No abstract

Amid increases for low-volume production, additive manufacturing is being used to produce metal parts, especially for aircraft and automobiles, because it eliminates the cost-bearing need for jigs and assemblies and improves design freedom. When additive manufacturing is done with lasers, they can be used to melt and deposit the material. The heat generated by the laser and from the just deposited material is cation might take time, during which the shape can collapse. To prevent such heat problems, Mitsubishi Electric ensured adequate cooling time by combining unique laser and CNC (computerized numerical control) technologies: a pulsed laser and minimized heat input. Shape accuracy is 70% more precise with new dot-forming technology that synchronously controls the supply of wires and shield gas as well as the position and moving speed of the laser irradiation point. Since high temperatures are limited to a point-like narrow area, the antioxidant action of the shield gas spreads over the entire high-heat area to suppress oxidation.

We propose the use of the line section method with crossed line beams for the process control of laser wire deposition. This method could be used to measure the height displacement in front of a laser spot when the processing direction changes. In laser processing, especially laser deposition of metal additive manufacturing, the laser process control technique that controls the processing parameters based on the measured height displacement in front of a laser processing spot is indispensable for high-accuracy processing. However, it was impossible to measure the height displacement in front of a processing laser spot in a processing route in which the processing direction changes as the measurement direction of the conventional light-section method comprising the use of a straight-line beam is restricted although the configuration is simple. In this paper, we present an in-process height displacement measurement system of the light-section method using two crossed line beams. This method could be used to measure the height displacement in a ±90° direction by projecting two crossed line beams from the side of a laser processing head with a simple configuration comprising the addition of one line laser to the conventional light-section method. The height displacement can be calculated from the projected position shift of the line beams irrespective of the measurement direction by changing the longitudinal position on the crossed line beams according to the measurement direction. In addition, the configuration of our proposed system is compact because the imaging system is integrated into the processing head. We could measure the height displacement at 2.8–4 mm in front of a laser processing spot according to the measurement direction by reducing the influence of intense thermal radiation. Moreover, we experimentally evaluated the height displacement measurement accuracy for various measurement directions. Finally, we evaluated continuous deposition in an “L” shape wherein the deposition direction was changed while using a laser wire direct energy deposition machine for the laser process control based on the in-process height displacement measurement result. We achieved highly accurate continuous deposition at the position wherein the processing direction changes despite the acceleration and deceleration of the stage by laser process control.