Diffractive beam shaping for enhanced laser polymer welding

Abstract

Laser welding of polymers increasingly finds application in a large number of industries such as medical technology, automotive, consumer electronics, textiles or packaging. More and more, it replaces other welding technologies for polymers, e. g. hot-plate, vibration or ultrasonic welding. At the same rate, demands on the quality of the weld, the flexibility of the production system and on processing speed have increased.Traditionally, diode lasers were employed for plastic welding with flat-top beam profiles. With the advent of fiber lasers with excellent beam quality, the possibility to modify and optimize the beam profile by beam-shaping elements has opened.Diffractive optical elements (DOE) can play a crucial role in optimizing the laser intensity profile towards the optimal M-shape beam for enhanced weld seam quality. We present results on significantly improved weld seam width constancy and enlarged process windows compared to Gaussian or flat-top beam profiles. Configurations in which the laser beam diameter and shape can be adapted and optimized without changing or aligning the laser, fiber-optic cable or optical head are shown.

Influence of the Laser-Beam Distribution on the Seam Dimensions for Laser-Transmission Welding: A Simulative Approach

“…The integrated intensity S is obtained by integrating the intensity I(x,y) along the weld direction (x-coordinate) [19] S y ð Þ ¼…”

“…Recently, a so called M-shape intensity distribution has been introduced, which results in (almost) homogenous distribution of the delivered heat in the joining zone [19,20]. The intensity of such rotational symmetric distribution has a local minimum at the center and a maximum at the outer edges.…”

“…The M-shape can be formed from a Gaussian-or a top-hat beam using diffractive optical elements (DOE) [19] or refractive optical elements (ROE) [20]. Instead of the delivered heat a quantity called integrated intensity is introduced in [19]. It is discussed by the authors as a quality attribute of the laser beam influencing the weld seam.…”

“…The intensity of such rotational symmetric distribution has a local minimum at the center and a maximum at the outer edges. The M-shape can be formed from a Gaussian-or a top-hat beam using diffractive optical elements (DOE) [19] or refractive optical elements (ROE) [20]. Instead of the delivered heat a quantity called integrated intensity is introduced in [19].…”

High fidelity laser beam shaping using liquid crystal on silicon spatial light modulators as diffractive neural networks

“…In laser materials processing, application-adapted intensity distributions gain importance, as they enable an increase in productivity and/or the quality of the processing result [1][2][3][4][5]. Such intensity distributions can range from simple homogeneous distributions (so-called top-hat distributions) [6] or donut shapes [7] to process-specific distributions, which are derived by solving the inverse heat-conduction problem [8].…”