Several problems with laser welding of plastic parts of automobiles

The release of the National VI standard has brought many new demands to the automotive industry, including laser welding of injection molded parts. For example, common welding processes include welding of oil-gas separators, fuel lines and plastic joints, mufflers, combined valve bodies, and valve bodies such as check valves.

In summary, the plastic laser welding parts used in the above various fuel systems mainly use two materials: nylon with glass fiber and POM material. Both of these plastic materials have been verified by long-term application in the automotive industry, and there is no problem as laser welding materials themselves. The key points are as follows:

1. In the welding area, the laser should not penetrate too 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.

Second, when using a laser penetrating 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 mix with ordinary black plastic materials during the injection molding process. Before injection molding, be sure to use the same plastic material to thoroughly clean the screw.

Laser welding of plastic parts in the fuel system can use three different processes, namely rotary contour welding, flat contour welding and quasi-synchronous welding.

1. Perform rotary contour welding.

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

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

There are many different variations for rotary contour welding of plastics, the main ones being fuel pipe rotary laser welding and fuel pipe stationary laser welding.

2. Welding of plane contours

Flat contour welding is a standard plastic laser welding process, which is mainly used for welding flat welds. During the welding process, the laser head focuses the light spot, and then the laser head moves in sequence along the weld through a motion platform or a robot to complete the welding task.

In practical applications, the quality requirements for injection molded workpieces are high, especially in application scenarios such as oil-gas separators with complex weld lines, contour welding is crucial. In the plastic laser welding process, contour welding can achieve a certain weld line penetration depth, but this penetration depth is small and cannot be controlled, so the deformation of the injection molded part should 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 quasi-synchronous welding, the welding ribs can achieve a greater depth of penetration 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 the fuel system, no matter what welding method is used, special attention should be paid to the design of the welding ribs of the welding products. Reasonable design of welding ribs and products that meet the requirements of laser plastic welding technology can greatly simplify the future process development process.