What is a laser?
“The laser cuts iron like mud”, this statement is not an exaggeration.
Let's look at the laser in more detail.
What is a laser?
A laser is a type of enhanced light produced using stimulated radiation.
Its main features include:
- High intensity and high brightness
- Wavelength frequency determination, good monochromatic
- Good coherence and long coherence length
- Good directionality, it's almost a lot of parallel light
When the laser beam is directed at the surface of the part, light energy is absorbed and transformed into thermal energy.
This causes the temperature at the irradiation point to increase rapidly, melt and vaporize, forming a small pit.
The metal around the pit melts due to thermal diffusion. The steam in the small pit expands rapidly, causing a microexplosion, and the molten material is expelled at high speed, generating a highly directional anti-shock wave.
This results in the formation of a hole with a large upper side and a small lower side on the surface to be processed.
Comparison of common light and laser:
The laser generation
Laser Generator Gas
Laser generating gas is different from cutting gas.
Composition of laser generating gas:
- N 2 : The energy generated by the RF generator first excites N 2 causing it to be in a transition state.
- CO 2 : N 2 in the transition state will excite C0 2 which causes CO 2 to transition and releases the laser.
- It: Absorb CO 2 and excess energy, cool the system and transform it into heat.
The proportional relationship between the three gases mentioned above is:
N 2 :CO 2 :He = 1:4:5
What is fiber laser cutting
Fiber laser cutting is a hot cutting method that uses a high power density focused laser beam as the main heat source. This causes the irradiated materials to melt, evaporate, disappear quickly, or reach the point of ignition.
At the same time, the use of high-speed airflow coaxial with the laser beam helps to blow away the molten material, allowing the part to be cut.
In recent years, the technology behind high-power fiber laser generators has matured and improved, leading to an ever-expanding range of applications.
Fiber laser cutting machine has become a popular focus of industrial research and development.
In the domain of thin sheet cutting, fiber laser generators are gradually replacing traditional CO2 and YAG lasers for several reasons:
(1) Lower cost:
The photoelectric conversion efficiency of fiber lasers is about 30%, while the photoelectric conversion efficiency of CO2 lasers is 6 to 10%, and the photoelectric conversion efficiency of YAG lasers is only 3%. Additionally, fiber laser generators have no vulnerable parts, so there is no cost associated with late maintenance.
(2) Compact and flexible design:
Fiber lasers are small in size, light in weight, and offer a flexible and mobile working position.
(3) Better cutting quality:
The use of a flexible light guiding system in fiber lasers and a constant beam transmission distance prevents poor cutting quality caused by changes in the light path length of CO2 laser generators.
This ensures consistent cut quality across the entire cutting width, making it ideal for large format laser processing systems.
(4) Cost Savings:
The beam from a fiber laser travels along an optical fiber, so there is no need for an external reflected light path system, saving the cost of reflective lenses and organ shields.
There is also no need for external adjustments of the optical path, which reduces the risk of pollution of the optical path by dirt and reduces the weight of moving parts.
(5) Better performance for metal cutting:
The wavelength of a fiber laser is 1.06 μm, which is more easily absorbed by metallic materials compared to the wavelength of CO2 (10.6 μm).
This is particularly beneficial for cutting sheet metal, with cutting speeds 2 to 4 times faster than CO2.
Fiber lasers also have a better cutting effect for highly reflective materials such as aluminum alloys, copper alloys and copper alloys.
See too:
- Laser Cutting Basics: Knowledge You Should Know
Fiber laser cutting process
(1) lens
(2) the laser beam
(3) air flow
(4) the line
(5) cast material
(6) cutting surface
(7) nozzle
(8) cutting direction
A: Empty height
B: Puncture height
C: Cutting height
T: Sheet thickness
The world's first laser cutting machine was invented in the 1970s. Over the past thirty years, the application of laser cutting machines has continuously expanded and the technology has constantly improved.
Many companies now manufacture various types of laser cutting machines to meet market demand, including 2D plate laser cutting machines, 3D space laser curve cutting machines and tube laser cutting machines.
Some of the top laser cutting machine companies include: Trumpf (Germany), Prima (Italy), Bystronic (Switzerland), Amada (Japan), MAZAK (Japan), NTC (Japan) and HGLaserLab (Australia).
