An apparatus for a laser transmission welding process for attaching a synthetic filter material to a filter tower frame in an ink jet printer cartridge. The apparatus includes a laser beam source and a filter clamping fixture containing a base, slide rods attached on first ends thereof to the base, an optics support plate attached to second ends of the slide rods, a movable platform for holding an ink cartridge slidably disposed on the slide rods between the base and the optics support plate, a platform moving device for translating the platform to and from a laser welding position, a laser beam transparent plate suspended by support legs from the optics support plate to a position between the movable platform and the optics support plate. The apparatus greatly improves synthetic filter attachment to a filter tower frame in an ink cartridge.