In the aerospace, automotive, and electronics industries, there is a growing demand to enhance the strength, rigidity, toughness, corrosion resistance, and fracture resistance of components while reducing their weight. To meet these requirements, thin-walled monolithic structures made from lightweight alloys are widely used. These structures not only improve performance but also reduce the total number of parts and assembly work. However, the material removal rate for such parts can be as high as 90% or more, making it crucial to control processing distortion and increase efficiency. High-speed cutting has emerged as an advanced manufacturing technology that offers high processing efficiency, low cutting forces, and reduced surface temperatures, which significantly improves machining accuracy—especially for thin-walled monolithic parts.
A notable example of this technology is its application in the production of aircraft fuselage components by Boeing and Airbus. Using high-speed milling, the thickness of fins has been reduced, and their height increased, resulting in lighter aircraft and lower fuel consumption. This advancement has enabled non-stop flights between the Far East and Western Europe. Despite its potential, the development of high-speed cutting technology in China is still in its early stages. In this paper, we focus on aluminum alloy triple waveguides to study the optimization of high-speed milling processes for thin-walled monolithic structures.
The test involved a triple waveguide with a minimum wall thickness of 2mm and a mass of 2.35kg. It was made from a rust-proof aluminum LF21 (GB1173-86) rectangular plate, weighing approximately 12.25kg. After milling, the material removal rate reached 80.8%. The challenge was to minimize deformation due to the thin walls and low rigidity. Traditional CNC milling required up to 50 hours, including intermediate heat treatment to relieve stress. To improve efficiency, the process was optimized using high-speed milling.
The test was conducted on a German Hermle C1200U five-axis high-speed milling machine. Its key specifications include a spindle speed of 20–24,000 rpm, a maximum power of 23kW, and a positioning accuracy of 0.01mm. The Heidenhain iTNC 530 CNC system allowed faster command processing, reducing cycle times. A 30-tool magazine and online tool and workpiece detection systems were also used.
The part was modeled using UG NX software, and a high-speed milling process was developed. The tool path was generated, post-processed, and sent to the machine via network. To prevent deformation, the workpiece was clamped at four points on both sides, avoiding the need for a special fixture. The clamping force was minimized to avoid additional deformation.
The process was arranged to follow the principle of separate roughing and finishing. Roughing was done first, followed by finishing, with minimal re-clamping to improve accuracy. The tool paths were designed to maintain symmetry and avoid stress concentration. High-speed cutting was applied with axial spiral feed and layered passes to ensure stability and surface quality.
Cutting parameters were carefully selected, with a maximum cutting speed of around 1,130 m/min. The axial depth of cut was limited to 1mm, and the feed per tooth varied depending on the tool diameter. Cooling was provided through emulsified cutting fluids to reduce heat and improve tool life.
Through these optimizations, the trial processing eliminated the need for intermediate heat treatment. The total machining time was 14.13 hours, below the target of 16 hours. The final dimensions met the required tolerances, with a flatness of 0.16mm and a surface roughness of Ra ≤ 1.6μm.
This study demonstrates that high-speed milling can effectively control deformation and improve efficiency when machining thin-walled monolithic parts. Key factors include proper blank selection, clamping methods, tool path design, cutting parameters, and cooling. High-speed cutting requires not only high spindle speeds but also fast feed rates, acceleration, and advanced CNC systems. With proper implementation, this technology can revolutionize the manufacturing of complex, lightweight components.
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