The metal structure serves as the primary load-bearing framework for light-duty lifting systems; its design soundness, material selection precision, and manufacturing accuracy directly determine the equipment's load-bearing stability, service life, safety factor, and operational precision. Unlike heavy-duty cranes, light-duty lifting systems do not require massive, ultra-rigid structures; however, they demand stricter control over dead weight and deformation, as well as higher standards for fatigue strength and environmental adaptability. Design and material selection must strictly adhere to the *Code for Design of Cranes* (GB/T 3811-2008)—specifically its standards for load calculation, structural strength, rigidity, and stability—while accounting for specific operating conditions.
The design of metal structures for light-duty lifting systems adheres to four core principles: lightweight construction, high rigidity, fatigue resistance, and minimal deformation. The core calculations comprise four modules: strength, rigidity, stability, and fatigue verification. Strength calculations incorporate rated loads, dynamic load coefficients, and impact load coefficients to analyze tensile, compressive, and bending stresses in key components such as main girders, columns, and brackets; this ensures that maximum stress values remain below the material's allowable stress limits, thereby eliminating the risk of structural fracture. Rigidity is a critical control parameter; under full-load operation, the maximum deflection of the main girder must be kept within 1/1000 of the span to prevent excessive deformation that could cause hoist jamming, load swaying, or structural fatigue damage, while also ensuring precise positioning during lifting. Stability calculations focus on slender structures—such as cantilevers and long-span main girders—verifying both overall and local stability of compression members to prevent buckling or overturning. Fatigue verification is essential for high-frequency equipment, assessing structural fatigue life under conditions of frequent start-stop cycles and alternating loads to ensure reliability during routine industrial operations.
Material selection must be precisely matched to operating conditions. Mainstream industrial materials fall into three categories—carbon structural steel, low-alloy high-strength steel, and aerospace-grade aluminum alloy—each suited to specific application requirements. For standard drying workshops and general mechanical processing environments, Q235B high-quality carbon structural steel is the preferred choice. This material offers excellent weldability, good ductility and toughness, and high cost-effectiveness; it meets the standard load-bearing requirements for light-duty lifting equipment (up to 10 tons) and serves as the foundational material for general-purpose light-duty cranes. For applications involving long spans, high operational frequency, or heavy loads, Q355 low-alloy high-strength steel is selected. It outperforms Q235B in yield strength, impact resistance, and bending strength, allowing for reduced component cross-sections and lower equipment deadweight under identical load conditions—making it suitable for equipment such as LD single-girder cranes and long-span KBK rail systems.
For specialized environments—such as cleanrooms, precision manufacturing facilities, and pharmaceutical or food processing plants—6061-T6 age-hardened aluminum alloy is used. Weighing only one-third as much as steel, this material offers advantages such as rust resistance, freedom from dust shedding, oxidation resistance, and low noise operation. It completely eliminates issues associated with carbon steel, such as rust contamination and excessive deadweight. Furthermore, processed via extrusion, the material ensures high structural precision and minimal deformation, making it ideal for high-precision, high-cleanliness operations. In environments exposed to coastal salt spray, chemical corrosion, or outdoor conditions, carbon steel structures require specialized anti-corrosion treatments—such as hot-dip galvanizing, fluorocarbon coating, or multi-layer anti-corrosion painting—to enhance corrosion resistance and extend the equipment's service life.
Regarding manufacturing processes, the metal structures of light-duty lifting equipment are fabricated using modular welding techniques. Key welds are executed via submerged arc welding or argon arc welding to ensure full penetration without porosity, cracks, or slag inclusions. Post-welding stress-relief annealing is performed to completely eliminate residual welding stresses, thereby preventing future structural deformation or cracking. All components undergo straightening and grinding after fabrication to ensure structural flatness and verticality meet standards, laying the structural foundation for smooth operation and precise positioning. Scientific structural design and precise material selection are the core guarantees for the safe, efficient, and long-lasting operation of light-duty lifting systems.
