What Is A Laser?
“The laser cut clean through iron as though it were mud”, this is no exaggeration.
Let’s take a look at the laser first!
What is a laser?
The laser is a kind of enhanced light obtained by stimulated radiation.
Its basic characteristics:
- High intensity and high brightness
- Wavelength frequency determination, good monochrome
- Good coherence and long coherence length
- Good directionality, it’s almost a bunch of parallel light
When the laser beam is irradiated onto the surface of the workpiece, the light energy is absorbed and converted into heat energy, so that the temperature at the irradiation spot is rapidly increased, melted, and vaporized to form a small pit. The metal around the spots melts due to thermal diffusion. The metal vapor in the small pit rapidly expands, causing a micro-explosion, and the molten material is ejected at a high speed to generate a highly directional anti-shock wave, so that a hole with a large upper side and a small lower side is formed on the surface to be processed.
Comparison of ordinary lighting and laser:
The Generation of Laser
Laser Generating Gas
Laser generating gas is different from cutting gas.
Laser generating gas composition:
N2: The energy generated by the RF generator first excites N2, causing it to be in a transition state.
CO2: N2 in the transition state will excite C02 which causes CO2 to transition, and releases the laser.
He: Absorb CO2 and excess energy, cool the system and turn it into heat.
The proportional relationship between the above mentioned three gas is:
N2:CO2:He = 1:4:5
Definition of Laser Cutting
Laser cutting is a hot cutting method which makes use of the focused high power density laser beam as the main heat source to illuminate the workpiece, cause the irradiation materials rapidly melting, evaporation and ablation or reach the ignition point.
At the same time with the aid of high-speed airflow which coaxial with the laser beam to blow away molten material, so as to realize the cutting of the workpiece.
With the mature and perfect technology of high power fiber laser generator in recent years, its application field is expanding continuously, and the fiber laser cutting machine has become the hot spot of industry research and development.
In the area of thin plate cutting, traditional CO2 laser and YAG laser is gradually occupied by fiber laser generator, mainly for the following reasons:
⑴ Low cost. The photoelectric conversion efficiency of the fiber laser is about 30%, the photoelectric conversion efficiency of the CO2 laser is 6~10%, and the photoelectric conversion efficiency of YAG laser is only 3%.
In addition, the fiber laser generator has no vulnerable parts, and there is no late maintenance cost.
⑵ Optical fiber laser has a small volume, light weight, movable and flexible working position.
⑶ The adoption of flexible light guiding system of optical fiber laser and beam transmission distance is constant, fundamentally avoid poor cutting quality which caused by the length of the light path changes of the CO2 laser generator. It ensured the cutting quality consistency throughout the cutting width, especially suitable for large-format laser processing system;
⑷ The beam of optical fiber laser transmit along the optical fiber, without external reflected light path system, saving the cost of reflection lens, the organ shield, without external optical path adjustment, avoid the light path pollution by dirt, but also reduce the weight of the moving parts;
⑸ The wavelength of the optical fiber laser is 1.06μm, is more easily absorbed by the metal material compared with the wavelength of CO2 which is 10.6 μm and is especially beneficial for sheet metal cutting.
The sheet cutting speed is 2 ~ 4 times of CO2.
At the same time, it has a better cutting effect for high reflective material such as aluminum alloy, copper, copper and various copper alloys.
Laser Cutting Process
2) the laser beam
4) the line
5) molten material
6) cutting surface
8) cutting direction
A: Empty height
B: Puncture height
C: Cutting height
T: Sheet thickness
The world’s first laser cutting machine was born in the 1970s.
Over the past 30 years, with the continuous expansion of the application and continuous improvement of the laser cutting machine, many enterprises have been engaged in the production of various laser cutting machines to meet the demand of the market, including 2D plate laser cutting machine, 3D space laser curve cutting machine, pipe laser cutting machine.
The best laser cutting machine companies include:
Trumpf (Germany), Prima(Italy), Bystronic (Switzerland), Amada (Japan), MAZAK (Japan), NTC (Japan), HGLaserLab (Australia).
Laser cutting equipment can cut stainless steel below 4mm, and can cut up to 8 ~ 10mm thick stainless steel in laser beam if add oxygen.
However, when oxygenated, a thin oxide film is formed on the cutting surface.
The maximum thickness of cutting can be increased to 16mm, but the size error of the cutting part is larger.
