Application Of Laser Cleaning in Locomotive Friction Sealing

Laser cleaning, as a new "environmentally friendly" technology that will replace traditional cleaning methods in the future, and a new industrial cleaning process with no pollution or consumables, has been widely used in the production of various components such as power battery systems, transmission bearings, axles, wheel rims, and tires in automobiles, thanks to its micron level process precision and integrated advantages of unmanned automation. 

 

 

 

 

The principles of laser cleaning can be roughly divided into three types: thermal effect, light peeling, and oscillation. It is the use of different types of lasers to generate various laser beams. By utilizing the difference in the absorption coefficient of laser energy between the substrate and surface pollutants at a certain wavelength, the substrate material and surface pollutants absorb energy and undergo thermal expansion and detachment. The instantaneous high temperature causes the dirt to evaporate, gasify or decompose instantly, while generating ultrasonic waves on the solid surface, generating mechanical resonance and causing the dirt layer or condensate to vibrate and shatter.

Principle diagram

Compared to traditional industrial cleaning methods such as sandblasting or shot blasting, the characteristics of laser cleaning are non grinding and non-contact. It has no thermal effect, does not generate mechanical force on the cleaned object, does not damage the surface of the object, does not damage the substrate, and does not produce secondary pollution. It is a green, environmentally friendly, and consumable free cleaning method.

 

 

 

After long-term use, the components of a car will accumulate some dust, rust, oil stains, and so on. If car parts are too dirty, it can lead to poor filtering and cleaning effect, excessive impurities entering the oil cylinder, exacerbating the wear of the parts and increasing the possibility of faults. For the safe operation of automobiles, important components such as wheel hubs, brake pads, brake discs, and engine covers need to be regularly inspected and maintained. Ensuring the cleanliness of various workpieces and components is an essential part of the maintenance process.

 

 

In the production process of brake pads, after flat friction and before spraying, it is necessary to clean the brake pads, which has a large output and a wide range, and is typical. Therefore, we take the cleaning application of brake pads as an example to compare the advantages and disadvantages of steel brush, sandblasting, and laser cleaning:

 

• Cleaning efficiency: The steel brush equipment is unable to clean the residual adhesive on the surface of the brake pads after smooth grinding, resulting in the production of pitting in the next spray molding process, which is not satisfactory. Both sandblasting equipment and laser cleaning can completely clean the surface residue after the flat grinding process. The cleaning speed of sandblasting is faster than that of laser cleaning. However, if we consider the production time of complete production lines such as the oven before flat grinding and the curing process after spray molding, the cleaning speed of sandblasting is redundant. Although the excitation cleaning is slower, it can also adapt to the production line speed.

 

• Energy consumption: The energy consumption of the steel brush machine is around 8KW/H, ranking second among the three. The sandblasting process has a high energy consumption, with a total energy consumption of up to 70KW/H. This is because although the energy consumption of the sandblasting machine's three motors for sandblasting, walking, and swinging is around 15KW/H, the energy consumption of the air compressor supplying gas is as high as 55KW per hour, making it a major energy consumer. Our laser cleaning equipment has a total energy consumption of only 7KW/H, which is one tenth of that of sandblasting equipment, and the energy consumption is the smallest among the three.

 

• Economic and Environmental Protection: In terms of economic applicability, sandblasting equipment requires 5KG of quartz sand as consumables per hour. The longer the usage time, the more consumables are needed. With the gradual improvement of national environmental protection requirements, some local governments have listed sand washing machines as non compliant types of environmental protection. Both steel brush equipment and laser cleaning only require electricity, and laser cleaning can save 1-2 manual labor compared to sandblasting and steel brushes due to automated operations; From the perspective of environmental protection and low-carbon, laser cleaning equipment has no consumables, no emissions, low energy consumption and no noise, and is also one of the equipment that meets the requirements of low-carbon environmental protection.

 

 

 

The application of laser cleaning in the sealing industry mainly includes the removal of oil stains on the surface of stainless steel strips in the production process of metal gaskets, cleaning of oil stains and residual glue on the surface of sealing ring molds, and surface modification of special sealing materials. There are many types of seals, typical of which are O-ring seals, skeleton oil seals, and sealing washers. Through the irradiation of a laser beam, the oil stains on the sealing gasket evaporate instantly and peel off from the metal, achieving a cleaning effect.

Before entering the winding machine, the metal wound gasket needs to clean the oil film attached to the surface of the stainless steel coil. The existing process generally uses chemical soaking for surface treatment. Laser cleaning in this process can meet the manufacturer's requirements for cleaning effect. The main difficulty in application is the inability to adapt the bandwidth and production line speed. Generally, the width of laser cleaning equipment is between 150-200mm, while the width of stainless steel strip is between 1100-1500mm; And the production speed of steel coil cleaning is too fast, usually above 10M/min, which is about ten times higher than the adaptation speed of laser cleaning. Our company can solve the problem of cleaning width adaptation through our independently developed ultra wide width laser cleaning equipment. Although it can solve the process application in terms of production line speed, the current industry solution cost is too high and further optimization is needed.

 

In the application of cleaning oil stains and residual glue on the surface of sealing ring molds, we have developed a flat mold laser cleaning equipment with three-dimensional five axis motion and high degree of freedom, suitable for various types of flat molds such as brake pad molds in the friction industry and sealing ring molds in the sealing industry. It can remove rust proof oil and clean residual residue on the surface of the mold cavity after multiple presses. Additional displacement machines can be added to adapt to complex molds. During the cleaning process, the electroplating layer can be retained to protect the blade pattern and extend the lifespan of the mold. Compared to sandblasting cleaning, it is not only more environmentally friendly, but also ensures that the mold cavity is not damaged, reducing product defect rates.

 

Non metallic sealing gaskets are another major category in the sealing industry. These products have a strong absorption rate for fiber laser in the wavelength range of 1064-1080nm, which can cause damage under normal circumstances. They are not suitable for process applications, such as when pulsed laser is applied to the surface of rubber materials, it can cause 10% damage μ The damage is about m, but it can also be used as a modification method for a few special materials, such as rubber materials with attached polymethylhydrosiloxane, which can improve the surface friction coefficient to 35mN/m and surface tension to above 38dyne/cm while removing the coating.

 

At the same time, laser cleaning has shown good performance in cleaning the oxide layer and roughening the sealing components of ceramic and composite materials, and has also achieved satisfactory results in removing sealant on metal surfaces. It can be seen that laser cleaning has differential performance in the application of products with different materials due to its different laser absorption rates. Therefore, it can also be used as a supplementary process for surface modification of a few special sealing materials.