A laser scanner, also known as a laser galvanometer, consists of an X-Y optical scanning head, an electronic driving amplifier, and an optical reflector. The signal provided by the computer controller drives the optical scanning head through a driving amplifier circuit, thereby controlling the deflection of the laser beam in the X-Y plane.
In a laser demonstration system, the waveform of optical scanning is a vector scanning, and the scanning speed of the system determines the stability of the laser pattern. In recent years, high-speed scanners have been developed with a scanning speed of 45000 points per second, making it possible to demonstrate complex laser animations.
Scanning principle: The scanning pattern is a two-dimensional effect pattern, so the scanning motor uses two motors, X and Y, to determine the position of a point at a time. The scanning frequency controls the position of different points at different times to achieve the transformation of the entire scanning pattern. The lower the scanning frequency (speed), the more obvious the pattern flickers, which can be understood using the principle of cinema.
Principle and troubleshooting of laser marking galvanometer:
Simply put, a galvanometer is a scanning galvanometer used in the laser industry, and its professional term is called the high-speed scanning galvanometer Galvo scanning system. In simple terms, it is mainly used for laser marking, laser engraving, stage lighting control, laser drilling, and so on. The scanning laser galvanometer is the core component of the marking machine, and the performance of the marking machine mainly depends on the performance of the scanning laser galvanometer.
Introduction to scanning laser galvanometer
The high-speed scanning laser galvanometer system is a high-performance rotating motor designed specifically for optical scanning applications. The motor part adopts a high-precision position sensor. Mainly used for fast and accurate positioning of light beams. High speed laser galvanometer is the result of years of experience in the development and prodction of industrial laser galvanometer scanning systems.
A motor specifically designed for lens loading can achieve optimal scanning performance. Special treatment is applied to the bearing part, which can withstand long-term uninterrupted operation. The special design of bearings can achieve the highest dynamic performance and harmonic characteristics of the system. Internationally leading digital control methods can effectively avoid various electromagnetic interference in the working environment, and advanced control algorithms can ensure that the system has faster response speed.
The photoelectric sensor used in high-speed scanning laser galvanometer has high resolution, excellent repeatability accuracy, and very small drift. The motor is equipped with a heating device and temperature sensor, which can still operate stably in the event of environmental fluctuations. High speed scanning laser galvanometer can ensure long-term stable operation.
The principle of laser galvanometer marking
Its working principle is to incident a laser beam onto two mirrors (scanning mirrors), and control the reflection angle of the mirrors using a computer. These two mirrors can scan along the X and Y axes respectively, achieving the deflection of the laser beam. This allows the laser focal point with a certain power density to move according to the required requirements on the marking material, leaving permanent marks on the material surface. The focused light spot can be circular or rectangular.
In the galvanometer scanning system, vector graphics and text can be used. This method adopts the processing method of graphics software in the computer, and has the characteristics of high drawing efficiency, good graphics accuracy, and no distortion, greatly improving the quality and speed of laser marking. At the same time, the galvanometer marking method can also use the dot matrix marking method, which is very suitable for online marking. Depending on the production line at different speeds, one scanning galvanometer or two scanning galvanometers can be used.
Common faults in the galvanometer of laser marking machines
1. Mirror motor not self-locking
Firstly, check whether there is an open circuit or short circuit in each connecting wire, whether the connection is correct, and whether the fuse is intact. After confirming that there is no error, turn on the power and observe whether the indicator light on the galvanometer drive board is green or yellow. If the light is not on or the red light is on, unplug the power cord of the driver board and use a multimeter to measure whether the voltage at each terminal of its input terminal is ± 24V. If the voltage is normal, it is necessary to test whether the voltage is normal with the driver board and the machine load on the side. If both are not normal, open the control box and test the switch power supply voltage without the load. If the voltage is not normal, the switch power supply will be damaged. After the power input is normal and all wires are connected, the motor usually emits a two click sound when powered on. If there is no sound, gently push the vibrating lens with your hand, with a slight force. If the vibrating lens is not self-locking, the drive board is damaged. Of course, under normal voltage output, if the drive board light is not on or the red light is on, it indicates that there is a problem with the vibrating mirror drive board or motor. At this time, find a confirmed intact drive board and connect it correctly, If the power is turned on and the galvanometer motor is not self-locking, it means that the galvanometer motor is damaged. Similarly, find a confirmed good galvanometer motor and connect it to the drive board that is not powered on. Turn on the power, and if it is not powered on, the galvanometer drive board is damaged. Repeat the process of connecting and unplugging the wires, making sure to do so while the power is off.
2. The galvanometer motor has self-locking, but it is not strong enough
Connect a confirmed intact galvanometer drive plate and a intact galvanometer motor to the drive plate and galvanometer to be tested, power on normally, and gently rotate the galvanometer shaft by hand. If it becomes "hard", it is normal; Otherwise, it can be determined that the galvanometer drive plate and galvanometer motor are damaged.
