Scorching at the edges of wood is a common and critical issue during paintbrushing. Scorching not only affects the aesthetics of the finished product but can also reduce the structural strength and lifespan of the paintbrush. This phenomenon is closely related to laser energy control, wood characteristics, and processing parameter settings, requiring multi-faceted optimization to achieve precise engraving and edge protection. Precise control of laser energy is key to avoiding scorching. Laser engraving uses a high-energy beam to instantly vaporize the surface material of the wood to create patterns. If the energy is too high, the heat generated when the beam penetrates the wood will diffuse to the surrounding area, causing the edge areas to carbonize and scorch due to overheating. Therefore, the laser power and pulse frequency must be adjusted according to the type of wood. For example, hardwoods such as oak and walnut have high density and poor thermal conductivity, requiring a reduction in power and a longer pulse interval to allow sufficient time for heat dissipation. Softwoods such as pine and birch have faster thermal conductivity, allowing for a higher power but shorter single irradiation time to prevent heat accumulation. By repeatedly testing different parameter combinations, a balance was found that ensured both carving clarity and edge temperature control.
The moisture content of the wood has a significant impact on the carving effect. Wood with excessively high moisture content will absorb some energy during laser irradiation due to the evaporation of heat, leading to a sudden increase in local temperature and exacerbating the risk of scorching. Conversely, wood with excessively low moisture content lacks a moisture buffer, allowing heat to directly act on the wood fibers, also easily causing carbonization. Therefore, the wood must be dried before processing to stabilize its moisture content within the suitable range of 8%-12%. For dried wood, a small amount of even water mist can be sprayed before carving to form a thin water film, which can aid heat dissipation and reduce carving dust contamination of the laser lens, further improving processing accuracy.
Carving path planning and speed matching are key to optimizing edge quality. Laser carving typically uses vector paths or bitmap filling methods; improper path planning can lead to repeated heating of the same area. For example, when using a spiral filling path, if the spiral spacing is too small, the laser will scan the edge area multiple times, causing heat accumulation; while if the spacing is too large, the engraving may be incomplete. Therefore, the filling density needs to be adjusted according to the complexity of the pattern. Complex patterns use fine filling, while simple patterns can have a wider spacing. Simultaneously, the engraving speed needs to be adjusted in conjunction with the power and filling density. High-speed engraving can reduce the heat residence time, but it needs to be paired with high power to ensure the engraving depth; low-speed engraving requires reduced power to avoid overheating, achieving efficiency and precision through dynamic balance.
The combined use of auxiliary gases and dust collection devices can effectively improve the engraving environment. During laser engraving, the introduction of auxiliary gases such as compressed air or nitrogen can disperse the smoke and molten particles generated during engraving, reducing heat retention on the wood surface. For example, nitrogen, as an inert gas, not only assists in heat dissipation but also inhibits oxidation reactions, reducing the probability of scorching. At the same time, a high-efficiency dust collection device can promptly remove dust and gases generated during engraving, preventing them from adhering to the wood surface and forming a heat-insulating layer that prevents heat dissipation. The suction power of the dust collection device must be matched to the carving speed. Excessive suction may pull up lightweight wood, affecting processing accuracy; insufficient suction will fail to completely remove dust. Optimal parameters must be determined through experimentation.
The influence of wood grain direction on the carving effect must be considered. Wood conducts heat better along the grain than perpendicular to it. If the carving direction is perpendicular to the grain, heat easily accumulates at the edges, leading to scorching. Therefore, in the layout design, the carving direction should be parallel to the wood grain as much as possible, utilizing the grain's thermal conductivity to disperse heat. For patterns that must be carved perpendicular to the grain, the power can be reduced and the carving speed increased, or multiple shallow carvings can be used to gradually form the shape, reducing the heat input per carving.
Post-processing can also repair minor scorching. If slight carbonization appears at the edges after carving, it can be repaired by sanding or flame treatment. Sanding can remove the surface scorch layer, but the pressure must be controlled to avoid excessive abrasion; flame treatment uses high temperatures to oxidize and remove the carbonized layer, while simultaneously forming a protective film, but the flame temperature and time must be strictly controlled to prevent secondary scorching. For finished products with high requirements, dyeing or painting processes can be used to cover up scorch marks and improve the overall appearance.