Laser cutting equipment is very expensive, but it is still possible to use the device in large production because of the lower cost of subsequent processing.
Since there is no tooling cost, the laser cutting equipment is also suitable for small batches of parts that can not be processed previously.
Laser cutting equipment usually adopts device with computerized digital control technology (CNC). After the device is adopted, the cutting data can be received from the computer-aided design (CAD) workstation.
Laser Light Path
- The core component adjusts the curvature of the lens surface by water pressure, thereby changing the divergence angle of the laser beam, and finally adjusting the laser focus up and down movement.
- Compensation for focus changes due to different spot diameters at different working positions of the machine.
- The high-quality laser beam, laser energy can achieve stepless regulation
- Using RF technology, low gas loss rate
Laser Cutting Head
In practical applications, the height of the focus varies with the material and the cutting machine.
Focus position selection
In the process of laser cutting, the laser focus position has a great influence on the surface quality of the parts after cutting, and different materials have different requirements on the focus position.
For example, when cutting carbon steel, the focus is on the upper surface of the plate;
When cutting stainless steel, the focus is about 1/2 of the thickness of the plate.
When cutting aluminum alloy, the focal position is close to the lower surface of the plate.
When cutting the 2mm stainless steel sample in below FIG, the focus position is about 0.8 ~ 1.2mm below the surface of the plate.
Fig. Laser cutting sample
During the cutting process, due to the uneven surface of the material, the focal position of the laser will change, thus affecting the cutting quality.
In order to overcome this phenomenon, placed the high sensitivity of the capacitive sensor on the cutting head, to realize the real-time feedback of the distance information between the nozzle and panel to the CNC system.
According to the feedback information, the height of the cutting head is adjusted in real time through the transmission mechanism, the focal position closed-loop control of high dynamic response is formed to avoid the defect caused by the change of focus position during plate cutting.
Laser Cutting Power & Speed
The laser power has a great influence on cutting thickness, cutting speed, cutting width and cutting quality.
Generally speaking, the larger the laser power, the thicker the cutting board and the faster-cutting speed.
Under certain plate thickness and cutting speed, there is an optimal range of laser power.
The roughness of the cutting surface is the smallest in this range.
The surface roughness of the workpiece increases when it deviates from the optimal power range.
Low processing efficiency and increase cost.
Further increase or decrease in power will result in a burning or slagging defect.
When the laser power and the auxiliary gas pressure are certain, the cutting speed and the slit width maintain a nonlinear inverse relationship.
As the cutting speed increases, the slit width decreases.
As the cutting speed decreases, the slit width will increase.
The cutting speed shows the parabolic relationship with the surface roughness of the cutting section.
As the cutting speed increases from zero, the surface roughness of the section decreases gradually and the cutting speed continues to increase.
When the optimum cutting speed is reached, the surface roughness of the cutting section is the minimum.
As the cutting speed continues to increase, the surface roughness of the section will decrease.
When the cutting speed increases to a certain value, it will be unable to cut through the plate.
In addition, the NC system can automatically adjust the cutting power according to the cutting speed.
For example, the cutting speed is usually lower when the small circle and sharp angle are cut. At this time, the NC system can reduce the cutting power according to the actual cutting speed, and can get excellent cutting precision and sectional quality.
Laser Cutting Auxiliary Gas
As a green hand in laser cutting field, do you often feel a headache in the laser cutting process?
It seems that you have tried various plates, with various gases, various air pressures, different powers, etc… and then it seems that you’re still very confused about it.
Then…, how to choose an auxiliary gas? ! ! !
- What aspects of cutting quality will be affected by different gases? ! ! !
- Which auxiliary gas should be selected for different plates?
- How is the pressure of the auxiliary gas controlled?
- Also, the purity requirement is…?
First of all, are you aware of the role of the auxiliary gas, what is it?
- Use the auxiliary gas to blow away the slag in the coaxial kerf
- Cool the surface of the processed object to reduce the heat affected zone
- Cool the protective lens to prevent contamination of the lens and cause the protective lens to overheat
- Some cutting gases can also protect the base metal
Auxiliary gas types and characteristics
The auxiliary gases commonly used in laser cutting are nitrogen, oxygen and air.
