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2025-02-19
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Stress Relief Techniques in Aerospace Thin-Wall Machining — A Practical Guide for 2024, 6061, and 7075 Aluminum Alloys
In the aerospace industry, thin-wall structures play a vital role in reducing weight without compromising strength. However, machining these thin-walled aluminum components—especially with alloys like 2024, 6061, and 7075—poses a common yet costly challenge: residual stress-induced deformation.
Without proper stress relief strategies, even precisely designed CNC parts can warp during or after machining, leading to dimensional inaccuracies, poor assembly fit, and high scrap rates.
This article shares proven techniques for stress control during CNC machining of aerospace-grade aluminum, offering practical value for manufacturers, machinists, and buyers of carbide cutting tools.
Why Residual Stress Is a Problem in Thin-Wall Aluminum Parts
High-strength aluminum alloys such as 2024-T6, 6061-T6, and 7075-T6 are commonly used in aerospace structural parts due to their excellent strength-to-weight ratios and machinability. However, these alloys often retain internal stresses due to processes like extrusion, rolling, and heat treatment.
During CNC milling—especially when material is unevenly removed—these internal stresses become unbalanced, causing parts to warp, twist, or distort.
Alloy | Strength | Machinability | Residual Stress Sensitivity | Notes |
---|---|---|---|---|
2024 | High | Moderate | High | Common in structural aircraft parts |
6061 | Medium | Excellent | Medium | Versatile and widely used |
7075 | Very High | Good | Very High | High strength but stress-sensitive |
Proven Techniques for Stress Relief in CNC Aluminum Machining
1. Start with Stress-Relieved Material (T651, T73)
Choose aluminum in the T651 or T73 tempers, which have undergone stretching and stress relief after heat treatment. These conditions significantly reduce internal stress compared to T6 tempers and are ideal for precision CNC milling.
2. Rough Machining + Natural or Artificial Aging
Use a three-step strategy:
Rough machining to remove bulk material, leaving uniform stock.
Natural aging (air rest 24–72 hours) or artificial aging (mild heat treatment) to allow residual stresses to redistribute.
Finish machining with precision.
This method is especially effective for large or complex parts such as aircraft frames, ribs, or enclosures.
3. Symmetrical and Balanced Machining
Design your toolpaths to remove material symmetrically from both sides of the workpiece. Balanced cutting forces reduce distortion risk. Some strategies include:
Alternating face milling on both sides
Evenly spaced pockets or holes
Equal depth of cut on mirrored features
4. Stepwise Thin-Wall Machining
Don’t machine the thin wall all at once. Instead, reduce thickness in stages. Each stage allows stress to release gradually, minimizing distortion after the final pass.
5. Use Advanced Fixturing and Clamping
Employ vacuum fixtures, soft jaws, or custom workholding that avoid over-constraining the part. Clamping forces themselves can distort thin walls—especially during stress release. Allow slight movement to absorb internal strain.
Stress Relief = Cost Reduction + Precision
For aerospace thin-walled aluminum machining, residual stress is the invisible enemy. But with proper material selection, machining sequence, and fixturing, you can achieve stable, high-accuracy parts—without expensive trial and error.
👉 If you’re experiencing warping, inconsistent surface quality, or high scrap rates in aluminum CNC parts, contact us today. Whether you need optimized carbide tools or precision CNC services, we can help you machine better—faster and more reliably.