Design and research of high-power laser cleaning head

ＺｈａｎｇＳｈｅｎｇｊｉａｎｇ， ＷａｎｇＭｉｎｇｄｉ＊ ， ＧｕｏＭｉｎｃｈａｏ， ＷａｎｇＸｉａｎｂａｏ， ＬｉｎＹａｏ， ＸｕＹｏｕｙｕａｎ， ＹｉｎＺｉｈａｎｇ

（ＳｃｈｏｏｌｏｆＭｅｃｈａｎｉｃａｌａｎｄＥｌｅｃｔｒｉｃａｌＥｎｇｉｎｅｅｒｉｎｇ，ＳｏｏｃｈｏｗＵｎｉｖｅｒｓｉｔｙ，Ｓｕｚｈｏｕ，Ｊｉａｎｇｓｕ２１５１３１，Ｃｈｉｎａ）

Ａｂｓｔｒａｃｔ

In order to prevent lens breakage or burning during long-term high-power laser cleaning and ensure the service life and stability of the optical head, Solidworks software is used.

Mainly for the structural design and three-dimensional modeling of the collimation system, galvanometer system and focusing lens group in the laser cleaning head, and feasibility analysis of the structural parameters of each system of the optical head

Research; use ANSYS Workbench to conduct temperature field simulation, and verify the reliability of the model design through temperature detection and laser cleaning tests. The results show that each lens

The incident light spot energy density is lower than the corresponding damage threshold, and the temperature changes of each component of the laser head obtained by simulation are within a reliable range. The designed bald head model is reliable and can satisfy

It meets the work requirements and provides corresponding theories and methods for independent research and development of high-power laser cleaning heads.

Laser cleaning technology is a green and environmentally friendly cleaning method

Formula [1] has attracted more and more attention in China. Currently, it is more popular in the market

The cleaning efficiency and cleaning effect of low-power laser cleaning equipment are

Certain limitations, high-power laser cleaning equipment has greater applicability.

However, high-power laser cleaning will cause equipment damage after long-term operation.

Problems such as heating can easily cause key components such as reflectors and focusing mirrors to break.

Or cauterized, greatly reducing the use of lenses and laser cleaning heads

life.

At present, the laser cleaning industry’s research on laser cleaning heads is mainly

Focus on appearance and functional design. Sun Bao et al. [2] optimized the method

The structure of the hand-held laser cleaning head facilitates long-term use by staff.

operation; Li Chaoyang et al. [3] designed a distance sensor

The laser cleaning head can automatically control the cleaning spacing and cleaning range; Zhang Zhi

Yan et al. [4] designed a laser cleaning system with simple structure and convenient operation.

head, the beam can form line spots on the surface of the cleaning object, which improves the overall

Body cleaning effect; Li[5] designed an adjustable focus laser cleaning oscillator

Mirror, in certain embodiments, the adjustable lens group can be used to align the laser

1 Research on the design of laser cleaning bald head model

The structure of the laser cleaning optical head mainly includes the laser beam expansion collimation system

system, galvanometer system and focusing lens group, etc. For different internal systems

The structural design and optimization plan are as follows.

1.1 Laser beam expansion collimation system

In order to ensure the beam quality, through the existing beam expansion system scheme [6], it is planned to

The calculated data of the laser beam expansion collimation system are shown in Table 1.

The incident surface of the second lens is a plane. For beam expansion collimating lenses

group, it is also necessary to coat a layer of SiO2 and polymer polyvinyl alcohol on the mirror surface.

Films made of butyraldehyde [7], the polymer polyvinyl butyraldehyde in the film

The mass fraction of aldehyde is 1%, and the central laser transmittance can reach 99.9%.

The laser damage threshold is 40.1J/cm2, which can improve the durability of the lens.

Durability, reducing the reflectivity of the lens to the laser beam, thereby increasing the energy

Utilization rate, increasing the use range and use time of the lens.

1.2 Galvanometer system

The galvanometer system includes the scanning galvanometer motor, motor control system, and feedback system.

Reflective lens, reflective lens clamping device and base [8].

1.2.1 Reflector design

The structural parameters of the reflective lens can be determined by the designed parameters of the outgoing beam.