Auxiliary gas plays a very important role in laser cutting. It can blow the cutting piece be melted and vaporized, can also blow the smoke in the process of cutting, so as to reduces the barriers to cutting the workpiece.
The pressure and flow requirements of auxiliary gas are different for materials with different thickness and different materials. Cutting low carbon steel plate generally USES oxygen. The role of oxygen in the cutting process of carbon steel is to fuel and blow off the molten material.
The purity of oxygen is generally higher than 99.5%. The higher the purity, the brighter the cutting surface.
It is important to note that the oxygen contains impurities such as water, which can seriously affect the cutting quality of the plate surface.
If oxygen purity is not high, and the processed parts have higher surface quality requirements, it is necessary to add oxygen drying and other devices to improve the purity of oxygen.
Nitrogen is usually used for cutting stainless steel and aluminum alloy materials.
The role of nitrogen in the stainless steel cutting process is to eliminate oxidation and blow off the melt.
The thicker the plate thickness, the higher the pressure value of nitrogen work. When cutting stainless steel, the required purity of nitrogen is generally higher than 99.999%. Low purity nitrogen can lead to yellowing of the cutting surface and lower brightness.
The sample in the laser cutting sample FIG was cut with a high purity of 99.99% pure liquid nitrogen, and the gas pressure was 0.8 ~ 1.0mpa.
Auxiliary gas purity standard
The laser processing of different materials requires the use of matching auxiliary gases.
Impurities in the auxiliary gas can damage the lens, causing fluctuations in the cutting power and also causing inconsistencies in the front and back cutting surface.
Auxiliary gas pressure standard
The amount of air pressure that can be used for various types of auxiliary gases is different.
Based on the characteristics of the gas, such as flammability and combustion, and various attempts, the following experience is obtained.
The auxiliary gas can prevent slag from returning during the cutting process, thereby protecting the internal lens of the laser head.
That is to say, in the case where the processing power, the material, and the thickness of the sheet are the same, the larger the gas pressure, the more smoke dust that can be blown off at the unit speed.
Therefore, the higher the air pressure value used, the faster the laser cutting speed can be. This is why we use nitrogen when cutting thin sheets.
According to the above inference, the general rule of the cutting speed of the thin plate can be obtained:
Oxygen < Air < Nitrogen
The freshman can also use this rule as the basis for selecting auxiliary gases.
Note: Laser cutting of thick plates does not apply to the above general rules. The type of cutting gas to be targeted needs to be selected according to the characteristics of the individual sheets.
I believe that you have a preliminary understanding of some of the characteristics of the three auxiliary gases when you read here. Let’s take a closer look.
Mainly used for cutting carbon steel.
While the oxygen reaction heat is used to increase the cutting efficiency, the resulting oxide film increases the beam spectral absorption factor of the reflective material.
The end of the slit is black or dark yellow.
Mainly used for rolling steel, rolled steel for welding structure, carbon steel for mechanical construction, high tension plate, tool plate, stainless steel, electroplated steel sheet, copper, copper alloy, etc.
Its purity requirement is generally 99.95% or higher.
The main function is to help burn and blow off the cut melt.
The pressure and flow rate are different, which is inseparable from the size of the nozzle model and the thickness of the cutting material.
Generally, the required pressure is 0.3-1Mpa, and the flow rate varies according to the thickness of the cutting material. For example, cutting 22mm carbon steel, the flow rate should reach 10m3/h (including the protection oxygen of the double-nozzle).
Some metals use oxygen to form an oxide film on the cutting surface during cutting, and nitrogen can be used to prevent oxidation-free cutting of the oxide film.
Therefore, there is a feature that it can be directly welded, smeared, and has high corrosion resistance.
The end face of the slit is whitish.
The main applicable plates are stainless steel, plated steel, brass, aluminum, aluminum alloy, etc. The role is to prevent oxidation and blow off the melt.
There is a high requirement for the purity of nitrogen (especially stainless steel of 8mm or more, which generally requires 99.999% purity), and the pressure requirement is relatively large, generally about 1.5Mpa.
If you want to cut stainless steel of 12mm, or thicker to 25mm, the pressure is required to be 2Mpa or higher.
The flow rate varies depending on the type of nozzle, but generally it is large. For example, cutting 12mm stainless steel requires 150m3/h, while cutting 3mm requires only 50m3/h.
Air can be supplied directly from the air compressor, so it is very cheap compared to other gases.
