CNC Aerospace Machining​: Benefits, Applications, and Materials

The aerospace industry is a powerhouse of modern technology and innovation that relies heavily on precision and efficiency. Key to achieving these attributes is CNC machining, a process that can significantly improve the productivity of critical aerospace components.

This introduction explores how CNC machining is not only a part of the aerospace industry, but a key element to its continued growth and success.

1.What is aerospace?

The aerospace industry encompasses a wide range of sectors, including commercial aviation, space exploration, and military applications, with a global market value of approximately $800 billion.

In the United States, key stakeholders such as the Department of Defense and NASA are major purchasers of aerospace components, highlighting the importance of the industry.

Aerospace manufacturing involves a multitude of technologies, from traditional casting and welding to advanced metal additive manufacturing processes.

In between these two extremes is CNC aerospace machining, which is renowned for its precision and ability to innovate materials and design processes, which is essential to the dynamic needs of the industry.

2.What is CNC aerospace machining?

Aerospace CNC machining, one of the many applications of CNC machining technology, is a specialized manufacturing technology that combines advanced digital technology with precision engineering to produce critical components for the aerospace industry.

Since its introduction around 1942, CNC machining has played a major role in manufacturing critical aerospace components such as bulkheads and wing skins that require high precision and consistency.

The process involves removing material from a workpiece using a computer-controlled, powered cutting tool. Digital technology allows for the rapid and precise production of new parts.

Today, aerospace CNC machining processes have evolved to include a wide range of components such as gearboxes, landing gear, and electrical components. The technology is also essential for adding detailed features to existing parts or engraving critical information such as serial numbers.

The precision requirements of the aerospace machining process are very demanding, with some parts, especially jet engine parts, requiring tolerances as low as 4 microns, which is much tighter than standard CNC machining tolerances. High-quality 5-axis CNC machining centers are often used to achieve this accuracy, highlighting the role of the technology in producing end-use parts and creating prototypes for research and development.

This dual capability ensures that CNC aerospace machining remains at the forefront of technological manufacturing, meeting both current production demands and future technological advances.

3.What are the benefits of using CNC to machine aerospace parts?

CNC machining has significantly improved the manufacturing process and enhanced the performance of aerospace parts. This section explores the many benefits of CNC machining, with a particular focus on its contribution to the manufacture of lightweight, error-free, and highly consistent components.

1) Lightweight components

One of the most significant advantages of CNC aerospace machining is its ability to create lightweight components. Aerospace engineers are always looking for ways to reduce the weight of components to improve fuel efficiency and aircraft performance.

CNC machining can produce complex geometries that are not only strong but also much lighter than those made by traditional manufacturing methods.

Utilizing materials such as aluminum and titanium, which are known for their strength-to-weight ratio, CNC technology ensures that aerospace components are in optimal condition without compromising durability.

2) Minimizing part errors

The precision inherent in the CNC machining process is essential to minimizing errors in the production process of aerospace parts.

Advanced CNC machine tools have high repeatability and tight tolerances, which is critical in the aerospace industry where every micron is critical.

This precision reduces the risk of part failure, thereby improving the safety and reliability of aerospace components. By automating the machining process, CNC technology also minimizes human error, ensuring that each part is produced to exact specifications.

3) Accuracy and Precision

CNC machining offers unparalleled accuracy and precision, which is indispensable in the aerospace industry. The ability to adhere to strict manufacturing standards and achieve tolerances accurate to a few microns makes CNC machining ideal for aerospace applications.

This level of precision is essential for components that must withstand extreme conditions and pressures to ensure they perform reliably in critical applications, such as in engines and structural components of spacecraft and aircraft.

4) Consistency

Another advantage of CNC machining is the consistency it brings to part production. Whether it is a single part or thousands of parts, CNC machines can produce each component with the same accuracy and specifications, reducing the variability that can affect the performance of aerospace parts.

This consistency is essential to maintaining the quality and reliability of different batches of parts, supporting the aerospace industry’s need for consistency in a high-volume production environment.

5) Efficiency

CNC machining stands out in the aerospace field because of its efficiency. The integration of CNC machines facilitates automation of the production process, allowing for continuous operation without the inconsistencies associated with manual labor. This not only speeds up the manufacturing cycle, but also maximizes the utilization of materials and resources.

The precision of CNC machinery ensures that each component is produced with minimal waste, thereby optimizing the use of precious materials such as titanium and aluminum alloys. This efficiency is critical in an industry where time and resource management directly impact financial and operational success.

