A method for the comprehensive monitoring of gas environments during selective laser melting

Modern additive technologies, in particular selective laser melting, allow the creation of products with complex geometries and the required physical and mechanical characteristics. The quality of the final product is infl uenced by the composition of the gas environment in the working chamber of selective laser melting installations. The most critical factor is the oxidation of molten metal, which leads to the formation of shape defects and deterioration of the mechanical properties of the finished product. Existing standard monitoring systems based on remote sensors do not provide suffi cient information about the gas environment in the working chamber of the installations, for example, about local fl uctuations in its composition directly in the melt bath and the formation of gaseous oxidants – nitrogen oxides NOx and water vapour. A method for comprehensive monitoring of the gas environment has been proposed and experimentally validated, based on the detection of the total concentration of molecular oxygen, NOx and moisture indicators H2, NH3. The architecture of an information and measurement system for comprehensive monitoring of the gas environment has been developed. The system can be integrated into existing industrial equipment without any design changes. Experimental studies on EOS M 280 (Electro Optical Systems, Germany) and Farsoon FS 121M (Farsoon, China) technological machines have confi rmed the formation of NOx during the melting process and shown that the proposed method can provide more accurate information about the state of the atmosphere than standard systems. The developed information and measurement system for comprehensive monitoring is designed to prevent oxidative processes in the working chamber of a selective laser melting installation by means of multi-level control of the gas environment composition. Automatic gas supply control based on real-time multi-parameter analysis provides a more complete picture of the chemical composition of the environment and allows for an adequate response to oxidation risks, minimising defects and improving product quality.

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