A list of top laser cutting machine manufacturers around the world is available for reference.
Fiber laser cutting equipment can effectively cut stainless steel less than 4mm thick. If oxygen is added, it can even cut stainless steel up to 8 to 10 mm thick using a laser beam.
However, when oxygen is used, a thin oxide film forms on the cutting surface. The maximum cutting thickness can be increased to 16 mm, but the size tolerance of the cut part becomes larger.
Although fiber laser cutting equipment is expensive, it is still economically viable for large production runs due to the lower cost of subsequent processing.
Furthermore, as there is no tooling cost, laser cutting equipment is also suitable for small batches of parts that were previously unprocessable.
Fiber laser cutting equipment typically utilizes a computer numerical control (CNC) system. With this technology, cutting data can be received from a computer-aided design (CAD) workstation.
Path of laser light
The central component adjusts the curvature of the lens surface through water pressure, modifying the divergence angle of the laser beam and thus allowing adjustment of the up and down movement of the laser focus.
Furthermore, it compensates for focus changes that occur as a result of varying dot diameters in different machine working positions.
laser generator
- High-quality laser beam and laser energy can achieve stepless regulation
- Using RF technology, low gas loss rate
fiber laser cutting head
Focus position
In practical applications, the focus height varies depending on the material and cutting machine.
Focus position selection
In laser cutting, the position of the laser focus has a great impact on the surface finish quality of the cut parts, and different materials have different focus requirements.
For example, when cutting carbon steel, the focus should be on the top surface of the sheet; when cutting stainless steel, the focus should be approximately half the thickness of the sheet; When cutting aluminum alloy, the focus should be close to the bottom surface of the plate.
In the case of cutting a 2mm stainless steel sample as shown in the figure below, the focus position should be about 0.8 to 1.2mm below the surface of the plate.
Fig. Laser cutting sample
During the cutting process, the uneven surface of the material can cause changes in the focal position of the laser, thus impacting the quality of the cut.
To solve this problem, a highly sensitive capacitive sensor is placed on the cutting head to provide real-time feedback on the distance between the nozzle and the panel to the CNC system.
Based on this feedback, the height of the cutting head is adjusted in real time via a transmission mechanism, creating a closed-loop control system with high dynamic response that helps prevent defects caused by changes in focus position during cutting the sheet.
Laser cutting power and speed
Laser power significantly affects the thickness, speed, width and quality of the cut. In general, the higher the laser power, the thicker the material that can be cut and the faster the cutting speed.
However, there is an ideal range of laser power for a given plate thickness and cutting speed, where the roughness of the cutting surface is minimal.
Deviating from this ideal power range results in an increase in surface roughness, reduced processing efficiency and increased costs.
Furthermore, if the power is increased or decreased further, burning or slagging defects may result.
Finally, it is worth noting that when the laser power and auxiliary gas pressure are fixed, the cutting speed and slit width have an inverse nonlinear relationship.
As the cutting speed increases, the slot width decreases and as the cutting speed decreases, the slot width increases. The relationship between the cutting speed and the surface roughness of the cut section is parabolic.
When the cutting speed increases from zero, the surface roughness of the cut section gradually decreases and continues to decrease as the cutting speed increases.
When the ideal cutting speed is reached, the surface roughness is minimal.
However, if the cutting speed continues to increase beyond a certain point, it becomes impossible to cut the material and the surface roughness will begin to increase again.
The NC system can automatically adjust the cutting power based on the cutting speed.
For example, when cutting small circles and sharp angles, the cutting speed is normally slower and the NC system can reduce the cutting power to ensure excellent accuracy and quality of the cut section.
Fiber Laser Cutting Assist Gas
As a beginner in the laser cutting field, do you often feel overwhelmed during the process? It can be confusing to try different plates, gases, air pressures and powers and still not get the results you want.
Have you ever wondered about choosing the right auxiliary gas and what factors affect cut quality? Which auxiliary gas should be used for different materials? How is the auxiliary gas pressure controlled and what is the requirement for its purity?