3. The galvanometer motor does not swing
Check if the marking card has a control signal output (note that the signal is a DC voltage signal of -5V to+5V). If so, check if the galvanometer signal connection wire is properly connected. After confirming that the connection is correct, mark the card. If there is still no oscillation, check if the signal wire is reversed or broken. Otherwise, it can be concluded that the drive board is damaged.
4. Wave lines appear during marking, and the marking head machine makes a slight noise
If the heat generation of the galvanometer drive board is slightly high (interference occurs), check whether the grounding wire is correctly connected (the best grounding method is: X galvanometer signal ground, Y galvanometer signal ground, shielding wire, 220V power supply ground, and the marking machine casing should be connected). If there is still interference after the grounding wire is connected, first check whether the marking card is normal (the inspection method is to replace it with a confirmed intact marking card and mark it to see if there is still interference). If there is still interference, Further check if the connecting wire of the galvanometer motor is intact and if there is any entanglement with other wires. If everything is normal, first replace it with a confirmed intact galvanometer drive plate. If there is no interference, it can be concluded that there is a problem with the galvanometer drive plate; If there is interference, there is a problem with the galvanometer motor. (Of course, if the company goes out for laser maintenance personnel, please make sure. If the customer's galvanometer is a product from three years ago, the product's anti-interference ability will definitely be poor. If there are mobile phone signals, motors, motors, magnetic fields, or RF signals of the Q switch exposed around the galvanometer marking head, it may affect it. This phenomenon can occur with new galvanometers.)
5. Generate a howling sound
Just like the fourth step, test the marking card signal, wiring, external interference, etc. If there is still a howling, debug the potentiometer on the filter board of the galvanometer drive board. If the howling still cannot be eliminated, you need to return to the company for precise calibration. (Note: Do not remain in a howling state for a long time to avoid burning out the galvanometer motor)
6. Unsealed or over sealed in marking
Change the "jump delay", light output and light off delay in the marking software. If none of the methods are effective, the galvanometer has not been fully calibrated and should be returned to the company and the supplier. Qualified laser repair and after-sales personnel can make certain adjustments according to the galvanometer debugging steps, but it is important to note that several potentiometers are not randomly moved. (Refer to the steps for adjusting the galvanometer)
7. When marking, there is no laser output below the marking head, but there is a laser in the laser output hole
The software marking speed is fast, the field mirror is not installed, the galvanometer does not move and the position is not normal, the galvanometer lens falls off, and the galvanometer lens is dirty. Follow the above method to solve the first few problems. If the vibrating lens comes off and cracks, you need to return to the company and replace it with a new lens and adjust the laser. If the vibrating lens is dirty, use 99% alcohol and degreased cotton to wipe it. If it cannot be wiped and is the center part of the vibrating lens, or if the edge part is larger than 1 square millimeter, you need to replace the vibrating lens and handle it the same way as if the vibrating lens comes off.
How to avoid secondary pollution of laser resonators
In general power output lasers, most of the lenses have high absorption of specific laser wavelengths due to manufacturing processes or external pollution, which over time shortens the lifespan of the lenses. Damage to the lenses can affect their use or even cause downtime.
The increase in absorption of laser wavelength by the lens can cause uneven heating, leading to reflection of the lens and changes in refractive index. When the laser wavelength passes through or reflects from a high absorption lens, the uneven distribution of laser power causes the center temperature of the lens to be high and the edge temperature to be low. This change is called the lens effect in optics.
Due to pollution, the high absorption and heating effect of lenses can cause many problems. The generation of irreversible thermal stress on the lens substrate, the power loss caused by beam propagation through the lens, the deviation of the focusing point position, and premature damage to the coating layer can all lead to the destruction of the lens. For lenses exposed to the air, when cleaning, they often do not follow the requirements and precautions for lens cleaning, and randomly select materials, resulting in new pollution or even scratches on the lenses, causing irreparable losses. Therefore, based on years of experience, it is believed that maintaining cleanliness is the most important for any type of optical lens. It is important to have good cleaning habits to carefully clean the lens, which can reduce or eliminate pollution caused by human factors.
As a common sense, when operating optical systems by hand, it is necessary to wear fingertips or medical gloves during cleaning, disassembly, and installation. Always follow the requirements and precautions for cleaning lenses. During the cleaning process, only specified materials such as optical wiping paper, cotton swabs, and reagent grade ethanol can be used. Taking shortcuts in cleaning, disassembling, and installing any lens will result in shortened lens life and even permanent damage. So, common sense should be used to prevent lenses from being contaminated by other reasons, such as moisture, smoke, dust, and so on. After determining the contamination of a certain lens, it is best to use an ear wash ball to blow the lens until there are no particles on its surface. Do not use your mouth to blow. Because most of the air blown out contains oil, water, etc., which will further contaminate the lenses. If there is still contamination on the surface after ear wash treatment, it must be gently wiped with a specialized cotton swab dipped in laboratory grade acetone and ethanol. This can remove most of the thin layers of pollution. The contamination of the lenses in the laser can cause serious collection errors to the laser output and even the data acquisition system. If we can keep the lenses clean regularly, it will undoubtedly prolong the service life of the entire machine.
