CO2 Best for New Interior Panels
Richard Gaughan
Automobile manufacturers constantly seek to improve their product's marketability, performance and profitability. One innovation is the replacement of standard interior trim materials with polymers that are reinforced with natural fibers such as sisal or flax. The panels are more environmentally friendly than the glass fibers they replace, which enhances product image, and they are strong but up to 40 percent lighter, which improves fuel economy.
But whenever a new material is proposed, its impact on manufacturing processes must be assessed. Researchers at the University of Vigo have evaluated methods of cutting the fiber-reinforced polymer panels and have found that cutting with a CO2 laser is the most effective.
Abrasive water jet cutting is commonly used in similar applications, but the nature of water cutting -- using small particles suspended in a high-velocity water stream -- produced undesirable side effects. When tested on 5-mm-thick panels at a cutting speed of 50 mm/s, water-cut edges displayed a powdery residue and loose fibers that had been released by the impact. In addition, the exposed surface of the edge was open and microscopically rough, which could allow water to seep into the material and lead to mildew growth.
An alternative to abrasive water jets is the Nd:YAG laser. This technique has the advantage of fiber delivery, and the researchers used a 10-m-long, 400-µm-diameter optical fiber to direct the output from a 500-W Rofin-Sinar Nd:YAG laser to the test surface. But the YAG-cut edges also were rough, and the optimal cutting speed was limited to 10 mm/s.
When they cut the samples with a 3.5-kW Rofin-Sinar open-flow CO2 laser, the cut was straight, but the edges were burned. Reducing the laser power to 300 W, however, yielded clean and smooth edges at a cutting speed of 67 mm/s.
Sealed is suitable
These results encouraged the researchers to investigate the effectiveness of a 200-W sealed CO2 laser, which does not require external gas tanks, gas lines or exhaust pumps. They found that the kerf width, surface roughness and cut quality were comparable to those produced by the open-flow system.
They suggest that the laser chemically degrades the natural fibers by combustion and also vaporizes the polymer matrix. This melts the polypropylene polymer, covering the cut fibers and leaving a sealed end face.
The team reported its findings in the June issue of Journal of Laser Applications.
Published: September 2001