LASER CUTTING MACHINE MANUAL
MARCH 4, 2024
WODA METAL INDUSTRY PLC
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Table of Contents
Fiber Laser Cutting Machine ........................................................................................................................... 1
Working Principle ........................................................................................................................................... 1
Structure .......................................................................................................................................................... 1
The overall structure ................................................................................................................................. 2
Fiber Laser Cutter Types ................................................................................................................................. 5
The connection method of water cooler ...................................................................................................... 8
Nozzle effect and adjust laser at nozzle mouth ........................................................................................... 9
Effect of the nozzle on cutting quality and nozzle size selection .............................................................. 10
Beam focus adjustment.............................................................................................................................. 12
Cutting speed selection ............................................................................................................................ 13
Laser cutting gas and pressure selection instructions .......................................................................... 14
Laser cutting power impact on cutting quality ..................................................................................... 16
Laser Cutter Safety ........................................................................................................................................ 16
Specifications ................................................................................................................................................ 16
1. Dedicated device. .................................................................................................................................. 16
2. Cutting perforation technology. ............................................................................................................. 17
3. Nozzle design and air flow control technology. .................................................................................... 17
Maintenance & Troubleshooting ................................................................................................................... 18
Machine Operation ........................................................................................................................................ 22
Laser Cutting Machine Safety ....................................................................................................................... 24
Laser safety notice ................................................................................................................................... 24
Electrical Safety ....................................................................................................................................... 25
Laser cutting machine’s protective measures ....................................................................................... 26
Common knowledge should be known by the operators ..................................................................... 26
Fiber Laser Cutting Thickness & Speed Chart .............................................................................................. 26
The effect of the beam on cutting quality .................................................................................................. 28
Effect of laser power on cutting quality..................................................................................................... 29
The effect of cutting speed on cutting quality ............................................................................................... 31
Nozzle function ......................................................................................................................................... 31
The relationship between nozzle and cutting quality ........................................................................... 32
The influence of focus position on cutting quality .................................................................................... 33
Appendix 1 – Different materials’ laser cutting defects and troubleshooting .................................................. 37
Carbon steel: cut with O2 ........................................................................................................................... 37
Stainless steel: cut with high pressure N2 ........................................................................................... 39
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Alloy: Cut with high pressure N2 ...................................................................................................... 41
Appendix 2 Physical photograph with cutting defect ............................................................................. 43
1．Stainless steel cutting defects ........................................................................................................ 43
2. Carbon steel cutting defects ............................................................................................................. 44
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Fiber Laser Cutting Machine
Working Principle
Laser cutting utilizes the laser beam as a heat source for hot cutting, with a working principle similar
to that of laser welding. The temperature of laser cutting exceeds 11000°C, causing materials to gasify,
which plays an important role in addition to melting during the cutting process. For some materials,
such as carbon and ceramics, the laser cutting process is purely a gasification process.
The laser cutting of metal is mostly performed using high-power carbon dioxide continuous laser
generators. During cutting, an inert gas flow is used to blow out the incision, smoothing and
straightening the melted metal. The addition of an oxygen flow from the jet increases the cutting speed.
Laser cutting offers a narrow incision, precise size, and smooth surface, resulting in better cutting
quality compared to other hot cutting methods. Most metal materials can be cut by laser, with a cutting
thickness ranging from a few microns to 50 mm.
Investment in laser cutting equipment is high, but it is mainly used for precision cutting of materials
with thicknesses under 12 mm, including stainless steel, titanium, titanium alloys, refractory metals,
and precious metals. It can also be used for cutting non-metallic materials such as plastic, wood, cloth,
graphite, and ceramics. For example, the wood processing industry uses lasers to cut plywood and
particle board, while the garment industry uses lasers to cut cloth.
Laser cutting is also suitable for special purposes, such as stone bearing drilling and surgery, where
lasers are used as scalpels. The parameters of the laser beam, performance and precision of the laser
cutting machine, and the NC system directly impact the efficiency and quality of laser cutting.
Structure
The main components of a CNC laser cutter include the machine host, control system, laser, chiller,
and regulator, among others. Each of these components has its own manual or operating instructions,
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but the main machine structure and composition of the electrical control system will be described in
detail here.
Machine Host Part:
The machine host part of the laser cutting machine is the most crucial aspect of the laser cutting
process. It is responsible for achieving cutting accuracy and function. The host part consists of six
components: the bed, laser, gantry part, Z-axis device, auxiliary parts of the working table (protective
cover, air, and water channel), and the operation panel.
Electrical Control Part:
The electrical control system of the laser cutting machine is vital in ensuring a variety of graphic
trajectories. The electrical control system mainly consists of the numerical control system and the lowvoltage electrical system. The laser cutting machine is equipped with CYPCUT software and operates
on the WINDOWS XP platform, ensuring stable and reliable operation. The system is equipped with
a 32-bit microprocessor and an Ethernet communication interface.
The system features fast interpolation operation speed, is easy to operate, has good dynamic
performance, and a strong load capacity. The control part of the low-voltage electrical system is located
in the electric control cabinet and serves as the electrical control interface. The components of the
electrical part adopt well-known, world-renowned brands to ensure stable operation and sensitive
response.
The drive motor is an AC servo motor, which is used to drive the X-axis gantry and Y-axis skateboard
of the laser cutter. It is characterized by good acceleration performance and fast response. The
maximum positioning speed is up to 50m/min. The Z-axis of the laser cutting machine is the feed axis,
which is driven by an AC servo motor. The Z-axis cutting head is characterized by good dynamic
response and can be controlled by both servo and NC control.
The overall structure
The main component of the laser cutting machine is crucial to the entire machine. The cutting precision
and function of the machine are achieved by the host component, which includes the bed (Y-axis),
beam (X-axis), Z-axis, working table, air and water channel.
Frame of the Laser Cutting Machine
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The bed is constructed from high-strength cast iron with a fully welded structure. It undergoes stress
relief processes, including annealing, roughing, semi-finishing, and finishing. This ensures thorough
stress reduction and reduces machine deformation, ensuring long-term accuracy.
The AC servo motor drive and coaxial drive beam are controlled by a numerical control system,
enabling the Y-axis to move in a reciprocating motion. This results in fast and rapid movement. The
machine’s movement stroke is 1500mm * 3000mm.
The gear rack and linear guide are equipped with a closed dust-proof device, featuring a lightweight
dust cover and reliable operation. These precision products effectively guarantee the drive accuracy.
The stroke at both ends of the machine is controlled by limit switches, and the machine is protected by
elastic cushions on both sides, ensuring the machine’s movement is safe.
Beam Section
The beam component is made by welding a high-strength square tube and undergoing machining after
artificial aging to enhance overall rigidity and strength. The processing process includes rough
processing, vibration aging, semi-finishing, vibration aging, and finishing.
The beam is mounted on the bed’s support rail, which features both linear and flat guide rails. The
servo motor drive and gear rotation through a reducer allow the Z-axis skateboard to move in the Xdirection reciprocally. The movement stroke is 1450mm.
The stroke is controlled by a limit switch during movement, and both ends are protected by elastic
cushions for the system’s safety. The upper and sides of the beam are enclosed by a cover, and a
retractable guard is located between the beam and the transverse skateboard to ensure a fully enclosed
environment for the rack and linear guide, free from external influences.
The optical path is partially sealed with a guard to create a fully enclosed optical path structure.
Exchangeable Workstation Base and Workstations (Optional)
The workstations are constructed using a robust overall welding structure for strength and stability.
The exchange table is divided into two sections: a switching device and two movable cutting tables.
The exchange device is fixed on the bed’s backside and is mainly used to swap the upper and lower
tables. When cutting a workpiece, the other cutting table can be utilized for feeding and unloading
material to improve the laser cutting machine’s efficiency.
Each movable cutting table consists of a welding frame with a support gate for the workpiece. The
worktable can hold up to 800 kg. The two tables can be automatically exchanged through a chain
device drive, significantly increasing production efficiency.
The center of the table is equipped with a universal ball seat, and four universal balls in the middle
support 44 workpieces. The cylinder drive and rack-and-pinion mechanism allow the swing pole to
rotate 180°.
The spiral tube quick connector is fed into the cutting station’s quick connector, and the pneumatic
switch is opened. The cylinder drive rotates the swing pole upward 180°, and the 44 universal balls
support the workpiece, allowing it to roll on the balls and avoiding scratches caused by the
workpiece sliding on a support grid.
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When the workpiece is positioned, the pneumatic switch is pressed, and the cylinder swings down
180° through the rack-and-pinion mechanism, bringing the universal balls just below the pendulum
to avoid damage during the cutting process.
This mechanism, where the workpiece rolls on the balls during feeding and positioning, instead of
sliding on a support grid (as in traditional methods), effectively protects the workpiece’s smooth
surface and reduces the operator’s labor intensity.
Z-axis Device
The Z-axis device is responsible for the lifting movement of the cutting head. This movement is
controlled by the numerical control system through a servo motor, which drives a ball screw to cause
the Z-axis skateboard to perform an up-and-down reciprocating motion.
The travel of the Z-axis is 100mm, and limit switches are used to control the stroke at the upper and
lower ends. Additionally, flexible cushions are placed on both ends of the ball screw to ensure the
safety of the movement.
High-quality ball screw and linear guides are used to ensure the accuracy of the transmission. The Zaxis can function as a CNC axis due to its separate interpolation movement and can move in tandem
with the X and Y axes. It can also be switched to servo control through the cutting head’s electronic
control to accommodate different requirements.
The servo control of the Z-axis is controlled by the CNC system, resulting in a high degree of
accuracy and stability, ensuring the quality of the cutting. The cutting head is sealed and cushioned
to prolong its lifespan.
A capacitance sensor, mounted on the cutting head, detects the distance between the nozzle and the
plate surface and sends the information back to the control system. The controller then uses this
information to control the Z-axis motor and keep the distance between the nozzle and the plate
constant, thereby ensuring the quality of the cut.
The cutting head has a nut for adjusting the focal length, allowing for the position of the focus to be
adjusted based on the material and thickness of the cutting material, leading to a good cutting
section.
Note: The nozzle is a wearing part of the process, and users can keep spare nozzles of different
diameters for easy replacement.
Electrical Control Section
The electrical control system of the CNC laser cutting machine is mainly composed of a numerical
control system, a servo system, and a low-voltage electrical system.
The laser cutting machine is equipped with the CYPCUT CNC system, which is based on the
WINDOWS XP PC CNC system and offers fast interpolation operation speed and ease of use.
The servo system employs a Japanese Yaskawa AC servo motor and drive, known for their stability,
reliability, and strong load capacity.
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The front panel of the laser cutting machine features two function buttons, two operation soft keys,
and two front USB ports, arranged in the following order from left to right: emergency stop switch,
power switch, cutting start button, and cutting stop button.
The operation soft keys have different functions depending on the mode of operation, reducing the
number of operation buttons and simplifying the operation panel.
The operation functions are displayed through a menu, making the operation intuitive in various
modes.
Fiber Laser Cutter Types
Based on the laser generator, the laser cutter can be divided into:
a. solid laser cutter. The solid laser cutter can be divided into the bonus stones laser cutter, YAG
laser cutter.
b. semiconductor laser cutter.
c. liquid laser cutter.
d. gas laser cutter.
If based on the structure, the laser cutter can be divided into:
1. According to the relative movement of the cutting head and the table, the CNC laser cutting
machine can be divided into:
 Beam fixed form (fixed light path)
 Beam movement form (flying ray)
 Semi-fixed and semi-mobile hybrid form
Besides, there is also an articulated movable arm fixed optical flight beam transmission form, known
as a constant flight path.
In the cutting process for the laser cutter which adopts flying ray, only the cutting head moves along
the X and Y direction, and the position of the table is fixed.
Such laser cutter featured:

