Laser processing technology is a processing technology that uses the characteristics of the interaction between laser beams and substances to perform cutting, welding, surface treatment, drilling and micro-processing of materials (including metals and non-metals).
Characteristics of laser processing technology
Compared with traditional processing technology, laser cutting technology has many advantages, so it is widely used. Especially in the development stage of new products, it has absolute advantages in the trial production of prototypes and the generation of small batches. Once the product drawings are formed, laser processing can be carried out immediately, and samples can be obtained in the shortest time. It has the following characteristics:
- The light spot is small, the energy is concentrated, and the heat-affected zone is small.
- No contact with the workpiece, no pollution to the workpiece.
- Free from electromagnetic interference, it is more convenient to apply than electron beam processing.
- The laser beam is easy to focus and guide, which is convenient for automatic control.
- Wide range: almost any material can be engraved and cut.
- Safe and reliable: Non-contact processing is adopted, which will not cause mechanical extrusion or mechanical stress to the material.
- Accurate and meticulous: the machining accuracy can reach 0.1mm.
- Consistent effect: ensure that the processing effect of the same batch is almost exactly the same.
- High-speed and fast: It can immediately carry out high-speed engraving and cutting according to the pattern output by the computer, and the speed of Laser Cutting is much faster than that of wire cutting.
- Low cost: not limited by the quantity of processing, laser processing is cheaper for small batch processing services.
- Small cutting seam: the laser cutting seam is generally 0.1-0.2mm.
- Smooth cutting surface: The cutting surface of laser cutting has no burrs.
- Small thermal deformation: laser processing has thin laser slits, fast speed, and concentrated energy, so the heat transferred to the cut material is small, and the deformation of the material is also very small.
- Suitable for the processing of large-scale products: the Mold manufacturing cost of large-scale products is very high, laser processing does not require any mold manufacturing, and laser processing completely avoids the collapse of the material when punching and shearing, which can greatly reduce the production cost of the enterprise Improve the grade of products.
- Material saving: Laser processing adopts computer programming, which can cut products of different shapes into materials, maximize the utilization rate of materials, and greatly reduce the cost of materials for enterprises.
Classification of lasers
The commonly used lasers in laser processing technology are YAG laser and CO2 laser. As an emerging laser technology, fiber laser is not as popular as the above two.
- 1. CO2 laser: The working substance is a mixed gas, the wavelength is 10640nm, it belongs to the mid-infrared frequency band, it is a continuous laser, the cutting surface is smooth during cutting, the cutting quality is good, and it can cut metal and non-metal;
- 2. YAG laser: The working substance is Nd-YAG, the wavelength is 1064nm, it is a pulse laser, and the heat-affected zone is very small, which is incomparable to other lasers. The wavelength of YAG laser is not easy to be absorbed by non-metal, so it cannot cut non-metal materials. Can cut metal.
03 Application of laser processing technology
1. Laser cutting
The material to be cut is irradiated with a high-power-density laser beam, so that the material is quickly heated to the vaporization temperature, and evaporates to form holes on the material to be cut. As the beam moves to the material, the holes are continuously formed with a narrow width (such as 0.1mm) left and right) to complete the cutting of the material. It is the most widely used in sheet metal cutting.
2. Laser welding
Laser welding is to use high-energy laser pulses to locally heat the material in a small area. The energy of the laser radiation diffuses to the inside of the material through heat conduction, and the material is melted to form a specific molten pool, which can realize spot welding, butt precision welding and stitch welding. , Seal welding, etc. Laser welding, using a laser beam with a lower power than cutting metal, melts the material without vaporizing it, and becomes a continuous solid structure after cooling.
3. Laser engraving
Laser engraving, also called laser marking or radium engraving, is an engraving method that uses high-energy-density laser to partially irradiate the workpiece to vaporize the surface material or undergo a chemical reaction of color change, thereby leaving a permanent mark. Play various characters, symbols and patterns, etc.
Laser engraving is characterized by non-contact processing, which can be engraved on any special-shaped surface without deformation and internal stress on the workpiece. It is suitable for marking metal, plastic, glass, ceramics, wood, leather and other materials. At the same time, due to the small size of the focused laser, the small heat-affected zone, and fine processing, it can complete some processes that cannot be realized by conventional methods. .
For metal materials:
Apart from the background color, the metal material can print three types of pattern text:
1. Colorless pattern text:
Use an ordinary laser marking machine to mark on ordinary iron materials, and the printed fonts have no color, and the patterned text is printed by knocking off the surface of the iron product. as follows
2. Type black font:
We usually call the black font black on aluminum oxide. This machine belongs to the mopa laser marking machine. Ordinary fiber laser marking machines can also mark black on stainless steel, and it can be realized by adjusting the marking power and frequency.
3. Print color pattern text:
Materials suitable for color marking include stainless steel, titanium, chromium alloy plate and niobium, among which stainless steel is more commonly used than others, and the color can be printed by adjusting the power and marking frequency to the corresponding parameters.
Its principle is mainly:
- 1) Stainless steel is oxidized to form a layer of colored oxide layer when the surface is melted by laser at high temperature;
- 2) Under the action of chemical, electrochemical or laser, a very thin colorless and transparent oxide film is formed on the surface of stainless steel, and the oxide film produces an interference effect, which can show color on the surface;
- 3) There is a mixed state of colored oxide and oxide film at the same time.
- 4) Under the continuous action of the laser, the laser thermal effect is generated on the surface of the stainless steel. Through the laser thermal effect, it is obtained that the laser energy density is proportional to the thickness of the film. As the laser energy increases, the color of the stainless steel surface shows regular changes: yellow, red, blue, green until the green gradually becomes darker. By controlling the laser energy density, the desired color can be printed on stainless steel products.
For example, the main component of the black mark marked on the surface of stainless steel is ferric oxide or iron oxide, while the green is manganese monoxide. If you need to change the color of the laser marking text on the stainless steel, you can change the photothermal effect between the laser and the stainless steel by adjusting the energy density of the laser emitted by the laser. Different power and different oxide film thickness will change the color of the marking characters.
However, due to many reasons such as immature color laser marking technology and high price, it has not been widely used in industrial production.
04 Laser drilling
Some parts need to process holes with small diameters, especially in materials with high hardness and high melting point. I am afraid that it is not easy to do it with ordinary machining tools. Even if it can be done, the processing cost will be very high. However, with The solution of laser drilling is very easy to do.
Compared with conventional drilling methods, laser drilling has the following significant advantages:
- The laser drilling speed is fast, the efficiency is high, and the economic benefit is good.
- Laser drilling can obtain a large depth-to-diameter ratio.
- Laser drilling can be performed on various materials such as hard, brittle and soft.
- Laser drilling without tool loss.
- Laser drilling is suitable for group hole processing with large quantity and high density.
- Small holes can be processed on the inclined surface of difficult-to-machine materials with laser.
For punching holes in metal parts, it can also be done by metal etching.