Thermoplastic Forming Process for Manufacturing Arbitrary Blade Edge Geometries From Bulk Metallic Glass

Abstract

In corneal surgery, several incision instruments including the curvilinear or straight incision blades are required to construct a scleral tunnel to ensure that the wound is self-sealing after the operation. Bulk metallic glass (BMG) is proving to be a good candidate for making surgical blades, where sharp edges can be produced through a thermoplastic molding and a drawing process implemented by designing and controlling the drawing velocity at supercooled temperature. This article presents a mechanistic approach to obtain drawing velocity profile of drawing actuators that accommodates various shapes of the blade edges without having to carry out the entire extensional drawing process, which is extensive and tedious. To manufacture the multi-facet BMG knife blade edges that result in good quality, the velocity profile is developed based on the filament stretching process and the geometry and shape of the mold along with the blade profile to maintain the imposed flow stress during the blade edge formation. Two types of geometrical transformational features including drawing distance and offset angle of the draw direction to the profile, are considered to ensure that the flow stress of the drawing process is in the desirable Newtonian region. To demonstrate the feasibility of the proposed approach, H∞ control design is used to facilitate consistent good quality necking of the blade formation. The velocity profile of 45° and crescent BMG blades are generated and used to manufacture these blades. The 45° blade edge samples are successfully manufactured with the average of X-Z, X-Y straightness, and the edge radius of the blade of 1.4 ± 0.5 μm, 1.4 ± 0.5 μm, and 42.4 ± 2.3 nm, respectively. The crescent blade edge samples are manufactured with roundness deviation, and the edge radius of the blade of 5.4 ± 1.6 μm, and 35.7 ± 4.2 nm, respectively. The effects of BMG sample temperature settings on the quality of the manufactured blades are presented.