Although the air contains about 20% oxygen, the cutting efficiency is far less than that of oxygen, and the cutting ability is similar to that of nitrogen.
A trace oxide film appears on the cut surface, but it can be used as a measure to prevent the coating layer from falling off.
The end of the incision is yellow.
The main applicable materials are aluminum, stainless copper, brass, electroplated steel sheet, non-metal and so on.
However, when the quality requirements of the cut product are high, aluminum, aluminum alloy, stainless steel, etc. are not suitable for air because the air will oxidize the base material.
In general, many gases are versatile. The key considerations are the cost of cutting and the requirements for the product.
For example, when cutting stainless steel materials, when the requirement for the quality or surface quality of the products is not high (for example, after the cutting the products need to be painted and through other processing processes), air can be used as the cutting gas, which can reduce the cost.
When the cut product is the final product, there is no subsequent process, and it is necessary to use a protective gas, such as a craft product.
Therefore, in the process of cutting materials, it is necessary to select the auxiliary gas according to the characteristics of the product.
From Drawings to Parts
Factors Affect Laser Cutting
Laser Cutting Classification
Laser vaporization cutting.
Using a laser beam with high energy density to heat the workpiece, the temperature rises rapidly, reaching the boiling point of the material in a very short period of time, and the material begins to vaporize and form vapor.
These vapors spew out very fast, making an incision in the material at the same time as the vapor.
The heat of vaporization of materials is usually very large, so the laser vaporization requires a large amount of power and power density.
Laser vaporization is used to cut thin metal materials and non-metallic materials (such as paper, cloth, wood, plastic and rubber, etc.).
In the process of vaporization, the steam takes away the melting point and scour debris, forming holes.
In the vaporization process, about 40% of the material is dissolved into steam, while 60% of the material is expelled by the flow in the form of a droplet.
Laser melting cutting.
When the power density of the incoming laser beam exceeds a certain value, the material inside the beam irradiation point begins to evaporate and then forming a hole.
Once the hole is formed, it absorbs all the incoming beam energy as a black body.
The holes are surrounded by molten metal walls, and the auxiliary airflow along the shaft of the beam takes away the molten material around the hole.
With the moving of the workpiece, the hole is synchronized horizontally to form a slit in the direction of cutting.
The laser beam continues to irradiate along the edge of the seam, and the melting material continues or pulsates been blow away through the cracks.
The laser fusion cutting does not require the complete vaporization of the metal, the required energy is only 1/10 of the vaporization.
Laser fusion cutting is mainly used for the cutting of non-oxidizable materials or active metals, such as stainless steel, titanium, aluminum and alloys.
Laser oxygen cutting.
The principle of laser oxygen cutting is similar to that of oxyacetylene cutting.
It uses the laser as the preheating source and uses the oxygen and other active gases as the cutting gas.
On the one hand, the gas is produced by the cutting of metal, and the oxidation reaction occurs, which gives off a lot of oxidation heat.
On the other hand, the molten oxide and the melt are blown out of the reaction area, forming an incision in the metal.
Due to oxidation produced a large amount of heat in the process of cutting, so the energy needed of laser oxygen cutting is just 1/2 of molt cutting, and cutting speed is more than laser vaporization cutting and melting cutting.
Laser oxygen cutting is mainly used in carbon steel, titanium steel and heat treatment steel and other easy oxidized metal materials.
Specific description is as follows:
(1) the surface of the material is heated to the point of ignition rapidly under the irradiation of the laser beam, and with the intense combustion reaction with oxygen, a large amount of heat is released. Under this heat, the material is formed by a small hole filled with steam, surrounded by molten metal walls.
(2) combustion material is transferred into slag to control the combustion rate of oxygen and metal, and the speed of oxygen diffusion through the slag to the ignition front has a great impact on the combustion speed. The higher the oxygen flow rate, the faster the combustion chemical reaction and the removal of slag.
Of course, the oxygen flow rate is not the higher the better, because the fast velocity can lead to the rapid cooling of the metal oxide, which is also detrimental to the cutting quality.
(3) obviously, there are two heat sources in the process of oxidation melting, namely, laser irradiation and the heat energy produced by the chemical reaction of oxygen and metals.
It is estimated that when the steel is cut, the amount of heat released by the oxidation is about 60% of the total energy required for cutting.
