I. Core Principle and Scope of Application
1. The essence is molecular diffusion and interfacial fusion to form a homogeneous joint. 2.
2. Only applicable to thermoplastics (PE/PP/ABS/PC/PVC, etc.), thermosetting plastics can not be welded. 3.
3. Three elements: temperature, pressure and time, which determine the strength and appearance of the weld.
II. Mainstream process and selection
| Process | Principle | Speed | Precision | Typical Applications | Typical Materials |
|
Ultrasonic |
High-frequency vibration friction | Extremely Fast (0.1-0.5s) | High | Small precision parts (electronics, medical, toys) |
ABS,PS,PMMA |
| Hot Plate |
Heated plate contact melting |
Medium (5-60s) | Medium | Large structures (fuel tanks, water tanks) |
PP,PE,PVC |
| Vibration Friction | Reciprocating friction heat | Medium-Fast | Medium-High | Fluid components, filters |
PP,PA,PBT |
| HF Induction | Electromagnetic induction | Extremely Fast (0.1-0.3s) | High | Mid-to-small structures (appliances, medical) |
PP,PE,ABS |
| Laser | Transmission-absorption heating | Fast | Extremely High | Medical, high-end electronics (sterile/hermetic) |
PC,PMMA,PP |
| Spin Welding | Rotational friction heat | Medium | Medium | Circular/Symmetrical parts (valves, containers) |
PP,PE,PA |
III. Key Parameters & Optimization
Temperature: PP (190-210°C), PVC (200-230°C); PE is typically 20°C lower than PP.
Pressure: Must be sufficient and uniform to prevent cold welding, flash (overflow), or deformation.
Time: Sufficient melting and cooling phases are required to avoid pseudo-welding or over-melting.
Surface Cleanliness: Removal of oil and dust is essential to enhance bonding force.
Material Matching: Best results are achieved with identical materials; dissimilar materials require compatible melting points and chemical affinity.
IV. Application Fields
Automotive: Headlights, bumpers, fuel tanks, and interior trim; supporting vehicle lightweighting.
Medical: Infusion tubes, pulse oximetry probes, and dialysis equipment; ensuring sterile, leak-proof seals.
Electronics & Appliances: Washing machine water boards, AC components, waterproof phone housings, chargers, and earbuds; focusing on high efficiency and precision.
Piping & Containers: PE/PP pipes and storage tanks; ensuring high strength and sealing reliability.
Packaging: Sealing for food and daily chemicals; eco-friendly as no adhesives are required.
V. Common Defects & Countermeasures
Flash / Deformation: Parameters too high → Reduce temperature, lower pressure, or shorten melt time.
Cold Welding (Pseudo-weld): Insufficient energy → Increase temperature, increase pressure, or extend melt time.
Porosity: Moisture or impurities → Pre-dry materials and clean surfaces.
Insufficient Strength: Material incompatibility → Switch to compatible materials or optimize the welding process.
VI. Industry Trends
Intelligence: Integration of digital controls, online monitoring, and automated systems to improve yield rates and efficiency.
Sustainability (Green): Zero VOC emissions and no consumables, aligning with global environmental standards.
Precision: Increasing adoption of non-contact processes like laser welding to meet the demands of high-end manufacturing.
