The cut edge of this red glass shows a brittle, underside dross that removes easily to expose a cleanly cut edge.
These small 1.375” (35 mm) diameter circles were cut out of a translucent yellow glass using 400W at a speed of 50 IPM.
When cutting glass with a CO2 laser, the best “laser only” applications are typically thin glass substrates in the range of 30 to 600 microns (0.0012” 0.0236”) thick. Without using specialized, and in some cases, proprietary processes, thicker types of soda-lime (float) glass are difficult to laser cut in one step.
Fortunately, the exceptions to the rule are these stained glass samples that cut very well using a Synrad sealed-CO2 laser. As with standard float glass, straight-line cutting of stained glass is easily done by scoring and snapping. The difficulty, as any stained glass artist will tell you, is in creating irregular shapes. Traditionally, curved shapes are made by nibbling away at the contour, by grinding on a diamond wheel, or by cutting using a diamond-bladed bandsaw all being time- and labor-intensive processes.
Our cutting setup for these opaque and translucent stained glass samples consisted of a Firestar f400 laser with beam delivery provided by an XY “flying optics” system. Beam focus was through a 2.5” positive meniscus lens that provides a 100-micron (0.004”) spot with a 1.8 mm (0.07”) depth of focus.
In addition to creating the brilliant hues and colors seen in stained glass, the addition of metallic oxides or metallic salts to the glass formulation appears to alter the glass structure so that the laser’s intense, localized heating does not lead to unintended thermal fracturing of the glass substrate. Cut edges exhibit the same type of striation patterns seen in metal cutting where vaporized and molten material is blown through the cut area by a high-pressure assist gas.
The straight line and circular cuts shown (from sample thicknesses of 0.130”) were obtained using 400 watts of power at a cut speed of 50 to 60 inches per minute (IPM). We used 60 PSI of air as a gas assist during cutting. The photos show discolored dross present on the bottom edge of all cut faces, however the dross is brittle and easily removed leaving a clean laser-cut edge!