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Fiber laser VS CO2 laser, see here for in-depth comparison

Views:0     Author:hu     Publish Time: 2021-08-24      Origin:dapeng

Market sales and trends of laser cutting machines


At present, there are two main types of metal sheet metal cutting laser cutting machines in the sheet metal processing industry. One is a CO2 laser cutting machine that was transformed from an industrial laser into a product about 20 years ago, and the other is a CO2 laser cutting machine that was officially converted from an industrial laser about 5 years ago. Fiber laser cutting machine transformed from industrial laser into product. Judging from the number of laser cutting machines sold in China's sheet metal equipment market in recent years, CO2 laser cutting machines accounted for 40% and fiber laser cutting machines accounted for 60%. Although in 2007, 100% of the laser cutting machines sold in the market were basically CO2 laser cutting machines, we know that in recent years, the momentum of fiber laser cutting machines has been fierce, and they are continuously being recognized by the market, and the number of sales is gradually expanding. .


  The basic difference between CO2 laser and fiber laser


  Although the current market trend is towards fiber laser cutting machine, is fiber laser cutting machine really the best choice? CO2 laser and fiber laser have different physical characteristics of the laser, so the laser processing technology is also different. Of course, in fact, the two have their own strengths and weaknesses. According to the different processing objects, each has advantages and disadvantages.


The CO2 laser is a gas beam obtained by exciting carbon dioxide molecules, and its wavelength is 10.6μm; while the fiber laser is a crystal of Yb (ytterbium) compound inserted as a medium in the optical fiber, and the crystal is irradiated with the beam. The solid-state laser has a wavelength of 1.08μm. The physical characteristics of different wavelengths have a great influence on the processing characteristics of the two.

  The concept of fiber laser was originally recognized because it was a laser that can propagate through optical fibers. The reason for being able to propagate through optical fiber lies in its wavelength. It is precisely because of its 1.08μm wavelength that it can propagate through optical fiber. The advantage of using optical fiber for transmission is that its optical components have a longer service life and higher maintenance performance.

  CO2 laser cutting machine transmits the laser light from the vibrator to the processing point by means of a reflector, generally in the optical path isolated from the outside air. Although the light path is filled with air without ordinary dust or foreign matter, the surface of the reflector will be attached to it after a long period of use, and it needs to be cleaned. In addition, the reflector itself is also lost due to absorbing a small amount of laser energy, and needs to be replaced. In addition, to propagate the laser light from the vibrator to the processing point, multiple mirrors are needed to adjust the reflection angle of the laser light to propagate. Therefore, to maintain normal operation, certain technical capabilities and management are required.

  However, from the vibrator to the processing point of the fiber laser cutting machine, the laser is propagated through one optical fiber. This fiber is generally called a light guide fiber. Since there is no need for optical parts like mirrors, and the laser light is transmitted in the light guide fiber isolated from the outside air, the laser light is almost not lost, but strictly speaking, the laser light propagates repeatedly on the periphery of the light guide fiber , So the light guide fiber itself will have some loss, but compared with the mirror in the CO2 laser cutting machine, the service life is several times longer. In addition, if the propagation path is above the minimum curvature of the light guide fiber, the path can be determined freely, so it is very convenient to adjust and maintain it.

  In the laser generation process (laser vibrator structure), the two are also different. The CO2 laser oscillator generates laser light by placing the gas mixed with CO2 in the discharge space. In order to ensure the normal operation of the resonance length derived from the laser output power, optical parts are arranged inside the vibrator, and the optical parts inside the vibrator need to be cleaned and replaced regularly.

  Fiber laser oscillator, as mentioned earlier, the laser is generated inside the optical fiber and is isolated from the outside air. There are no optical parts, so there is almost no need for regular maintenance.

  The cleaning and maintenance cycle of the CO2 laser oscillator is set at about 4000 hours, while the fiber laser oscillator is set at about 20000 hours. The aforementioned aspects of service life and maintenance performance can be said to have great advantages for fiber laser cutting machines.

