CNC Machining in Aerospace: Precision Engineering at the Limits of Possibility

In modern manufacturing, the aerospace sector is undoubtedly one of the most demanding application scenarios for machining technology. From the airframe structures of commercial airliners to the critical blades of jet engines, CNC machining supports every journey into the sky with unparalleled precision, reliability, and material-processing capability.

1. The Ultimate Challenges of Aerospace Manufacturing

Aerospace component machining is often described as "the ultimate challenge of manufacturing." The challenges stem from three main aspects:

Material Strength and Machinability: Materials such as titanium alloys and superalloys have strengths exceeding 1400 MPa but extremely poor thermal conductivity, leading to high temperatures and rapid tool wear during cutting. Machining heat-resistant superalloys (HRSA) can be four to five times slower than conventional steels.

Geometric Complexity: Parts like blisks and honeycomb structures have extremely complex geometries-thin blades, high twist, long spans, and vulnerability to deformation, with narrow, deep channels between blades and poor accessibility.

Extremely Tight Tolerances: Critical dimensional tolerances are often required to be within ±0.01 mm, surface roughness must reach Ra 0.4 μm or better, and all processes must comply with the AS9100 quality management system and full traceability requirements.

2. Core Applications and Typical Parts in Aerospace CNC Machining

2.1 Aircraft Structural Parts

Aircraft structural parts include fuselage frames, wing ribs, door tracks, and other critical components. In June 2025, Kede CNC, together with Shenyang Aerospace Production and Shenyang Aircraft Corporation (SACC) Civil Aircraft, established China's first "large-aircraft structural part process verification pilot base" based entirely on domestic 5-axis CNC machine tools.

The base is equipped with dozens of domestic high-end machines and systematically tackles key machining technologies for typical aerospace structural parts, including titanium-alloy structural parts (material adaptability and extreme-condition stability), aluminium-alloy frame and panel parts (surface accuracy and deformation control), joint and bracket parts (multi-axis coordinated machining of complex surfaces), and long-shaft, deep-hole, thin-walled parts (ultra-precision machining and vibration-damping processes).

2.2 Skin Panels

Skin panels are critical for the aircraft outer shell. The metal skin of next-generation tactical guided vehicles can be as thin as 0.5 mm at its thinnest point-comparable to an eggshell. A certain wing titanium-alloy skin panel has a main web thickness of 1 mm, dimensions of approximately 0.8×0.3 m, and sidewall thicknesses of just 0.5 mm, with a raw billet of 5-mm-thick titanium sheet and a material removal rate of 92.6%.

2.3 Engine Casings and Combustion Chamber Components

Aircraft engine casings, combustion chambers, and other parts often use difficult-to-machine materials such as nickel-based superalloys. For the deformation and residual stress issues in the machining of domestic aircraft engine combustion-chamber casings, optimising the tooling system (upgrading from standard tools to custom non-standard formed tools) has effectively improved machining accuracy and efficiency.

3. Material Challenges in Aerospace CNC Machining

Every material used in the aerospace sector presents unique machining challenges.

Titanium Alloys (Ti-6Al-4V / TC4 / TA15)

Titanium alloys offer an extremely high strength-to-weight ratio, excellent corrosion resistance, and high-temperature performance, making them ideal for aerospace structural parts and engine components. However, their low elastic modulus (causing "tool push-off"), poor thermal conductivity, and work-hardening characteristics make them extremely difficult to machine.

Superalloys (Inconel 718)

Superalloys are widely used in high-temperature sections of aircraft engines, but their cutting speeds are four to five times slower than those of conventional steels. Hyundai Wia's XF series 5-axis machining centres, equipped with 45 kW high-torque spindles (623 N·m) and PCD/CBN super-hard coated tools, have achieved cutting efficiency for Inconel 718 that is 2.1 times that of conventional equipment, with a 40% reduction in tool wear.

