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In-Situ Melt Pool Thermal Signature Defect Detection of Recoater Failure Using Co-Axial Planck Thermometry

Executive Summary

Sigma Labs has developed a new method to mine and digitalize the thermal signatures of the melt pool created by using direct metal laser sintering (DMLS) in 3D printing. Using emission spectroscopy, Sigma created its proprietary Thermal Energy Planck (TEP™) metric to identify disturbances in the production of these parts.

The detection of variation in thermal signatures advances the compliance and certification of 3D manufactured parts without costly, time-consuming and destructive testing and CT scanning that do not always yield accurate results. Using TEP™ also allows for intervention and adjustment of the additive manufacturing process in real time, making the process more efficient and cost-effective.

DMLS additive manufacturing uses a high power-density laser to melt and fuse metallic powders together to create a three-dimensional part layer by layer. Producing these parts, especially for demanding industries like aerospace and defense, requires exquisite attention to numerous variables to create a high-quality finished product. These variables, whether known (i.e., power and speed), or unknown (i.e., fusion, porosity and powder quality), directly effect the part’s final quality.

In this case, Sigma Labs sampled the radiated light emitted during the laser sintering process to chart its thermal signature over the course of the build. The TEP™ metric was shown to be an excellent indicator of part failure, as it captures thermal signatures over the course of the manufacture of each layer of an individual part, and can be compared from part to part and from machine to machine.

In fact, by using the resulting TEP™ process control chart, a process engineer can observe variance to specs before those variations can been seen by optical sensors, and of course, through destructive or CT testing. This allows the process engineer to change the parameters of the build or stop the build prior to total part failure. This in turn saves time, money and can ensure product quality in metal additive manufacturing.

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