Design selection is made based on the number. The wavelength of the emitted light beam is 1064nm.

Diameter is 12 mm. Since the galvanometer is in contact with the incident beam during operation,

random angle, the reflective lens should ensure that the light is within the working scanning angle.

The beam forms total reflection, and the lens volume should meet the requirements

As small as possible, the reflectivity of the beam is required to be very high. In addition, in the mirror

A layer of high-reflective film is coated on the chip to make two beams of reflected light with equal intensity

The path difference satisfies the interference strengthening and weakening conditions, while increasing the reflectivity

Increase the mirror damage threshold[9-12].

According to the principle of geometric optics, it can be deduced that the reflector has different

angle, the same cylindrical beam irradiates the ellipse on the reflector

The long axis and short axis of the light spot, the formula is as follows:

In the formula: D is the diameter of the incident beam; L is the long axis of the elliptical spot; W is

The minor axis of the elliptical spot; a is the difference between the reflector and the incident light when it is in the initial position.

The angle between the incident beams; x is the deviation of the galvanometer mirror from the initial position

Angle.

When x is the maximum value of galvanometer deflection, the resulting elliptical light spot

The size is the maximum spot size, and the designed reflector size must

Larger than this size can avoid leakage during laser irradiation. Book

In the design of the secondary laser head, the diameter of the laser beam after collimation is

12mm, the deflection angle of the galvanometer motor is set to ±8°, so it can

Calculate the reflector size according to formula (1).

Taking into account the processing technology requirements and the above design requirement data,

The final structural parameters and various data of the reflective lens are shown in Table 2.

This reflective lens uses beryllium content (mass fraction) of 62%.

Beryllium aluminum alloy material. The density of this material is less than that of ordinary glass

Degree, the thermal conductivity is 212 W/(m·K). Compared with glass materials, its thermal expansion coefficient is smaller, thermal conductivity is high, specific heat capacity is large, and elastic modulus is large.

Strong stiffness and good dimensional stability. After a series of treatments and coatings,

The surface roughness of the lens is less than 3 nm, and the maximum working temperature is

150 ℃ and high precision, it can perfectly replace transmission in some optical fields.

traditional glass materials. After the reflective lens design is completed, according to the structure of the lens

Design the clamping device according to the structural dimensions, and then design the galvanometer motor.

1.2.2 Galvanometer design

In order to realize the design requirements of the galvanometer system, the galvanometer electronics can be first

When designing the machine, the resolution and repeatability of the motor must be taken into consideration.

etc. The relevant parameters are shown in Table 3.

After the galvanometer motor is designed, according to the relative incidence of the laser beam

The radiation position and the structural parameters of the reflector are designed, and the internal parameters of the base are designed, and then

Design the base outline parameters based on the approximate internal dimensions of the laser cleaning head

number. The internal parameters of the base are determined based on the relative incident position and vibration of the laser beam.

Design of structural parameters of mirror motor and reflector. Galvanometer system structure model

The model is shown in Figure 1

1.3 Focusing lens group

After the laser beam is emitted from the galvanometer system, it needs to be focused. In the design of this laser cleaning head, this article uses f-theta transparent

Mirror [13-14]. This kind of lens is used in laser marking and laser cleaning industries

is widely used in.

For a general focusing lens, when the beam is at the incident angle θ

When incident, the image height h formed should satisfy the following formula:

h=f·tanθ (2)

In the formula: f is the focal length of the focusing lens group, and θ is the scanning angle.

There is a deviation between the ideal image height and the actual image height, and this deviation can

It is expressed by relative distortion q, such as formula (3):

In actual design applications, relative distortion needs to be controlled at 0.5%

As follows, it can be considered that the designed f-theta lens group meets the usage requirements.

beg. The structural parameters of each lens of the f-theta lens designed this time are shown in

Table 4

The maximum field curvature of this f-theta lens group is 0.6mm, which is effective

The focal length is 164mm, the incident aperture diameter is 12mm, and the field of view is

±28°, the length of the optical tube is 40.5mm, and the maximum relative distortion is

0.1%, the maximum astigmatism is 0.1 mm. The last mirror surface is flat

surface, the rear working distance is 185 mm, and the diameters of each lens are respectively

58, 62, 66mm. The lens group model is shown in Figure 2

2 Feasibility study of laser head

2.1 Damage threshold calculation

In order to verify the feasibility of laser head design, it is necessary to calculate and compare

Laser energy density and damage threshold. The laser used in this article is a single

Color laser, its relevant parameters include: laser wavelength is 1064nm, laser

The operating power of the light generator is 500 W, and the pulse width is 80ns.