It is important to understand the role of auxiliary gas in laser cutting. It is used to blow away slag in the cutting cut, cool the surface of the material being processed to reduce the heat-affected zone, cool the protective lens to prevent contamination, and in some cases protect the base metal.
Types and characteristics of auxiliary gases
The auxiliary gases commonly used in laser cutting are nitrogen, oxygen and air.
The auxiliary gas is essential in laser cutting, as it helps to remove melted and vaporized material from the cut and also removes the smoke generated during the cutting process, reducing any obstacles to the cutting process.
Auxiliary gas pressure and flow requirements vary depending on the thickness and type of material being cut.
When cutting low carbon steel plates, oxygen is typically used. The purpose of using oxygen in cutting carbon steel is to ignite and remove the molten material.
As a beginner in the laser cutting field, do you often encounter difficulties during the laser cutting process? Despite experimenting with various plates, gases, air pressures, and wattages, you may still be unsure of the ideal combination.
To choose the best auxiliary gas, it is essential to understand its role and the factors that affect the quality of the cut, such as pressure and flow, as well as the purity of the gas.
To cut low carbon steel plates, oxygen is typically used. The role of oxygen in the cutting process is to supply and remove molten material.
Oxygen purity must be greater than 99.5%, with higher purity resulting in a brighter cutting surface.
However, impurities such as water can have a significant impact on the cutting quality of the sheet. If the oxygen purity is not high enough, or if the parts have higher surface quality requirements, it may be necessary to improve the purity through oxygen drying or other methods.
Nitrogen is generally used to cut stainless steel and aluminum alloy materials. The role of nitrogen is to eliminate oxidation and remove melt.
Nitrogen pressure increases with plate thickness.
To cut stainless steel, nitrogen purity must be greater than 99.999%. Low purity nitrogen may result in yellowing of the cut surface and decreased gloss.
A sample in the laser cutting figure was cut with high purity (99.99%) liquid nitrogen with a gas pressure of 0.8 to 1.0 MPa.
Auxiliary Gas Purity Standard
The use of corresponding auxiliary gases is necessary for laser processing of different materials.
Impurities in the auxiliary gas can have detrimental effects on lenses, resulting in fluctuations in cutting power and inconsistencies in the front and rear cutting surfaces.
Auxiliary gas pressure standard
The amount of air pressure that can be used for various types of auxiliary gases is different. Based on gas characteristics such as flammability and combustion, experience shows that auxiliary gas can prevent slag from returning during the cutting process, thus protecting the inner lens of the laser head.
In other words, with the same processing power, material and sheet thickness, the higher the gas pressure, the more smoke and dust can be expelled at the unit speed.
Therefore, a higher air pressure value results in a faster laser cutting speed, which is why nitrogen is used to cut thin sheets.
It can be concluded that the general rule for the cutting speed of thin sheets is: Oxygen < Air < Nitrogen. This rule can be used as a starting point for auxiliary gas selection by novice users.
Note: The above general rule does not apply to laser cutting of thick sheets. The type of cutting gas used must be selected based on the individual characteristics of the sheet.
After reading this, you should have a basic understanding of the characteristics of the three auxiliary gases. Let's take a closer look.
Oxygen
Oxygen is mainly used to cut carbon steel. The heat of the oxygen reaction is used to increase the cutting efficiency, but the resulting oxide film increases the beam spectral absorption factor of the reflective material.
This makes the end of the crack appear black or dark yellow.
Oxygen is mainly used to cut rolled steel, rolled steel for welding structures, carbon steel for mechanical construction, high voltage plates, tool plates, stainless steel, galvanized steel sheets, copper, copper alloys, etc.
The oxygen purity requirement is generally 99.95% or higher. Its main function is to help burn and blow the cut casting.
The required pressure and flow rate are different and are determined by the size of the nozzle model and the thickness of the cutting material. In general, the required pressure is 0.3-1Mpa and the flow rate varies depending on the thickness of the cutting material.
For example, when cutting 22mm carbon steel, the flow rate should be 10m3/h, including the double nozzle protection oxygen.
N nitrogen
Some metals require the use of nitrogen to prevent oxidation during cutting and to maintain the quality of the cutting surface. This results in a whitish end face of the slot and a high resistance to welding, staining and corrosion.
