6061-T6 and 7075-T6 aluminum alloys are the two most widely used materials for lightweight robot structural frames, joint brackets, mounting bases and moving arm components. 6061 features excellent machinability and corrosion resistance, while 7075 boasts ultra-high strength and toughness, ideal for high-load dynamic robotic parts. However, over 80% of unstable precision issues in robot aluminum parts stem from uncontrolled residual stress, rather than tool error or machine accuracy.
Most ordinary CNC factories adopt conventional one-time full machining process. The instantaneous removal of large-area material breaks the original internal stress balance of aluminum blanks, resulting in invisible delayed warpage. The parts may be qualified after production, but will deform within 24–72 hours or after assembly, causing assembly gaps, robot jitter and out-of-tolerance positioning. Most peers ignore the material difference between 7075 and 6061 and use unified processing schemes, which is the core reason for high scrap rates of high-end robot parts. This article shares Runsom’s mature segmented stress relief and stabilization process tailored for robotic aluminum structural parts, helping global clients eliminate delayed deformation risks from the source.
Essential Difference: Residual Stress of 6061 VS 7075 for Robotics
Although both belong to aerospace aluminum alloys, 6061 and 7075 have completely different stress release rules after CNC material removal. Blindly applying the same process will inevitably lead to precision failure.
6061-T6: Mild Residual Stress, Slow Delayed Deformation
6061 aluminum has uniform internal stress and low hardness. After conventional machining, the deformation amplitude is small, usually within 0.02mm–0.05mm. It will not deform immediately after processing, but gradually warp during anodizing, assembling and long-term operation. It is often misjudged as “assembly error” rather than machining process defect. It is suitable for static robot brackets, outer covers and non-load-bearing structural parts.
7075-T6: High Residual Stress, Violent Instant Deformation
7075 high-strength aluminum has extremely high internal residual stress after extrusion and forging. Large-scale material removal will cause rapid stress release, resulting in bending, torsion and thin-wall collapse. The deformation can reach 0.1mm–0.3mm in severe cases, directly causing part scrap. It is widely used in dynamic load-bearing parts such as robot joint shells and moving arm frameworks, which have the highest requirements for dimensional stability.
Why Ordinary CNC Processes Cause Irreversible Robot Part Deformation
Most suppliers pursue fast delivery and adopt one-time roughing and finishing integrated processing. This method is suitable for ordinary mechanical parts but completely unsuitable for high-precision robot structural parts.
After the blank is cut in place at one time, the internal stress has no buffer release cycle. The stress is locked inside the part. With the change of ambient temperature and assembly stress, continuous micro-deformation occurs. For medical robots requiring repeated positioning accuracy within ±0.01mm, even 0.03mm warpage will cause surgical instrument jitter and positioning deviation. Meanwhile, unbalanced cutting force and thermal accumulation will further amplify structural deformation of thin-wall robot parts.
Runsom Stabilization Solution: Segmented CNC Stress Relief Process
Runsom formulates differentiated stress relief and finishing strategies for 6061 and 7075 materials respectively based on medical and automation robot mass production experience. The whole process matches ISO 2768-M general tolerance standard, with critical functional dimensions strictly controlled within ±0.01mm, ensuring zero delayed deformation of finished parts.
1. Blank Pre-Stress Relief Treatment
Before formal processing, 7075 blanks are placed for natural aging or low-temperature heat treatment to release surface concentrated stress. For 6061 blanks, we adopt stress leveling cutting to remove surface stress layers, reducing subsequent processing deformation by more than 40% in advance.
2. Segmented Roughing + Stress Release Buffering
We abandon one-time full cutting. Reserve 0.1mm–0.15mm uniform finishing allowance after roughing. Place the parts for 12–24 hours to allow internal stress to fully release and stabilize. This step is the core of avoiding delayed deformation, which most peer factories omit to save time.
3. Low-Stress Finishing & Symmetrical Cutting Strategy
Adopt layered symmetrical cutting to balance unilateral cutting force and avoid structural torsion. Optimize spindle speed and feed parameters to reduce cutting heat accumulation. For thin-wall robot structures with wall thickness less than 2mm, we match low-vibration tool paths to suppress elastic deformation during processing.
4. Post-Processing Aging & Full Inspection Calibration
After finishing, the parts undergo secondary stress relief aging. We use three-coordinate detector to inspect flatness, perpendicularity and key dimensional tolerance. All qualified parts have stable internal stress, no post-delivery warpage or size drift. General dimensions comply with ISO 2768-M, and critical functional holes and assembly surfaces are controlled within ±0.01mm.
Measurable Client Value
Most CNC suppliers only focus on dimensional qualification at the time of delivery and ignore long-term dimensional stability, bringing invisible losses to robot OEMs. Runsom’s standardized stress relief process brings four core benefits for European, American, Japanese and Australian medical robot clients:
First, reduce part scrap rate caused by deformation by over 60%; second, eliminate assembly gap and robot low-speed jitter problems, improving equipment operation stability; third, avoid after-sales rework caused by delayed deformation, saving time and labor costs; fourth, stable batch consistency supports ISO13485 medical certification and high-end equipment factory audit standards.
Free DFM Stress Analysis & Precision Machining Quotation
If you are troubled by post-machining warpage and dimensional drift of 6061/7075 robot structural parts, do not blindly replace materials or tolerate unstable suppliers. The root cause is unreasonable process design rather than material defects.
Runsom provides free professional DFM process optimization and stress risk analysis for global robot manufacturing clients. Submit your CAD/STEP drawings, and our native English engineering team will complete process evaluation, deformation risk prediction and accurate quotation within 24 hours, ensuring long-term dimensional stability of your robot parts.
Contact Info
Website: https://www.runsom.com
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Phone: +86-180 5795 7848