The repetition frequency is 500kHz. The energy density of laser is calculated according to the formula

(4):

In the formula: I is the energy density; P is the average laser power; S is the spot

area; f is the pulse repetition frequency.

The first side that the laser light path with the smallest spot and the largest power passes through

The lens has a constant power of 500 W and a spot diameter of 2mm, which can be calculated

The maximum energy density is calculated to be 31.83J/cm2. collimating beam expander lens

There is a layer of antireflection coating on the surface of the group, and its laser transmittance can reach 99.9%;

By calculating the damage threshold of the lens [15], the laser damage threshold can be obtained.

The value is 40.14J/cm2. Since the damage threshold of the lens film is greater than that of the laser

energy density, so the selected lens and anti-reflection coating meet the usage requirements.

For the reflective lens on the galvanometer motor, it is coated with a high-reflective film

Made of beryllium aluminum alloy material, the reflectivity is greater than 99.7%, laser light

When the beam propagates to the reflecting mirror, the beam diameter is 12 mm and the power is small.

At 500W, the incident angle is calculated as 45°, and can be calculated by formula (4)

The output laser energy density is less than 0.63J/cm2. Obtained by calculation

The laser damage threshold of reflective lenses is greater than 600J/cm2. due to anti

The laser energy density of the irradiating lens is far less than its damage threshold, so the

Choose reflectors and high-reflective films that meet the usage requirements.

2.2 ANSYS Workbench temperature field simulation

In order to make the calculation data more reliable, ANSYS is used

Workbench is used to conduct thermal analysis [16-17] to ensure the feasibility of model design.

sex. In the simulation of the overall laser cleaning head, the settings are limited

The meta-analysis type is Temperature, the simulation time is 300s, and the

The number of steps is 17 and the number of iterations is 17.

2.2.1 Collimated beam expansion system

The collimated beam expansion system includes two lenses. The two lenses are used in laser illumination.

The temperature field after stabilizing for 300 seconds is shown in Figure 3

.It can be seen from Figure 3 that after stabilizing, the collimating beam expander lens 1

The highest temperature is 27.172℃, and the collimating beam expander lens 2 has the highest temperature.

It is 42.364 ℃, which is less than the maximum temperature of the lens anti-reflection coating.

85.000 ℃, meeting the usage requirements.

2.2.2 Galvanometer system

In temperature field simulation, since aluminum alloy is more suitable for use than glass,

It is a reflective lens, so the reflective lens is replaced with beryllium aluminum alloy. exist

In the temperature field simulation after replacing the lens material, the temperature field of the entire galvanometer system that tends to be stable after 300 seconds of laser irradiation is shown in Figure 4.

It can be seen from Figure 4 that after stabilizing, the reflector on the galvanometer motor

The maximum temperature of the chip is 37.300 ℃, and the maximum temperature of the galvanometer motor is

27.172 ℃, the maximum temperature of the other reflective surface is 29.704 ℃,

The maximum operating temperature of beryllium aluminum alloy lenses is 150 ℃, and the galvanometer electromagnetic

The maximum operating temperature of the machine is 40°C. Obviously, the simulated galvanometer system

The temperature meets the working requirements of each component.

2.2.3 Focusing lens system

The focusing lens group consists of three lenses, which simplify the laser spot.

into a diameter of 12mm, then these three lenses will be exposed to laser light for 300 seconds.

The temperature field that tends to stabilize later is shown in Figure 5.

It can be seen from Figure 5 that the maximum temperature of the three lenses after stabilization

Neither exceeds 44.896 ℃, which is far less than the maximum operating temperature of the antireflection coating.

85.000 ℃, meeting the working requirements.