Aluminium Alloys (7075 / 2024)

Aluminium alloys are the most commonly used materials for aircraft structural parts. 7075 and 2024 are two high-strength, heat-treatable aluminium alloys widely used in aerospace. For 7075 aluminium-alloy aerospace structural parts, high-speed machining combined with high-speed spindle performance enables efficient cutting. Deformation control in thin-walled aluminium parts remains an ongoing research focus.

Composite Materials (CFRP)

Carbon-fibre-reinforced polymers (CFRP) are increasingly used in aerospace, but they are prone to delamination and burr defects during machining. For the pain point of delamination in CFRP drilling, optimising drilling speeds and feed rates, combined with high-pressure coolant systems, can reduce delamination defect rates from over 30% to near zero.

4. Key Technologies in Aerospace CNC Machining

4.1 5-Axis Simultaneous Machining

5-axis simultaneous machining is the standard for aerospace parts. The development of 5-axis CNC machining technology for aircraft engine parts focuses on key areas such as toolpath planning and optimisation, as well as error control and compensation. The 5-axis RTCP (Rotational Tool Centre Point) interpolation algorithm is used to plan machining trajectories.

4.2 High-Speed and High-Efficiency Machining

Efficient machining strategies are critical for aerospace structural parts. For 7075 aluminium-alloy aerospace structural parts, combining high-speed spindle performance significantly shortens machining cycles. In the aerospace sector, high-speed 5-axis machining of aluminium alloys and high-power, high-efficiency 5-axis machining of titanium alloys have become new requirements for the development of CNC machine tools for aircraft structural parts.

4.3 Deformation Control in Thin-Walled Parts

The machining accuracy and efficiency of thin-walled parts directly affect aircraft performance and reliability. For thin-walled parts, the material removal rate per operation must be controlled to no more than 50% to prevent excessively rapid stress release. Using CNC cutting parameters with "small depth of cut and high feed rate" effectively addresses the common problem of poor machining rigidity in thin-walled, hollowed-out aluminium parts.

4.4 Mirror Milling Technology

For large-format ultra-thin skin parts, dual-5-axis mirror milling technology synchronously and symmetrically operates the tool and a support on opposite sides of the part, improving the wall-thickness accuracy of large thin-walled parts to ±0.08 mm. The mirror-milling method for large flexible curved surface parts, invented by a team from Shanghai Jiao Tong University, has achieved an upgrade from chemical milling to mechanical milling.

4.5 Electrical Discharge Machining (EDM) as a Complementary Process

For extremely complex parts such as blisks, 5-axis CNC EDM is an important complementary process. The establishment of a 6-axis linkage EDM technology chain for closed-impeller blisks-through innovations such as multi-electrode machining, 6-axis linkage perturbation feeding, and 6-axis linkage rocking finishing-has multiplied machining efficiency.

5. Future Trends

5.1 Smart Manufacturing and Digitalisation

CNC machining in aerospace is actively embracing smart manufacturing processes, using data analytics and prediction to optimise the machining process. Specific applications-including intelligent programming, real-time monitoring and adaptive process control, machining parameter optimisation, intelligent process-data analysis, and process-flow optimisation and intelligent reconfiguration-are driving the evolution of aerospace CNC machining towards greater intelligence.

5.2 AI-Driven Process Optimisation

Artificial intelligence is profoundly transforming aerospace CNC machining. Siemens and Rolls-Royce, through AI-driven digital-twin technology, have achieved a 32% reduction in the weight of jet-engine sub-components and a 15% reduction in fatigue stress.

5.3 Reusable Rockets and Commercial Space

In 2025, China completed 92 space launches, with commercial missions accounting for more than half. The demand for machining complex flow channels and lightweight structures is driving sustained demand for 5-axis simultaneous CNC machines and advanced cutting tools. Reusable rocket programmes and low-orbit constellation projects are further accelerating this trend.

5.4 Sustainable Manufacturing

Modern aerospace manufacturing places increasing emphasis on the "sustainable application" of machine tools. High precision and high quality reduce material consumption, efficient chip recycling saves resources, and intelligent recovery of cooling lubricants cuts waste. When machining superalloys, process optimisation and intelligent control can significantly reduce energy consumption and tool wear while maintaining quality.