  In addition, we can also try to compare from the perspective of operating costs such as power consumption. The photoelectric conversion rate of the CO2 laser oscillator is said to be about 10-15%, while the fiber laser oscillator is about 35-40%. Due to the high photoelectric conversion rate, less electrical energy is converted into heat dissipation, and the fiber laser cutting machine can control the power consumption of cooling devices such as coolers to be lower. Generally speaking, the vibrator of fiber laser cutting machine requires higher precision for the cooling temperature management of the vibrator than the CO2 vibrator. However, under the same laser output power, the vibration of the fiber laser cutting machine The cooling capacity of about 1/2 to 2/3 of the CO2 laser oscillator for the device is sufficient. Therefore, considering the power consumption of all devices of the laser cutting machine, the fiber laser cutting machine can run at about 1/3 of the power consumption of the CO2 laser cutting machine, which can be said to be a very energy-saving laser cutting machine.

  The difference in processing characteristics


  In the processing of CO2 laser and fiber laser, there is a big difference between the two because of their different wavelengths.


When processing stainless steel materials, the comparison chart of the processing speed of CO2 laser cutting machine and fiber laser cutting machine. The output power of the laser is 4kW. We can see that in the field of plate thickness below 4.0mm, the fiber laser cutting machine can process at 2 to 3 times the cutting speed of the CO2 laser cutting machine.


  Why is there such a big gap in processing speed even at the same output power? First of all, it can be said that there is a big difference in the absorption rate of laser energy to metal materials. Not only metal materials, but everything in the world, due to the different physical properties of matter, the absorption rate of light energy is also different at different wavelengths of light. For example, the above-mentioned stainless steel material has an absorption rate of about 12% for CO2 lasers, and an absorption rate for fiber lasers of about 35%, a difference of about 3 times. The so-called high absorptivity means that after the laser is irradiated to the metal material, the time for the step of melting the metal material after the light energy is converted into heat energy is very short, so the cutting process can be formed at a very fast processing speed.


  If you want to use a laser cutting machine to cut quartz glass, then a CO2 laser cutting machine can be used for cutting processing, but a fiber laser cutting machine cannot be used for cutting processing. This is caused by the physical principle that quartz glass can absorb the wavelength of CO2 laser, but instead of absorbing the wavelength of fiber laser, it will penetrate. In addition, what we usually call fiber lasers is more advantageous than CO2 laser cutting machines in the cutting of highly reflective materials such as aluminum and copper. This is also because metal materials can better absorb the physical characteristics of the wavelength of fiber lasers.


  When comparing the processing speed of stainless steel materials, we can see that the processing speed of the two is basically the same in the area where the plate thickness exceeds 6.0mm. From the perspective of the cutting process, it is more important to refer to the coefficient of how to remove the molten metal more efficiently than to refer to the coefficient of the instantaneous molten metal. When cutting with laser, it is necessary to spray auxiliary gas (generally refers to nitrogen, oxygen, etc.) to the processing point while irradiating the laser to the material, so that a good processing state can be obtained. The auxiliary gas used is different for different cutting object materials. In addition, another major function of the auxiliary gas is to isolate the molten metal from below the material. In the case that the processing object is a thick plate, in order to obtain a good cutting state, the auxiliary gas is required to function to isolate the metal to be melted from under the lower part of the material, and finally the effect of increasing the processing speed can be achieved.


  However, from the point of view of processing field and cutting quality, CO2 laser cutting machine can be said to be even better. The CO2 laser processing machine has experienced about 30 years since its practical application in the industry. Many characteristics of its processing technology have been thoroughly studied by everyone, so it has been able to correspond to the processing field from thin plate to thick plate. In addition, the processing technology is also very mature, which can guarantee a certain processing quality. It not only has the processing technology for cutting various shapes, but also has the processing technology to ensure that the cut surface reaches a certain roughness.


