In response to the need for drastic surface finish improvement on additively manufactured metal components, Voxel Innovations Inc. has developed a novel manufacturing process termed: oscillatory pulsed electrochemical machining (O-PECM). O-PECM is a heat-free, stress-free, surface finishing technique capable of producing sub-200 nm Ra roughness. In O-PECM, a thin envelope of build material is printed around the workpiece (as a direct offset of the surface) in situ with the initial AM build. Precise oscillation of the printed envelope, in combination with a flowing electrolyte bath and multi-phase pulsed voltage waveform allow for the simultaneous finishing of the surface and removal of the envelope to reveal the part in its final state. The precision oscillation allows for proximity-controlled surface smoothing, giving O-PECM a significant advantage over competing technologies when starting finish is poor. O-PECM provides significant design freedom as it is not limited by line of sight. The proposed project will 1) optimize process parameters to achieve a fine surface finish with minimal material removal, subsequently mapping material removal vs. surface finish curves, 2) develop an optimal oscillatory pattern and design rules for the metal envelope and 3) demonstrate the improvement that O-PECM imparts on component fatigue life.
Benefit: Oscillatory pulsed electrochemical machinings greatest strengths are 1) the ability to post-process a range of challenging metal materials, 2) relative insensitivity to large starting roughness, and 3) the ability to achieve mirror-like surface roughness in minimal time. These strengths will aid the current effort to transition metal additive manufacturing capabilities into markets requiring a high level of structural integrity in the components, enhancing the fatigue life by removing stress concentration sites from the surface. An expected first market for this technology is high temperature AM parts, particularly turbomachinery components such as impellers and turbine blades. The ability to use AM parts will not only allow a faster design cycle in these industries, it will create an economical method for turbine blade tip replacement as the parts experience wear. Voxel has already created partnerships in this critical industry and is currently working with customers to post-process their AM turbine blade prototypes. While we expect turbomachinery to be our initial target market, this novel technique will find use in all applications where metal 3D printing is applied, a market that is estimated to increase to $10B annually by 2027.
Keywords: additive manufacturing, additive manufacturing, Electrochemical Machining, roughness, oscillation, surface finish, Turbine Blade, voxel
