Processing of Bulk Metallic Glass by Pulsed Electrochemical Machining

Bulk metallic glass (BMG) has gained popularity over the last two decades as alloys have been developed that can remain in a supercooled state at sufficient intervals to allow for processing in a similar manner to plastics. Their physical properties, including an unusual combination of hardness, strength, and elasticity, have made them ideal candidates for the production of strain wave gears. Both the lack of ability to produce thick components and the cost per gram of the material result in preclusion of subtractive manufacturing methods as the primary mode of part formation. Instead, components are formed from metallic glass using injection molding, thermoplastic forming or 3D printing. Unfortunately, draft requirements associated with molding techniques and the lack of precision in 3D printing often make some form of subtractive post-processing inevitable. This creates a manufacturing challenge for both high volume and rapid prototyping applications. Currently, CNC milling and electric discharge machining (EDM) are the primary methods for post-processing of near net shape BMG components. Unfortunately, CNC milling is unable to deliver on needed thin features due to the hardness and elasticity. EDM on the other hand imparts thermal stress on the components and can promote crystallization near the affected machining surface. We propose using pulsed electrochemical machining (PECM) as both a manufacturing solution for volume production and for prototyping. Traditionally, PECM is used as a volume solution to manufacturing and is already capable of filling this need for the BMG community. Voxel Innovations is currently working with BMG manufacturers to incorporate PECM in this way. In the proposed research, we present a method for allowing PECM to meet BMG rapid prototyping needs (specifically targeting this effort towards strain wave gears), allowing prototyping and volume manufacturing to maintain continuity in how it is accomplished.