  The cutting process with fiber laser cutting machine still has some problems that have not been solved in ensuring the cutting quality. Especially in the area where the plate thickness exceeds 3.0mm, the products processed by the fiber laser cutting machine will have some obvious small particles attached to the surface under the cutting surface and difficult to peel off. These small particles are what we often call scum. In addition, the cutting surface is also rougher than the CO2 laser cutting machine. This is the phenomenon caused by the high absorption of metal materials mentioned above. Laser processing is a process in which laser light is reflected to the surface of the material, and then the metal is melted and then dropped. When the fiber laser is reflected on a metal surface with a relatively high absorptance, it will cause back absorption to melt the metal on the cut surface, resulting in a rough cut section after cutting.

Processing quality is one of the items that is difficult to quantify, so many customers do not pay much attention to laser cutting machines. However, the scum problem mentioned above is related to processing quality. Even if the speed of the fiber laser cutting machine becomes faster, the cost is controlled very low. After the laser cutting process, if the subsequent processes such as removing scum are required, the total processing cost is about the same as that of the CO2 laser cutting machine. This means that everyone needs to pay more attention to the processing quality of laser cutting machines.


  Motion performance of laser cutting machine


  Although I have compared the concept of fiber laser and CO2 laser, when choosing a laser cutting machine, can I just make this comparison? The concept of optical fiber and CO2 has always been a comparison of the constituent elements of a laser cutting machine-a vibrator. There are also drive shafts called X, Y, and Z in the composition system of the laser cutting machine. The motion performance and control performance of this drive shaft are also a big constituent element.


  In addition to round holes, square holes, and rectangles, the shapes processed by the laser cutting machine also have complicated appearance shapes such as irregular holes, wedge shapes, and bumps. Therefore, no matter how fast the processing speed is, if the motion performance of the XY drive axis that determines the processing shape is low, there is no hope for shortening the processing time. Assuming that the processing speed is 40m/min with a fiber laser machine, and the processing speed is 20m/min with a CO2 laser cutting machine, the processing time of the fiber laser machine will be because its speed is twice that of a CO2 laser cutting machine. So when processing a certain shape, the processing time is also 1/2 of the CO2 laser cutting machine? If the processed shape is complicated and the number of processed holes is large, the answer becomes NO. To clearly reflect the poor processing speed, it is necessary to improve the motion performance of the drive shaft, especially the acceleration and deceleration capabilities during cutting.


  Comprehensive capabilities of laser cutting machine


  With high acceleration and deceleration performance, a strong, high-rigidity frame that can withstand its motion performance is also required. In order to maintain the processing accuracy of the product, it is necessary to control the internal structure of high mobility. To maximize the laser processing capabilities of the vibrator, it is necessary to improve the comprehensive capabilities of the laser cutting machine including the drive shaft.


  Because the components of the fiber laser cutting machine are relatively simple, when considering the design and manufacture of the laser cutting machine, without laser processing technology, a certain quality fiber laser cutting machine can be manufactured. In addition, many components of the fiber laser cutting machine are available on the market, and the cutting machine made by assembling these components is basically not inferior in processing capacity. This is one of the reasons why manufacturers of fiber laser cutting machines have been flooded recently.


  But in the CO2 laser cutting machine, a lot of processing technologies such as laser transmission are required, so differences in characteristics and performance between various cutting machine manufacturers are prone to appear. The manufacturer of a real laser cutting machine should have mature technology and the ability to design and manufacture CO2 laser cutting machines, and the processing technology accumulated from the production of CO2 laser cutting machines can be used to design and manufacture fiber laser cutting machines. Such a processing technology manufacturer is what the processing machine market needs in the future.


  Although processing accuracy and processing quality are difficult to express with numerical values, a laser cutting machine that can always maintain high processing accuracy and processing quality, and also has very high motion performance, is the best choice. However, it is necessary to make a calm judgment based on the processing content before making a decision. If there are more thin plates in the processed materials, the production volume is relatively large, and you want to control the processing cost, the fiber laser cutting machine is the best choice. However, if you need to process thick plates over 6.0mm in many cases, or need to achieve a certain processing quality, a CO2 laser cutting machine is more suitable. Subsequent operations need to be carried out by another process, and if manual operations are used, the total processing cost is very high. When choosing a laser cutting machine, in addition to judging the laser processing process, please make a comprehensive judgment from the perspective of your product and manufacturing.


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