The main materials that can be cut with nitrogen are stainless steel, plated steel, brass, aluminum and aluminum alloys. The purpose of using nitrogen is to prevent oxidation and eliminate melt.
For high-quality cutting, high nitrogen purity is required (generally 99.999% is required for stainless steel with a thickness of 8 mm or more). The pressure requirement is relatively high, generally around 1.5 MPa. For thicker stainless steel (12 mm or more, up to 25 mm), a pressure of 2 MPa or greater may be required.
The nitrogen flow rate varies depending on the type of nozzle used, but is generally quite high. For example, cutting 12 mm stainless steel requires a flow rate of 150 m 3 /h, while cutting 3 mm stainless steel requires only 50 m 3 /h.
Going
Using air as an auxiliary gas in laser processing is economical as it can be obtained directly from an air compressor. Although it contains 20% oxygen, the cutting efficiency is low compared to oxygen and is similar to nitrogen.
A trace of oxide film may appear on the cut surface, but it can also help prevent the coating from falling off. The tip of the cut has a yellowish appearance.
Mainly used for cutting materials such as aluminum, stainless copper, brass, galvanized steel sheets and non-metals. However, when high-quality products are required, air is not suitable for cutting aluminum, aluminum alloy and stainless steel as it will oxidize the base material.
The selection of auxiliary gas depends on the cutting cost and product requirements. For example, when cutting stainless steel for low-quality products that will undergo additional processing, air can be used to reduce costs.
On the other hand, when the cut product is the final product, a protective gas such as nitrogen must be used, as in artisanal products.
Therefore, it is necessary to choose the auxiliary gas based on the characteristics of the product in the cutting process.
From drawings to parts
Factors Affecting Fiber Laser Cutting
Fiber Laser Cutting Classification
Laser vaporization cutting
Using a high energy density laser beam to heat the workpiece, the temperature increases rapidly and reaches the boiling point of the material in a very short time, causing the material to vaporize and form vapor.
This fast-moving vapor creates an incision in the material as it evaporates.
The heat of vaporization of materials is generally high, requiring a large amount of power and high power density for laser vaporization.
This technique is used to cut thin metallic materials and non-metallic materials such as paper, fabric, wood, plastic and rubber.
During the vaporization process, the steam carries away the molten material and debris, forming a hole.
About 40% of the material is dissolved in vapor while 60% is expelled in the form of droplets by the flow during the vaporization process.
laser fusion cutting
When the power density of the received laser beam exceeds a certain threshold, the material at the beam's irradiation point begins to evaporate and form a hole. The hole absorbs all the energy from the incoming beam, acting as a black body.
The holes are surrounded by walls of molten metal, and auxiliary airflow along the beam axis carries the molten material surrounding the hole.
As the part moves, the hole is synchronized horizontally, forming a cut in the cutting direction. The laser beam continues to radiate along the edge of the seam, causing the molten material to be continuously or periodically blown through the cracks.
Laser fusion cutting does not require full vaporization of the metal, using only 1/10 of the energy required for vaporization.
This method is mainly used to cut non-oxidizable materials or active metals such as stainless steel, titanium, aluminum and alloys.
Oxygen laser cutting
The principle of oxygen laser cutting is similar to that of oxyacetylene cutting. It uses laser as a preheating source and employs oxygen and other active gases as cutting gas.
On the one hand, the gas reacts with the metal to be cut and causes an oxidation reaction, releasing a significant amount of heat.
On the other hand, the molten oxide and molten metal are expelled from the reaction area, forming a cut in the metal.
Due to the large amount of heat generated during the oxidation reaction, oxygen laser cutting requires only half the energy required for fusion cutting and has a faster cutting speed compared to laser vaporization cutting and laser cutting. by fusion.
This method is mainly used to cut carbon steel, titanium steel, heat-treated steel and other easily oxidizable metal materials.
The oxygen laser cutting process can be described as follows:
- The surface of the material is quickly heated to the ignition point under the irradiation of the laser beam, and the intense combustion reaction with oxygen releases a large amount of heat. This heat forms a small hole filled with steam, surrounded by walls of molten metal.