The plate of processing is in big size, with a heavyweight.

The equipment covers a small area.

No need clamping for fabricating workpiece which is convenient for loading and discharge the
materials.

The machine has good acceleration and high positioning accuracy.
Therefore, it is highly regarded by the market as the mainstream model of the international market.
2. Several typical structures of modern laser cutting machines are mainly included:

Gantry frame movable flying ray structure.

Beam traveling flying ray.

Beam upside down movable flying ray.

Cantilever movable flying ray structure.

Robot structure & Large format hybrid flying ray.
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
Laser flexible processing system.
3. In terms of the structure of the laser cutting equipment, the frame of the machine includes:

casting structure

welding structure

marble structure

the beams are made of aluminum alloy castings or welds and profiles.
Other components use engineering plastics, fiberglass and stainless steel, etc.
4. The laser generator required by the laser cutter shall be selected according to the user’s
processing performance, processing materials, shapes and sizes, etc.
The available laser generators include co2 axis fast-flow laser generator, RF board debugging laser
generator, swirl laser generator, the solid-state laser generator and a fiber laser generator.
5. Based on the driving method, there are:

X and Y axis are selected with a single – side servo motor and equipped with the corresponding
speed reducer, which is driven by the high precision gear rack.

The X axis is selected with the servo motor and equipped with the corresponding reducer, which is
driven by the high precision gear rack. There are two gears to eliminate reverse clearance.

Directly driven by high precision ball screw with the servo motor. The machine is driven by direct
gear and rack with disc large inertia motor.

Direct drive by the linear motor.
6. CNC laser cutting machine is usually equipped with the high precision linear guide, and
equipped with an automatic lubrication device.
Single-side linear guide rail with roller structure is a cost-effective and convenient solution for
economic applications. The alternative structure is the drive unit, which integrates the drive and guide
rail, making installation, debugging, and precision easier to ensure, though slightly more expensive.
Connection of Parts in the Distribution Cabinet
To start, identify the parts according to the requirements, as outlined below:
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After installation is completed, connect each distribution cabinet as follows:
 Check if the three joints at the end of the Y-axis extension have been damaged during transportation
(the three connectors are: a 16-core heavy-duty connector, a 19-core aviation plug, a 4-encoder
plug, and an amplifier plug) as shown below:
Aviation Plug
Heavy-duty Connector
Encoder Plug
Amplifier Plug
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Insert the plugs into their corresponding positions (the positions are unique). The encoder plug
should be inserted into the appropriate servo drive based on the number, and the amplifier plug
should be inserted into the height adjuster.
 Connect the power cord of the water cooler in the distribution cabinet to the designated
location, as illustrated below:
Power Plug
Power Plug Connection Position

