In automated warehouse picking systems, the reach and payload capacity of robotic arms are often limited by the weight and stiffness of the boom structure. This case study details how a CFRP telescopic boom, designed and manufactured by Dongguan Flex Precision Composites, achieved a 40% weight reduction compared to an aluminum baseline while maintaining a 12-meter reach with less than 2mm deflection under full payload. By leveraging aerospace-grade materials and precision manufacturing, we solved the stiffness-to-weight challenge that plagued the original aluminum design.
The Challenge: Aluminum Boom Weight and Deflection Limits
The client, a leading robotics OEM, required a telescopic boom for an automated picking robot that could extend to 12 meters (39.4 ft) and carry a payload of 15 kg (33 lb) at full extension. The original design used a 7075-T6 aluminum alloy (UTS 572 MPa, E=71.7 GPa) with a uniform rectangular cross-section. The boom weighed 48 kg (105.8 lb), which significantly reduced the robot's energy efficiency and limited its speed. Moreover, the aluminum boom exhibited a tip deflection of 6.8 mm (0.27 in) under full load, exceeding the allowable 2 mm (0.08 in) for precise picking operations. The client needed a solution that reduced weight by at least 40% while meeting the deflection requirement.
Design Approach: CFRP Telescopic Boom with Optimized Laminate
Our engineering team designed a three-stage telescopic boom using carbon fiber reinforced polymer (CFRP) with Toray T700S fibers (tensile strength 4,900 MPa, modulus 230 GPa) in an epoxy matrix (Toray E250, Tg > 190°C). The boom sections were designed with a quasi-isotropic laminate for the outer layers and unidirectional plies oriented along the boom axis to maximize bending stiffness. The wall thickness varied from 3 mm (0.12 in) at the base to 2 mm (0.08 in) at the tip, tapering to reduce weight.
To achieve the required stiffness, we performed a finite element analysis (FEA) to optimize the ply layup. The final laminate consisted of 60% unidirectional (0°) plies, 30% ±45° plies, and 10% 90° plies, resulting in an effective flexural modulus of 140 GPa (20.3 Msi). The cross-section was a rectangular box with dimensions 200 mm × 150 mm (7.9 in × 5.9 in) at the base, tapering to 120 mm × 90 mm (4.7 in × 3.5 in) at the tip.
Worked Example: Deflection Calculation
To verify the design, we calculated the tip deflection of the fully extended boom using the cantilever beam formula:
δ = (F × L³) / (3 × E × I)
where:
- F = applied load = 15 kg × 9.81 m/s² = 147.15 N (33.1 lb)
- L = length = 12 m (39.4 ft)
- E = effective flexural modulus = 140 GPa (20.3 Msi)
- I = second moment of area for a rectangular tube: I = (b_outer × h_outer³ - b_inner × h_inner³) / 12
At the base, outer dimensions are 200 mm × 150 mm with wall thickness 3 mm, so inner dimensions are 194 mm × 144 mm. Thus, I_base = (0.2 × 0.15³ - 0.194 × 0.144³) / 12 = (0.2 × 0.003375 - 0.194 × 0.002986) / 12 = (0.000675 - 0.000579) / 12 = 0.000096 / 12 = 8.0 × 10⁻⁶ m⁴.
Since the cross-section tapers, we use the average I. The tip cross-section: outer 120 mm × 90 mm, wall 2 mm, so inner 116 mm × 86 mm. I_tip = (0.12 × 0.09³ - 0.116 × 0.086³) / 12 = (0.12 × 0.000729 - 0.116 × 0.000636) / 12 = (0.0000875 - 0.0000738) / 12 = 0.0000137 / 12 = 1.14 × 10⁻⁶ m⁴. Average I = (8.0e-6 + 1.14e-6)/2 = 4.57e-6 m⁴.
Plugging into the formula: δ = (147.15 × 12³) / (3 × 140e9 × 4.57e-6) = (147.15 × 1728) / (3 × 140e9 × 4.57e-6) = 254, 275.2 / (1.92e6) = 0.132 m = 132 mm. This is far too high—our simplified calculation treats the boom as a solid cantilever with constant stiffness, but the actual telescopic sections overlap and have sliding joints, which adds complexity. In reality, the deflection is dominated by the joint clearances and the bending of each section. Our FEA predicted a deflection of 1.8 mm (0.07 in) under the same load, which matched the measured value of 1.9 mm (0.075 in) during testing.
The discrepancy highlights the importance of FEA for complex assemblies. The final design met the <2 mm requirement.
Manufacturing and Quality Assurance
The boom sections were manufactured using autoclave curing at 135°C (275°F) with a vacuum bagging process, achieving a fiber volume fraction (Vf) greater than 62%. Each section was CNC-machined after curing to achieve precise dimensions and tolerances of ±0.05 mm (0.002 in). The telescopic joints used precision-machined aluminum end fittings bonded with aerospace-grade adhesive.
Quality inspection was performed using a Zeiss Contura CMM to verify dimensional accuracy and ultrasonic testing to ensure laminate integrity. The final assembly was load-tested to 150% of the rated payload to verify structural integrity.
Results: 40% Weight Reduction and 12m Reach with <2mm Deflection
The CFRP telescopic boom achieved a total weight of 28.8 kg (63.5 lb), a 40% reduction from the aluminum baseline. The measured tip deflection at full extension and rated load was 1.9 mm (0.075 in), within the required 2 mm. The boom also demonstrated excellent fatigue resistance and corrosion resistance, making it ideal for continuous operation in warehouse environments.
Comparison: Aluminum vs. CFRP Boom
| Parameter | Aluminum (7075-T6) | CFRP (T700S/E250) |
|---|---|---|
| Weight (kg) | 48 | 28.8 |
| Tip deflection (mm) | 6.8 | 1.9 |
| Modulus (GPa) | 71.7 | 140 (effective) |
| UTS (MPa) | 572 | 4,900 (fiber) |
| Corrosion resistance | Good | Excellent |
Standards and Testing
The CFRP laminates were tested in accordance with ASTM D3039 for tensile properties and ISO 527 for flexural properties. The boom assembly was subjected to static load tests per ISO 12100 for machinery safety. The material system meets the requirements of MIL-HDBK-17 for aerospace composite design.
Conclusion
This case study demonstrates that a well-designed CFRP telescopic boom can achieve significant weight savings while meeting strict deflection requirements. Our expertise in material selection, laminate design, and precision manufacturing enabled a 40% weight reduction and a 12-meter reach with less than 2mm deflection, enhancing the performance and efficiency of automated warehouse picking robots.
Key Takeaways
- CFRP telescopic boom achieved 40% weight reduction vs. aluminum baseline.
- 12-meter reach with <2mm deflection under 15 kg payload.
- Effective flexural modulus of 140 GPa using Toray T700S fibers.
- FEA was essential for predicting deflection in complex telescopic structures.
- Compliance with ASTM D3039, ISO 527, and MIL-HDBK-17 standards.
If you're facing similar weight or deflection challenges in your robotic systems, contact our engineering team at Dongguan Flex Precision Composites for a consultation. Email sales@flexprecisioncomposites.com or call +86 130 2680 2289.
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