Life cycle assessment of motor spindles in machine tools - comparison of SynRM and PMSM spindles and structural lightweight construction measures

Motor spindles are a central component in machine tools, significantly influencing their performance. Even though performance and acquisition costs are currently the primary selection criteria for motor spindles, rising energy prices, CO 2 emission costs, and challenges related to raw material extraction and availability are shifting the focus toward the environmental impact over the entire life cycle. In this study, four concepts are compared regarding their environmental impact: a conventional steel spindle with a permanent magnet synchronous motor (PMSM), replacing the PMSM with a synchronous reluctance motor (SynRM), a lightweight spindle made of carbon fiber reinforced polymer (CFRP), and the combination of a SynRM with lightweight construction measures. The life cycle assessment and comparison are conducted in accordance with ISO 14040/14044 including materials, manufacturing processes, usage phase, and end-of-life phase. As energy consumption during the usage phase varies with operational conditions, different usage scenarios were analyzed. The results show that the usage phase has the greatest environmental impact in the scenarios considered. While a SynRM has a lower manufacturing impact compared to a PMSM due to the absence of rare earth magnets, the slightly higher efficiency of the PMSM can offset this advantage in the usage phase. Using CFRP doubles the carbon emissions during manufacturing, also strongly depending on the impact of the electricity. During the usage phase, the lightweight measures allow for break-even with a steel motor spindle in dynamic applications.