	:	CEMACS, CONFERENCE ROOM, SCHOOL OF PHYSICS
Sypnosis	:	Processing of wood by conventional mechanical tools leaves behind a layer of squeezed wood only slightly adhering to the solid wood surface. Laser wood cutting could improve the quality of cutting. This research is focused on optimizing laser wood cutting. Result of experiments by continuous wave CO2 laser on surfaces of different Malaysian light hardwood types and cut orientations are shown. The depth and surface diameter of penetration was measured by using ultrasound imaging. Moreover surface morphology observation using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) for elements and compound identification have also carried out. The process parameters examined were laser power, PWM duty cycle percentage, exposure time, incident angle, distance of wood sample from laser source and density of wood samples. It is found that the density of wood has significant effect on the depth and surface diameter of penetration in wood samples. The microcracks are found in the resolidified wood at the cutting surface, which is due to non-uniform and rapid cooling of the resolidified wood at the surface. SEM microphotography of the cut was achieved for detailed investigation of the effects of cutting parameters of the cut geometry. Damages and burns occurred around and inside the cutting cross-section with the laser beam of 10600 nm. The EDX result shows that irradiation reduced the percentage of the elements in wood samples. The PWM duty cycle increases with the laser power. The laser power did not depend on the exposure time and the distance from laser source. Melunak: The depth of penetration and surface diameter of penetration depend linearly on the exposure time and increases with the laser power of 5.2 W, 7.1 W and 8.6 W. The depth of penetration decreases with the incident angle from 0° until 50°. The surface diameter of penetration increases with the incident angle from 0° until 20°, after that it remained decreased until 50°. The depth of penetration and surface diameter of penetration decrease as the power density increases. The hole area of penetration decreases with the power density. Getah and pulai: The depth of penetration decreases with the distance of wood samples from laser source from 5 cm until 30 cm while the surface diameter of penetration increases with the distance of wood samples from laser source from 5 cm until 30 cm. The depth of penetration and surface diameter of penetration of pulai was higher than getah. For getah the power density decreases with the distance of wood samples from laser source while the hole area of penetration increases with the distance of wood samples from laser source. For pulai the power density increases with the distance of wood samples from laser source while the hole area of penetration decreases with the distance of wood samples from laser source. Meranti bakau, durian and medang: The depth of penetration and surface diameter of penetration has a linearly PWM duty cycle percentage from 10% until 60% on the exposure time of 4 minutes. The degree of depth of penetration and surface diameter of penetration are durian > medang > meranti bakau. The depth of penetration and surface diameter of penetration of durian, medang and meranti bakau decrease as the power density increases, while the depth of penetration and surface diameter of penetration of medang and meranti bakau, increase as the power density increases. The hole area of penetration decreases with the power density. Meranti bakau, plywood and jelutung: The depth of penetration decreases with the incident angle from 0° until 50°. The surface diameter of penetration for meranti bakau and plywood increases with the incident angle from 0° until 20°, after that it remained decreased until 50° while the surface diameter of penetration for jelutung remained increases from 0° until 50°. The degree of depth of penetration and surface diameter of penetration are meranti bakau > plywood > jelutung. The depth of penetration and surface diameter of penetration for jelutung and plywood decrease, as the power density increases while the surface diameter of penetration for meranti bakau increases with the power density. The hole area of penetration decreases with the power density. The depth of penetration decreases with the distance of wood samples from laser source from 5 cm until 30 cm. The surface diameter of penetration increases with the distance of wood samples from laser source from 5 cm until 30 cm. The power density decreases with the distance of wood samples from laser source while the hole area of penetration increases with the distance of wood samples from laser source. Yellow meranti and light red meranti: The depth of penetration and surface diameter of penetration depend linearly on the exposure time. The depth of penetration and surface diameter of penetration of light red meranti is higher than that of yellow meranti. The depth of penetration of light red meranti decreases as the power density increases while the depth of penetration of yellow meranti increases as the power density increases. The depth of penetration and surface diameter of penetration decrease with the power density. The hole area of penetration decreases with the power density. Meranti bakau and yellow meranti: The depth of penetration and surface diameter of penetration depend linearly on the exposure time. The depth of penetration and surface diameter of penetration of yellow meranti is higher than that of meranti bakau. The depth and surface diameter of penetration decrease as the power density increases. The hole area of penetration decreases with the power density. SEM showed that wood structure was damaged after irradiated by laser especially at high laser power and long laser exposure time. In addition, the atomic percentage of carbon increased after the interaction with CO2 laser whereas the percentage of oxygen atom decreased after irradiated by CO2 laser beam. It was also found that after irradiated by laser beam, the mineral elements inside the wood with a lower density are acquitted easily compared to wood with more dense. The results have relevance to CO2 laser applications in the wood industry. Several chemical processes contribute to the effect of the CO2 laser radiation. The processes depend on several factors one of which is the amount of absorbed energy. The stage of degradation’s degree of sample highly depends on the laser power. Changes in absorption become significant with the density of different wood types. It shows that by proper control of the cutting parameters, good quality cut are possible at a low laser power, incident angle of 0°, short distance between wood sample from laser source and short duration of exposure time.

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