Surface Qualification Toolpath Optimization for Hybrid Manufacturing

Austen Thien,Thomas Kurfess,Christopher Saldana

doi:10.3390/jmmp5030094

Abstract

Hybrid manufacturing machine tools have great potential to revolutionize manufacturing by combining both additive manufacturing (AM) and subtractive manufacturing (SM) processes on the same machine tool. A prominent issue that can occur when going from AM to SM is that the SM process toolpath does not account for geometric discrepancies caused by the previous AM step, which leads to increased production times and tool wear, particularly when wire-based directed energy deposition (DED) is used as the AM process. This work discusses a methodology for approximating a part’s surface topology using on-machine contact probing and formulating an optimized SM toolpath using the surface topology approximation. Three different geometric surface approximations were used: triangular, trapezoidal, and a hybrid of both. SM toolpaths were created using each geometric approximation and assessed according to three objectives: reducing total machining time, reducing surface roughness, and reducing cutting force. Different prioritization scenarios of the optimization goals were also investigated. The optimal surface approximation that yielded the most improvement in the optimization was determined to be the hybrid surface topology approximation. Furthermore, it was shown that when the machining time or cutting force optimization goals were prioritized, there was little improvement in the other optimization goals.

Highlights

While additive manufacturing (AM) has demonstrated its potential to be a disruptive technology it still suffers from many drawbacks with regard to the creation of functional part surfaces, low dimensional accuracy, and defects from the deposition process
One of the most common defects that is especially detrimental in all metal AM processes is the build-up of deposited material that occurs during the start and stop points and the corners of a deposition track
Sample Part Fabrication tool’s deflection during cutting [28,29]. This would be beneficial in decreasing chatter as well, since Chuangwen et al [30] found that increased tool wear and cutting depth led to increased amplitude of cutting vibrations that can lead to regenerative chatter [31]

Summary

Introduction

While additive manufacturing (AM) has demonstrated its potential to be a disruptive technology it still suffers from many drawbacks with regard to the creation of functional part surfaces, low dimensional accuracy, and defects from the deposition process. To counter these disadvantages, modern subtractive manufacturing (SM) machine tools are incorporating AM technology to create hybrid machine tools [1]. Of the many deposition processes available, a popular one is wire feedstock-directed energy deposition (DED) This process uses a focused heat source, such as a laser or an electrical arc, to melt inexpensive welding wire and deposit it on to a substrate.

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Conclusion