Connect the main power, which is a three-phase four-wire system, with the yellow and green
wires serving as the zero line and the remaining three serving as the live line. With this, the
electrical external circuit connection is completed. In the next section, we’ll discuss the water
connection.
Warning:
The ground wire of the power cord must be grounded securely to prevent disturbance of the signals
inside the machine cabinet and reduce the risk of leakage.
The connection method of water cooler
Installation Requirements
The chillers should be placed smoothly and have a sufficient distance from the wall. The installation
site of the chillers must have adequate air inlet and outlet space to prevent poor cooling and avoid high
temperatures in the distribution cabinet.
Inspection of the Equipment
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Prior to installation, it is important to clean any debris inside the water tank and ensure that the water
is free of impurities. Then, inspect the water pipe system joints to make sure they are tight.
Installation Procedure
Connect the inlet and outlet pipes on the chiller according to the signs on the chiller’s shell and connect
them to the inlet and outlet doors of the laser, ensuring that the direction of the inlet and outlet of the
water pipe is not dislocated. Before connecting the water pipe, make sure that the outside of the chiller
is free of debris and foreign matter.
Water Quality Standards
Check that the sewage valve is closed and add water to the tank. The water level should be less than
30mm to 50mm in the tank to prevent overflowing. It is strictly prohibited to use general tap water in
the chilled water units, and high-quality pure water, distilled water, or deionized water must be used.
Adding any corrosive liquids is strictly prohibited.
Power on Commissioning
There is an air switch behind the water cooler. When the water channel is connected well, turn on the
switch to test operation. After the pump starts, check for any water leaks in the joints and if found, turn
off the power and fix the problem before turning it on again.
Water Temperature Regulation
In an air-conditioned room, the water temperature is generally set at 22-24 degrees Celsius. In a nonair-conditioned room, the water temperature is set lower than the room temperature by 2-5 degrees
Celsius. If the water condenses on the pipe wall, it indicates that the temperature of the water cooler is
set too low.
Nozzle effect and adjust laser at nozzle mouth
Nozzle action and regulation
A) Nozzle
The design of the nozzle and the flow conditions of the jet have a direct impact on the quality of the
cutting; the accuracy of the nozzle manufacturing is closely related to the cutting quality.
B) Main Functions of the Nozzle:
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▲ To prevent cutting debris and other debris from bouncing into the cutting head and damaging the
focus lens.
▲ The nozzle can change the situation of cutting gas discharge, control the size and area of gas
diffusion, thus affecting the cutting quality.
The figure below shows the case of ejection when the nozzle is installed and not installed.
Steps to adjust the nozzle to pass the laser from the center of the nozzle
Compared to CO2 laser cutting machine, fiber laser cutting machine is no optical path, only need to
adjust the laser at the nozzle mouth.
Compared to CO2 laser cutting machines, fiber laser cutting machines do not have an optical path,
and only require adjusting the laser at the nozzle.
1. Coat the end of the nozzle with Indian mud (or transparent tape if not using mud), then attach
white stickers to the end.
2. Adjust the laser output power to between 30W to 50W, open the mechanical shutter, and quickly
switch the electronic shutter once while observing the phenomenon.
Turn off the mechanical shutter, remove the white stickers while being careful not to change its
relative position.
If the difference between the nozzle position and laser center is too large, the stickers will not be able
to align with the center hole. Since the laser center is fixed, the center of the nozzle can be adjusted by
turning the adjustment screw on the cutting head handle to match the laser center.
Repeat the above steps until the laser hole on the white sticker coincides with the center of the
nozzle, confirming that the laser center aligns with the nozzle center.
See below:
Effect of the nozzle on cutting quality and nozzle size selection
The relationship between the nozzle and cutting quality:
When the center of the nozzle is different from the center of the laser: the impact on cutting quality
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1. Cutting Section
When the cutting gas is jetted, an uneven gas volume can result, causing the cutting section to be more
prone to stair-stepping on one side and not on the other. The impact of this is small when cutting sheets
below 3mm, but when cutting plates above 3mm, the impact is more serious, and cutting may not even
be possible.
2. Sharp Corners
In the cutting of sharp corners or workpieces with smaller angles, local over-melting is prone to occur,
and cutting thick plates may not be possible.
3. Perforation
During piercing, instability makes it difficult to control the time, and penetration of thick plates can
cause melting. This can also make it difficult to control penetration conditions, and the impact on small
pieces is small.
In conclusion, the center of the nozzle and the concentricity of the laser are important factors in cutting
quality, especially when the workpiece is thicker. Therefore, it’s necessary to adjust the center of the
nozzle to align with the laser concentricity to achieve better cutting.
Note:
Deformation of the nozzle or fouling can have the same impact on cutting quality as described above.
Therefore, the nozzle should be handled with care to avoid deformation, and any stains should be
cleaned promptly. The manufacture of the nozzle requires higher precision, and proper installation
methods must be followed. If the nozzle’s poor-quality leads to changes in cutting conditions, the
nozzle should be promptly replaced.
Selection of nozzle aperture
The difference in nozzle diameter is shown below:
The diameter of the nozzle has φ 1.0mm, φ 1.4mm, φ 2.0mm, φ 2.5mm, φ 3.0mm and so on. The
current nozzle diameter often uses φ 1.4mm, φ 2.0mm. As shown below:
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The difference between the two diameters mentioned above is as follows:
1. For thin plates below 3mm:

Using a φ4mm nozzle will result in a smaller cutting surface.

Using a φ2mm nozzle will result in a thicker cutting surface, with a higher likelihood of melted
stains at the corners.
2. For thick plates above 3mm:

The cutting power is higher, which results in a longer heat dissipation time and a longer cutting
time.

Using a φ1.4mm nozzle will result in a small gas diffusion area, which may cause instability
during use, but is still generally usable.

Using a φ2mm nozzle will result in a larger gas diffusion area and a slower gas flow rate, which
results in more stable cutting.
3. A nozzle with a diameter of 2.5mm can only be used for cutting plates thicker than 10mm.
In conclusion, the nozzle size has a significant impact on the quality of cutting and perforation.
Currently, laser cutting machines mostly use nozzle apertures of φ1.4mm and φ2mm.
Note:
The larger the nozzle aperture, the more likely it is that sparks and melt splashes during cutting will
cause damage to the lens, reducing its lifespan.
Beam focus adjustment
In the laser cutting process, the relationship between the beam focus and the surface of the cutting
sheet greatly affects the cutting quality, and it is crucial to adjust the focus position correctly.
This is typically done by adjusting the focus through a test cut, where the focus is at its proper position
when the cut has the least hanging slag and the smallest size on the corresponding steel plate.
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If the position of the cutting head relative to the board changes, it is also necessary to adjust the zero
points of the cutting head and the sensor. Fine-tuning can be accomplished by adjusting the cutting
height in the software.
When larger adjustments are necessary, it may be necessary to adjust the position of the sensor and
its bracket to properly adjust the focus.
Take care when performing these adjustments, as a misstep could cause the cutting head to hit the
surface and result in damage to the parts.
The relationship between the focus position and the cutting effect
Cutting speed selection
The selection of cutting speed in laser cutting machine is crucial and depends on the material and
thickness of the plate being cut. The cutting speed has a significant impact on the quality of the laser
cutting.
Choosing an appropriate cutting speed not only enhances the efficiency of the laser cutting machine,
but also ensures a high-quality cut.
Here are the effects of different cutting speeds on the cutting quality:
The effect on cutting quality with too fast laser cutting feed rate

may cause no cutting, sparks scattered.

