How are aircraft engines manufactured?
Manufacturing jet or piston engines for aircraft, involves raw materials being converted into extremely dependable accurate machines. It requires the use of a broad range of high-strength materials. Manufacturing methods utilized can be both conventional and unique.
Metallic components are what most aircraft engines are primarily constructed of. In recent years, however, plastic composites for certain parts have been introduced. Where strength and light weight are required – usually in structural components, engine frames and compressor sections – various aluminum and titanium alloys are used. On the other hand, for parts where resistance to high temperature and corrosion are required – usually in the combustor and turbine sections) – high temperature metals such as cobalt, chromium and nickel alloys are used. Intermediate locations require the use of numerous steel alloys.
Practically all known metalworking and machining operation is used in the manufacture of aircraft engines. This includes:
- Hot forging (for airfoils and compressor disks)
- Casting (for structural components and engine frames)
Other processes include electroplating, metal finishing (chromating, anodizing, etc.), thermal (plasma or flame) spraying, and heat treating. Because of the hardness and high-strength of the alloys used, notwithstanding their odd and complex shapes and accurate tolerances, the need for more rigorous and challenging machining becomes inevitable.
Chemical and electrochemical milling, electron-beam welding, laser drilling, and electro-discharge machining are some of the more unique metalworking processes used in aircraft engine manufacturing.
Electro-Chemical And Chemical Milling
With chemical and electro-chemical milling, metal from large surfaces are removed in a way where a contour is created or retained. Depending on the specific alloy, the parts are placed in a caustic or electrolyte bath or a highly concentrated controlled acid. The electro-chemical or chemical reaction will cause the metal to be removed. Often used after forging of airfoils that will bring wall thicknesses into specification without ruining the contour is chemical milling.
Laser Drilling And Electro-Discharge Machining
These processes are used for making intricate contours and small-diameter holes in hard metals. The combustor and turbine components are the usual parts where such holes are required for cooling purposes. The high-frequency thermo-mechanical action of electro-spark discharges will help remove metal. This process is carried out in a dielectric oil or mineral bath.
Where deep weld penetration in hard to reach geometries is required, electron-beam welding is used. A focused and accelerated beam of electrons within a vacuum chamber generates a weld. The work-piece struck by the kinetic energy of the electrons is transformed into heat for welding.
Inspection And Testing
The reliability of aircraft engines is determined through a number of testing, inspection and quality-control procedures performed during fabrication and on the final product. The usual inspection methods include ultrasonic, fluorescent penetrant, radiographic, and magnetic particle. These methods are used for the detection of cracks or internal flaws within the parts. Instrumented test cells are where assembled engines are tested before delivery to the customer.
Are you familiar with these processes?