Environmental analysis of a co-axial 15 GHz diode detector using R-strategies approach for circular economy

Abstract

The object of this study is the box of a 15 GHz diode detector consisting of 2 parts that are joined together with screws, creating a shell for a circuit board that can be connected with SMA and SMB connectors on the sides. The device is made by the split-block technique and also the thread, serving for connecting SMB connector, is split. Two blocks of the device are almost identical, except for countersinks for screw heads and the pocket for the diode, that are included only in one of them. The adjacent components and connectors, are standardized.

The study of the 15 GHz diode detector was included in the broader LUT research project, together with the study of many other MW/RF components.

"In spring 2024, a thesis was completed at LUT University on this MW/RF component, which preliminarily examined the tolerancing and material selection of the part. However, this thesis will focus on aspects of environmental friendliness and circular economy from the viewpoint of mechanical engineering." The objective is to study the environmental footprint of a co-axial 15 GHz diode detector from the viewpoint of mechanical engineering, both from the perspective of life cycle thinking and circular economy, and to assess the most optimal solution. The environmental friendliness of the product was analyzed during all the phases of its lifecycle to answer the following research question: What changes in material, manufacturing process or product design could decrease the environmental footprint of the co-axial 15 GHz diode detector, while maintaining all the qualities needed for its proper functioning? The basis for the research was provided by the expert interview, clarifying the details about the product and the requested properties for its proper functioning. The R-strategies approach for circular economy was further applied, supported by the Sustainability module of the SolidWorks and backed up by literature review. As far as design is concerned, the original design using the split-block technique was confirmed to be the environmentally suitable solution from the point of view of life cycle thinking, helping to prolong the life of the product by easiness of reuse and remanufacturing. Only minor adjustment was made to make both parts of the shell interchangeable and prolong the lifetime of the product during the Use phase. For the choice of the most environmentally friendly manufacturing method and material, the results of the Sustainability module of SolidWorks were assessed. The analysis lead to the choice of milling for the manufacturing method and the choice of malleable cast iron as the material with the smallest environmental footprint. Comparing to material of aluminium alloy 6061 T6 originally proposed in the previous thesis the malleable cast iron was shown to cause the environmental impact of only 19.89%, 26,02%, 8,52%, and 29,63% fraction of the aluminium alloy one in frames of carbon footprint, consumed energy and impact on air and water, respectively. Using a weighted factor, its total negative environmental impact was only 20% of the one of aluminium alloy. The aluminium alloy, even after being recalculated to higher recycled content by the help of data from literature, did not provide better environmental friendliness comparing to either malleable cast iron, or plain carbon steel. Therefore, in the future, DFMA analysis could be performed also for slightly changed design and the material choice of malleable cast iron. The results may be compared with the ones received for aluminium alloy 6061 T6. Next, the quality assurance actions for a coaxial 15 GHz diode detector produced by machining from malleable cast iron could be analyzed.