6) Reduced Manufacturing Costs

CNC aerospace machining can significantly reduce costs.By automating many processes that are traditionally done by hand, CNC machines reduce the need for a large labor force, which is a significant expense in any industry.

In addition, the high precision of CNC machining minimizes material waste and reduces the incidence of errors that can result in costly rework or scrap. The ability to quickly and accurately produce parts also reduces time to market, further reducing overhead costs and increasing the profitability of aerospace manufacturing operations.

7) Achieve Complex Geometries

CNC machining is able to achieve complex geometries, which is particularly useful in the aerospace industry. Aerospace components often require complex designs with precise dimensions and tolerances, which are difficult to achieve with traditional manufacturing methods.

CNC machines, especially those with 5-axis capabilities, can create detailed, complex shapes that meet the stringent requirements of aerospace parts. This capability allows for the design and production of more advanced and efficient aerospace systems, which helps to improve aircraft performance and functionality across the board.

8) Speed

Speed ​​is another key benefit of CNC machining. CNC machining can produce parts significantly faster than traditional manufacturing methods, which is critical in an industry where meeting project deadlines can make or break an aerospace program.

The rapid production capabilities of CNC machines also allow for faster prototyping, allowing aerospace engineers to test and improve their designs more quickly. This speeds up development cycles and brings innovations to market faster, providing a competitive advantage in the rapidly evolving aerospace sector.

4.What Materials Are Used in Aerospace Machining?

In aerospace CNC machining, the choice of materials is critical due to the harsh environments these parts are subjected to.

Not only must the materials used have extraordinary strength and durability, they must also meet specific criteria, such as weight, corrosion resistance, and high-temperature performance. Let’s take a look at some of the main materials that are indispensable in aerospace machining.

1) Carbon Steel

Carbon steel is highly valued in aerospace machining for its versatility and strength. It is primarily used to make structural components due to its high tensile strength and ability to withstand tremendous stress without deforming.

The material’s robustness makes it ideal for making parts that are critical to the safety and stability of aerospace vehicles, such as landing gear assemblies and components of aircraft frames.

2) Brass

Brass is another commonly used material in aerospace machining, especially for parts that require corrosion resistance and electrical conductivity. It is often chosen for electrical connectors, terminals, and housings in aerospace engineering.

The machinability of brass allows it to have precise dimensions and clean surfaces, which is essential for precise and high-risk aerospace applications.

3) Bronze

Bronze stands out in aerospace CNC machining for its corrosion resistance and resistance to metal fatigue. These properties make it suitable for bearings, bushings, and similar components that are subject to considerable mechanical wear and need to maintain a long service life under harsh operating conditions.

The durability and strength of bronze ensure that these parts can withstand the rigors of aerospace operations without frequent replacement.

4) Copper

Copper is indispensable in the aerospace industry due to its excellent thermal and electrical conductivity, making it an essential material for cooling systems and electrical components.

In aerospace CNC machining, copper is often used in heat exchangers, wiring, and other heat-dissipating components that play a key role in maintaining the operational integrity of aerospace systems. Its efficient thermal conductivity helps manage the extreme temperature changes encountered in flight and space exploration missions.

5) Aluminum and Aluminum Alloys

Aluminum and its alloys have long been a staple in aerospace machining, highly regarded for their light weight yet high strength. Aluminum alloys, especially aluminum alloys such as 7075, are favored for their high tensile strength and corrosion resistance.

This resistance is largely due to the oxide coating that naturally forms when aluminum is exposed to air, a property that greatly enhances its durability in harsh environmental conditions.

The main alloying element of 7075 alloy is zinc, and although it is not as easy to machine as other alloys, it has extremely high fatigue strength. This makes it an ideal choice for critical structural components such as wings, fuselages, and support structures.

Other aluminum alloys are also widely used, such as 4047 (which can be used as a cladding or filler), 6951, which is often used in tail fins, and 6063, which is known for structural applications. The 6000 series alloys are known for their machinability, making them the first choice for complex aerospace components that require precision and complex machining capabilities.

6) Titanium and Titanium Alloys

Titanium alloys are indispensable in the aerospace industry, where the demand for materials with excellent strength-to-weight ratios and excellent performance at high temperatures is non-negotiable. Titanium’s strength and corrosion resistance make it a preferred material for airframe and jet engine components, including disks, blades, shafts and casings.

Titanium is widely used in commercial and military aircraft, as evidenced by models such as the Airbus A380, Boeing B787, F-22, F/A-18 and UH-60 Black Hawk helicopter.

