High frequency welding of PU conveyor belts

Polyurethane (PU) conveyor belts are widely used in industries such as food processing, electronics manufacturing, and logistics sorting due to their exceptional properties, including wear resistance, oil resistance, and tear resistance. High-frequency (HF) welding, as a core joining process, enables seamless bonding of belt segments, ensuring stable operation of conveyor systems. This technology is analyzed below in terms of its principles, procedures, and advantages.

Principle: Molecular Friction Heating
High-frequency welding utilizes high-frequency currents (typically 13-40 MHz) applied via electrodes to PU materials. Under the action of the electric field, molecular friction caused by dielectric polarization losses generates localized temperatures of 150–250°C within milliseconds. This directional heating melts the PU surface layer. Simultaneously, pressure rollers apply precise pressure (5–10 MPa) to promote molecular chain interpenetration at the molten interface, forming a homogeneous welded layer.

Standardized Workflow

1. Pre-treatment: Precisely cut belt ends with verticality error ≤0.3 mm.
2. Alignment: Achieve 0.1 mm-level seam alignment using laser positioning systems.
3. Parameter Setup: Adjust output power (2–8 kW) and pressurization time (3–15 s) based on material thickness (commonly 0.8–6 mm).
4. Welding Execution: The electrode head moves uniformly along the seam during HF generator activation, with molten zone width controlled at 2–5 mm.
5. Post-treatment: After water-cooling, weld tensile strength exceeds 90% of the base material.

Technical Advantages
• Efficiency & Sustainability: Single welding cycle <2 minutes, tripling productivity compared to traditional adhesive bonding, with zero VOC emissions.
• Structural Integrity: Eliminates stress concentration from mechanical fasteners, enhancing dynamic flexural lifespan by 40%.
• Hygienic Compliance: Seamless welding meets FDA food-grade standards, preventing microbial growth.
• Versatility: Compatible with fabric-reinforced composite structures and belts with ±15% thickness variation.