Application of plastic laser welding in instrument panel

In the past two years, the processing technology of automotive interior parts has made great progress, and various interior parts including dashboards, doors, and seats have become more and more refined.

Conventional dashboards are welded by vibration friction plastic welding. High-frequency vibration will scratch the surface of the dashboard during welding. Therefore, the vibration friction welding fixture needs to be covered with soft materials to prevent scratches on the dashboard surface during welding. Another small problem with vibration friction welding is the generation of welding slag during welding and poor cleanliness. For dashboard welding, the biggest problem with vibration friction welding is that a large amount of overflow glue will be generated after welding, and the welding line or welding area is very unsightly. The conventional practice is to hide these welding lines. However, with the continuous compactness of automotive interior design, the space for plastic welding design is getting smaller and smaller. In many cases, the weld of the dashboard is completely exposed visually. Therefore, finding a new beautiful plastic welding process has become a practical need.

Advantages of laser plastic welding:

Compared with traditional vibration friction welding technology, plastic laser welding technology has the advantages of instrument panel welding

1. There is no vibration during welding. Plastic laser welding is a non-contact welding method. The upper and lower workpieces are clamped and stationary, and there is relative displacement during welding. Therefore, plastic laser welding technology is particularly easy to protect the appearance of the product.

2. There is almost no overflow, and the appearance of the welding line is very beautiful. The welding line formed by plastic laser welding is very beautiful and can be used directly as the appearance surface. During the laser welding process, there is a lot of overflow in the welding area, which will not cause overflow in the welding area due to the large collapse of the welding ribs like vibration friction welding, and the welding line is very ugly. This is also the main reason for laser welding of automotive interior and exterior trims.

Difficulties of laser plastic welding of instrument panel:

The primary difficulty of instrument panel plastic laser welding technology is design. When plastic products are laser welded, product design must be carried out according to the design requirements of the selected laser plastic welding technology. The most important thing in the laser welding design of the instrument panel is the design of the welding ribs. During the plastic laser welding process, the welding ribs must have sufficient welding pressure, which is obtained by applying pressure to the fixture. Therefore, when designing the welding ribs for laser welding of instrument panel plastic, it is necessary to ensure that there is enough space under the welding line to provide for the fixture, and the fixture must be able to fully support the welding line (refer to the figure below).

In addition to the difficulty of welding line design, the deformation of injection molded parts is also a major difficulty in laser welding of instrument panel plastics. The size of the instrument panel is generally large, so there will be deformation during injection molding. The lower housing material is generally PC/ABS material, and the upper lens material is PMMA material. PMMA material is a fragile material. If the welding pressure is too high during laser plastic welding, it is very likely to crush or crush the PMMA upper shell. The lower housing is generally a high-wall structure with a thin wall thickness but a high height. This structure is prone to bending and deformation under pressure, causing welding defects.

In order to cope with the deformation of the injection molded workpiece of the instrument panel, when designing the laser plastic welding fixture, an adjustable mechanism must be designed, and adjustment blocks must be designed in the areas that are prone to deformation and stress concentration to ensure that the fixture is adjustable during subsequent process adjustments.

In addition to designing a flexible fixture, in the process of laser plastic welding of the instrument panel, finding the accurate process window is also an important factor in the laser welding process of the instrument panel. In the process of finding process parameters, high-wall products such as instrument panels generally cannot use too much welding pressure. Otherwise, under a larger welding pressure, the workpiece will deform more and plastic laser welding will easily produce welding defects.