abstract
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Digital Glass Forming (DFG) uses a laser to locally heat a glass filament at the point that it intersects the workpiece. The heated glass can be deformed by loading from the unheated filament and workpiece. If it is sufficiently heated, the glass can wet to the workpiece to form a continuous glass structure. Typically, a CO
2 laser is used which directly couples to phonon modes in the glass and provides a surface heat flux. The deposition rate is limited by time required for thermal diffusion through the glass to make it workable. Increasing the laser power can reduce this time; however, the result is often excessive temperatures that lead to vaporization and bubble generation. This paper explores the potential for volumetric heating in the DFG process. A fiber laser (¿ = 1070 nm) is used in a coaxial configuration. Soda lime glass filament is heated by the laser beam. This glass is transparent to the laser, but dopants are added which change the optical penetration depth of the glass. Experiments show that the behavior of the deposition process is highly dependent on the optical penetration depth, and that tracks with good morphology can be fabricated at deposition rates exceeding 15 mm3/s (constrained only by the achievable scan velocity of the experimental system). These results are consistent with a constructed 1D transient thermal model that explains the temperature profile in the glass as a function of optical penetration depth. This thermal model predicts an optimum optical penetration depth exists and can be used to deposit glass at significantly greater speeds. © 2024