It is obvious that using oxygen as an auxiliary gas can achieve high cutting speed compared with the inert gas.
(4) in the process of oxidation melting and cutting with two heat sources, if the combustion rate of oxygen is higher than that of the laser beam, the slit appears wide and coarse.
If the laser beam moves faster than the oxygen, the cut slit is narrow and smooth.
Controlled fracturing cutting.
For brittle materials prone to heat damage, high speed and controllable cutting through laser beam heating are called controlled fracturing cutting.
The main content of this cutting process is:
The laser beam heats the small area of the brittle material, causing the large thermal gradient and serious mechanical deformation in the region, causing the material to crack.
As long as the balanced heating gradient is maintained, the laser beam can guide the cracks in any desired direction.
It is important to note that this controlled fracturing cutting is not suitable for cutting acute angle and arm of angle.
It is also not easy to achieve success by cutting a very large and closed shape.
The cutting speed of the controlled fracturing cutting is fast and does not require too much power, otherwise, it will cause the surface of the workpiece to melt and break the edge of the cutting.
Its main control parameters are laser power and spot size.
Laser cutting classified by cutting gas:
|Flame burning cutting||Melt cutting|
|Features||Large cutting thickness||Cutting section without oxide layer|
|Fast cutting speed||Less cutting burrs|
|Has oxidized layer||Cutting gas is expensive|
|Cutting section with a rear tow line||Slow cutting speed|
|Part of the material requires oxygen to participate in the puncture|
|Applicable material||Carbon steel||Stainless steel, aluminum, galvanized sheet|
Laser Cutting Features
Compared with other thermal cutting methods, laser cutting is characterized by high cutting speed and high quality.
Specifically summarized as the following aspects.
(1) Good cutting quality
Laser cutting can achieve better cutting quality due to the small laser spot, high energy density and fast cutting speed.
The laser beam focuses on a small point of light, which makes the focal point reach a high power density.
At this point, the heat input of the beam is far more than the part of the material reflected, transmitted or diffused.
The material is quickly heated to the degree of vaporization, and the pore is formed by evaporation.
With the relative linear movement of the beam and the material, the hole is continuously formed into a narrow slit.
The cutting edge is affected very small by the heat, and there is no deformation of the workpiece.
In the cutting process, the auxiliary gas suitable for the cut material is added.
When the steel is cut, oxygen is used as the auxiliary gas and molten metal to produce exothermic chemical reaction oxidation material, while helping to blow away the slag in the slit.
When cutting plastics such as polypropylene, compressed air is been used.
When cutting flammable materials such as cotton, paper, the inert gas is been used.
The auxiliary gas entering the nozzle can also cool the focus lens, prevent the dust from entering the lens seat to contaminate the lens and cause the lens to overheat.
Most organic and inorganic materials can be cut by laser.
The heavy metal processing industry which means a lot to the industrial manufacturing system, many metal materials, no matter how hard it is, can be cut without deformation.
Of course, for high-reflectance materials such as gold, silver, copper, and aluminum, they are also good heat transfer conductors, so laser cutting is difficult and can’t even be cut.
Laser cutting without burr, wrinkle. It’s in high precision, better than plasma cutting.
For many mechanical and electrical manufacturing industry, due to modern laser cutting system controlled by the microcomputer program can easily cut workpieces in different shapes and sizes, it often is preferable than blanking, mold forming process;
Although its processing speed is still slower than the die punch, it has no mold consumption, no need to repair the mold, and also saves the time of replacing the mold, thus saving the processing cost and reducing the production cost. Therefore, it’s much more economical generally.
① The laser cutting incision is narrow, the slits are parallel and perpendicular to the surface, and the dimensional accuracy of the cutting parts can reach ±0.05mm.
② The cutting surface is smooth and beautiful, the surface roughness is only a few tens of micrometers, and even laser cutting can be used as the last process. No machining is required, and the parts can be used directly.
③ After laser cutting, the width of the heat-affected zone is small, the performance of the material near the slit is almost unaffected, and the deformation of the workpiece is small, the cutting precision is high, the geometry of the slit is good, and the shape of the slit cross-section is relatively regular rectangular.
The comparison of laser cutting, oxyacetylene cutting and plasma cutting methods is shown in Table 1. The cutting material is low carbon steel plate with 6.2mm thickness.
