A comprehensive analysis of technology characteristic of laser cutting machine

A comprehensive analysis of technology characteristic of laser cutting machine

With the development of laser technology and mature, laser equipment has been widely application in all walks of life, such as laser marking machine, laser welding machine, laser drilling machine and laser cutting machine, and so on, especially CNC laser cutting machinery and equipment in recent years rapid development, is widely used in sheet metal, metal products, steel structure, precision machinery, auto parts, glasses, jewelry, nameplate, advertisement, arts and crafts, electronics, toys, packaging and other industries. Compared with other cutting equipment, CNC laser cutting machine is mainly reflected in the following aspects:

1, with high cutting speed, cutting quality is good, high precision;      
2, cut line is narrow, the cutting surface is smooth, does not damage the work piece;          
3, not affected by the shape of the workpiece, the material is not affected by the hardness;          
4, in addition to the processing of metal materials, but also for non metal cutting processing;          
5, saving investment, saving materials, more effective cost savings;      
6, the operation is simple, safe, stable performance, improve the speed of new product development, with a wide range of adaptability and flexibility.

Mechanical structure of metal CNC laser cutting machine is the most important part, not only most of the components are installed in the rack, and also the work gravity and acceleration and deceleration during the full impact loads.

CNC laser cutting machine design and development work including:

1, determine the CNC laser cutting equipment in a variety of conditions and the environment of fast, high precision, stable operation of the conditions.       2, according to the functional requirements of the frame structure, parameters, combined with the structural characteristics of the laser cutting machine, the establishment of the corresponding dynamic model.          
3, the structure and parameters of the frame are studied, the influence of the parameters on the static and dynamic stiffness and thermal stability of the frame are studied, and the theoretical basis for the design of the frame is provided. 4, determine the frame and other parts of the mutual coupling relationship

Therefore, CNC metal cutting machine designed in how to arrange the metals to reduce weight, increase body stiffness, reduce the effects of temperature change on accuracy, it is necessary to focus on the problems in the design process.
Therefore, in CNC metal cutting machine design how reasonable layout of metal, reduce weight, improve the body stiffness, reduce the influence of temperature change on the accuracy, is should be focus on the problem of the design process.
In the metal cutting laser circuit, there is a strong interference between analog signal and digital signal problem. Photoelectric isolation circuit is in electrical isolation to light for coal medium of transmission signal, the input and output circuit can isolate. So it can effectively suppress noise in the system, to clear the earth loop interference, responds faster, long service life, small volume, shock resistance etc. the benefits the in the strong - weak interface, especially in microcomputer system of backward and to the channel obtained widely application.

Photoelectric coupler has three characteristics:          
1, the signal is transmitted to take the form of electric light electricity, the light emitting part and the light receiving part are not in contact, which can avoid the feedback and the interference of the output end to the input end;     2, the ability to suppress noise interference;          
3, with a durable, high reliability and high speed and other advantages, the response time is generally within a few, the response time of high-speed optoelectronic coupler and some even less than 10ns.
Therefore, in the numerical control laser cutting machine system circuit design, should pay attention to the isolation of the input signal circuit and SCM connection. Here, the use of photoelectric coupling is the most commonly used method.
In the industrial manufacturing system of heavy metal processing industry, a lot of metal materials, no matter what kind of hardness it is, can be carried out without deformation cutting. Of course, for high reflectivity materials, such as gold, silver, copper and aluminum alloys, they are also good heat transfer conductor, so the laser cutting machine is difficult, and even can not be cut.
In spite of the laser cutting machine specific technology was a huge advantage, but as a high-tech equipment to use laser cutting machine to achieve the ideal cutting and processing effect, must also master the processing technical parameters and operation processes. Especially in the metal laser cutting machine cutting process, to select the appropriate cutting speed, or may cause some undesirable cutting results, mainly in the following:
1, when the laser cutting speed is too fast, it will cause the following adverse results:          
①.Method of cutting, spark spraying;          
②.The cutting surface is inclined to the lines, and the lower part of the production of molten stains;          
③.Cause the whole section is rough, but no melt stain is produced;
2, on the contrary, when the laser cutting speed is too slow, it will cause:   ①.Melting condition, the cutting surface is rough.          
②.The slit width, in sharp parts of the whole.          
③.Affect the cutting efficiency.
Therefore, in order to make the laser cutting machine equipment to better play its cutting function, you can cut the spark from the laser equipment to determine whether the feed rate is suitable:          
1, if the spark from the top down, it indicates that cutting speed is appropriate;          
2, if the spark back tilt, it indicates that the feed rate is too fast;       3, if the spark is not diffusion and less, together, it indicates that the speed is too slow.          
Most organic and inorganic materials can be used as laser cutting machine. Compared with other traditional cutting methods, laser cutting has obvious advantages compared with other traditional methods. Laser cutting machine has the characteristics of narrow slit, small deformation of the workpiece and high speed, high efficiency, low cost, safe operation, stable performance and so on.