Some areas can be cut off, but some areas cannot be cut off.
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
resulting in the entire cutting section thicker, but no fusible generation.

cutting feed rate is too fast, resulting in the plate cannot be cut off in time, cutting section showing
oblique lines, and the lower part generate fused stains. As shown below:
The effect on cutting quality with too slow laser cutting feed rate:

Result in over-melting of the cutting plate and a rough cutting section
 The width of the slit will increase, causing the entire area to melt in smaller fillets or sharp
corners, resulting in poor cutting quality.
 low cutting efficiency, affecting production capacity.
 To determine the appropriate cutting feed speed, observe the cutting sparks: if they spread from
top to bottom and tilt, the feed rate is too fast. If the sparks are condensed and not spreading,
the feed rate is too slow. With the correct cutting speed, the cutting surface will show a
smoother line, and the bottom half of the plate will not fuse.
As shown below：
Laser cutting gas and pressure selection instructions
The choice of cutting gas in laser cutting depends on the material being cut. The selection of cutting
gas and pressure has a significant impact on the cutting quality.
The main function of the cutting gas is to aid combustion and dissipate heat by blowing away the
residue and preventing it from entering the nozzle and damaging the focus lens.
Impact of Cutting Gas and Pressure on Cutting Quality

A suitable cutting gas helps with combustion and heat dissipation, leading to a better-quality cut.
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
When the pressure of the cutting gas is insufficient, the cutting process will be affected by the
buildup of residue, and the cutting speed will not meet the production requirements.

When the pressure of the cutting gas is too high, the cutting surface will be rough and the slot will
be wide, causing part of the cut to melt, resulting in poor cut quality.
Impact of Cutting Gas Pressure on Perforation

If the gas pressure is too low, the laser will struggle to penetrate the cutting plate, resulting in
longer drilling times and lower productivity.

If the gas pressure is too high, the penetration point will melt and form a larger melting point,
which will affect the cutting quality.

For laser drilling, a high sheet metal punching pressure is generally used, while a lower pressure is
used for punching thick plates.

When cutting ordinary carbon steel, the thicker the material, the lower the pressure of the cutting
gas.
When cutting stainless steel, the cutting gas pressure remains high, regardless of the material
thickness.
In conclusion, the selection of laser cutting gas and pressure must be adjusted according to the
specific conditions and circumstances of each application.
Our laser cutting equipment is delivered with two gas pipelines, one for oxygen and air, and one for
high-pressure nitrogen use. These two gas channels must be connected to a pressure reducing valve,
as shown in the figure below.
Pressure relief valve description: the left side of the table shows the current pressure; the right table
shows the remaining gas capacity.
Warning

Nitrogen supply pressure should not exceed 20kg;

Oxygen supply pressure should not exceed 10Kg, or likely to cause the gas pipe burst.
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Laser cutting power impact on cutting quality
The choice of laser power size has an impact on the cutting quality, and it is important to determine
the cutting power based on the material and thickness of the plate. Having too small or too large of a
laser power will result in poor cutting quality.
A) Too small of a laser power will result in no cutting. B) When the laser power setting is too large,
the entire cutting surface will melt and the slit will be too wide, resulting in poor cutting quality. C)
When the laser power setting is insufficient, cutting fouling will occur and scars will appear on the
cutting section.
Therefore, setting an appropriate laser power, along with the appropriate cutting gas and pressure,
will result in a good cutting quality with no fused stains.
Laser Cutter Safety
Specifications
1. Dedicated device.
To reduce the variation in focal spot size caused by changes in beam size before focusing, laser cutting
systems manufacturers offer several options for users to choose from:

Parallel optical tube. This option involves adding a parallel optical tube to the output end of the CO2
laser, which increases the beam diameter and reduces its divergence angle, resulting in near and far
ends of the beam being close to the same size.

Independent moving lens. An independent moving lens can be added to the lower shaft of the cutting
head, separate from the Z-axis that controls the distance between the nozzle and material surface.
This lens moves in tandem with the machine tool table or light axis, ensuring the focal spot diameter
remains consistent throughout the processing area.

Control of focusing mirror water pressure. This method, usually in a metallic reflection focusing
system, reduces the focal curvature of the focal spot by automatically adjusting water pressure, thus
reducing the beam size and increasing the focal spot size.

X and Y-directional compensation optical path system. This option involves adding a compensation
optical path system to the flying ray cutting machine. The length of the compensation optical path
decreases as the distance of the far end cutting increases, while increasing the compensation flying
ray to keep the length of the optical path consistent when cutting the near end.
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2. Cutting perforation technology.
Almost all hot cutting technologies, except for a few exceptions, must start by drilling a small hole in
the board. In the past, a laser punch was used to punch out the hole before the laser cutting began.
There are two basic methods for laser cutting machines without a stamping device:
1. Blast Drilling:
After continuous laser irradiation, a pit is formed in the center of the material, which is then quickly
removed by the oxygen flow along with the laser beam. The average hole size is dependent on the
plate thickness, and the average diameter of blast holes is half the plate thickness. This method is not
suitable for high-precision parts (such as oil screen seam pipes) because of its large hole diameter and
poor roundness. It is only used for scrap. Additionally, the oxygen pressure used for perforation is the
same as that for cutting, leading to significant splashing.
2. Pulse Drilling:
A pulsed laser with a peak power is used to melt or vaporize a small amount of material, with air or
nitrogen used as an auxiliary gas to reduce hole expansion due to exothermic oxidation. The oxygen
pressure used is lower than during cutting. Each pulsed laser creates only small, deep particles, so it
takes a few seconds to perforate thick plates. Once the perforation is complete, the auxiliary gas is
immediately replaced with oxygen for cutting. This method results in a smaller perforated diameter
and better perforation quality than blast drilling.
The laser must have high output power as well as time and spatial characteristics of the beam, so the
general CO2 laser generator cannot meet the requirements of laser cutting. Additionally, pulse
perforation must have a reliable gas control system to control gas type, pressure switching, and
perforation time. The transition technology from pulse perforation to continuous cutting should be
emphasized in order to achieve high-quality incisions.
In theory, the cutting conditions that normally change during the acceleration section include focal
length, nozzle position, and gas pressure. However, it is unlikely that these conditions will change in
such a short period of time.
3. Nozzle design and air flow control technology.
When cutting steel with a laser, the laser beam and oxygen are directed through a nozzle and onto the
material to form an airflow. For the incision to be effective, the airflow must be high in speed and
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volume to promote oxidation and remove the molten material. The quality of the cut is affected not
only by the laser beam but also by the design of the nozzle and air flow control (such as the nozzle
pressure and the position of the material in relation to the airflow).
The laser cutting nozzle has a simple design, with a small round hole at the end of a tapered opening.
The nozzle is usually made of copper, which is prone to wear and tear, so it needs to be frequently
replaced. As a result, fluid mechanics calculations and analysis are not typically performed. The nozzle
pressure is referred to as the pressure of the gas being ejected from the side of the nozzle, measured in
gauge pressure (Pg).
When used, the gas is expelled from the nozzle and reaches the surface of the material at a certain
distance, referred to as the cutting pressure (Pc). The gas then expands to atmospheric pressure (Pa).
Research shows that as the nozzle pressure increases (Pn), so does the flow velocity and cutting
pressure. A formula can be used to calculate the airflow speed:
V = 8.2d2 (Pg + 1)
Where: V = gas flow velocity in L/min d = nozzle diameter in mm Pg = nozzle pressure (gauge
pressure) in bar
There are different pressure thresholds for different gases. When the nozzle pressure exceeds a certain
value, the airflow transitions from subsonic to supersonic. This threshold is dependent on the ratio of
Pn to Pa and the freedom degree of the gas molecules. For example, in the case of oxygen, the threshold
is Pn = 1 bar x (1.2)3.5 = 1.89 bar. If the nozzle pressure is even higher (Pn/Pa = (1 + 1/n)1 + n/2,
where Pn = 4 bar), the airflow transitions from a normal oblique shock wave to a positive shock wave,
which reduces the cutting pressure, airflow speed, and causes vortex formation on the surface of the
material, which weakens the airflow’s ability to remove the molten material and affects the cutting
speed.
Therefore, the tapered nozzle with a small round hole is used, and the pressure of the oxygen nozzle
is often kept below 3 bar.
Maintenance & Troubleshooting
Summary
To ensure the proper functioning of a laser cutting machine, it requires routine maintenance. As the
machine uses high-precision components, it is important to handle the maintenance process carefully
and follow the operating procedures strictly. It is also recommended to appoint a specific person to
perform the maintenance to prevent any damage to the components.
Users should always have the following spare parts on hand:
A) Acetone (99.5% purity, with less than 0.3% water and 500ml capacity) B) Absorbent cotton (5
packs, medical grade or optical grade) C) Alcohol (500ml, with 99.5%+ purity) D) Dropper (medical)
E) Cotton swab (two packs) F) Multimeter (one).
The instructions for installing or replacing the internal lens of the cutting head are also provided.
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(1) Before installing the optical lens, it’s important to: wear clean clothes, clean your hands with soap
or detergent, and wear clean white gloves; do not touch any parts of the lens with your bare hands;
take the lens from the side, without touching the lens coating surface directly.
(2) When assembling the lens, avoid using your mouth to blow on it; place the lens on a clean desktop
and put a few sheets of professional paper under it.
Handle the lens carefully to prevent bruising or falling, and do not apply any force to the lens coating
surface. Clean the lens holder before installing the lens, using a clean air spray gun to remove any dust
and dirt. Then, gently place the lens into the lens holder.
(3) When installing the lens in the lens holder, do not use excessive force to secure the lens, as this can
cause lens deformation and affect the beam quality.
(4) Precautions when replacing the optical lens:

Handle the lens with care when removing it from the box to prevent scratching

Do not apply any pressure to the lens until the wrapping paper is removed

Wear clean gloves when removing the protective lens and focusing lens from the box and remove
it from the side of the lens

Avoid dust and other objects falling on the lens when removing the packaging paper

Use a clean air gun to remove dust from the lens and put it on optical lens paper

Remove any dust and dirt on the lens holder and supports to avoid foreign matter falling on the
lens during assembly

Do not use too much force when installing the lens in the lens holder to prevent lens deformation

After lens assembly is complete, use a clean air gun to remove any dust or foreign matter on the
lens.
Steps to clean the lens of the laser cutting machine:
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First, blow out the dust on the mirror with a clean air gun. Then, use a clean cotton swab to remove
any dirt. Dip the cotton swab in new high-purity alcohol or acetone and make circular motions starting
from the center of the lens and moving outward.
Repeat the process until the lens is clean, exchanging to a new clean cotton swab after each round. Use
a clean cloth to remove any residual marks on the mirror, taking care not to scratch it. Observe the lens
with plenty of light to see if the reflection is good, indicating that the lens has been cleaned. If the
reflection is not good, continue the cleaning process.
Finally, place the cleaned lens in the mirror base using the above method. It is prohibited to use the
same cotton swab for cleaning again.
Storage of optical lenses

Proper storage of the optical lens is essential to maintain its quality.

The storage environment should be between 10-30°C, as placing the lens in a freezer or similar
environment may cause condensation, which can easily damage the lens.

The temperature of the storage environment should not exceed 30°C, as this may affect the lens
surface coating.

When storing the lens in a box, it should be placed in a non-vibrating environment to prevent
deformation of the lens and maintain its performance.
Electrical inspection
Maintenance mainly involves checking the stability of the daily power supply voltage, maintaining
cleanliness and proper ventilation of the machine’s electrical cabinet, and ensuring the integrity and
safety of each electrical component.
Maintenance cycle
A) The maintenance cycle of the laser, chiller, and air compressor should be in accordance with the
schedule specified in the instruction manual.
B) The first maintenance of the machine should be performed after 24 hours of use, followed by
another maintenance after 100 hours of use, then an overhaul after six months, and thereafter
maintenance should be performed every six months or once a year (depending on specific customer
circumstances).
Maintenance during operation
Before operating the machine, it’s important to perform a daily check and maintenance on the laser
cutting machine according to the daily inspection list. If you notice any abnormal sounds while the
machine is in use, stop it immediately and conduct a thorough inspection. After you have finished
using the laser cutting machine, be sure to turn it off in the correct order and clean up both the machine
table and the area surrounding it. Do not leave any unrelated items on the machine table or control
panel.
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
Regularly check the oil level of the lubrication pump and refill it as necessary to ensure that the Xaxis and Y-axis guides are fully lubricated, maintain the accuracy of the machine, and extend the
life of the X and Y-axis guides.

Clean the Z-axis linear guide and the dust on the screw shaft once a week and add engine oil.

Check the water and air pipes once a week for damage, and promptly notify the company staff
for maintenance if any damage is found.

Clean the air every week to filter out debris and dust.

Check the internal cooling water level of the water cooler every week and add more if
necessary.

Check the contamination of the focusing lens every two weeks and clean it as necessary to
ensure its service life.

Check the protective mirror once a day to maintain its cutting effect.

Check the gas path once a month to remove any potential dangers.

Regularly check the external cables for damage, and check the distribution cabinet line
interfaces for looseness.

Adjust the levelness of the machine after six months of use to ensure its cutting accuracy.
Maintenance for long-term not use
When the machine is not in use for extended periods of time, apply a protective coating, such as oil or
grease, to the moving parts. Wrap them in anti-rust paper and regularly check for any rust, removing
it promptly and performing rust prevention measures on affected areas. (Consider adding a dust cover
if budget allows.) Maintain regular cleaning and inspections of the machine.
Troubleshooting
Page 21 of 47
Machine Operation

Before using the laser cutting machine, it is important to understand the operation of its various parts
and follow the proper operation methods for both machine performance and personal safety.
 Before use, perform the following checks:
 Check the oil level of the machine and fill as necessary to keep it within the normal range.
 Check the water and gas channels for leaks and ensure the quality of the air and water is normal
and not contaminated.
 Verify that the laser beam is being emitted from the center of the gas nozzle by checking the
coaxial alignment of the laser and the nozzle.
 Ensure the mouth of the cutting gas nozzle is appropriate for the cutting process and replace if
necessary.
 Check the connection of the auxiliary gas for cutting and adjust the gas pressure to the proper
level if needed.
Safety precautions and safety signs before use and in use
Represents “Attention”, does not follow the correct operation could result in personal injury or damage
to the equipment.
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Represents there is a laser beam through, do not pass from the beam, otherwise, it will cause burns on
the human body or even life-threatening.
Represents there is a high-voltage power supply danger, do not close to high pressure, otherwise, it
will cause electric shock or even life-threatening
Precautions:










Never look directly into the laser, including the red light.
Keep people and non-work items out of the laser’s range when opening the shutter.
The operator must wear protective glasses and remain present during the operation of the laser
cutting machine.
If an issue arises during use, immediately hit the emergency stop switch or turn off the main
power supply.
Continuously monitor the cooling water temperature and working gas pressure during use.
Only operate the machine with proper training and following safe operating procedures.
Unauthorized personnel are strictly prohibited from operating the machine.
The laser on the laser cutting machine is a Class 4 laser product, and the invisible laser beam, lens
reflection, and scattered light can be harmful to the human body, particularly the eyes. Personnel
must take necessary precautions and prevent fire incidents.
The exhaust gas generated during laser cutting can be harmful to the operator, so make sure the
machine’s vacuum cleaner is functioning properly.
Maintain the laser cutting equipment in a clean and organized manner, lubricating as directed and
properly managing tools and accessories to avoid loss. If any malfunctions occur, stop the machine
immediately and inform relevant engineers if the operator is unable to resolve the issue.
To prevent electrical shock damage, only professional maintenance personnel are allowed to
inspect or repair the electrical control part of the laser cutting machine.
Switch On/Off Sequence:






Start by turning on the external power source to supply electricity to the control cabinet.
Ensure that the water cooler switch is turned on (do not turn off the water cooler switch after
use).
Check that the emergency stop switch is in the released position.
Turn the key switch to the “on” position.
Turn on the computer.
Finally, turn on the laser power to the left.
To shut down the laser cutting machine, reverse the order of these steps.
Software Use and Programming:
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For instructions on using the software, please refer to the manual. The details will not be discussed
here.
Automatic Calibration for Height Sensor:
If you need to calibrate the height sensor when changing the nozzle or if the servo distance is not
accurate, calibration can correct the height of the follower. The steps are as follows:




Move the cutting head down to approximately 5mm from the surface of the plate.
Select “Calibration” on the height control torch → “Floating Head Calibration” → “Confirm”.
The cutting head will drop twice during the process, which takes about 10 seconds. Check the
position of the plate during this time.
The calibration curve will be displayed on the height control torch when the calibration is finished.
The curve should be smooth for a normal calibration result. If the calibration result is poor, it will
affect the cutting effect and the calibration needs to be done again.
There are several factors that can affect the calibration results, including:



An unstable surface on the board.
Shaking of the Z-axis slide.
Serious electrical interference from external sources.
Calibration results are classified as A, B, C, or D. The laser cutter can be used normally if the
calibration result is above “C”, and re-calibration is required to eliminate interference if the result is
“D”.
Laser Cutting Machine Safety
“Precautions”

Appoint safety administrators to establish their responsibilities and provide safety training to
laser processing operators.

Define the laser safety management area and display warning signs at the entrance. The signs
should include information about the machine’s power, laser type, prohibition of entry for
outsiders, and the importance of eye protection. The name of the safety manager should also be
included.

