As an important branch of laser processing equipment, CO₂cutting machine is widely used in the cutting field of metal and non-metal materials due to its high energy density and precise controllable characteristics. Its core principle is to use the specific wavelength laser generated by CO₂ laser, focus it through the optical system and act on the surface of the material to achieve efficient and precise cutting operations.
1.Core structure and laser generation mechanism
The core of CO₂ cutting machine is CO₂ laser, and its laser generation depends on gas discharge excitation mechanism. The resonant cavity of the laser is filled with a mixture of CO₂, nitrogen and helium, in which CO₂ is the activation medium, and nitrogen and helium play an auxiliary role. When the electrode applies a high-voltage electric field in the resonant cavity, the gas glow discharges, and the nitrogen molecules are excited to a high energy level by electron collision. The nitrogen molecules at a high energy level collide with the CO₂ molecules, transferring energy to the CO₂ molecules, causing them to transition from the ground state to a high energy level of vibration. When the high-energy CO₂ molecule transitions to the low-energy level, it releases an infrared laser with a wavelength of 10.6μm. This wavelength of laser has a strong absorption for non-metallic materials (such as wood, plastic, and cloth), and can also be absorbed by some metal materials.
After the laser is generated, it needs to be amplified and directed by the reflector system of the resonant cavity. The reflectors at both ends of the resonant cavity (a full reflector and a partial reflector) make the laser reflect and oscillate multiple times in the cavity, continuously enhancing the energy, and finally output a stable laser beam by the partial reflector.
2.Beam transmission and focusing system
The output laser beam needs to be transmitted and processed through a series of optical elements. First, the laser beam is enlarged in diameter by a beam expander, reducing the divergence angle and improving the parallelism of the beam. Then, the beam enters the reflector group, and by precisely adjusting the reflection angle, the laser is guided to the focusing lens of the cutting head.
The focusing lens is a key component for achieving high-precision cutting. Its function is to converge the parallel laser beam into a very small spot with a diameter of only tens of microns. According to the thickness and material of the cutting material, the focal length of the focusing lens can be flexibly selected (common focal lengths are 50mm, 100mm, and 127mm). The shorter the focal length, the smaller the diameter of the focused spot and the higher the energy density, which is suitable for fine cutting of thin materials; the longer the focal length, the greater the focal depth, which is suitable for cutting of thick materials.
3.Physical process of material cutting
When the high-energy-density laser spot acts on the surface of the material, it will trigger a series of physical and chemical reactions, and finally achieve cutting. The process can be divided into three stages:
- Material absorption and heating
After the 10.6μm infrared laser is absorbed by the surface of the material, the light energy is converted into heat energy. For non-metallic materials (such as acrylic and paper), the molecular vibration intensifies and the temperature rises rapidly to the melting point or even the boiling point; for metal materials, the surface metal absorbs heat and melts quickly, and part of the energy diffuses to the inside through heat conduction, but due to the concentration of laser energy, the heat-affected zone (HAZ) can be controlled at the micron level.
- Material removal mechanism
Depending on the type of material and the laser energy density, the cutting process presents different removal methods. For non-metallic materials (such as plastics and wood), the laser energy causes the material to vaporize or melt instantly, and the molten material is blown away from the cutting area by the auxiliary gas to form an incision; for metal materials (such as carbon steel and stainless steel), the high-energy laser first melts the metal, and at the same time, the high-pressure auxiliary gas (oxygen, nitrogen, etc.) ejected from the nozzle blows away the molten metal. Oxygen can also react with the metal to release additional heat and accelerate the cutting process.
- Cutting trajectory control
The movement of the laser beam is controlled by a two-dimensional workbench or galvanometer system driven by a CNC system. The workbench drives the workpiece to move along a preset trajectory, or the galvanometer controls the laser beam to scan on a fixed workpiece. The two work together to achieve cutting of complex shapes. The CNC system accurately controls the movement speed and laser switch through instructions such as G codes to ensure smooth incisions and accurate dimensions.
- Synergy of auxiliary systems
The efficient operation of the CO2 cutting machine is inseparable from the cooperation of the auxiliary system. The cooling system controls the temperature of the laser and optical components through circulating water cooling or air cooling to avoid performance degradation or damage caused by high temperature; the auxiliary gas system selects the gas type according to the material characteristics (such as nitrogen for anti-oxidation of stainless steel and oxygen for combustion of carbon steel), and controls the gas pressure and flow through precision valves; the exhaust system promptly discharges the smoke and dust generated during the cutting process to protect the health of operators and avoid contaminating optical components.
- Summary
The working principle of the CO2 cutting machine is a collaborative process of “energy generation – transmission – focusing – material action”: the CO2 laser generates a 10.6μm infrared laser, which is focused into a high-energy density spot by the optical system, acts on the surface of the material to melt or gasify it, and then removes the melt through the auxiliary gas, and finally completes the precise cutting under the control of the CNC system. This process combines high efficiency and high precision, making it a core equipment in the field of modern industrial cutting, especially in the processing of non-metallic materials.