Several major problems of laser cutting thick metal plate

Several major problems of laser cutting thick metal plate

Laser processing, as an advanced material cutting method, has been more and more accepted by the sheet metal producers. With the progress of computer control technology and optical technology, increasingly high expectations for its processing capacity, looking forward to this is not only to cut, it is to cut and sliced expectations. But can give the answer of course can not be separated from the processing machine performance, while the quality of processed materials directly affect the effect of the answer.
Laser processing started earlier in the Europe and the United States and Japan, in the eighties of the last century began by laser processing machine manufacturers of steel production put forward specific quality requirements, and the difference from the ordinary steel but the price is on the high side of laser special steel. And with the laser processing as the main cutting tool is accepted, 25mm the following common steel plate on the laser professional materials as a standard material. However, due to China's development is too fast, too late to adapt to the production of steel, there is a difference between China's steel and imported steel. The main difference is that the content of impurities in steel and the processing of steel surface and transport custody and a series of reasons, resulting in the current situation of Chinese sheet metal cutting.
Today, China's crude steel production is not only the world's first, is more than 50% of global output, developing countries, and even some like Australia, South Korea and other developed countries in order to save costs also used in a large number of board of China, so instead of expecting China steel to adapt to laser cutting as research and put forward to quality processing of inferior materials methods and proposal. Some of these ideas are presented in this paper.
Problems encountered in the processing of medium and heavy plate
1.Carbon steel plate perforation in processing thick plates perforated time accounted for a large proportion, the laser manufacturers have developed a technique for rapid perforation, more representative is high-energy perforation (hole), the advantages of this method is fast (1 second, to t16mm as an example, following the same), but the drawback is that the enormous energy not only affects the processing of small shape, perforation injection of the plate temperature elevated and the impact on the rest of the whole cutting process. With a small power pulse perforation, then a long time (12 seconds), will lead to the cutting efficiency and the unit cost of the increase.
2.Cutting surface quality problem          
Figure 1 and Figure 2 shows a section cutting processing plate often meet, such cutting not only product quality has been questioned, but also with the slag sticking of burn and severe, that reflected not expensive laser processing machine difference to other ways of cutting the value.

3.Stability of whole plate processing          
In the whole process of domestic steel, there will often be a local area of the phenomenon of poor processing. This kind of phenomenon is sometimes very random, even if the machine is in good condition, it will appear. In order to deal with the local fault products and greatly affect the whole work progress, this is not the cause of the processing failure also gives some of the author's analysis and countermeasures.

Solutions of the above problems
1.Peak perforation (HPP) scheme          
As the name suggests is the use of a small duty cycle of the peak pulse laser, combined with the material on the surface of the fuel injection is not fuel to clear the opening edge of the attachment, the reasonable frequency of the control pulse edge cooling edge. Is characterized by relatively deep hole, although a slightly longer time (3 seconds), but penetrated aperture small (about diameter 4mm) and open hole edge without attachments and into the heat is low, to facilitate the next normal cutting, compared to ordinary perforated is to improve the efficiency of 4 times. Figure 3 shows the difference between an ordinary perforation, a HPP perforation, and a high energy punch.

2.Cutting section improvement program          
For the carbon steel, the important factor to improve the cutting section is to control the heat input to the plate and to ensure the full combustion of the laser irradiation. MITSUBISHI motor development K-CUT processing conditions better to complete the mission. Fig. 4 Comparison of the effects of traditional and K-CUT conditions on the same piece of domestic plate. For stainless steel, the important factor to improve the cutting section is the improvement of the beam (improving the depth of focus) and the effective utilization of the auxiliary gas. The bright surface cutting technique is to improve the results obtained by the oscillator and the nozzle. Figure 5 is the effect after improvement. The lower part of the upper part of the section of rough 8 mu and 12 Mu as mechanical processing.