These applications highlight the critical role of titanium in modern aerospace engineering. However, machining titanium presents unique challenges due to its high hardness, which can lead to increased tool wear and heat buildup.

To address these issues, aerospace machining often requires adjustments to the machining process, such as reducing machine speed and increasing chip loads.

Despite these challenges, advanced CNC machining equipment common in aerospace environments can still handle titanium alloys well, ensuring that the advantages of titanium alloys are fully utilized without compromising the quality or integrity of the machined parts.

7) Inconel Superalloys

Inconel superalloys, especially Inconel 718, play a vital role in aerospace machining due to their excellent heat resistance and high-temperature strength.

Developed by Specialty Metals, Inconel 718 is a nickel-chromium-based superalloy designed for demanding applications. It was originally used in jet engine diffuser housings for the Pratt & Whitney J58 engine, which powers iconic aircraft such as the Lockheed SR-71 Blackbird.

The properties of this alloy are also used in modern aerospace projects, including SpaceX’s Falcon 9 launch vehicle, where it is used in the engine manifold of the Merlin engine. Its use also extends to various aerospace components such as turbine blades, ductwork, and engine exhaust systems.

Machining Inconel 718 requires care to minimize work hardening; therefore, it is typically machined using slow but aggressive cutting techniques, using hard tools to control its toughness and reduce tool wear.

Despite these challenges, its excellent weldability and durability make it a top choice for aerospace applications, where reliability under extreme pressures and temperatures is critical.

8) Engineering Plastics

In addition to metals, the aerospace industry is increasingly relying on high-performance engineering plastics such as PEEK, polycarbonate, and Ultem. These plastics are a valuable alternative to metals due to their lightweight and excellent mechanical properties, including impact and vibration resistance, sealing capabilities, and chemical resistance.

They also have superior electrical insulation properties compared to metals, which is critical to the safety and functionality of aerospace applications.

Engineering plastics are used in a variety of aerospace components, from cabin interiors (such as tray tables and armrests) to critical operating components (such as insulation, piping, and valve components).

These materials must meet stringent flame, smoke, and toxicity regulatory requirements to ensure safety in aerospace environments. Notable plastics used in aerospace CNC machining include Nylon 6, PEEK, Ultem, and PPS, each favored for their ability to meet specific performance standards required for commercial and military aerospace applications.

5.What are the machining processes for CNC aerospace machining?

CNC machining processes are an integral part of aerospace manufacturing, providing the precision and flexibility required to produce complex components that meet stringent industry standards.

Let’s explore how different CNC machining processes are used in the aerospace sector and why they are particularly suitable for this sector.

1) CNC Milling

CNC milling is a versatile process that is widely used in the aerospace industry to manufacture complex components such as fuselages, engine mounts and aerospace prototypes. The process involves using a rotating multi-point cutting tool to remove material from the workpiece, resulting in precise shapes and details.

Capable of machining a wide range of materials, including aluminum alloys, titanium and advanced composites, CNC milling is ideal for aerospace applications where lightweighting and strength are critical. Its precision allows for the production of parts with tight tolerances, which is essential for the safety and functionality of aerospace components.

2) CNC Turning

CNC turning is another technology used in the aerospace industry, particularly for the production of round or cylindrical parts such as shafts, pins and bushings. The process involves a single-point cutting tool that is parallel to the material being cut, allowing for high-precision machining.

The turning process is valued in the aerospace industry for its ability to achieve an excellent surface finish and meet the tight tolerances required for parts that must withstand high stresses and temperatures during flight.

3) CNC Drilling

CNC drilling is used to drill holes in aerospace components that are often used to fix parts or hydraulic systems. The process uses a multi-point drill to accurately and efficiently drill holes in the material.

CNC drilling can be performed on flat or curved surfaces, making it highly adaptable to aerospace applications, where drilling precise holes is often critical to both the structural integrity and functionality of the part.

4) 5-axis CNC Machining

5-axis CNC machining stands out in the aerospace manufacturing industry because it is capable of machining the extremely complex geometries that are often required by modern aerospace designs.

Unlike traditional 3-axis machining, 5-axis machines can rotate on two additional axes, allowing the cutting tool to approach the workpiece from any direction.

This feature reduces the need for multiple setups, improves productivity and significantly reduces machining time. 5-axis CNC machining is particularly useful for parts such as turbine blades, fuselage components, and wing panels, which require complex shapes and deep cuts with the highest precision.

6.What are important aerospace mechanical certifications?

There are several major certifications within the industry that underscore the commitment to excellence and compliance in the aerospace sector. The following is a detailed list of key certifications that are essential in aerospace machining, reflecting their importance in various applications.

