Laser wax joinery method and apparatus

Abstract

A laser wax joinery method and apparatus are disclosed. Molded wax segments, such as those used to produce patterns for investment casting, are immobilized relative to one another, with their conforming marginal edges in abutted relationship, on a two axis rotatable tilt table. A laser beam of controllable energy density scans the edges of the wax segments, forming therealong a wax weld pool that, while molten, is maintained generally horizontal by rotation of the tilt table. The laser beam's energy density is modulated to correspond with the varying thickness of the edges to be joined. A laser beam delivery system includes a process robot and a lens and mirror system for directing the beam generally vertically toward the surface of the wax segments. Shrinkage by wax dripping or filler vaporization is avoided by precisely controlling the energy density adjacent the weld joint. By coordinating the operation of the tilt tables and the laser beam delivery system under the programmable control of a master controller, it is possible repeatably to produce strong, smooth, uninterrupted weld joints. In modifications, the wax weld pool is controlled by preparatory covering of the surface adjacent the abutted edges with a fluid-resistant, conformable, and laser beam-transmissive polyethylene, or thermally conductive metal foil, material that, while transmitting, or conducting, a substantial portion of the laser energy to the wax segments, prevents loss of wax by dripping. In another modification, the weld pool is controlled by multiply scanning the abutted edges at a reduced energy density.