- The combustion material turns into slag to regulate the combustion rate of oxygen and metal, and the diffusion speed of oxygen through the slag to the ignition front has a significant impact on the combustion speed. The greater the oxygen flow rate, the faster the combustion reaction and slag removal. However, a high oxygen flow rate is not always better as it can lead to rapid cooling of the metal oxide, reducing the quality of the cut.
- In the oxidation fusion process, there are two sources of heat: laser irradiation and thermal energy produced by the chemical reaction of oxygen and metals. It is estimated that 60% of the total energy required for cutting is released in the form of heat during the oxidation of steel. Oxygen is therefore more effective as an auxiliary gas, providing a higher cutting speed compared to inert gases.
- During oxidation melting and cutting with two heat sources, if the combustion rate of oxygen is greater than that of the laser beam, the cut will appear wide and rough. However, if the laser beam moves faster than the oxygen, the cut will be narrow and smooth.
Controlled frac cutting
For brittle materials that are prone to heat damage, cutting by heating the laser beam with high speed and control is known as controlled fracture cutting.
The key aspect of this cutting process is that the laser beam heats a small area of the brittle material, leading to a large thermal gradient and significant mechanical deformation in the region, causing cracks in the material.
As long as the heating gradient is kept balanced, the laser beam can guide the cracks in any desired direction.
It is important to note that this type of cut is not suitable for cutting sharp angles or corners. It is also challenging to be successful when cutting a large, closed shape.
The cutting speed of controlled fracture cutting is fast and does not require excessive power, otherwise it will cause the surface of the workpiece to melt and break the cutting edge.
The main control parameters are laser power and spot size.
Laser cutting classified by cutting gas:
| Flame burning cut | melt cut | |
|---|---|---|
| Cutting Gas | Oxygen | Nitrogen |
| Characteristics | Great cutting thickness | Cutting section without oxide layer |
| Fast cutting speed | Fewer cutting burrs | |
| Has an oxidized layer | Cutting gas is expensive | |
| Cutting section with rear tow rope | Slow cutting speed | |
| Part of the material requires oxygen to participate in the puncture | ||
| Applicable material | Carbon steel | Stainless steel, aluminum, galvanized sheet |
Laser C revealing F foods
Compared to other thermal cutting methods, laser cutting stands out for its high cutting speed and superior quality.
Specifically, the following aspects can be summarized:
(1) Good cutting quality
Laser cutting offers better cutting quality due to its small laser spot, high energy density and fast cutting speed.
The laser beam is focused to a small spot, resulting in a high power density at the focal point.
The heat input from the beam is significantly greater than that reflected, transmitted or diffused by the material.
This leads to rapid heating and vaporization of the material, creating a pore through evaporation.
With the relative linear movement of the beam and material, the hole is continuously formed into a narrow slit.
The cutting edge is very little affected by heat and there is no deformation of the workpiece.
During the cutting process, the appropriate auxiliary gas is added to the cut material.
When steel is cut, oxygen is used as an auxiliary gas and molten metal to produce oxidation material by exothermic chemical reaction, while also helping to blow the slag into the crack.
When cutting plastics such as polypropylene, compressed air is used.
When cutting flammable materials such as cotton and paper, inert gas is used.
The auxiliary gas entering the nozzle can also cool the focusing lens, prevent dust from entering the lens seat to contaminate it and cause the lens to overheat.
Most organic and inorganic materials can be laser cut.
Heavy metal processing industry, which means a lot to the industrial manufacturing system, many metal materials, no matter how hard they are, can be cut without deformation.
Of course, for high reflectance materials such as gold, silver, copper and aluminum, they are also good conductors of heat transfer, so laser cutting is difficult and cannot even be cut.
Laser cutting without burrs, wrinkles. It is high precision, better than plasma cutting.
For many mechanical and electrical manufacturing industries, due to modern laser cutting system controlled by microcomputer program, it is possible to easily cut workpieces into different shapes and sizes, it is often preferable to molding and molding process;
Although its processing speed is still slower than that of the punch, there is no mold consumption, no need for mold repair, and it also saves mold replacement time, thereby saving processing cost and reducing production cost. Therefore, it is much more economical overall.
- 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.
- 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.