3.Scheme to ensure processing stability          
At present, in order to improve the running speed of the processing machine, the laser machine adopts the structure that is called the flight light path, that is, the material tray does not move and the processing head can move in the whole processing area. In order to compensate for the change of the relative position of the working head and the light source, the manufacturers can also ensure the consistency of the light spot in the range of processing. Although this method has simple structure, it will change the depth of focus, so that in the depth of the depth of the plate is very sensitive to cutting the thick plate will appear to be inadequate (both to keep the light spot and keep the focus depth constant). MITSUBISHI motor using the same length of light path (in the range of light source and the processing of the optical path between the processing head) can avoid the depth of focus changes, so that the spot and the depth of focus are consistent. In addition, the heat gained by the hot plate is controlled, which can solve the stability problem. Figure 6 shows the principle of long path and in the processing area at different points in the processing effect.

Take seriously the problems in the process, study the mechanism and find the solution to the problem. Through the traditional laser technique, a series of exploration and improvement, for more complex plate cutting developed new technology and its application to the ex plus, Rx, XL, etc. series of products, to meet the actual needs of customers in the domestic plate materials processing, thereby greatly improving the production efficiency. We will further efforts to explore new technologies to solve more difficult problems in the processing of the majority of users.

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The essential difference between the four types of laser cutting technology

The essential difference between the four types of laser cutting technology
Laser cutting is irradiated materials rapidly melting, vaporization and ablation or achieve ignition, with high power density laser beam irradiating a work, at the same time with coaxial with the beam of high speed airflow blow in the molten material, so as to realize the workpiece cut. Laser cutting is one of the hot cutting methods.
Laser cutting can be divided for laser vaporization cutting, laser fusion cutting, laser oxygen cutting and laser scribing and breaking control four categories.

1.Laser vaporization cutting
Using high energy density of laser beam heating the workpiece, so that the temperature rose rapidly, in a very short period of time to reach the boiling point of the material, the material began to vaporization, the formation of steam. The steam jet is very large, and in the same time, it forms a notch on the material. The vaporization heat of the material is generally very large, so the laser vaporization cutting requires a great deal of power and power density.
Laser vaporization for cutting thin metal materials and nonmetal materials. (such as paper, cloth, wood, plastic, rubber, etc.)

2.Laser melting and cutting
Cutting laser melting and laser heating to melting of metal materials, followed by blowing a non oxidizing gas (AR, he, N, etc.) and beam coaxial nozzle, gas rely on the strong pressure of the molten metal is discharged, the formation of incision. Laser melting and cutting does not require the complete vaporization of the metal, the energy required for vaporization of the 1/10.
Laser melting and cutting are mainly used for the cutting of materials or active metals, such as stainless steel, titanium, aluminum and its alloys.

3.Laser oxygen cutting
The principle of laser oxygen cutting is similar to that of oxygen acetylene cutting. It uses a laser as a heat source, with oxygen and other active gas as the cutting gas. On the one hand, the injection of the gas and the cutting metal, the oxidation reaction, the release of a large number of oxidation heat; on the other hand, the molten oxide and melt blown out from the reaction zone, the formation of the incision in the metal. Because of the oxidation reaction in the cutting process produces a lot of heat, so the energy required for laser oxygen cutting is only the melting of 1/2, and the cutting speed is much larger than the laser vaporization cutting and melting cutting.
Laser oxygen cutting is mainly used for metal materials and heat treatment of carbon steel, titanium steel oxidation.

4.Laser scribing and breaking control
Laser scribing is the high energy density of laser scanning on the surface of brittle materials, the material is heated to evaporate a small groove, and then applying a certain pressure, brittle materials will be along the slot at the split. Laser laser scribing generally used for Q switch and CO2 lasers.
The control fracture is the steep temperature distribution generated by the laser engraving, which produces the local thermal stress in the brittle material, which causes the material to be broken along the small groove.

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Safe operation of laser cutting machine

Safe operation of laser cutting machine

When laser cutting machine working,the failure is dangerous.Novice must undergo professional training in order to operate independently, the following to learn the 13 details of laser cutting machine safety work. 

1.Please follow the general cutting machine safety operation rules.Please start the laser in strict accordance with the laser start procedure. 

2.The operator must be trained to be familiar with the structure and performance of the equipment, and to master the relevant knowledge of the operating system. 

