Pulse Welding of TPU Film: Process Principle and Application Analysis

I. Process Principle: Pulsed Thermal Energy Control and Material Fusion

Pulsed welding uses periodically varying current or laser energy to create intermittent heat input at the TPU film contact surface. Its core principle is as follows:

1. Energy Pulsation

Current Pulsed Welding: The output current alternates between a peak (high current) and a base value (low current). The peak current rapidly melts the TPU surface, while the base current allows partial cooling of the molten pool, reducing heat accumulation.

Laser Pulsed Welding: Utilizes an intermittent high-energy laser beam. Each pulse forms an independent weld point on the workpiece. Heat input is controlled by adjusting the pulse energy, width, and frequency.

2. Heat Conduction and Fusion

Pulsed energy melts the TPU film contact surface, forming a molten pool. Under pressure, molten material molecules diffuse into each other, forming a weld upon cooling. After the pulse ends, the molten pool solidifies rapidly (laser welding solidification time can reach the 10-second level), reducing the heat-affected zone and preventing material deformation or degradation.

3. Key Parameter Control

Pulse Energy: Determines the amount of melting and must be matched with the TPU film thickness. Pulse width: Affects weld penetration; too wide a pulse may cause burn-through, while too narrow a pulse results in insufficient fusion.

Frequency: High-frequency pulses (e.g., 10-500Hz) produce dense weld points and smooth welds; low-frequency pulses are suitable for manual welding, facilitating control of the molten pool.

Duty cycle: The percentage of peak current over time; adjusts the heat input ratio to avoid overheating or insufficient penetration.

II. Technical Advantages: Precise, Efficient, and Low-Damage

1. Small Heat-Affected Zone: Concentrated pulse energy and rapid heating-cooling cycle result in low overall temperature rise of the TPU film, reducing thermal deformation and performance degradation (such as elasticity loss).

2. High Weld Quality: Weld strength close to the base material, with a smooth surface free of spatter or porosity, meeting the sealing and cleanliness requirements of medical, electronic, and other fields.

3. Wide Material Adaptability: Can weld TPU films of different hardness and thickness, and is even compatible with composite welding of TPU with other materials (such as PC and PMMA).

4. High Automation Potential: Pulse parameters can be precisely programmed, easily integrated with robots or vision inspection systems, enabling high-speed, stable automated production.

III. Core Application Scenarios

1. Medical Field

Implantable Devices: Welding TPU airbags or catheters results in thin, smooth welds, reducing irritation to biological tissues.

Surgical Gowns/Protective Clothing: Pulse welding replaces traditional sewing, achieving seamless seals with excellent waterproof and antibacterial properties.

Blood/Drug Bags: Laser pulse welding produces high-strength welds; after sterilization with ethylene oxide or gamma rays, there is no risk of leakage.

2. Industrial Products

Waterproof Membrane Structures: Welding TPU coated fabric for tents and inflatable boats provides strong weather resistance.

Automotive Interiors: Welding TPU airbag covers or sealing strips ensures high burst pressure test pass rates and strong safety.

Electronic Packaging: Welding TPU protective sleeves achieves an IP68 dustproof and waterproof rating, extending equipment lifespan.

IV. Process Types and Selection Criteria

1. Current Pulse Welding: Applicable Scenarios: Manual welding or low-speed automated production lines, such as micro-assembly of medical devices. Advantages: Low equipment cost, flexible operation, suitable for small-batch production.

2. Laser Pulse Welding: Applicable Scenarios: High-speed, high-precision welding, such as 3C product casings or electronic component packaging. Advantages: Narrow weld seam and minimal heat-affected zone, suitable for thin-material welding.

3. Mask Pulse Welding: Applicable Scenarios: Microelectronic or medical micro-device packaging, requiring localized heating. Advantages: Achieves micron-level precision by masking non-welding areas with a template, avoiding damage to surrounding materials.