Hybrid Manufacturing Systems Combining Additive and Subtractive Processes

Abstract

Modern manufacturing demands increasingly complex geometries, superiorsurface finish, and tight dimensional tolerances that neither additivemanufacturing (AM) nor conventional subtractive manufacturing (SM) canoptimally achieve in isolation. Hybrid manufacturing systems that sequentially or simultaneously integrate additive and subtractive processes within a single machine platform have emerged as a transformative paradigm addressing these limitations. This paper presents a comprehensive experimental investigation of a hybrid manufacturing system combining directed energy deposition (DED) laser metal deposition with five-axis CNC milling on an integrated machine platform for the fabrication of high-performance aerospace-grade Ti-6Al-4V components. The research systematically evaluates the influence of critical process parameters—including laser power (800–1,600 W), powder feed rate (4–12 g/min), scanning speed (400–1,000 mm/min), and subsequent milling parameters (spindle speed, feed rate, depth of cut)—on part quality metrics encompassing surface roughness, dimensional accuracy, microhardness, tensile strength, and residual stress distribution. Experimental validation was performed on a Mazak INTEGREX i-200S AM hybrid machining center using 18 test specimens fabricated under a Taguchi L18 orthogonal array design of experiments. The optimized hybrid process achieved surface roughness of Ra 0.42 µm (compared to Ra 8.6 µm for as-deposited DED), dimensional accuracy of ±0.025 mm, microhardness of 368 HV, and  ultimate tensile strength of 1,048 MPa, all meeting or exceeding AMS4999A aerospace material specifications. The findings confirm that intelligently sequenced hybrid additive-subtractive manufacturing canproduce near-net-shape metallic components with properties comparable to wrought material, enabling significant reductions in material waste, lead time, and manufacturing cost for complex aerospace structures [1], [2]. KEYWORDS: Hybrid Manufacturing, Additive Manufacturing, SubtractiveManufacturing, Directed Energy Deposition, CNC Milling, Ti-6Al-4V, SurfaceRoughness, Aerospace Manufacturing, Taguchi Method, Process Optimization