3.Wear good labor protective equipment according to regulations, must wear the protective glasses in line with the provisions in the vicinity of the laser beam.

4.Pls don't working the material when be not sure if it is suitable for laser,invoide producing the harmful fumes and vapors.

5.Operator is not allowed to leave the position when the equipment is running, if need to leave, please stop or cut off the power switch. 

6.Please put fire extinguishers in your fingertips; stop processing, please turn off the laser or optical gate; do not put paper, cloth or other flammable substances in the unprotected laser beam around.

7.When the abnormal appearance in the processing process, should be immediately shut down, in a timely manner to eliminate the failure or reported to the competent personnel. 

8.Keep the laser, bed and around the site clean and orderly, no pollution, waste, according to the provisions of the workpiece, sheet piling. 

9.When using gas cylinders, should avoid crushing welding wire, so as to avoid leakage accident. The use of gas cylinders, transport should comply with the rules of gas cylinders. The ban of gas cylinders in the sun or near the heat of the sun. When the valve is opened, the operator must stand on the side of the bottle mouth. 

10.Please observe the high pressure safety rules when repare laser machine.Follow the rules and procedures for 40 hours or one week per operation, 1000 hoursor six months of maintenance. 

11.After the boot, please first manual low speed Y, X direction of the machine, check to confirm whether there is abnormal situation. 

12.The new work program input, please try to run, and check its operate situation. 

13.During the work, observe the operation of the machine, so as to avoid the cutting machine out of the effective range or two sets of collision caused the accident.

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Effect of laser output power on laser cutting

Effect of laser output power on laser cutting 
When using laser cutting machine,the laser output power is a parameter that has a direct relation with the melting ability of the processed. For getting good effect of cutting,we need increase the output power in order to improve the processing ability.

Improve processing capacity:
1, improve the laser cutting speed.          
2, increase the thickness of the processing plate.          
3, processing of aluminum, copper and other high reflection spectral reflectance factor.          
4, zoom lens from the short focal length lens.          
5, the focus of the location from the surface of the processed material changes.

We can determine whether the use of the processing conditions of the output energy is appropriate, according to the processing of the cutting surface and machining in the case of the spark. When the output power is much larger than the standard value, the thermal effect of the incision increases, and the melting loss occurs at the corner. And cut the noodles to become thick, from the upper to the lower part of the vertical.
If the output power value is far less than the standard value, the lower part of the cut is significantly thicker, become the state of digging into. And with the increase of the amount of adhesion of slag, it is difficult to remove. Mars is lagging in the cutting process in the opposite direction in the cutting process.
Suitable for the processing of the output conditions exist within a certain range, the thinner the thickness of the processing board, the wider the range of output conditions. Output processing in proper conditions, the cutting surface streak fine, lower relative to the speed of light slow.

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Common problems and treatment methods in laser cutting

Common problems and treatment methods in laser cutting

1.Any kind of thermal cutting technology, in addition to a small number of cases can be from the edge of the board, the general must wear a small hole in the board. Before the laser punching compound machine with a hole punch out first, and then again from the hole at the beginning of laser cutting. Basic method for two kinds of perforation of laser cutting machine without punching device:

Blasting perforation
After the material is irradiated by a continuous laser, a concave hole is formed in the center, and the oxygen flow from the laser beam is quickly removed to form a hole. And sheet thickness is related to the size of the hole and blasting perforation average diameter is half of the plate thickness, so for thick plate blasting perforation diameter larger diameter, should not require higher in precision machining parts, can only be used for waste. In addition, due to the use of oxygen pressure and cutting the same, the splash is larger.

Pulse perforation
Pulsed laser with high peak value is used for melting or vaporization of a small amount of material, air or nitrogen is used as an auxiliary gas to reduce the expansion of the pores due to heat release and the gas pressure is less than the oxygen pressure during the cutting process.
Each pulse laser produced only a small particle injection, and gradually deepened, so thick plate perforation time takes a few seconds. Once the perforation is completed, the auxiliary gas is changed to oxygen for cutting. The perforation diameter is smaller and the perforation quality is better than that of the blasting hole. The laser used in this system should not only have high output power, but also more important is the time and spatial characteristics of the beam, so the general cross flow CO2 laser can not meet the requirements of laser cutting. In addition, a more reliable pneumatic control system is needed in order to realize the gas type, gas pressure switch and perforation time control.In the case of using pulse perforation, in order to obtain high quality cut, from the workpiece at rest, the pulse perforation to the workpiece constant velocity continuous cutting transition technology should be paid attention to. Theoretically, it is usually possible to change the cutting conditions of the accelerating section, such as the focal length, the position of the nozzle and the gas pressure, but in fact, the possibility of the above conditions is not very much due to the time is too short. In the process of industrial production, the method of changing the average power of laser is used to compare the reality, the specific method is to change the pulse width, change the pulse frequency, and change the pulse width and frequency.