Table 1 laser cutting vs. oxyacetylene cutting vs. plasma cutting
|Cutting Methods||Slit Width/mm||Heat Affected Zone Width/mm||Slit Form||Cutting Speed||Equipment Cost|
|Oxyacetylene cutting||0.9-1.2||0.6-1.2||Relatively Parallel||Slow||Low|
|Plasma cutting||3.0-4.0||0.5-1.0||Wedge & Tilt||Fast||Medium|
(2) High cutting efficiency
Due to the transmission characteristics of the laser, the laser cutting machine is generally equipped with multiple numerical control worktables, and the entire cutting process can realize numerical control.
During operation, it is only necessary to change the numerical control program to apply the cutting of different shapes of parts, which can perform two-dimensional cutting and three-dimensional cutting.
(3) Fast cutting speed
Cutting a 2mm low carbon steel plate with a fiber laser cutting machine in the power of 1200W, the cutting speed can reach 600cm/min; and if cutting a 5mm polypropylene resin plate, the cutting speed can reach 1200cm/min.
The material does not need to be clamped and fixed during laser cutting, which saves the fixture and saves the auxiliary time of loading and unloading.
(4) Non-contact cutting
The laser beam is focused to form a very small operating point with strong energy, and it is applied to cutting with many characteristics.
First of all, laser light can be converted into amazing thermal energy in a very small area, which can provide:
(1) A narrow straight cut slit;
(2) The smallest thermal impact zone adjacent cutting edge;
(3) The minimal local deformation.
Second, the laser beam does not exert any force on the workpiece. It is a non-contact cutting tool, which means:
(1) No mechanical deformation of the workpiece;
(2) No tool wear, no tool conversion problem;
(3) The cutting material does not need to consider its hardness, that is, the laser cutting ability is not affected by the hardness of the cutting material, and any material with hardness can be cut.
Third, the laser beam is controllable and highly adaptable and flexible, thus:
(1) It is convenient to combine with automation equipment, and it is easy to automate the cutting process.
(2) Because there is no restriction on the cutting workpiece, the laser beam has infinite copy cutting ability.
(3) Combined with the computer, the whole plate can be arranged to save material.
(5) Many types of cutting materials
The materials that can be cut by a laser cutting machine including metal matrix composites, leather, wood and fiber.
However, for different materials, due to their different thermophysical properties and different absorption rates of laser light, different laser cutting adaptability is exhibited.
The laser cutting performance of various materials is shown in the following table when using a CO2 laser source.
|Materials||Ability to absorb laser light||Cutting performance|
|Metal||Au, Ag, Cu, Al||Low absorption of laser light||In general, it is more difficult to process, and 1-2mm Cu and Al sheets can be cut by laser.|
|W,Mo,Cr,Ti||Large absorption of laser light||If low-speed processing is used, the thin plate can be cut, and metals such as single Ti and Zr need to use air as the auxiliary gas.|
|Fe,Ni,Pb,Sn||Easier to process|
|Non-metal||Organic material||Acrylic, polyethylene, polypropylene, polyester, PTFE||Permeate to incandescence light||Most materials can be cut with a small power laser. Because these materials are flammable, the cut surface is easily carbonized. Acrylic acid and polytetrafluoroethylene are not easily carbonized. Generally, nitrogen or dry air can be used as an auxiliary gas.|
|Leather, wood, cloth, rubber, paper, glass, epoxy, phenolic plastic||Can’t permeate to incandescence light|
|Inorganic material||Glass, fiberglass||Large thermal expansion||Glass, ceramics, porcelain, etc. are prone to cracking during or after processing, and quartz glass with a thickness of less than 2 mm has good cutting properties.|
|Ceramic, quartz glass, asbestos, mica, porcelain||Small thermal expansion|
(6) Adaptability and flexibility
Compared with other conventional machining methods, laser cutting has more adaptability.
First of all, the other methods of thermal cutting cannot cut on a very small area like the laser beam, as a result, it has a wider incision and large heat affected zone and obvious deformation.
Secondly, lasers can cut nonmetals, while other hot cutting methods cannot.
Analysis of Laser Cutting Materials
The material will get better results when it is cut with oxygen.
When oxygen is used as a processing gas, the cutting edge is slightly oxidized. For plates with a thickness of up to 4mm, nitrogen can be used as the gas for high-pressure cutting. In this case, the cutting edge will not be oxidized.
