An Auto-Regressive Exogenous-Based Temperature Controller for a Hybrid Thermoplastic Microforming of Surgical Blades From Bulk Metallic Glass

Abstract

Temperature control is critical in manufacturing of the multifacet bulk metallic glass (BMG) knife edge. The temperature control in thermoplastic forming process could make a significant effect on the type of deformation, which ultimately results in the final blade edge shape. The controller selection is based on the knowledge of the model from system identification, the performance of the controllers, and the feasibility of the implementation to the testbed. In this study, temperature control, using fuzzy logic, is implemented along with auto-regressive exogenous, ARX model, which can maintain the steady-state temperature within the range of ±2.5 K. With this proposed controller, experiments have shown similar or better results of multifacet blade geometries than those manufactured using proportional–integral–derivative (PID) controller. The blade edge samples are successfully manufactured with the average straightness and the edge radius of the blade of 3.66 ± 0.5 μm and 25.7 ± 6 nm, respectively.

Thermoplastic micro-forming process of bulk metallic glass surgical blades using drawing velocity regulation

“…The 90° blade edges are manufactured from the BMG sample with Do of 15, 20, and 25 µm at temperature, Td of 683 ± 0.03 K. 10 Blade edges manufactured from Do of larger than 30 µm are found to be inconsistent due to the significant change in the drawing force over the drawing distance behavior dFd/dLp which is a time-consuming process to determine the duration at which the extensional flow is fully developed. 14 The blade quality assessment of 15 samples per Do is then performed and shown in Table 1.…”

“…In this setup, we have enabled thermally assisted micro molding and thermally assisted micro-drawing process. [3][4][5] Apart from maintaining the temperature of the BMG sample, the drawing velocity is found to be a significant parameter that determines the shape of the resulting blade edges. Poorly controlled drawing velocities lead to inappropriate strain rates, which cause abrupt shifts to viscosity deformations.…”

“…This undesired transition between Newtonian and non-Newtonian regimes can lead to shear-localized failure, 2 and hence result in blade edges with poor finish. 3,4 In previous studies, voice call actuators (VCAs) used proportional-integral-derivative (PID) controllers [3][4][5] to make the drawing velocity V t track reference signal V t ref .…”

“…In previous studies, voice call actuators (VCAs) used proportional-integral-derivative (PID) controllers 3–5 to make the drawing velocity Vt track reference signal Vreft. However, the existing control strategies are unable to produce blades consistently with desired shape specifications.…”