SYNRAD, INC. - http://www.synrad.com |
Applications at a glance |
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Engraving Balsa Wood |
Cutting Thermoplastics |
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SYNRAD's sealed CO2 lasers are used in a variety of industrial processes including cutting, welding, drilling, and marking. This news brief showcases some of the interesting materials and products that are processed daily by Synrad's line of CO2 lasers and marking heads. |
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Laser marking on this balsa wood sample resulted in clean, crisp marks. The eagle image was marked using 25 W of power in a cycle time of 4.28 seconds.
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Cutting Thermoplastics
There are two main types of plastics: thermoplastics, which lend themselves to being shaped and molded when hot; and thermosets (crosslinked polymers), which are shaped "cold" and then set by the crosslinking, or heating, process. Thermoplastics will exhibit much better cut edge quality with no apparent discoloration while the edges of thermoset materials tend to char and discolor. The table at the end of this article lists common types of thermoplastic and thermoset materials, and categorizes them by the type of edge quality typically obtained when laser cut. As examples, we cut three different thermoplastic materials. The first sample, 3.4 mm (0.135") thick acrylic, was cut using 400 watts of power at a speed of 12.1 meters per minute (475 inches/minute - IPM). Notice that the cut edge is clean and smooth with no discoloration or charring - a typical acrylic cut! Our 3.3 mm (0.130") thick HDPE (high density polyethylene) sample was cut using 400 watts at 1.7 meters/minute (65 IPM). The cut edge is clean and char-free with only a slight melt back visible. The last thermoplastic sample was a strip of LDPE (low density polyethylene). This piece, 3.2 mm (0.125") thick, was cut using 400 watts at a speed of 2.4 meters/minute (95 IPM). Although the cut edge is clean and exhibits no charring or discoloration, it does show some melt back on both upper and lower surfaces. |
A 0.125"-thick section of LDPE was cut using
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All samples were cut on our XY stage using a firestar f400 laser. For gas assist, we used 0.7 bar (10 PSI) nitrogen for the acrylic samples and 1.4 bar (20 PSI) nitrogen when cutting the polyethylene samples. Beam delivery was via a 63.5 mm (2.5") focusing lens, which provides a 100-micron (0.004") spot size with a 1.8 mm (0.07") depth of focus.
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After the appropriate lens is chosen, the key to laser marking curved surfaces in a fixed focal length setup is to place the focal point midway between the points of highest and lowest curvature. In this application, our mark surface has a radius of curvature of 241 mm (9.5") and our desired text mark has a length of 62 mm (2.44") along the chord of the arc, which equates to a difference in height of 2 mm (0.079"). By placing the position of focus 1 mm (0.039") below the part surface, in the center of the mark, we will remain within 1 mm of our optimum focal plane at both the highest and lowest points, ensuring a consistent power density across the mark. Our marking setup included a Synrad 100 watt laser and FH Series marking head equipped with a 125 mm, high-power lens. This lens provides a 180-micron (0.007") focused spot with a 3 mm (0.118") depth of focus. Although in this case our 2 mm change in height falls within the lens' overall depth of focus, careful attention to the exact point of focus will always yield the most uniform laser processing results.
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SYNRAD and Synrad product names are trademarks or registered trademarks of SYNRAD, Inc. All other trademarks or registered trademarks are the property of their respective owners. |