The release of the National VI standards has brought many new demands to the automotive industry, including laser welding of injection molded parts. For example, common welding processes include the welding of oil and gas separators, fuel lines and plastic joints, silencers, combination valve bodies, one-way valves and other valve bodies, etc.

To sum up, the plastic laser welded parts used in the above various fuel systems mainly use two materials: nylon containing fiberglass and POM materials. Both plastic materials have been proven in the automotive industry for a long time and have no problems as laser welding materials themselves. The key points are mainly as follows:

Several problems with laser welding of plastic parts of automobiles (Figure 1)
                    

1. In the welding area, the laser should not penetrate through thick plastic parts. The thickness of nylon material should not exceed 2mm, and the thickness of POM material should not exceed 3mm. If the wall thickness is too thick, it will increase the process difficulty of laser plastic welding and significantly reduce the welding speed.



2. When using a laser penetration layer, if you choose a black laser-transparent plastic material, please ensure that the laser transmittance of the plastic material meets the standard requirements and will not be mixed with ordinary black plastic materials during the injection molding process. Before injection molding, be sure to thoroughly clean the screw using the same plastic material.

Three different processes can be used for laser welding of plastic components of the fuel system, namely rotating profile welding, flat profile welding and quasi-synchronous welding.

1. Carry out rotating contour welding.

Rotary contour welding is a method used to weld fuel pipe and fitting joints. In the rotating profile welding process of plastic laser welding, the laser head focuses the laser into a spot, and then the pipe is rotated for welding.

In practical applications, we found that when some customers used low-end plastic laser welding equipment, in order to obtain a wider weld seam, they adopted the method of synchronous movement through the motion axis. However, if low-end lasers are used, welding defects can easily occur in mass production.

There are many different variations for rotary profile welding of plastics, primarily rotary laser welding of fuel pipes and stationary laser welding of fuel pipes.

Several problems with laser welding of plastic parts of automobiles (Figure 2)

                    

2. Welding of flat contours

Flat profile welding is a standard plastic laser welding process mainly used for welding flat seams. During the welding process, the laser head focuses on the light spot, and then the laser head moves sequentially along the weld seam through a moving platform or robot to complete the welding task.

In practical applications, contour welding is crucial for injection molded workpieces with high quality requirements, especially in application scenarios such as oil and gas separators with complex welding lines. In the process of plastic laser welding, contour welding can achieve a certain welding line penetration. However, this penetration is small and cannot be controlled, so the deformation of the injection molded parts must not be too large.

Quasi-synchronous welding

In the automotive industry, quasi-synchronous welding is one of the widely used laser plastic welding processes. During the quasi-synchronous welding process, the welding ribs can achieve larger penetration depth to compensate for certain deformation of the injection molded parts. Therefore, the quality requirements for injection molded parts are relatively low.

When applying plastic laser welding to fuel systems, no matter what welding method is used, special attention needs to be paid to the welding rib design of the welded product. Reasonable design of welding ribs and products that meet the requirements of laser plastic welding technology can greatly simplify the future process development process.