Medium Wavelength Infrared (MWIR) Imaging for High Speed Control of Laser Metal Deposition (LMD)

Laser metal deposition (LMD) is a material processing technique widely used in industry for part reconstruction, coating or rapid prototyping. The inherent non-repetitiveness of the technique makes mandatory a closedloop control of the process when homogeneous results are required, since it is affected by the material, size, and geometry of the part. Based on the use of uncooled PbSe image sensors working in the medium wavelength infrared (MWIR) range (1 to 5 mu m), we present a novel high speed closedloop control for LMD. Controlling laser power at high speed (1 kHz) based on measurements from the melt pool thermal image down to 200 degrees C enhances current solutions based on complementary metal-oxide-semiconductor (CMOS) images, blind to temperatures under 600 degrees C. To demonstrate the performance of the controller, claddings on different surfaces and geometries were carried out. Experimental results demonstrate the advantage of this approach in terms of sensitivity to process related magnitudes an overall control stability.