The plates with a thickness of more than 10mm can be used to apply the special plate to the laser and oil can be applied to the surface of the workpiece in the process in order to get better cutting quality.
Oxygen can be used when the cutting edge oxidization is acceptable. The use of nitrogen to get the edge of non-oxidized and no burr which does not need to be dealt with again.
The coating oil film on the surface of the plate will get better perforation effect without reducing the processing quality.
Despite high reflectivity and thermal conductivity, aluminum with a thickness of less than 6mm can be cut, depending on the alloy type and the laser generator capability.
When cutting with oxygen, the cutting surface is rough and hard. When using nitrogen, the cutting surface is smooth.
Pure aluminum is very difficult to cut because of its high purity. Only when the system is equipped with “reflective absorption” device can the aluminum be cut, otherwise the optical component will be destroyed by reflection.
Titanium plates are cut with argon and nitrogen as processing gases. Other parameters can refer to nickel-chrome steel.
Copper and brass
Both materials have high reflectivity and very good thermal conductivity.
Brass with a thickness of 1mm can be cut with nitrogen. Copper with a thickness of less than 2mm can be cut and processed, the gas must be oxygen.
Copper and brass are cut only when there is a “reflective absorption” device installed on the system, otherwise, the reflection will destroy the optical components.
Laser Cutting Advantages and Disadvantages Compared to Other Cutting Method
Compared with other thermal cutting methods, laser cutting is characterized by fast cutting speed and high cutting quality.
The obvious advantages of laser cutting technology over other cutting methods are:
(1) Good cutting quality.
Narrow incision width (generally 0.1–0.5mm); High precision (general hole center distance error 0.1–0.4mm, profile size error 0.1–0.5mm); The surface roughness of the incision is good (general Ra is 12.5–25μm), cut seam generally do not need reprocessing to be able to weld.
(2) Quick cutting speed.
For example, the laser cutter with 2KW laser power been adopted, the cutting speed of carbon steel with 8mm thickness is 1.6m/min. The cutting speed of stainless steel with 2mm thick is 3.5m/min, and the thermal influence area and the deformation are very small.
(3) Clean, safe and pollution-free.
The working environment of the operator has been greatly improved.
- Laser Cutting Makes Traditional Sheet Metal Processing Advantages Gone
- 4 Methods to Improve Laser Cutting Efficiency
It is summarized as follows:
(1) Good cutting quality.
Because the laser light spot is small, the energy density is high, the cutting speed is fast, so the laser cutting can obtain better cutting quality.
① The laser cutting incisions are narrow, and the cutting edges are parallel and perpendicular to the surface. The size accuracy of the cutting parts can be up to + 0.05mm.
② The surface of the cutting surface is clean and beautiful, the surface roughness is only a few tens of microns, even laser cutting can be used as the last procedure, no need machining, the parts can be used directly.
③ After laser cutting, the thermal effect area is very small. The properties of the material near the slit are also almost unaffected. And the workpiece deformation is small, the cutting precision is high, the geometry of the slit is good, and the shape of the cross-section of the slit is a regular rectangle.
⑵ High cutting efficiency.
Due to the laser transmission characteristics, the laser cutting machine is usually equipped with multiple CNC workstations, and the whole cutting process can be achieved in all CNC. In operation, the cutting of different shape parts can be applied only by changing the NC program, which can be cut in 2D as well as 3D.
⑶ Fast cutting speed.
The cutting speed can reach 600cm/min for 2mm mild steel with 1200W laser cutter while the speed can reach 1200cm/min for 5mm Polypropylene resin plate. The material does not need to be clamped in the laser cutting, which can save not only the tooling but also the auxiliary time of loading and unloading materials.
⑷ Non-contact cutting.
Cutting torch during laser cutting has no contact with the workpiece and no tool wear. The machining of parts with different shapes does not require replacement of the “cutter”. Only the output parameters of the laser need to be changed. The laser cutting process has low noise, small vibration and no pollution.
⑸ Numerous varieties of cutting materials.
Compared with oxyacetylene cutting and plasma cutting, there are many kinds of laser cutting materials, including metal, non-metal, metal base and non-metal matrix composites, leather, wood and fiber. However, for different materials, due to their own thermal physical properties and different absorption rate of the laser, they will have different laser cutting adaptability.