1. AS9100 Certification: The AS9100 standard is an SAE International standard for quality assurance in the design, development, production, installation, and service of the aerospace sector. An extension of ISO 9001, this certification is not mandatory for all aerospace part production, but it is highly valued. Suppliers with AS9100 certification are generally preferred because this certification demonstrates their ability to meet stringent aerospace quality requirements and follow strict manufacturing specifications.
2. ITAR (International Traffic in Arms Regulations): ITAR is a set of regulations controlled by the U.S. Department of State that governs the manufacture, sale, and distribution of defense and military-related technologies. For companies producing technology listed on the U.S. Munitions List, ITAR compliance is critical to ensure that aerospace parts meet strict security and confidentiality guidelines.
3. AS9102 First Article Inspection Report: This certification involves a detailed validation process for aerospace parts. AS9102 certification ensures that each batch of parts manufactured meets the strict specifications required by the aerospace industry before full production begins. While not always necessary for prototyping, this certification is critical for parts intended for active use in aerospace vehicles to ensure their precision and reliability.

7.What is the standard surface finish for CNC aerospace machining aircraft parts?

Surface finishes for CNC machined aircraft parts are important to improve the durability, performance, and aesthetics of the parts. These surface finishes also protect the parts from environmental factors and reduce wear.

Here is an overview of 8 standard surface finishes used in aerospace machining:

1) Anodizing

Anodizing is a process that enhances corrosion and wear resistance by electrochemically converting the metal surface into a durable, corrosion-resistant anodized coating. This coating is particularly useful for aluminum parts and helps them withstand the harsh conditions of the aerospace environment.

2) Passivation

Passivation involves treating or coating a metal to reduce the chemical reactivity of its surface. In the aerospace sector, stainless steel parts are often passivated to remove surface contaminants and enhance corrosion resistance, ensuring longevity and reliability.

3) Polishing

Polishing makes the surface smooth and shiny by physically rubbing the material or using chemicals. This surface treatment not only enhances the beauty of aerospace parts, but also reduces the adhesion of surface contaminants.

4) Powder coating

Powder coating uses a free-flowing dry powder that forms a skin-like coating after heat curing. It has excellent durability and resists chipping, scratching, fading and wear, making it ideal for parts exposed to harsh operating conditions.

5) Painting

Spray painting is used to apply aerospace parts with a specific color or protective layer. It is corrosion-resistant and solar reflective, and can also be used to apply company colors or visibility markings that are critical to safety and branding.

6) Hard coating

Hard coating refers to applying a hard and durable film to the part substrate to improve wear resistance and service life. In the aerospace industry, this could mean ceramic coatings that also provide thermal insulation.

7) Thermal Spray Coatings

Thermal spraying involves spraying molten or semi-molten material onto a surface to form a coating. The process is used to improve or restore the properties or dimensions of a surface, thereby extending the life of aerospace components by providing protection from heat, corrosion, and wear.

8) Electroplating

Electroplating is the process of adding a metallic coating to an object by applying a negative charge to it and then immersing it in a solution containing the metal salt to be deposited. The process is used in aerospace to increase conductivity, reflectivity, corrosion resistance, or reduce friction on parts.

8.What are the applications of CNC aerospace machining?

Aerospace CNC machining plays an important role in various areas of the aerospace industry.

1) Rapid Prototyping

CNC machining plays an important role in the rapid prototyping of aerospace components. The process can quickly, accurately, and cost-effectively produce parts to test form, fit, and function.

Engineers can quickly iterate designs and make necessary adjustments based on test results, which is invaluable in high-risk industries where every detail counts.

Rapid prototyping not only speeds up the development process, but also improves the overall safety and functionality of aerospace systems by enabling thorough testing prior to mass production.

2) Aerospace

In the aerospace sector, CNC machining is used to produce both structural and nonstructural components. From machining complex engine components that must withstand extreme conditions to precisely manufacturing flight control systems and landing gear, CNC technology enables the tight tolerances and high-quality surface finishes that are critical.

The reliability provided by advanced CNC machining processes supports critical safety requirements and helps maintain the stringent performance standards required for commercial, military, and private aviation.

3) Space Travel and Exploration

The role of CNC machining is not limited to the atmosphere, but also extends to space travel and exploration. CNC machining is necessary to manufacture parts that can withstand the harsh conditions of space, such as extreme temperature fluctuations and radiation, and can be used to manufacture space shuttle components, satellite parts, and space station modules.

