Laser Polishing and Annealing Injection Mold Using Dual-Beam Laser System

One of the challenges regarding the application of laser polishing in injection mold manufacturing is to eliminate the tensile residual stress on a polished cavity surface without the extra expenses of an annealing vacuum furnace. This study aims to develop a fast laser annealing method using a dual-beam laser system by which a mold cavity can be laser-polished and then laser-annealed. Fourteen mold steel specimens were laser-polished by a dual-beam laser, resulting in a roughness reduction from the initial state, Sa 1.11 mu m, to Sa 0.16 mu m, a smoother surface finish. A numerical simulation of laser annealing using the current CW laser was implemented to optimize the laser annealing parameters to guide the experiment of CW laser annealing. XRD measurement results showed that the tensile residual stress dropped from an initial 638 MPa to 10 MPa in an annealing cycle time of 40 min at 750 degrees C; therefore, fatigue cracks or stress corrosion cracks (SCC) on the mold cavity will no longer occur. Confocal microscopy, X-ray diffraction, and scanning electron microscopy were used to obtain the microstructure and phase composition of the microstructures, demonstrate that laser polishing and laser annealing by a dual-beam laser is a fast and effortless technique which can be effectively employed in injection mold manufacturing.

Automated summary

The application of laser polishing in injection mold manufacturing faces the challenge of eliminating tensile residual stress on the polished cavity surface without using an annealing vacuum furnace. This study developed a fast laser annealing method using a dual-beam laser system to polish and anneal the mold cavity. The results showed a significant reduction in surface roughness and tensile residual stress, making laser polishing and annealing an effective technique in injection mold manufacturing.