3. Experimental verification

3.1 Physical picture and cleaning test platform

This test chooses aluminum alloy welding spots as the cleaning object. electric car

The aluminum alloy battery tray will form welding spots after welding and needs to be

Online cleaning to meet the operation of workshop process flow. To increase excitement

The applicability of the optical cleaning head can ensure the conditions of the internal system of the laser head.

Under the condition, design the appearance and use lightweight materials to make the actual object.

As shown in Figure 6

This laser cleaning head can be mounted on a robotic arm for cleaning operations

Industry, as shown in Figure 7. By setting the robot speed on the controller

And write a path program to achieve controllable laser focus. This way

It is more stable and more operable than hand-held cleaning.

3.2 Temperature verification and cleaning effect verification

This article uses a temperature sensor to detect the temperature change during the cleaning process.

The temperature reaches a maximum of 28.7 ℃ during cleaning, as shown in Figure 8.

The temperature is within the cleaning threshold and in line with the simulation test results, which verifies the reliability of the laser head design.

In order to further verify the feasibility of the high-power laser head model, this

This paper uses a designed high-power laser head to conduct inspection on aluminum alloy welding spot samples.

Conduct laser cleaning test, as shown in Figure 9.

Visual inspection shows that during the laser cleaning process, the light output from the laser head is stable, forming

A higher quality laser beam can achieve good cleaning results and

This further verifies the reliability of the bald head design.

4 Conclusion

This article optimizes the structural parameters based on the existing laser cleaning head

model, and carried out threshold calculation and simulation test research to verify its feasibility

The performance is summarized as follows:

(1) Optimize the materials and structures of each component of the laser cleaning head

After optimization, the overall compactness and heat dissipation are improved, effectively reducing the overall cost.

body operating steady-state temperature.

(2) The temperature field simulation of ANSYS Workbench can

It is concluded that the laser cleaning head designed in this article performs well in long-term laser cleaning operations.

The maximum temperature during operation is approximately 44.896℃, and the maximum temperature of each component part is

The high temperature is in compliance with its working requirements, and is finally verified by experiments.

The rationality and feasibility of the design are guaranteed to a certain extent.

(3) The basic design of high-power laser cleaning optical head has been formed. system can better adapt to market promotion, and the model verification method in the system The method still needs further optimization.

