Overcoming the Challenges of Chip Breaking and Multi-Angle Machining: An In-Depth Analysis of Hole-Making Technology for Aerospace Hard-to-Machine Materials

Release time:

2026-04-17

In the modern aerospace manufacturing sector, aircraft structural components are increasingly trending toward monolithic integration, lightweight design, and greater geometric complexity. Faced with “difficult-to-machine materials” such as titanium alloys, high-temperature superalloys, and carbon-fiber composites, conventional drilling processes are confronting significant challenges. Achieving high-precision hole machining while simultaneously addressing issues like chip entanglement, burr formation at the exit, and multi-axis positioning on complex curved surfaces has become a critical benchmark for evaluating the level of aerospace manufacturing.

Pain Point Analysis: The “Chip Breaking” Dilemma in Difficult-to-Machine Materials

In aerospace structural components, titanium alloys and high-temperature alloys are widely used due to their high specific strength and excellent high-temperature resistance. However, these materials exhibit extremely poor machinability during drilling, primarily manifested in the following aspects:

Poor thermal conductivity leads to heat concentration: the thermal conductivity of titanium alloys is only about one-fifth that of steel. During drilling, cutting heat cannot be rapidly dissipated, resulting in localized heat buildup at the cutting edge. This极易 causes thermal wear and plastic deformation of the tool. Work-hardening and high toughness: materials such as nickel-based superalloys exhibit severe work-hardening during machining, coupled with exceptionally high ductility. Consequently, chips are difficult to break and tend to form continuous, ribbon-like chips. The hazards of chip entanglement: when chips cannot be promptly evacuated, they tightly wrap around the drill’s helical flutes. This not only scratches the machined hole wall, degrading surface quality, but in more serious cases can cause a dramatic increase in torque, leading to tool breakage and outright scrapping of expensive aerospace structural components.

Technological Breakthrough: From Tool Geometry to Ultrasonic Assistance

To address the aforementioned challenges, current industrial solutions primarily focus on integrating innovative tool geometries with advanced machining processes.

Innovation in Cutting Tool Geometry Design

Conventional twist drills can no longer meet the machining requirements for aerospace laminated materials, such as carbon-fiber/titanium-alloy laminates. Modern high-performance drill bits feature more complex geometries:

Dual-cone and dual-angle design: For example, a dual-angle drill tip geometry, with an optimized secondary apex angle, not only enhances the drill’s centering capability but also effectively suppresses delamination and burr formation at the exit edge in laminated materials. Experimental data show that, compared with conventional drills, the optimized dual-angle geometry can reduce exit-edge burr size from 0.48 mm to below 0.06 mm. Split cutting-edge design: For composite materials, a split fiber-reinforced drill tip design, combined with a multilayer chemical vapor deposition diamond coating, significantly reduces carbon-fiber tearing and delamination.

Ultrasonic-Assisted Machining Technology

Ultrasonic machining is a powerful tool for overcoming the challenge of chip evacuation in difficult-to-machine materials. The underlying principle involves introducing high-frequency vibrations during the cutting process, which induce periodic separation between the cutting tool and the workpiece.

Forced chip breaking: This periodic separation interrupts the continuous flow of chips, forcing them to fracture into small fragments and thereby resolving the issue of long,缠绕 chips in titanium alloys and high-temperature alloys. Reduction of cutting forces: Measured data show that, when machining carbon-fiber/titanium-alloy laminated composites, ultrasonic-assisted drilling significantly improves the quality of both the hole entrance and exit. For example, during the machining of the 25th hole, the burr size at the hole entrance reached 0.478 mm with conventional drilling, whereas with ultrasonic machining it was only 0.145 mm, representing a reduction of approximately 70% in burr length.

Process Advancement: Multi-Angle Machining Solutions for Aerospace Structural Components

In addition to material and chip-breaking challenges, aerospace structural components—such as wing skins and engine casings—typically feature complex spatial curved surfaces, which necessitate drilling and hole-machining equipment with exceptionally high flexibility and multi-axis machining capabilities.

Five-Axis Simultaneous Machining and Mirror Milling Technology

Traditional drilling processes often require multiple setups to adjust the tool orientation, which is not only inefficient but also introduces cumulative errors. Modern solutions, however, employ five-axis simultaneous machining technology:

Multi-face machining in a single setup: By coordinating the B and C axes, five-axis machine tools can orient the cutting tool at any desired angle relative to the workpiece. For complex components such as aeroengine blades, five-axis machining can consolidate what would otherwise require six separate setups into a single operation, with positioning errors controlled within ±0.005 mm. Mirror milling: For large, thin-walled, curved skin panels, China has developed dual-five-axis mirror-milling equipment. This technology employs synchronized motion between two upper and lower five-axis spindles to overcome the challenges of precision machining for large, flexible, curved parts, increasing wall-thickness machining accuracy by a factor of five.

Lying-Vertical Conversion and Virtual-Axis Machine Tools

To further enhance efficiency, lathes capable of switching between vertical and horizontal configurations, as well as parallel kinematic machines (PKMs), have begun to attract attention in the aerospace manufacturing sector.

Vertical–Horizontal Conversion: The spindle can be freely switched between vertical and horizontal orientations, and when paired with a rotary table, a single workpiece setup suffices to machine all six faces of the part, significantly enhancing equipment utilization. High Dynamic Response: Thanks to its highly rigid structure, the virtual-axis machine tool achieves spindle speeds exceeding 30,000 rpm and rapid traverse rates of up to 50 m/min, making it ideally suited for high-speed hole-making in materials such as aerospace-grade aluminum alloys.

Conclusion

From addressing the micro-level challenge of chip breaking to developing macro-level multi-axis machining strategies, hole-machining technology for aerospace hard-to-machine materials is undergoing a profound transformation.

Future aerospace manufacturing will no longer rely on isolated tool improvements; instead, it will evolve toward systematic “tool–process–equipment” integrated solutions. By incorporating ultrasonic-assisted machining, five-axis simultaneous machining, and intelligent sensing technologies, we can not only achieve precision hole-making with zero damage but also significantly enhance the manufacturing efficiency and quality of domestically produced large aircraft and aero-engines.