EPB is the abbreviation of electric park brake. EPB controls parking brake through electronic circuit. The function is the same as mechanical lever hand brake. When starting, it is unnecessary to turn off the electronic handbrake manually. When you step on the accelerator, the electronic handbrake will turn off automatically.
In fact, what the electronic parking brake system shows us is the electronic handbrake button that replaces the traditional pull rod handbrake. It is safer than the traditional pull rod handbrake. It will not change the braking effect due to the driver's strength. It turns the traditional pull rod handbrake into a button within reach.
However, the EPB shell is a plastic part, which involves welding. Traditional welding such as ultrasonic welding uses high-frequency vibration wave to transmit to the surfaces of two objects to be welded. Under pressure, the surfaces of the two objects rub against each other to form the fusion between the molecular layers. This is very disadvantageous to the welding of the products with internal gear meshing. For example, the common reflection of the original ultrasonic welding is that after welding, the noise is high, the torque is affected, the appearance is unsightly, and the leakage is large. This is also promoting the application of plastic laser welding, plastic laser welding itself is a kind of non-contact welding processing, mechanical stress is low and does not damage the surface.
From the welding rib structure of the product, the design direction of EPB shell adopts the quasi synchronous laser welding design structure. The welding rib is designed in the light absorbing layer, and the laser scanning along the welding rib through the light transmission layer to realize welding. The advantages of this welding method are fast efficiency and can be used as the quality judgment standard by the welding collapse value.
The material of EPB product is PBT + GF30, which is difficult for laser welding. The light transmittance of materials is the most important factor. The light transmittance of general PBT materials is poor, and the surface is easy to be scalded during welding. In view of this situation, all major material manufacturers have targeted to develop PBT materials suitable for laser welding, such as BASF, Mitsubishi, domestic uktec, etc. However, the light transmittance of PBT material, welding window period and injection molding process requirements of each company are different. Therefore, in the selection of materials, we hope that customers choose a PBT material with high transmittance, long welding window period and low sensitivity of injection molding process.
The second is the injection molding process of PBT products. The process of polymer materials in injection molding also has a great impact on the later laser welding. The most important embodiment is the consistency of transmittance of transparent layer and the warpage of products. After injection molding, the light transmittance is uneven and inconsistent. When welding, it is easy to burn single point or multiple sections. The light transmission layer warps severely. After welding, it is easy to leak due to welding thermal stress. In view of the above problems, material suppliers and injection molding manufacturers have been plagued.