References 参考文献

［１］ＣＨＥＮＧＪ，ＦＡＮＧＳＣ，ＬＩＵ Ｄ，ｅｔａｌ．Ｔｅｃｈｎｏｌｏｇｙａｎｄ

ａｐｐｌｉｃａｔｉｏｎｏｆｌａｓｅｒｃｌｅａｎｉｎｇｆｏｒｍｅｔａｌｓｕｒｆａｃｅ［Ｊ］．Ａｐ－

ｐｌｉｅｄＬａｓｅｒ，２０１８，３８（６）：１０２８－１０３７．

成健，方世超，刘顿，等．金属表面激光清洗技术及其应

用［Ｊ］．应用激光，２０１８，３８（６）：１０２８－１０３７．

［２］ＳＵＮＢ，ＺＨＵ ＸＦ，ＺＨＡＮ Ｗ Ｈ，ｅｔａｌ．Ｌａｓｅｒｃｌｅａｎｉｎｇ

ｈｅａｄ：２０２０２１０４２００８．１［Ｐ］．２０２０－０６－０８．

孙豹，朱先锋，詹伟红，等．激光清洗头：２０２０２１０４２００８．１

［Ｐ］．２０２０－０６－０８．

［３］ＬＩＺＹ，ＺＨＵＸＦ，ＱＩＣ，ｅｔａｌ．Ａｈａｎｄｈｅｌｄｌａｓｅｒｃｌｅａｎ－

ｉｎｇｈｅａｄｔｅｓｔｄｅｖｉｃｅ：２０２０１０８３５００５．１［Ｐ］．２０２０－０８－１９．

李朝阳，朱先锋，齐 冲，等．一种手持式激光清洗头测试

装置：２０２０１０８３５００５．１［Ｐ］．２０２０－０８－１９．

［４］ＺＨＡＮＧＺＹ，ＬＩＮＸＣ，ＬＩＡＮＧ Ｈ，ｅｔａｌ．Ｌａｓｅｒｃｌｅａｎ－

ｉｎｇｈｅａｄ：２０１７１０７１６３９０．６［Ｐ］．２０１７－０８－１８．

张志研，林学春，梁浩，等．激光清洗头：２０１７１０７１６３９０．６

［Ｐ］．２０１７－０８－１８．

［５］ＬＩＧ Ｆ．Ａｄｊｕｓｔａｂｌｅｆｏｃｕｓｌａｓｅｒｃｌｅａｎｉｎｇｇａｌｖａｎｏｍｅｔｅｒ，

ｃｌｅａｎｉｎｇｓｙｓｔｅｍａｎｄｃｌｅａｎｉｎｇｍｅｔｈｏｄ：ＵＳ１０９０６０７３［Ｐ］．

２０２１－０２－０２．

［６］ＬＩＤＪ，ＬＩＡＮＧＳＹ，ＣＡＯＪＪ．Ｓｐａｔｉａｌｌａｓｅｒｂｅａｍｓｈａ－

ｐｉｎｇｕｓｉｎｇａｓｐｈｅｒｉｃＧａｌｉｌｅａｎｂｅａｍｅｘｐａｎｓｉｏｎｓｙｓｔｅｍ［Ｊ］．

ＬａｓｅｒＴｅｃｈｎｏｌｏｇｙ，２００８，３２（４）：４２７－４２９．

李殿军，梁思远，曹建建．非球面伽利略扩束系统实现激

光束空间整形［Ｊ］．激光技术，２００８，３２（４）：４２７－４２９．

［７］ＹＥＬＱ，ＫＡＮＧＳ，ＺＨＡＮＧ Ｗ Ｈ，ｅｔａｌ．Ｓｏｌ

－ｇｅｌｐｒｅｐａ－

ｒａｔｉｏｎ ｏｆ ａｎｔｉ

－ｆｏｇｇｉｎｇ ＳｉＯ２／ＳｉＯ２－ＴｉＯ２ ｄｏｕｂｌｅ－ｌａｙｅｒ

ａｎｔｉｒｅｆｌｅｃｔｉｖｅｃｏａｔｉｎｇ［Ｊ］．ＣｈｅｍｉｃａｌＪｏｕｒｎａｌｏｆＣｈｉｎｅｓｅ

Ｕｎｉｖｅｒｓｉｔｉｅｓ，２０１９，４０（１１）：２２７４－２２８０．

叶龙强，康硕，张 伟 豪，等．溶 胶－凝 胶 法 制 备 ＳｉＯ２／ＳｉＯ２－

ＴｉＯ２双层防雾增透 膜［Ｊ］．高等学校化学学报，２０１９，４０

（１１）：２２７４－２２８０．

［８］ＱＵ ＹＢ，ＣＯＮＧＬＹ．Ｄｅｓｉｇｎｉｎｇｏｆｔｈｅｓｔａｂｉｌｉｚａｔｉｏｎｉｍ－

ａｇｉｎｇｓｃａｎｎｉｎｇ－ｍｉｒｒｏｒｓｙｓｔｅｍ［Ｊ］．Ｅｌｅｃｔｒｏ－ＯｐｔｉｃＴｅｃｈ－

ｎｏｌｏｇｙＡｐｐｌｉｃａｔｉｏｎ，２０１０，２５（６）：２５－２６．

屈玉宝，丛龙洋．稳像振镜系统的设计［Ｊ］．光电技术应

用，２０１０，２５（６）：２５－２６．

［９］ＸＵ ＬＬ．Ｔｈｅｄｅｓｉｇｎｏｆｓｃａｎｎｉｎｇｃｏｎｔｒｏｌｓｙｓｔｅｍｂａｓｅｄ

ｏｎ２Ｄｌａｓｅｒｇａｌｖａｎｏｍｅｔｅｒ［Ｄ］．Ｃｈａｎｇｃｈｕｎ：Ｃｈａｎｇｃｈｕｎ

ＵｎｉｖｅｒｓｉｔｙｏｆＳｃｉｅｎｃｅａｎｄＴｅｃｈｎｏｌｏｇｙ，２０１２．

徐亮亮．二维激光振 镜 扫 描 控 制 系 统 设 计［Ｄ］．长 春：长

春理工大学，２０１２