Due to restricted by laser power and equipment volume, the laser cutter can only cut the small thickness of plate and pipe material, and with the increase of workpiece thickness, the cutting speed decreases significantly.
Laser cutting equipment costs high, which means a high one-time investment.
How to Measure Laser Cutting Quality
Laser cutting machine is a kind of equipment that can partially replace traditional metal cutting method. It has the characteristics of fast cutting speed and high cutting quality.
In recent years, optical fiber laser cutting machine has been widely used to make metal laser cutting more convenient and efficient.
But how can we judge whether a laser cutter is good?
The cutting quality of the laser cutting machine is an important standard to judge whether the cutting machine is qualified.
Based on the years of cutting experience, the following nine criteria are summarized, which can be used as a reference for customers.
How to Improve Cutting Quality
- Is the lens clean?
- Is the laser beam at the center of the nozzle?
- Is the actual focal length position matches the focal length position on the scale
- Relative to the sheet surface position
- Cutting speed
- Cutting pressure
- Cutting power
Laser Cutting Applications
Most laser cutting machines are controlled by CNC programs or made into cutting robots.
As a sophisticated machining method, laser cutting can cut almost all materials, including 2D or 3D cutting of thin metal sheets.
In the field of automobile manufacturing, the cutting technology of space curves such as car roof windows has been widely used.
Volkswagen AG uses a 500W laser to cut complex body sheets and various curved parts.
In the aerospace industry, laser cutting technology is mainly used for the cutting of special aviation materials, such as titanium alloy, aluminum alloy, nickel alloy, chrome alloy, stainless steel, cerium oxide, composite materials, plastics, ceramics and quartz.
Aerospace components processed by laser cutting include engine flame tube, titanium alloy thin-wall machine, aircraft frame, titanium alloy skin, wing long stern, tail siding, helicopter main rotor, space shuttle ceramic heat insulation tile, etc.
Laser cutting forming technology also has a wide range of applications in the field of non-metallic materials. It can cut not only materials in high hardness and brittle, such as silicon nitride, ceramics, quartz, etc., but also flexible materials such as cloth, paper, plastic sheets, rubber, etc., such as laser cutting for clothing, which can saving 10 %~12% material and improving the efficacy by more than 3 times.
The products suitable for laser cutting can be generally classified into three categories:
The first category:
Sheet metal which is not suitable to make the mold from the technical and economic point, especially the workpiece with complicated contour shape, small batch, general thickness such as 12mm low carbon steel and 6mm stainless steel so as to save cost for making the mold and shorten the time.
Typical products that have been adopted are:
automatic elevator structural parts, elevator panel, machine tools and food machinery outer cover, various electric gas cabinets, switchgear, textile machinery parts, construction machinery structural parts, large motor silicon steel sheet, etc.
The second category:
Stainless steel (general thickness of 3mm) used for decoration, advertisement, service industry or patterns, marking and font of non-metallic materials (general thickness 20mm). Such as the pattern of an art photograph album, Chinese and English fonts of the company, government department, the hotel, the shop sign, the station, the pier, the public place.
The third category:
Special parts requiring uniform cutting.
The most widely used typical parts are the die-cutting plate used in the packaging and printing industry. It requires a slot with a width of 0.7-0.8mm on a wooden plate of 20mm thickness and inserts a blade in the slot. Install it on the die-cutting machine to cut off a variety of printed graphics boxes.
A new area of application in recent years is the oil screen seam pipe.
In order to prevent the sediment from entering the pump, a uniform slit of 0.3mm wide was cut on the alloy steel tube with a thickness of 6~9mm. The hole diameter of the start cutting point cannot exceed 0.3mm. The cutting technology is difficult, but there are still many factories adopt this method and put into production.
In addition to the above application, the application is also expanded to:
（1）3D laser cutting system or industrial robot is used to cut the space curve. Develop various 3d cutting software to accelerate the process from drawing to cutting parts.
（2）Various special cutting systems, material conveying systems, linear motor drive systems are been developed in order to improve production efficiency. The cutting speed of the cutting system has exceeded 100m/min.
（3）In order to extend the application of engineering machinery and shipbuilding industry, the thickness of low carbon steel has exceeded 30mm. Special attention is paid to the study of the technology of nitrogen cutting low carbon steel to improve the cutting quality of the plate.