2. cutting holes (diameter and thickness) analysis of deformation
This is because the machine (only for high power laser cutting machine) in machining holes not take the blasting perforation, but with pulse perforation (soft puncture), which makes the laser energy in a very small area is too concentrated, non machining area was burned, cause deformation of the hole, the processing quality is affected. Then we should be in the process, pulse perforation (soft puncture) to blasting perforation (ordinary puncture) way to solve. For small power laser cutting machine is just the opposite, in machining should adopt way pulse perforation to achieve better surface finish.

3.when the laser cutting of low carbon steel, the solution to the work of burr
According to the working principle and design of CO2 laser cutting, and analysis the following reason is caused by machining burrs in the main reason: the laser focus on the position is not correct, need to be adjusted according to the focus position test, offset focus; the laser output power is not enough, need to check the laser generator is normal or not, if the normal, is to observe the effect of laser numerical control output button is correct, adjust the line; the cutting speed is too slow, the need to increase the line speed in operation control; the purity of cutting gas is not enough, need to provide high quality gas cutting work; laser focal shift, need to be adjusted according to the focus position test, offset the focus of the machine running time is too long; the stability, the need to shutdown and restart.

4.Laser cutting of stainless steel and aluminum plated zinc plate, analysis of the causes of burr formation.
The factors above, first consider the low carbon steel cutting burr, but not simply accelerate cutting speed, because increased speed sometimes sheet cutting not to wear, this kind of situation in processing aluminized zinc plate is particularly prominent. At this time should be integrated into other factors to consider the machine to solve, such as whether the nozzle to replace, rail movement is not stable, etc..

5.Analysis of laser machine can not cut through
Analysis revealed that several of the following is instable processing of: laser head nozzle selection and processing board does not match the thickness; laser cutting line speed is too fast, need to operate the control lines are reduced speed; in addition, also need to pay special attention to, in the laser cutting machine cutting more than 5mm carbon steel needs to be replaced laser lens focal length of 7.5 ".

6.Method for solving non normal spark in cutting low carbon steel
This situation will affect the cutting section of the parts finish machining quality. At this time, in the case of other parameters are normal, should consider the following: laser head nozzle loss, should be promptly replace the nozzle. In the case of no new nozzle replacement, the cutting work gas pressure should be increased; the nozzle and the laser head are connected at the screw thread. At this point should be immediately suspended cutting, check the laser head connection status, re good thread.

7.Selection of puncture point in laser cutting
Laser cutting the working principle of the laser beam is: in the process, material after the irradiation of laser in the center of the formation a pit, and then by the work flow and laser beam coaxial soon will be molten material removal of the formation of a hole. This hole is similar to line cutting of the thread hole, laser beam on this hole for the processing of opening and starting point of contour cutting, usually under flight light path laser beam walk line direction and the parts to be machined vertically cutting contour tangent direction. Therefore, laser beam in began to penetrate the plate into the cutting contour parts of this period of time, the cutting speed in vector direction will have a great change, namely the direction vector of 90 degrees rotation by vertical to the cutting contour tangent direction turn and cutting contour tangent coincidence, and contour tangent angle is 0 degrees. In this way, the cutting surface of the processed material is relatively rough cut surface, which is mainly in the short time, the laser beam in the direction of the movement of the vector is very fast. Therefore, in the use of laser cutting parts, we should pay attention to this aspect of the situation. , in the design of components of surface cutting fracture no roughness can not to do manual processing in laser cutting programming, to control the software automatically generates the puncture point; however, when design of machining cutting section has higher roughness requirements, note to this problem, usually in series laser cutting program of laser beam starting position be manually adjusted, namely artificial for the puncture point of control. The need to produce the original laser puncture point program moved to the reasonable position of need, to reach the surface precision requirements of the processing parts.