Machining Thin-Walled Aerospace Parts
Oct 16, 2024Intrex Aerospace provides an assortment of machined components for aerospace. These parts vary in size, shape, complexity, and material, but machining thin-walled aerospace parts is an area that Intrex excels. The reason for the thin-wall requirements has to do with weight reduction. In most aerospace/space applications minimizing weight while maximizing strength and rigidity is foundational. Both factors can impact aircraft performance.
At Intrex, machining thin-walled parts for aerospace applications is one of our core competencies. We have years of machining experience in a multitude of different materials and have developed specific work holding, and tooling considerations, necessary for producing thin-wall parts, all while maintaining part strength and shape integrity.
Some of the major materials we have machining experience with are:
- Aluminum Alloys: Aluminum has long been status quo material for making aircraft components because of its combination of high tensile strength, relatively light weight and easy machinability in addition to strong corrosion resistance. Pure aluminum also has a relatively low cost compared to many alloys (though this varies), There are many types of aluminum we have machined from the 2024 thru 7075 series).
- Stainless Steels: There are many different formulations of stainless steel—each one with its own unique characteristics. For example, grade 304 stainless steel has a higher ultimate tensile strength than aluminum—505 MPa (73,200 psi)—but weighs 8 g/cm3, nearly triple the weight of aluminum. Additionally, 304 stainless steel for aerospace applications is highly resistant to corrosion thanks to its protective oxide layer, which inhibits oxidation. In short, while stainless steel alloys are heavier than aluminum, they also have a higher tensile strength, and melting point than aluminum does.
- Titanium Alloys: The unique benefits of titanium alloys in aerospace, including weight reduction, corrosion resistance, and increased strength and durability, make them indispensable materials for modern aircraft manufacturing. but they can be challenging to machine.
- Composite Materials: Increasingly used for their high strength-to-weight ratios. They will never totally replace metal parts, but are finding application in aerostructures
CNC Machining: There are several methods used to manufacture thin-wall parts. Additive manufacturing, and stamping/hydroforming are becoming more common but are limited because of tolerance and finish requirements of aerospace parts. Our focus and expertise is machining. Machining, utilizing CNC machines is employed because of the precision and fine finish required in the aerospace/space marketplace. The bulk of the CNC machining is achieved by turning of cylindrical parts or milling for prismatic parts. We have machines for both applications, as well as combination machines that can both turn and mill, up to 5 axes simultaneously.
Manufacturing Challenges: Producing thin-wall parts in complex shapes using multiple materials presents challenges, that require diligence, knowledge, and experience.
- Distortion is common when machining thin walls in metal. Proper work holding is critical to prevent distorting or crushing the work piece. Another key is implementing proper cutting tools. Cutting tools with the correct geometries that produce proper rake angles and chip relief are vital to producing “positive” cutting conditions that prevent pushing the work piece.
- Surface Finish: Aerospace parts often require high levels of surface finish. Surface finish requirements serve both performance (less friction, no burrs) and aesthetics, finish parts must look good.
- Tool Wear: Machining thin materials may require cutting tools with “positive” cutting geometries. It requires an understanding of cutting tools that freely cut and minimize pushing the workpiece. Keeping the sharp tool edge of the tool engaged with the workpiece while maximizing tool wear and prolonging tool wear, takes knowledge, and experience. It also encompasses a working knowledge of tool geometries, tool grades and application of proper feeds and speeds.
- Inspection: Being able to properly inspect critical features and dimensions is essential. Regular in-process and post-process gauging needs to be incorporated into the manufacturing process. At Intrex we use a combination of hard gauges and coordinate measuring machines (CMM) in our work cells and in our inspection lab.
Conclusion
Successfully machining thin-walled parts for aerospace/space applications entails knowledge, experience and specific skill sets. In aerospace/space new boundaries are constantly being pushed for greater weight reduction/part strength ratios. Advancements in material technologies add to the challenge, as the aerospace designers develop more efficient, higher preforming aircraft/spacecraft. Being at the forefront is exciting and rewarding. We welcome the opportunity and the challenge.
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