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19 Mar 2008
A variety of laser-based etching and coating processes can produce decorative colours or designs on MDF, or simulate the appearance of expensive wood grains.
A collaboration between researchers at the WMG innovation centre based at the University of Warwick and seven academic, research and commercial organizations in the UK have developed the LaserCoat process, which uses a laser to produce wood grain effects in medium-density fibreboard or MDF. "MDF is a versatile material, but it looks dull in its raw state," explained Ken Young of WMG. "Until now there has been no way to liven it up other than painting it."
LaserCoat uses a 200 W CO2 laser coupled to a 3D scanning head, with the focal plane located 265 mm below the beam input. To etch patterns into the MDF, the laser is operated at 90% power on flat surfaces and 60% power at the edges, sufficient to burn the surface and create carefully designed darker regions that mimic the appearance of wood grain.
"By varying the power and speed of the laser we are able to produce lighter or darker marks," J Peter Hancocks of WMG told optics.org. "The marks are sufficiently deep to be visible when over-painted, giving a convincing real wood effect." Applying the technique to a material that already has a different colour top layer, such as melamine-faced chipboard, can produce a distressed wood effect.
Alternatively the laser can be used to selectively cure powder coatings applied electrostatically to the surface, producing a variety of patterns, colours or other design elements. Typical coating thicknesses are 0.05 to 0.1 mm, depending on the application conditions.
"Consolidating powder coatings needs different laser parameters," said Hancocks. "When coating, MDF's layered structure tends to absorb the molten powder, while when etching the laser tends to key into the structure." For coating processes the laser power is reduced to 40% for flat surfaces, and to 25–30% for edges.
"Etching is easier than coating, which depends upon some moisture content in the MDF for the electrostatic coating process to work," commented Hancocks. "This moisture can be problematic when curing the powder as it can cause bubbling through the paint film, so careful choice of conditions and parameters is required."
As a result, the more straightforward etching process is currently closest to market, but Hancocks points out that commercialization will depend on achieving the effects at viable speed and cost. "We are looking at the use of low-cost 'plotter' CO2 systems made in China primarily for the corporate gift market, and at the use of higher power lasers in our facility to increase production rates."
Another possibility is using a slower, and thus hopefully lower cost, system to produce etched panels on a 24/7 basis. "We have produced two sets of etched panels, built and finished by our partner Howarth Windows & Doors in the same way as production doors," noted Hancocks. "The results provide a strong incentive to find an economically viable production system."
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