Laser welding of plastic parts of EPB electronic parking system

EPB electronic parking brake system is a system that combines temporary braking after parking with long-term braking functions to achieve parking brake in an electronically controlled manner. The EPB system uses electronic buttons, manual operation, and automatic control. If you need to brake, press the EPB button, and the button operation signal is fed back to the electronic control unit, which controls the motor and reducer mechanism to brake the front and rear calipers.

The laser welding of plastic parts of the EPB electronic parking system mainly involves the laser welding of the EPB electronic parking controller housing and the plastic housing of the EPB electronic parking MGU component.

Among them, the design of the EPB controller and the MGU component shell adopts a quasi-synchronous welding design structure. The bottom shell is designed with welding ribs. The laser spot scans quickly along the welding ribs, so that the welding rod is completely melted to form a tatami. The advantages of quasi-synchronous laser plastic welding technology are: on the one hand, the deformation of the plastic part is compensated by the collapse of the welding ribs; on the other hand, monitoring the collapse of the welding rod is a quality monitoring standard.

The main difficulty in laser welding of plastic parts in the EPB electronic parking system is concentrated on the process, and laser welding of the materials used is the key technical difficulty. In the past, the shell of the EPB controller and MGU components was made of PBT material. Ordinary PBT materials have poor laser penetration performance, such as BASF B4300G6LT material; specially developed high-permeability PBT materials, such as the BASFLUX series, are not purchased by ordinary auto parts. At present, domestic engineering plastics suppliers are also actively developing PBT materials for laser welding. Well-known PBT series PBT materials such as the ECOT series PBT materials developed by Ningbo Youketai can reach about 50% (~1.5mm thickness). Injection molding is not affected by mold temperature, has a wide processing window, and is more suitable for national conditions. Recently, some customers have also begun to test the PBT laser penetrant specially developed by Mitsubishi for EPB, whose penetration rate can reach 50% (~1.5mm thickness), and the material processing window and laser welding window can achieve more than twice the rapid production.

BASFPBT materials have strict process requirements for injection molding, and unqualified injection molded parts will seriously affect the final molding quality of the finished product. First of all, it is necessary to ensure that the laser transmittance of the upper cover of the EPB casing is maintained above a certain level and uniform. The penetration detection equipment used by ordinary injection molding companies has great limitations, and almost all suppliers will choose samples for laser penetration testing of laser penetrating parts. This method can only give a comprehensive understanding of the laser penetration of the penetrating part, but it is not enough to have a stable understanding of the laser penetration and penetration of the entire weld surface. In the chart below, you can see that the penetration tester cannot detect local penetration.

Except for the PBT material penetrating the laser, the EPB and MGU shell manufacturers have a very narrow process window during the welding process. During the PBT laser welding process, if the laser power is too large, the PBT material is easy to leave marks or burn spots on the weld surface, affecting the appearance of the product.