Apr 02, 2020
The welds and bonding in the power assembly must meet strict quality standards. To achieve first-class performance, the mating surfaces must be thoroughly cleaned. The laser is an efficient cleaning tool, which can remove all traces of residual grease.
Components may be contaminated by drawing lubricants or cooling lubricants and rust preventive oils used in the manufacturing process. These residues are usually invisible, but can severely degrade the quality of subsequent high-energy bonding or bonding processes. Especially in the highly automated manufacturing environment of the automobile industry and its suppliers, the standards of component quality and reliability have been improving, and now surface contamination detection has become an indispensable part of the production process.
Traditional cleaning methods are time-consuming, cannot be automated, and usually have a harmful impact on the environment. At the same time, there is no reliable method to measure the cleaning effect. According to vda19 and other standards and the corresponding ISO guidelines, a unified inspection procedure for particulate pollution of automotive functional components is established. Recently, more attention to liquid pollution has led to laser cleaning. The pulse laser can make the residual liquid in the target area evaporate rapidly, the effect can be measured and repeated, and the process is environmentally friendly and can be automated.
Cleanliness improves reliability
In the production of large gear components, laser welding has become a common choice because of the low energy required, which can reduce the deformation. A large number of components in the automobile power assembly must meet strict quality standards. They are made of different materials and alloys. It is difficult or impossible to weld with traditional technology.
Powerful laser, a shorter period
Automakers need a fast, automated way to thoroughly clean up surface residues for strong, void-free, and microcrack free welding and bonding. The laser cleaning system, especially laser cleaning system using pulse solid-state laser, can meet all these requirements. The main factors that determine the choice of the laser are the required cleanliness and the cycle time to clean the components.
Fast and effective arrival at the designated location
In highly automated, mass production processes, time is critical. Unlike traditional cleaning methods that require immersion of the entire assembly in a solvent or the use of abrasives or thermal shock techniques, laser cleaning can be performed on specific functional surfaces, such as welds and bonds, which are usually less than a few square millimeters in size.
The time required for cleaning depends on the time required for laser welding, generally between 4-10 seconds. Another advantage of selective cleaning is that it eliminates the intermediate steps of transporting components from the cleaning station to the production line. The cleaning laser is integrated into the production line just upstream of the welding or bonding station.
To clean a specific surface, the scanner optics allow the laser beam to move quickly back and forth on the workpiece. Different scanning patterns and speeds can be used depending on the cleaning effect required. Linear scanning motion can be used to clean up slight pollution; if further cleaning is required, overlapping circular scanning motion can be used (similar to the action of an electric toothbrush). In this case, the laser pulse passes through the same point several times, thus strengthening the cleaning action.
Clean only the places that need to be cleaned
The laser can clean extremely sensitive surfaces, such as aluminum, carbon fiber composite, or coated parts, without damaging the underlying materials. Or, by choosing different parameter groups, the same laser can make the surface rough and improve the bonding strength. The flexibility of laser tools enables them to be applied to various tasks required. The laser power and pulse frequency suitable for various applications are determined according to the principle of "not exceeding the necessary limit, as little as possible". This method can benefit customers because the cost of laser cleaning is about five times lower than the equivalent wet chemical cleaning process.
Is it clean enough?
At present, standards and guidelines for particulate pollution inspection procedures have been established. It can be predicted that sooner or later, these standards and guidelines will cover liquid pollution. Therefore, it is not only a question of which cleaning method is applicable but also to verify and record the effect. This is the reason to promote the cooperation between TRUMPF and Sita Messtechnik GmbH.
Different cleaning effects can be obtained by changing the scanning method with scanning optics. If a part of the light beam is reflected through the mirror, the upper and lower surfaces of the component can even be cleaned at the same time without repositioning the workpiece.
Another cleaning option
"Cleaning" means not only that the effect of laser processing is very clean, but also that the processing itself is a green and environmental process. Different from the wet chemical process, it does not use a toxic solvent and avoids the noise produced by the abrasion method. In addition, laser cleaning is very soft, and the processing speed is obviously faster than other methods. These advantages have been recognized by the automobile industry, and other industries are also following up at present because laser is a multi-purpose cleaning tool.
Pulse laser can be used to selectively clean the bonding surface or small objects (such as ancient coins), while UV laser is very suitable for cleaning large components. They can be used to remove liquid residues on CFRP components, or by setting other parameters, they can help to remove stubborn paint or rust layers. As a high-tech cleaning tool, the laser has great potential.