The precision and adaptability of CNC machining make it ideal for producing complex parts that are critical to the operation and success of missions beyond Earth.

4) Aerospace Mechanical Parts

Aerospace machining is responsible for many aerospace parts, from important titanium jet engine components to lightweight plastic interior cabin parts.

Parts suitable for aerospace CNC machining are typically low-volume parts that require high strength and fine features.

The size of such parts is often limited by the size of the CNC machining center, but a variety of different materials can be used – typically titanium or aluminum alloys, but there are other options such as engineered plastics and composites. Some parts may only be post-machined after casting or extrusion.

Aerospace machining can be used for both prototypes and end-use parts. However, end-use parts must meet strict safety standards and certifications.

Aerospace parts that can be machined include (but are not limited to):

1. Landing gear components
2. Electrical connectors
3. Valve components
4. Oxygen generation components
5. Shafts
6. Turbine blades and other jet engine components
7. Engine casings
8. Oxygen generation systems
9. Filter elements for liquid and air filtration systems
10. Electrical connectors for electrical systems
11. Motion control
12. Actuators
13. Fuselage components
14. Wing ribs
15. Optical discs
16. Power transmission shafts
17. Missile casings and other components
18. Nacelle components
19. Seats, armrests, and trays

9.How important is precision when CNC machining aerospace parts?

Precision in CNC machining of aerospace parts is not only a requirement, but a fundamental aspect that determines the safety, performance, and reliability of aerospace vehicles. Whether manufacturing structural components of an aircraft or complex components of a spacecraft, the margin for error is minimal.

1. Safety: Aerospace components are critical to the safety of the aircraft and its occupants. Even the smallest deviation from design specifications can result in catastrophic failure. Precision machining ensures that parts meet exact dimensions and tolerances, which is essential to maintaining structural integrity and operational safety.
2. Performance: Aerospace vehicles operate under extreme conditions, and every component must perform its function perfectly. The precision of CNC machining ensures that components such as turbine blades, fuselage panels, and navigation instruments operate efficiently, thereby improving the overall performance of the aircraft or spacecraft.
3. Compliance with standards: The aerospace manufacturing industry is highly regulated and must adhere to international and national standards. Precision machining helps ensure that parts meet strict industry standards, such as those set by the Federal Aviation Administration (FAA) and the European Aviation Safety Agency (EASA).

10.Tips for Optimizing CNC Machining Processes

1. Leverage Advanced CNC Machinery: Employing state-of-the-art CNC machinery with enhanced capabilities, such as 5-axis CNC machining, can significantly improve the accuracy of aerospace components. These machines allow complex shapes to be machined with fewer setups, reducing the risk of human error.
2. Choose the right cutting tool: The choice of cutting tool has a profound impact on the accuracy of the final product. Tools designed specifically for aerospace materials such as titanium and high-strength alloys ensure better tolerances and surface finishes.
3. Implement strict quality control measures: Rigorous quality checks at every stage of the machining process help detect deviations early and prevent tolerance buildup. Using advanced measurement and inspection systems, such as coordinate measuring machines (CMMs), ensures that each part meets the required specifications.
4. Expert Programming for CNC Operations: Skilled CNC programmers play a vital role in machining precision parts. Detailed and accurate programming ensures that machine paths are optimized for specific materials and geometries, minimizing errors and material waste.
5. Regular Equipment Maintenance: Regular maintenance of CNC machines and tools prevents potential failures and inaccurately machined parts. Regular calibration and maintenance ensures that the machining process remains accurate and efficient.
6. Use of Quality Materials: The quality of raw materials used in aerospace machining has a significant impact on the results. Advanced metals and composites reduce issues such as tool wear and material deformation that can affect the accuracy of CNC machining.

11.What does the future hold for CNC aerospace machining?

Technology is constantly evolving and innovating at an incredible rate. Aerospace manufacturers must keep up with these trends to compete.

Several important trends are likely to drive the future of CNC machining in the aerospace industry:

1. Additive Manufacturing: Combining additive manufacturing (3D printing) with traditional CNC machining can produce complex parts with unique geometries that were previously impossible or too expensive to produce.
2. Smart Manufacturing: The adoption of Industry 4.0 technologies, such as IoT devices, will allow for real-time monitoring, data collection, and analysis during the CNC machining process. This will enable manufacturers to optimize operations, improve quality control, and reduce waste.
3. Digital Twins: Creating a digital replica of a physical CNC machine to analyze and optimize its performance is another technology that is receiving a lot of attention. This process can facilitate more efficient machine setup, preventive maintenance, and remote troubleshooting.