4. Principle of laser surface cleaning
The pulsed Nd:YAG laser cleaning process relies on the characteristics of the light pulses produced by the laser, based on photophysical reactions caused by the interaction between high intensity beams, short pulsed lasers, and contaminated layers. Its physical principles can be summarized as follows:
a) The beam emitted by the laser is absorbed by the contaminated layer on the surface to be treated.
b) Absorption of large energy forms a rapidly expanding plasma (a highly ionized unstable gas) that produces a shock wave.
c) Shock waves cause the contaminants to become fragments and are rejected.
d) The light pulse width must be short enough to avoid heat build-up that would damage the surface being treated.
e) Experiments have shown that when there is an oxide on the surface of the metal, the plasma is generated on the metal surface.
The plasma is generated only when the energy density is above a threshold, which depends on the contaminated or oxide layer being removed. This threshold effect is important for effective cleaning while ensuring the safety of the substrate material. There is also a second threshold for the presence of plasma. If the energy density exceeds this threshold, the substrate material will be destroyed. In order to ensure effective cleaning under the premise of ensuring the safety of the substrate material, the laser parameters must be adjusted according to the situation so that the energy density of the light pulse is strictly between two thresholds.
Each laser pulse removes a certain thickness of the contaminated layer. If the contaminated layer is thick, multiple pulses are required for cleaning. The number of pulses required to clean the surface depends on the degree of surface contamination. An important result produced by the two thresholds is the self-control of cleaning. Light pulses with an energy density above the first threshold will always reject contaminants until the substrate material is reached. However, because its energy density is lower than the destruction threshold of the substrate material, the substrate is not damaged.
5. Practical application of laser cleaning
Laser cleaning can be used not only to clean organic contaminants, but also to clean inorganic materials, including metal rust, metal particles, dust, etc. Here are some practical applications. These technologies are very mature and have been widely used.
5.1 Cleaning of the mold:
Every year, tire manufacturers around the world manufacture hundreds of millions of tires. The cleaning of tire molds must be fast and reliable during production to save downtime. Traditional cleaning methods include sandblasting, ultrasonic or carbon dioxide cleaning, but these methods usually have to be cooled in a hot mold for several hours, then moved to a cleaning device for cleaning, which takes a long time to clean and easily impairs the accuracy of the mold. Chemical solvents and noise can also cause safety and environmental issues. The laser cleaning method is very flexible in use because the laser can be transmitted by using an optical fiber; since the laser cleaning method can use optical fiber connection to clean the light guide to a dead angle of the mold or a portion that is difficult to remove, it is convenient to use; No gasification, so no toxic gases will be produced, which will affect the safety of the working environment. The technology of laser cleaning tire molds has been widely used in the tire industry in Europe and the United States. Although the initial investment cost is high, the benefits obtained by saving standby time, avoiding mold damage, working safety and saving raw materials can be quickly recovered. According to Quantel's LASERLASTE laser cleaning system, the cleaning test on the production line of Shanghai Dianqian Heavy Duty Truck Co., Ltd. shows that it can clean the mold of a large truck tire in just 2 hours. The economic benefits are obvious compared to conventional cleaning methods.
The anti-adhesive elastic film layer on the food industry mold needs to be replaced regularly to ensure hygiene, and laser cleaning without chemical reagents is also particularly suitable for this application.
Previous page next page
Galvanized Metal Watering Can,Galvanized Striped Large Watering Can,Galvanized Steel Watering Can,Semi-Circular Galvanized Metal Watering Can
xiacun factory , https://www.xiacunmetal.com