This example shows two 0.045” thick PMMA discs that are welded together circumferentially to form a disc measuring 0.090 inches thick.

Polymethyl methacrylate (PMMA), commonly called acrylic, is an exceptionally transparent thermoplastic sold under many trademarks including Plexiglas® and Lucite®. Bonding or welding PMMA is accomplished using chemicals (liquids such as methylene chloride or cyanoacrylate), ultrasonic welders, or by using CO₂ lasers. Of the three, lasers provide the greatest flexibility for controlling weld width, depth, or weld path.

To accomplish this sample, we setup a rotating fixture to clamp the two discs in position underneath the beam. Remember that laser welding adds no additional material to fill gaps between pieces, so proper part fit up is crucial to achieving a strong mechanical bond. Our beam delivery consisted of a 2.5” focusing lens fixed in place over a rotating stage operating at 100 revolutions per minute (RPM). Typically, this positive meniscus lens provides a 100-micron (0.004”) focused spot with a 0.07” depth of focus, however in this instance we adjusted the Z-axis, essentially defocusing the beam, to create a 0.51 mm (0.02”) diameter weld beam. We choose air, at 10 PSI, as an assist gas.

The rotation speed and diameter of the PMMA discs translates to a weld velocity of 1484 inches per minute (IPM). To achieve the desired weld penetration, we rotated the discs through five complete revolutions while welding at a power setting of 60 watts. Overall cycle time was three seconds.