- After laser cutting, the width of the heat-affected zone is small, the performance of the material near the slit is almost not affected, and the deformation of the workpiece is small, the cutting accuracy is high, the slit geometry is good , and the cross-sectional shape of the slit is relatively regular rectangular.
The comparison of laser cutting, oxyacetylene cutting and plasma cutting methods is shown in table 1 .
The cutting material is 6.2 mm thick low carbon steel sheet.
Table 1 Laser Cutting vs. Laser Cutting oxyacetylene cutting vs. plasma cutting
| Cutting methods |
Slit width /mm |
Width of heat affected zone /mm |
Slit shape | Cutting speed | Equipment cost |
|---|---|---|---|---|---|
| Laser cut | 0.2-0.3 | 0.04-0.06 | Parallel | Fast | High |
| 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 & Inclination |
Fast | Average |
(2) High cutting efficiency
Due to their transmission characteristics, laser cutting machines typically feature multiple numerical control worktables, allowing full numerical control over the cutting process.
During operation, different shapes of parts can be cut simply by changing the numerical control program. This allows for two-dimensional and three-dimensional cuts.
(3) Fast cutting speed
Cutting a 2mm low carbon steel plate with a 1200W fiber laser cutting machine can result in a cutting speed of 600cm/min.
When cutting a 5mm polypropylene resin board, the cutting speed can reach 1200cm/min.
The material does not need to be clamped or clamped during laser cutting, saving time in fixing preparation and loading and unloading process.
(4) Contactless cutting
The laser beam is focused to create a highly concentrated point of energy, which has several important advantages for cutting applications.
First, the laser beam can be transformed into intense thermal energy in a very small area, resulting in:
(1) a narrow, straight-cut slit;
(2) a minimum thermal impact zone near the cutting edge;
(3) minimum local deformation.
Secondly, the laser beam operates without physical contact with the workpiece, making it a non-contact cutting tool, providing the benefits of:
(1) no mechanical deformation of the part;
(2) no tool wear or breakage problems;
(3) the ability to cut any material, regardless of its hardness.
Finally, the laser beam is highly controllable and flexible, leading to:
(1) ease of integration with automation equipment, simplifying the automation of the cutting process;
(2) unlimited ability to repeat cuts on the same part;
(3) the ability to optimize material usage by organizing cuts across the board with the help of a computer.
(5) Many types of cutting materials
Materials that can be cut with a laser cutting machine include metal matrix composites, leather, wood and fiber.
However, each material presents different levels of adaptability to laser cutting due to its unique thermophysical properties and laser light absorption rates.
The laser cutting performance of different materials using a CO2 laser source is illustrated in the following table.
| 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 laser cut. | |
| W,Mo,Cr,Ti | Great absorption of laser light | If low-speed processing is used, thin plate may be cut, and metals such as simple Ti and Zr need to use air as an auxiliary gas. | ||
| Fe, Ni, Pb, Sn | Easier to process | |||
| Non-metal | Organic material | Acrylic, polyethylene, polypropylene, polyester, PTFE | Permeate in incandescent light | Most materials can be cut with a low power laser. As these materials are flammable, the cut surface is easily charred. Acrylic acid and polytetrafluoroethylene are not easily carbonized. Generally, nitrogen or dry air can be used as the auxiliary gas. |
| Leather, wood, fabric, rubber, paper, glass, epoxy, phenolic plastic | Cannot permeate incandescent 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 2mm has good cutting properties. | |
| Ceramics, quartz glass, asbestos, mica, porcelain | Small thermal expansion | |||
(6) Adaptability and flexibility
Compared to other traditional machining methods, laser cutting has greater versatility.
Firstly, other thermal cutting methods are unable to cut an area as small as the laser beam, leading to wider cuts, larger heat-affected zones, and significant deformation.
Secondly, lasers can cut non-metallic materials, which is not possible with other hot cutting methods.
Laser cutting materials analysis
Structural steel
Cutting with the aid of oxygen results in better results for the material.
When oxygen is used as the processing gas, slight oxidation occurs on the cutting edge. For sheets up to 4 mm thick, high pressure cutting can be carried out with nitrogen, resulting in no oxidation of the cutting edge.
