Introduction to the high-frequency welding principle of tpu flexible connectors

High-frequency welding of TPU soft joints is based on the skin effect and proximity effect of high-frequency current. Through an electromagnetic field, the material is rapidly heated locally to a molten state, followed by mechanical pressure to achieve molecular-level bonding, forming a high-strength sealed weld. Below are the detailed principles and implementation methods:

I. Core Physical Effects

1. Skin Effect
   When high-frequency current (typically 27.12 MHz or 300–450 kHz) passes through a conductor, the current concentrates and flows along the surface of the conductor, exhibiting "surface concentration." This characteristic ensures that during TPU welding, heat is concentrated on the material’s surface, preventing overall overheating and performance degradation while improving heating efficiency.

2. Proximity Effect
   When high-frequency currents flow in opposite directions in adjacent conductors, the current tends to concentrate on the adjacent sides of the conductors. In TPU welding, by designing the relative positions of the electrodes and the workpiece, the current path can be precisely controlled to focus heat on the welding area, enabling localized and precise heating.

II. Welding Process Implementation

1. Generation of Alternating Electric Field
   A high-frequency power supply creates an alternating electric field between the electrodes. The TPU, acting as a dielectric material, is sandwiched between the electrodes. The electric field causes intense molecular friction within the TPU, generating heat. Due to faster heat dissipation at the electrode-material contact surface, heat is concentrated at the internal junction of the TPU, forming a molten layer.

2. Melting and Pressure Bonding

   • Melting Phase: The high-frequency current continues to act, melting the TPU in the target welding area into a plastic state.
   • Pressure Phase: Mechanical pressure (e.g., from pressure rollers or molds) is applied to the molten area, expelling oxide layers and impurities, allowing molecular chains to interpenetrate and form atomic-level bonds.
   • Cooling and Solidification: After the high-frequency power is turned off, the molten area cools rapidly. The resulting weld exhibits strength close to that of the base material, with a smooth and raised-free surface.

III. Technical Advantages and Features

1. High Efficiency and Precision:

   • Extremely fast heating with short welding times (typically milliseconds), suitable for automated production lines.
   • Heat is concentrated in the welding area, preventing expansion of the heat-affected zone and reducing the risk of material deformation.

2. Excellent Sealing Performance:

   • Molecular-level bonding ensures high weld strength, excellent pressure resistance, and corrosion resistance, meeting the cleanliness requirements of industries such as food and medical.
   • Transparent TPU maintains high light transmittance after welding, facilitating real-time monitoring of internal fluid flow.

3. Strong Adaptability:

   • Capable of welding TPU materials of different thicknesses (0.1–5 mm) and hardness levels, including functional variants such as anti-static and conductive TPU.
   • By adjusting frequency and pressure, welding between flexible soft joints and rigid structures can be achieved.

4. Environmental Friendliness and Safety:

   • No adhesives or solvents are required, resulting in zero VOC emissions, complying with RoHS and REACH environmental regulations.
   • The welding process is free from sparks and splatter, ensuring high operational safety.