Advantages and disadvantages of plastic ultrasonic welding and plastic laser welding

Principle of Ultrasonic Welding:

Applying ultrasonic waves on the contact surface of thermoplastic plastics will generate tens of thousands of high-frequency vibrations per second. After the high-frequency vibrations reach a certain amplitude, the ultrasonic energy is transmitted to the welding area through the upper weldment. Since the welding area, i.e., the two welding interfaces, have large acoustic resistance, local high temperatures will be generated. In addition, due to the poor thermal conductivity of plastics, they cannot be dissipated in time and gather in the welding area, causing the contact surface of the two plastics to melt quickly, coupled with fusion under a certain pressure. After the ultrasonic wave stops, the pressure lasts for several seconds, solidifies and forms a solid molecular chain, achieving the purpose of welding.

Advantages of ultrasonic welding:

Short welding cycle;

Support non-planar welding.

Disadvantages of ultrasonic welding:

There are flash edges, which are easy to produce debris;

High mechanical stress;

The processing material is limited by the shape and size.

In laser projection welding, the laser beam penetrates the upper projection part and irradiates the lower laser absorbing part. The laser energy is converted into heat from the energy absorbed by the dye or auxiliary particles in the absorbed part. The absorbing part melts and conducts heat to the upper projection part through heat conduction. Before welding begins, the two parts are in contact with each other under the action of external pressure. During welding, the parts are locally heated and the thermal expansion of the material provides additional internal welding pressure. Under the combined action of internal and external welding pressure, the two parts are firmly welded together. The relative movement of the laser beam and the welding parts travels the entire welding process.

Advantages of laser plastic welding:

The welding equipment does not need to come into contact with the plastic parts being bonded;

Fast;

No burrs;

Firm welding;

Can produce airtight or vacuum-tight structures;

Reduce thermal damage and thermal deformation;

Resins of different compositions or colors can be stuck together;

The equipment has low maintenance cost.

Disadvantages of laser plastic welding:

The initial equipment investment cost is high;

Special requirements for substrate performance;

Compared with ultrasonic welding, the advantages of laser welding applied to plastic parts welding include: high welding accuracy, firm sealing, airtight, no water leakage, less resin degradation during welding, less debris generated, and the product surface can be closely connected around the weld. Laser welding has the advantage of no residue and is more suitable for pharmaceutical products and electronic sensors controlled by the State Food and Drug Administration.

It is easy to control and can weld small or complex-shaped workpieces. Since lasers are easy to control with computer software, the laser output can flexibly reach the details of the parts. Laser welding can weld areas that are difficult to reach with ultrasonic welding methods, and weld products with complex shapes or even three-dimensional geometries.

Compared with ultrasonic welding methods, laser welding greatly reduces the vibration stress and thermal stress of the product. This means that the aging rate of the internal parts of the product or equipment is slower, and it can be used for products that are easily damaged. A variety of different materials can be welded. For example, polycarbonate can be connected by near-infrared lasers, and glass fiber reinforced black polybutylene terephthalate can be connected, but ultrasonic welding methods cannot achieve this.