What are the limitations of plastic laser welding (advantages and disadvantages of plastic laser welding)

Laser welding of plasticsThe technology uses concentrated intense radiation waves to melt the plastic joint area, which is often in the infrared region of the electromagnetic spectrum. The type of laser and the absorption characteristics of the plastic determine the welding possibilities.

Laser welding also greatly reduces the vibration and thermal stress of the product. Compared with other joining methods, vibration and thermal stress are less, which means that the internal components of the product or equipment will age more slowly. This feature provides opportunities for laser welding to be applied to fragile products such as electronic sensors.

Many different kinds of materials can be welded together using lasers, which use near-infrared lasers (NIR), with wavelengths between 810 and 2000 nanometers. First, two products are clamped together under low pressure, and near-infrared laser light passes through one product (NIR laser transmission) and is absorbed by the other product (NIR laser absorption). The product that absorbs the NIR laser converts the light into heat, which then melts at the contact surface of the products. At the same time, heat is also transferred to the surface of the product that transmits the NIR laser, forming a welded area. The strength of the weld can exceed the strength of the raw materials. For example, laser welding can join together polycarbonate (PC) black polybutylene terephthalate and 30% glass fiber reinforced (PBT) using NIR lasers. Other welding methods cannot join two different polymers in terms of structure, softening point and reinforcement. Laser welding performs best for welding products with complex (even 3D) shapes and can weld areas that are difficult to reach with other welding methods.

The mature application of plastic laser welding technology in various fields, such as defense and medicine, has helped to enable its application in plastic joining. Since the mid-1990s, diode lasers and aluminum garnet lasers have been advancing toward the benefits of plastic joining. The power of these lasers has increased significantly, and their cost has dropped by about 90% in the past five years. It has been found that most plastics can effectively transmit lasers emitted by diode lasers (810 to 940 nanometers) and aluminum garnet lasers (1064 nanometers) at or near their wavelength bands. (CO2 laser absorption tends to burn)

The advantage of laser welding without residue also makes it more suitable for the following products. : FDA regulation of pharmaceutical products, automotive products, and other electronic sensors.

Diode lasers and aluminum garnet lasers have proven to be well adapted when used for plastic welding. For example, diode lasers can be arranged to produce complex linear welds. Diode laser emitters can also be stacked in combination to achieve the high welding power required for special applications.

There are also some limitations to the laser welding method for certain materials. : First of all, high-performance polymers such as PPS. Poly (PEEK) and LCP are not suitable for laser welding because these materials have a low transmittance to near-infrared light. Another disadvantage is that if both materials are filled with carbon black filler, they cannot be welded together because both are black. This is an obstacle to laser welding of devices under the automotive hull and other black devices. Now many material companies have also launched laser weldable black plastics, such as black PC, black PA66, etc.

By the same token, there are two materials that can transmit near-infrared lasers (usually they are transparent or white), but they are not suitable for laser welding because their absorption rate of near-infrared lasers is extremely low. This is a big disadvantage for medicine, packaging and consumer goods because these products require transparency.

Since many mineral-filled compounds can absorb near-infrared lasers, they are generally not suitable for laser welding. The use of glass fiber reinforcements with high filling rates can change the transmittance of near-infrared lasers, thereby reducing welding efficiency. However, the glass fiber content used by raw material suppliers in the formulation usually does not exceed this limit.