Operators of laser processing machines must undergo specialized training and only operate the
machine with the permission of the safety administrator.
Laser safety notice
The main harm from laser to the human body is to the eyes and skin. Laser exposure can result in burns
on any part of the body, so it is important to avoid placing any part of the body in the light path of laser
equipment to prevent damage from misuse.
Eye and Skin Protection
During laser processing, CO2 and YAG lasers are commonly used, and each type of laser can cause
different harm to the human body. The YAG laser is more harmful as its wavelength has a high
transmittance to human eyes, which may damage the retina. On the other hand, CO2 lasers cause
Page 24 of 47
damage mainly in the form of cornea burns to the eyes. Both types of laser exposure can lead to eye
cataracts and the risk of skin burns. Hence, it is important to use the appropriate protective measures
according to the type of laser being used during the adjustment process.
Fire Prevention
Laser cutting often involves the use of oxygen and sparks during the cutting process, which increases
the risk of fire. Therefore, the work area should not contain flammable or explosive materials and
should have the necessary preventive facilities in place.
Electrical Safety
A) Avoid Touching Switches with Wet Hands to Prevent Electric Shock
The areas of the laser cutting machine marked with lighting signs indicate that these parts have high
electrical voltage or electrical components. Operators who are close to these parts or performing
maintenance should be cautious to avoid electric shock. This includes the protective cover at the servo
motor’s position, the junction box behind the column, the laser cutting machine’s transformer cabinet,
and the electrical cabinet doors, etc.
B) Familiarize Yourself with the Functions and Keys
Make sure to read the machine manual and electrical schematic comprehensively so you can
familiarize yourself with the functions and keys of the laser cutting machine.
C) Prohibit Unauthorized Changes to the Machine Parameters
Do not easily open the electrical doors, and prohibit unauthorized changes to the machine parameters,
servo parameters, and potentiometer (matching with the exchange table). If a change is necessary, you
must be trained by the laser cutting equipment manufacturer and approved by the professional staff.
Remember to record the parameter values before making any changes so the original state can be
restored if needed.
D) Protect Yourself from High Voltage and X-rays
The general power supply voltage of the processing laser cutter is several thousand to tens of thousands
of volts, so it’s important to prevent exposure to the laser’s high voltage and X-rays generated by the
electron tube under high voltage.
E) Avoid Touching Live Parts of the Electrical Cabinet
Do not touch the live parts of the electrical cabinet when it’s energized, such as the numerical control
device, servo device, transformer, fan, etc.
Alert:
After a power failure, wait at least 5 minutes before touching the terminal. There may be high voltage
between the power line terminal for a period of time after the power failure, so to avoid electric shock,
do not touch it immediately.
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Laser cutting machine’s protective measures
“Designate a Safety Administrator”
Designate a safety administrator to determine their responsibilities and conduct safe operation and
safety education for laser processing operators.
“Laser Safety Management Area”
Specify the laser safety management area and place a warning card at the entrance to the area. The
warning card should include the laser processing machine power, laser type, a prohibition on entry
by outsiders, a warning to protect eyes, and the name of the safety manager.
“Machine Key Switch”
When the laser processing machine is not in use, be sure to pull out the key switch and keep it under
lock and key to avoid harm caused by misuse.
“Exhaust System for Smoke and Gases”
Ensure that smoke, gas, and laser working gases produced during fabrication are discharged outdoors
through the exhaust pipe. All cylinders should be stored neatly and securely.
Common knowledge should be known by the operators
Laser cutting machine operators must undergo special training to reach a certain level and only
operate under the agreement of the safety administrator.
When using the laser cutting machine or being close to the laser, the operator or person should wear
appropriate laser goggles and protective clothing. Adequate indoor lighting must be provided in the
area where protective goggles are worn to ensure the operator’s ability to perform smoothly.
To protect the operator, a processing room or protective screen must be provided. Safety devices
should be in place to prevent the diffusion of the laser and ensure the safety of the operators.
When the door of the processing room is opened, the laser shutter should be closed.
Fiber Laser Cutting Thickness & Speed Chart
Page 26 of 47
Laser Cutting Thickness and Speed Chart
Laser Cutting Defects: Quality Control Tips
The process of laser cutting involves absorbing light energy and converting it into heat energy, which
causes the material to melt and vaporize.
The high energy density laser beam is output by the laser generator. The beam is then focused through
the focusing lens, resulting in a highly concentrated energy source. The focused beam passes through
the center of the nozzle, which ejects an auxiliary cutting gas along the same axis as the light path. The
combination of the laser beam and cutting gas rapidly heats, oxidizes, and evaporates the cutting
material to achieve the desired cutting effect.
The basic principle behind laser cutting is the interaction between the laser and matter. This interaction
encompasses both complex microscopic quantum processes and macroscopic phenomena, such as the
absorption, reflection, refraction, energy conversion, and transmission of the material to the laser, as
well as the material’s state and the composition of the ambient gas.
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These macroscopic phenomena, along with other factors such as the tissue effect of a light beam on a
material surface, make the factors affecting the quality of laser cutting very complex.
In addition to the material being processed, other factors that influence the quality of laser cutting
include the characteristics of the light beam, laser power, cutting speed, type (aperture) and height of
the nozzle, focus position, and type and pressure of the auxiliary gas.
The effect of the beam on cutting quality
The width of laser cutting is closely tied to the beam mode and focal spot diameter. The power and
energy density of laser irradiation are related to the diameter of the laser spot, so it is desirable to have
a smaller spot diameter in order to achieve greater power and energy density in laser cutting. The size
of the spot diameter is determined by the diameter of the laser beam output by the oscillator and its
divergence angle, as well as the focal length of the focusing lens.
For the common use of ZnSe flat convex focusing lenses in laser cutting, the relationship between the
spot diameter (d), the focal length (ƒ), the divergence angle (θ), and the diameter (D) of the incident
laser beam can be calculated using the following formula:
（1.1）
As seen in the equation above, a smaller divergence angle in the laser beam will result in a smaller
spot diameter, thereby improving the cutting effect. Reducing the lens focal length (ƒ) is beneficial in
reducing the spot diameter, but doing so also shortens the focal depth and makes it difficult to achieve
an equal width of the incision on both the top and bottom sections when cutting thicker plates, which
affects the quality of the cut.
At the same time, reducing the lens focal length also reduces the distance between the lens and the
workpiece. During cutting, slag may splash onto the surface of the lens, affecting normal cutting
operation and the lens’s service life.
A short focal length lens has a high-power density but a limited focal depth, making it suitable for
high-speed cutting of thin plates as long as the spacing between the lens and workpiece remains
constant. In contrast, a long focal length lens has a low power density but a large focal depth and is
suitable for cutting thick sections of material.
As a general rule, the shorter the focal length, the smaller the focal spot and the shallower the focal
depth; conversely, the longer the focal length, the larger the focal spot and the deeper the focal depth.
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For example, when the lens focal length is doubled, the focal spot size will also double (from Y to
2Y), and the focal depth will increase fourfold (from X to 4X).
Fig.1 The focus of the focusing lens
The pattern of the laser beam is related to it focusing capability, which is similar to the sharpness of a
mechanical tool. The lowest order mode is TEM00, and the energy in the spot is distributed in a
gaussian-like manner. This mode is capable of focusing the beam to a theoretical minimum size, such
as a few microns in diameter, resulting in a highly concentrated energy density. The laser mode is
depicted in the figure.
In contrast, high-order or multi-mode beams have a more widespread energy distribution, resulting in
a larger focused light spot with lower energy density. Using this type of beam for cutting is like cutting
with a dull knife.
Fig.2 Beam energy distribution pattern
The quality of laser cutting is directly related to the mode of the beam. The lower the mode, the smaller
the spot size, the higher the power density and energy density, and the better the cutting performance.
For example, when cutting low carbon steel, a TEM00 mode beam cuts 10% faster and produces a
surface with a lower roughness (10μm less Rz) compared to a TEM01 mode beam. In optimal cutting
parameters, the roughness of the cutting surface can be as low as 0.8μm.
Therefore, for metal cutting, the TEM00 mode laser is often used to achieve faster cutting speeds and
better cutting quality.
Effect of laser power on cutting quality.
The size of the laser power directly affects the thickness of the steel plate that can be cut. The higher
the energy, the thicker the material can be cut.
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Additionally, it influences the dimensional precision of the workpiece, the width of the cut, the
roughness of the cut surface, and the width of the heat-affected zone.
The laser power density (P0, measured in W/cm²) and energy density (E0, measured in J/cm²) that is
illuminated on the workpiece during the laser cutting process have a significant impact on the laser
cutting process.
As the laser power density increases, the roughness decreases. However, when the power density (P0)
reaches a certain value (approximately 3 x 106 W/cm²), the roughness (Rz) value stops decreasing.
The larger the laser power, the thicker the material can be cut. However, for the same laser power, the
maximum thickness that can be cut will differ for different materials.
Table 1 shows the maximum thickness for CO2 laser cutting of various metals for different laser
powers.
Table 1. Laser power and metal maximum cutting thickness
For a laser generator with continuous-wave output, the size and mode of the laser power will have a
significant impact on the cutting quality. In practice, the maximum power is often set to achieve the
fastest cutting speed, increase production efficiency, or cut thicker materials. In theory, the larger the
output, the better.
However, when considering the cost of the laser generator, the output power should only be set close
to the maximum output power of the cutting machine. The figure below illustrates the problems that
arise when cutting low-carbon steel plates with insufficient laser power, such as not cutting through
(a), producing a lot of slag on the lower part (b), and producing a rough section (c).
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Fig.3 Effect of laser power on cutting quality of low carbon steel
The effect of cutting speed on cutting quality
The cutting speed plays a significant role in determining the quality of the cut on a stainless steel plate.
The optimal cutting speed produces a smooth cutting surface and eliminates slag on the bottom.
If the cutting speed is too fast, it may result in an inability to fully cut through the steel plate, leading
to sparks and slag on the bottom half, and even damaging the lens. This occurs because the fast cutting
speed reduces the energy per unit area and the metal is not fully melted.
Conversely, if the cutting speed is too slow, it may cause excessive melting, a wider cutting seam, an
enlarged heat-affected zone, and even burning of the workpiece. This is because the slow cutting speed
allows energy to accumulate at the cutting edge, causing the slit to widen, the melted metal to be unable
to discharge quickly, and slag to form on the bottom of the steel plate.
These defects are illustrated in Figure 4.
Fig.4 The effect of cutting speed on cutting quality
The cutting speed and laser output power have a direct impact on the input heat of the workpiece. This
means that the relationship between changes in input heat and processing quality due to changes in
cutting speed is the same as that between changes in output power and processing quality.
Typically, when the processing conditions are adjusted, only one side (either the output power or the
cutting speed) will be changed to alter the processing quality, rather than changing both at the same
time.
The type (shape) of the nozzle and the height of the nozzle (the distance between the nozzle outlet and
the surface of the workpiece) can also impact the quality of the cutting.
Nozzle function
Control the gas diffusion area to control the cutting quality.
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Fig.5 Gas ejection from the nozzle
The relationship between nozzle and cutting quality
The coaxiality between the center of the nozzle outlet hole and the laser beam is a crucial factor
affecting the cutting quality. The effect becomes greater as the thickness of the workpiece increases.
If the nozzle becomes deformed or melted, it will directly impact the coaxiality. The nozzle shape and
dimensional precision are high requirements, so it’s important to take care of the nozzle and avoid
collisions that may cause deformation. If the cutting conditions change due to a damaged nozzle, it is
advisable to replace it with a new one.
If the nozzle and laser are not coaxial, the cutting quality can be impacted as follows:
a) Effect on the cutting section
As illustrated in the figure, if the auxiliary gas is blown out of the nozzle unevenly, there can be melting
on one side and no melting on the other. This has limited impact on cutting thin plates less than 3mm,
but when cutting plates thicker than 3mm, the effect can be significant and may result in the plate not
being cut through.
Fig. 6 The influence of coaxial degree on the cutting section
b) Impact on the sharp angle
If the workpiece has a sharp angle or small angle, it is more susceptible to over-melting and thick
plates may not be able to be cut.
c) Impact on perforation
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Perforation can be unstable and difficult to control, especially for thick plates, which can cause overmelting and the penetration condition may be difficult to control. This has little effect on thin plates.
The influence of focus position on cutting quality
The focal position refers to the distance between the focal point and the surface of the workpiece,
with values being considered positive if the focal point is above the surface and negative if it is
below it.
Fig.7 Focal position
The focal position plays a critical role in determining the width of the incision, slope, roughness of the
cutting surface, and amount of slag attachment. The focal position affects the beam diameter and focal
depth of the processed object, resulting in changes to the shape of the groove and the flow of the
processing gas and molten metal. To produce a narrow slit, it’s important to minimize the focal spot
diameter (d), which is proportional to 4/πd^2 and the focal length of the lens. A smaller focal depth
results in a smaller d.
However, cutting can cause spatter, and the lens can easily be damaged if it is too close to the
workpiece. As such, the widely used focal length in the industrial application of high-power laser
cutting is between 5 inches (127 mm) to 7.5 inches (190 mm), with the actual focal spot diameter
ranging between 0.1 to 0.4mm. It is crucial to control the focal position to achieve optimal results.
Considering the factors such as cutting quality and cutting speed, in principle:

For the metal with thickness < 6 mm, the focal position is on the surface;

For the metal with thickness > 6 mm, the focal position is above the surface;

When cutting the stainless-steel plate, the focus position is generally below the surface.

When the cutting thickness < 4 mm, choose 5″ focus lens.
The length of the optical path is different when cutting the proximal and distal ends with a flight path
cutting machine, leading to a difference in the size of the beam before focusing.
The larger the diameter of the incident beam, the smaller the focal spot.
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To minimize the change in focal spot size due to changes in the size of the beam before focusing, an
optical path compensation system can be installed to maintain consistent optical paths at the proximal
and distal ends.
The laser beam is shown passing through the focusing lens in Figure 8.
Fig.8 The focal point of a beam passing through the lens
The spot diameter is calculated by the following formula:
（2）
Among them:

D——beam diameter before focusing;

K——beam quality factor
In addition, focus depth is another factor that influences the quality of cutting. Its calculation formula
is as follows:
（3）
It can be seen from the above analysis that the closer the focal position is to the middle of the steel
plate, the smoother the cutting surface will be in the absence of slag. The choice of focus position plays
a crucial role in determining the quality of the cutting for the stainless-steel plate.
When the focal position is appropriate, the material being cut is melted and the material along the edge
is not melted, resulting in a clean, non-stick cut seam, as illustrated in Figure (a).
When the focal position lags, the amount of energy absorbed by the cutting material per unit area
decreases, causing the cutting energy to weaken and the material to not completely melt and be blown
away by the auxiliary gas. This results in the partially melted material being attached to the surface of
the cutting plate and forming a sharp, short slag tail, as shown in Figure (b).
When the focal position is advanced, the average energy absorbed by the cutting material per unit area
increases, causing both the material being cut and the material along the edge to melt and flow in liquid
form. In this case, due to the constant pressure and cutting speed, the molten material forms a spherical
shape and adheres to the surface of the material, as illustrated in Figure (c).
Therefore, the focus position can be adjusted by observing the shape of the slag during the cutting
process to ensure the cutting quality.
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Fig.9 The influence of focus position on slag
Fig.10 The influence of different focus positions on cutting quality
In actual production, when cutting stainless steel plates with a laser cutter, the focus position is selected
on or within the surface of the material. This is done to increase the fluidity of the cutting gas and
molten material and improve the cutting quality by enlarging the smooth surface area. The focus
position will vary depending on the thickness of the steel plate and must be determined through
experimentation.
The choice of auxiliary gas (type and pressure) also plays an important role in determining the cutting
quality. The gas type, air pressure, nozzle diameter, and geometric structure can affect the edge
roughness and the formation of burrs. The gas consumption is determined by the nozzle diameter and
air pressure, with low pressure being below 0.5 MPa and high pressure being above 2 MPa. Coaxial
ejection of the auxiliary gas and the laser beam helps protect the focusing lens from contamination and
removes any slag from the cutting area. Commonly used gases for laser cutting include oxygen,
nitrogen, and air, with different cutting materials requiring different auxiliary gases.
The use of oxygen as an auxiliary gas is primarily for cutting carbon steel, stainless steel, and highly
reflective materials through tapping and high-speed cutting, as well as for oxidation cutting. The laser
cutting machine uses the heat generated by the oxidation reaction for efficient cutting, however, it also
results in the formation of an oxide film on the cutting surface.
Nitrogen is mainly utilized in the cutting of stainless steel plates without oxidation and galvanized
sheet metal without slag.
Air is primarily used for cutting aluminum and galvanized steel without slag and for cutting ordinary
non-metals.
The auxiliary gas pressure is dependent on the type of gas used, the cutting material, the thickness of
the plate, and the form of laser output (continuous wave/pulsed). The pressure of the auxiliary gas
affects the attachment of slag, the quality of the cut surface, and the size of the heat-affected area.
The air pressure condition of the nozzle outlet during processing is shown in the following table:
Table 2 The relationship between the cutting process and the auxiliary gas pressure
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Under the premise of determining the auxiliary gas type, the gas pressure size is an extremely important
factor.
If the auxiliary gas pressure is too high, a vortex will form on the surface of the workpiece, which will
weaken the ability of the airflow to remove the molten material, causing the cutting surface to become
rougher and the slit to widen.
If the auxiliary gas pressure is too low, the melted material of the incision will not be blown away,
leading to the formation of slag on the back of the cut material.
Therefore, there is an optimal value for the auxiliary gas pressure. High gas pressure is required when
cutting thin materials at high speed to prevent slag from forming on the backside of the incision.
Conversely, when the material thickness increases or the cutting speed slows down, the gas pressure
should be appropriately reduced.
For example, when laser cutting stainless steel plates, the use of auxiliary gas helps cool the
surrounding areas of the cutting seam, reducing the heat-affected zone and preventing lens damage
from the heat.
Additionally, using nitrogen as the auxiliary gas enhances the fluidity of the molten metal.
In actual machining, machining defects can be caused by improper process parameters.
With decades of experience in the laser cutting process, it is important to summarize countermeasures
for cutting defects to guide actual production. See the appendix for more information.
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Appendix 1 – Different materials’ laser cutting defects and troubleshooting
Carbon steel: cut with O2
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Stainless steel: cut with high pressure N2
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Alloy: Cut with high pressure N2
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Appendix 2 Physical photograph with cutting defect
1．Stainless steel cutting defects
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2. Carbon steel cutting defects
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