Design Method of Watertight and Airtight Ultrasonic Wire for Ultrasonic Plastic Welding
When performing ultrasonic plastic welding, we require the product to be waterproof and airtight. The positioning line and the ultrasonic line are important keys to success or failure. Therefore, the considerations in product design (such as location, material and thickness, and the corresponding ultrasonic fuse ratio) have an absolute relationship. In general watertightness requirements, the height of the fuse should be in the range of 0.5~0.8m/m (depending on the thickness of the product). If it is less than 0.5m/m, the watertight function should be realized. Unless the positioning settings are very standard and the meat thickness should be greater than 5m/m, the effect will be poor. Generally, the positioning and ultrasonic guided fuse methods for watertight products are as follows: Bevel type: suitable for welding watertight and large products, contact surface angle = 45°, x = w / 2, d = 0.3~0.8 mm is better. Stepped needle tip type: suitable for water tightness and to prevent protrusion or breakage. Contact angle = 45°, x = w / 2, d = 0.3~0.8mm. Peak-to-valley tip type: suitable for watertight and high-strength welding, the height h of the inner contact surface d = 0.3~0.6mm varies according to the shape and size, but h is about 1~2mm.
The ultrasonic operation of the product cannot achieve water tightness. In addition to ultrasonic fuses, fixture positioning and product positioning, ultrasonic setting conditions are also the main reason. Here, we discuss in more depth another reason for water and air tightness (welding conditions). When we perform ultrasonic welding operations, the pursuit of efficiency and speed is the most basic goal, but we often overlook the key points of efficiency. There are two phenomena:
1. The descent speed and buffer speed are too fast: the resulting speed will cause dynamic pressure and gravitational acceleration, which will squeeze the ultrasonic fuse, so that the fuse cannot play the role of the fuse and form a pseudo-phase welding.
2. Welding time is too long: plastic products will not only melt the plastic due to long-term thermal energy, but also cause the plastic tissue to coke, resulting in blistering, and water or gas will penetrate from the blistering. This is the most difficult place for ordinary production technicians to find.