Laser cutting involves using a laser beam to heat, melt and vaporize the material to be cut. The molten material is then blown with high-pressure gas to create a hole, and the beam continues to move along the material, forming a continuous cutting seam.
For most thermal cutting techniques, with the exception of some cases that may start at the edge of the sheet, it is necessary to create a small hole in the sheet before cutting can begin. The cut then proceeds from this small hole.
Laser drilling principle
The basic principle of laser drilling is that when a laser beam with a certain amount of energy is directed at the surface of a metal plate, a part of it is reflected, while the rest of the energy is absorbed by the metal. This leads to the melting of the metal and the formation of a weld pool.
The absorption rate of molten metal from the metal surface increases, allowing it to absorb more energy and speed up the melting process.
Proper control of energy and air pressure can be used to remove molten metal from the molten pool and continually deepen it until the metal is penetrated.
In practical applications, drilling is generally divided into two methods: pulse drilling and blast drilling.
01. Wrist piercing
The principle of pulsed drilling is to use a pulsed laser with high peak power and low duty cycle to irradiate the plate to be cut, melting or vaporizing a small amount of material, which is then discharged from the hole through the joint action of continuous beating. and auxiliary gas, penetrating the plate step by step.
The laser irradiation time is intermittent and the average energy used is relatively low, resulting in less heat absorption by the processed materials. As a result, there is less residual heat and debris around the drilling, and the through hole is small and regular, with minimal impact on the initial cut.
The process is shown in the following figure: after the laser beam irradiates the part, the material surface is first heated (as shown in A). As heating gradually deepens, perforation occurs (as shown in B W D) until penetration is achieved (as shown in E).
The entire drilling process is carried out gradually, step by step, until penetration is achieved. Therefore, the drilling time of this method is relatively long. However, the holes obtained are smaller and have less thermal impact on the surrounding areas.
02. Sandblasting drilling
The principle of blast drilling involves irradiating the target object with a continuous wave laser beam of a certain energy, causing it to absorb a significant amount of energy and melt, thus forming a pit. Then, with the aid of an auxiliary gas, the molten material is removed to create a hole, thus achieving the objective of rapid penetration.
However, due to continuous laser irradiation, the blast hole diameter is relatively large and the splash is severe. Therefore, it is not suitable for cutting applications that require high precision.
The entire process is shown in the figure above: adjust the focus higher than the surface of the material and increase the perforation opening for rapid heating.
Although this drilling method produces a considerable amount of molten metal that is sprayed onto the surface of the processed material, it can significantly reduce drilling time.
The actual effects of the two drilling methods are shown in the figure below.
In most cases, the quality of pulse drilling is superior to blast drilling.
