Comparative LCA of a Linear Motor and Hybrid Feed Drive under High Cutting Loads

Linear motor drives (LMDs) are well known to provide significant advantages in terms of positioning speed and accuracy over traditional screw drives (SDs), making them better suited for high-speed high-precision machine tools. However, their use in such machine tools is severely limited by their tendency to consume a lot of electrical energy and cause thermal issues, particularly under high cutting loads. A hybrid feed drive (HFD) has recently been proposed as a possible solution to this dilemma. The HFD switches between LMD and SD actuation depending on the mode of the manufacturing operation, thus achieving speeds and accuracies similar to LMDs while consuming much less energy. This paper presents a comparative life cycle analysis (LCA) of the proposed HFD with an LMD as the baseline for the comparison. The functional unit is taken as the production of parts that involve heavy cutting by a small-sized 3-axis precision milling machine for 250 8-hour work days per year over a 12-year first-use life span. Energy savings provided by the HFD during its use phase vis-a-vis the additional energy investments into the HFD at various phases in its life cycle are compared. The analysis predicts a net positive impact, in terms of energy and the environment, for the HFD compared to the LMD under high cutting loads.