Plastic injection molding has emerged as a vital and rapidly evolving manufacturing method in aerospace. While metals have traditionally dominated the industry, the ongoing need for lighter weight, improved fuel efficiency and integrated components has made high-performance polymers and advanced molding processes essential.
Below is a detailed overview of how plastic injection molding is being applied within the aerospace sector.
Advantages of Injection Molding in Aerospace Manufacturing
Weight Reduction:
This is the single most critical driver. Plastics can be up to 50 percent lighter than aluminum and more than 80 percent lighter than steel, leading to massive fuel savings and increased payload capacity.
Complex Geometry:
Injection molding allows for the creation of highly complex, single-piece components that would be impossible or prohibitively expensive to machine from metal. This includes parts with internal channels, intricate brackets, and living hinges.
Part Consolidation:
Multiple metal parts can be redesigned into a single, complex molded plastic component. This reduces assembly time, minimizes fasteners (which also add weight), and improves structural integrity.
Corrosion and Chemical Resistance:
Plastics are inherently resistant to corrosion, oxidation, and many chemicals, such as hydraulic fluids and de-icing agents, which degrade metals over time.
High-Volume Repeatability:
Once the mold is perfected, injection molding produces thousands of identical parts with minimal variation, ensuring consistency and reliability—a must for aerospace standards.
Materials Used in Aerospace Injection Molding
- Ultem (PEI): High heat resistance and chemical stability.
- PPS (Polyphenylene Sulfide): Excellent chemical resistance and dimensional stability.
- PEEK (Polyether Ether Ketone): High mechanical strength and temperature resistance.
- CFRP (Carbon Fiber Reinforced Polymers): Lightweight and high-strength composites.
- Titanium Alloys: High strength-to-weight ratio and corrosion resistance.
- Aluminum Alloys: High strength, corrosion resistance, and thermal conductivity.
Specific Applications in Aircraft and Spacecraft
The applications can be broadly categorized into interior, exterior, and structural components.
Aircraft Interior Components
This is the most common application area where weight savings directly translate to fuel efficiency.
Seating Components: Seat frames, armrests, tray tables, and recline mechanisms.
Cabin Features: Overhead storage bin latches, air vent grilles, window surrounds, and service module panels.
Ducting: Air conditioning and environmental control system (ECS) ducts.
Brackets and Housings: Countless small brackets for holding wiring, in-flight entertainment systems, and sensors.
Aircraft Exterior and Engine Components
These parts face harsher environments and require the highest performance materials.
Engine Components: Non-critical parts within the engine nacelle, such as brackets, sensor housings, and cable guides. These must withstand high temperatures and vibrations.
Aerials and Radomes: The housing for radar equipment (radomes) must be radio frequency (RF) transparent, which certain plastics like PEI are perfectly suited for.
Landing Gear Components: Small, high-strength components like clips, seals, and protective housings within the landing gear system.
Fluid System Components: Valves, connectors, and impellers in fuel and hydraulic systems.
Advanced Injection Molding Techniques in Aerospace
To meet extreme tolerances and performance requirements, the industry employs several advanced techniques:
Insert Molding: Metal threads, bushings, or electrical contacts are placed into the mold, and plastic is injected around them. This creates a strong, integrated assembly in a single step, common to connectors and sensors.
Overmolding: A soft, flexible material (like a TPE) is molded over a rigid plastic substrate to create seals, grips, or dampers.
Gas-Assisted Injection Molding: Nitrogen gas is injected into the mold cavity to create hollow sections within the thick-walled parts. This reduces the weight, minimizes the sink mark, and reduces the number of cycles. Ideal for large ducts or structural supports.
In-Mold Decorating (IMD): A pre-printed film is placed in the mold, and the plastic is injected behind it. This creates a durable, integrated finish for the cabin interior panels, eliminating the need for post-painting.
Challenges and Considerations
High Tooling Costs: Molds for aerospace parts, often made from hardened tool steel, are extremely complex and expensive.
Stringent Certification: Every material and process must be rigorously tested and certified to standards like AS9100. Traceability of every batch of material and production parameter is required.
Material Cost: High-performance thermoplastics like PEEK are significantly more expensive than commodity plastics or even some metals.
Design Expertise: Designing a part for injection molding in aerospace requires deep knowledge of both the manufacturing process and the operational demands of the final component.
Conclusion
Plastic injection molding has evolved from the production of simple, non-critical parts to a cornerstone technology for lighting and performance enhancement in modern aerospace. By leveraging high-performance polymers and advanced molding techniques, the industry can create components that are lighter, more complex, more durable and often more cost-effective in the long run than their traditional metal counterparts. Its role is only set to grow as the push for more efficient and advanced aircraft and spacecraft continues.