For sheets thicker than 10mm, the use of a special sheet in conjunction with the laser and the application of oil to the surface of the part can improve the quality of the cut.
Stainless steel
Oxygen can be used when oxidation on the cutting edge is acceptable. The use of nitrogen results in a non-oxidized, burr-free cutting edge that does not require additional processing.
Applying a coating oil film to the plate surface can improve the drilling effect without sacrificing processing quality.
Aluminum
Aluminum, despite its high reflectivity and thermal conductivity, can be cut with a thickness of less than 6 mm, depending on the type of alloy and the capacity of the laser generator.
When cutting with oxygen, the cutting surface is rough and hard. The use of nitrogen results in a smooth cutting surface.
Pure aluminum is difficult to cut due to its high level of purity.
Only when the system is equipped with a “reflective absorption” device can the aluminum be cut, as without it the optical component will be damaged by reflection.
Titanium
Titanium plates are cut using argon and nitrogen as processing gases. The other cutting parameters can be referred to those used for nickel-chromium steel.
Copper and brass
Both brass and copper have high reflectivity and excellent thermal conductivity. Brass plates with a thickness of 1 mm can be cut using nitrogen as the processing gas.
Copper plates with a thickness of less than 2 mm can be cut using oxygen as the processing gas.
However, it is essential to have a “reflective absorption” device installed in the system, otherwise the reflection will cause damage to the optical components.
Advantages and Disadvantages of Fiber Laser Cutting Compared to Other Cutting Method
Compared to other thermal cutting methods, laser cutting stands out with its fast cutting speed and high-quality cuts. Some of its main advantages include:
Excellent cutting quality:
Laser cutting has a narrow incision width (typically 0.1-0.5mm), high precision (with a hole center distance error of 0.1-0.4mm and a profile size error of 0.1-0.5mm) and a smooth surface roughness (with a Ra value of 12.5-25μm). Cut seams typically do not require additional processing before welding.
Fast cutting speed:
For example, a 2KW laser cutter can cut 8mm thick carbon steel at a speed of 1.6m/min and 2mm thick stainless steel at a speed of 3.5m/min with thermal influence and minimal deformation.
Clean, safe and environmentally friendly:
Laser cutting improves the working environment for operators as it is clean, safe and does not create pollution.
It is summarized as follows:
Advantages of laser cutting:
(1) Good cutting quality.
Due to its small laser light spot and high energy density, laser cutting can achieve better cutting quality.
(1) Laser cutting incisions are narrow, with cutting edges parallel and perpendicular to the surface, and the size accuracy of cut parts can reach +0.05mm.
(2) The cutting surface is clean and smooth, with a surface roughness of only a few tens of microns. In some cases, laser cutting can even be used as a final step, allowing parts to be used directly without additional machining.
(3) After laser cutting, the area affected by heat is very small, and the properties of the material near the cutting are practically not affected. Furthermore, there is minimal deformation of the part, resulting in high cutting precision and regular rectangular shape in the cutting cross section.
(2) High cutting efficiency.
Due to the characteristics of laser transmission, laser cutting machines typically feature multiple CNC workstations, allowing the entire cutting process to be carried out with CNC alone.
In operation, parts of different shapes can be cut by simply changing the NC program, and both 2D and 3D cutting can be performed.
(3) Fast cutting speed.
The cutting speed for 2mm carbon steel with a 1200W laser cutter can reach 600cm/min, while for a 5mm polypropylene resin board, the cutting speed can reach 1200cm/min .
Material does not need to be fixed in laser cutting, which not only saves tools but also reduces the time required to load and unload materials.
(4) Contactless cutting.
In laser cutting, the cutting torch does not come into contact with the part and there is no tool wear. No “cutter” replacement is required to machine differently shaped parts.
The only change required is in the laser output parameters. Furthermore, the laser cutting process is low noise, low vibration and does not result in pollution.
(5) Numerous varieties of cutting materials.
Compared to oxyacetylene and plasma cutting, laser cutting is capable of cutting a wide variety of materials, including metals, non-metals, metal and non-metal matrix composites, leather, wood and fibers.
However, the suitability of laser cutting for these materials varies due to their distinct thermal and physical properties, as well as their different laser absorption rates.
