Journal of Micromanufacturing | 2021
Guest Editorial
Abstract
Diamond turning, often referred as single-point diamond turning or diamond turn machining, produces parts with specular, mirror-like quality with roughness in the nanometer range and micrometer-level feature tolerance. Furthermore, diamond turning precludes cumbersome and error-prone post-processing operations, such as grinding and abrasive polishing. The stringent adherence to finish and form has established diamond turning as a cornerstone ultraprecision process in applications ranging from creation of free-form optics for astrophysics and defense-related instruments to production of customized ophthalmic lenses in healthcare. However, the crux of the scientific challenge in diamond turning is that the depth of cut is typically in the micrometer range, that is, the order of the tool nose and edge radii. As a result, the chip load in diamond turning is the same order of magnitude of the grain size of the workpiece material, leading to a highly negative rake angle-type cutting regime. Therefore, the causal phenomena governing material removal, including mechanism of chip formation, ratio of cutting and thrust forces and tribology at the tool-workpiece are distinctively different compared to conventional machining. Consequently, apart from the usual cutting conditions, the quality of the finished part from diamond turning is influenced by minute variations caused due to a multitude of difficult-to-control factors, including microstructure and crystal structure of the workpiece material, surface finish and wear behavior of the tool, vibrations from machine elements and surrounding environment, chemical properties of the coolant and thermalinduced perturbations. Accordingly, research in diamond turning remains an active area encompassing the following seven domains: (a) fundamental materials science for understanding of the process–structure–property interactions and insights for advancement of new tool and coolant materials; (b) process simulations at three scales, namely atomistic-scale molecular dynamics modeling for predicting tool wear, thermomechanical models to explain the dynamics at the tool–chip interface and computational models to estimate part-level aspects, such as residual stresses and surface finish; (c) design of machine elements such as precision air bearing spindles, machine structures to mitigate vibration, workpiece holding and clamping mechanisms, coolant delivery and ultrafast tool servos; (d) empirical process optimization and post-process metrology and characterization; (e) in-process sensing and measurement; (f) real-time monitoring, data analytics and closed-loop control; and (g) novel applications. This special issue presents nine manuscripts reflecting the aforementioned seven research areas in diamond turning. These peer-reviewed publications provide conclusions that we believe will engender avenues for further investigations and applications.