Disadvantages of laser cutting:
Due to limitations in laser power and equipment size, laser cutters are limited in their ability to cut thicker sheet and tube materials.
As the part thickness increases, the cutting speed decreases significantly.
Additionally, laser cutting equipment is expensive, resulting in a high initial investment.
How to measure laser cutting quality
Laser cutting machine is a type of equipment that can partially replace traditional metal cutting methods. It has fast cutting speeds and high cutting quality.
In recent years, the use of fiber optic laser cutting machines has made metal laser cutting more convenient and efficient.
To determine the quality of a laser cutter, the cutting quality of the machine is a crucial criterion. Based on years of cutting experience, the following nine criteria have been summarized as a reference for customers to evaluate laser cutters.
How to improve laser cutting quality
Hardware Factor
- Is the lens clean?
- Is the laser beam in the center of the nozzle?
- The actual position of the focal length corresponds to the position of the focal length on the scale
Parameter Factor
- In relation to the position of the sheet surface
- Cutting speed
- Cutting pressure
- Power cut
Laser cutting applications
Most laser cutting machines are controlled by CNC programs or integrated into cutting robots. As a cutting-edge machining method, laser cutting can cut a wide variety of materials, including 2D or 3D cutting of thin metal sheets.
In the automobile industry, laser cutting technology is widely used to cut complex car bodies and various curved parts such as automobile roof windows.
For example, Volkswagen AG uses a 500 W laser to cut these components. In the aerospace industry, laser cutting technology is mainly used to cut special aviation materials such as titanium alloys, aluminum alloys, nickel alloys, chromium alloys, stainless steel, cerium oxide, composite materials, plastics, ceramics and quartz.
Aerospace components processed by laser cutting include engine flame tubes, thin-walled titanium alloys, aircraft structures, titanium alloy skins, long wing sterns, tail sides, helicopter main rotors and space shuttle ceramic thermal insulation tiles.
Laser cutting is also widely used in the non-metallic materials industry. It can cut hard and brittle materials such as silicon nitride, ceramics, quartz, as well as flexible materials such as fabric, paper, plastic sheets and rubber.
For example, laser cutting can be used in the clothing industry to save 10% to 12% of material and increase efficiency by more than three times.
Products suitable for laser cutting can generally be classified into three categories:
- Sheet metals that are not suitable for mold manufacturing from a technical and economic point of view, especially parts with complex contours, small batches and general thickness, such as 12mm low carbon steel and 6mm stainless steel, to save manufacturing costs of molds and reduce time. Some typical products that have been adopted include structural parts of automatic elevators, elevator panels, machine and food machine covers, various electric gas cabinets, distribution boards, textile machine parts, construction machine structural parts, and large sheet metal. silicon steel for engines.
- Stainless steel (generally 3mm thick) used for decoration, advertising, service industry or patterns, markings and fonts of non-metallic materials (generally 20mm thick). Examples include artistic photo album patterns, company fonts in Chinese and English, signs for hotels, stores, stations, piers and public places.
- Special pieces that require uniform cutting. The most commonly used typical parts are die-cutting plates used in the packaging and printing industry. A groove with a width of 0.7-0.8 mm must be cut in a wooden board 20 mm thick and a blade inserted into the groove. The board is then installed in a die cutting machine to cut a variety of printed graphic boxes. Another application is oil screen seam pipes. To prevent sediment from entering the pump, a uniform slit 0.3 mm wide should be cut in an alloy steel pipe with a thickness of 6-9 mm. The diameter of the hole at the starting point of cutting cannot exceed 0.3mm, making the cutting process difficult, but still widely adopted by many factories.
Recent advances in laser cutting technology include:
- Using 3D laser cutting systems or industrial robots to cut spatial curves and developing various 3D cutting software to speed up the process from drawing to cutting parts.
- Development of various special cutting systems, material transport systems and linear motor drive systems to improve production efficiency, with cutting speeds exceeding 100m/min.
- Focusing on the study of nitrogen cutting technology for low carbon steel to improve the cutting quality of sheets, to expand the application of engineering machinery and shipbuilding industries, with low carbon steel thicknesses greater than 30 mm.
