Laser cutting offers several advantages such as minimal thermal deformation, high cutting precision and unmanned automatic cutting capability. By using a high-power laser source, the cutting speed and surface quality are superior to plasma cutting. As a result, laser cutting technology has evolved into a modern cutting tool.
A laser cutting machine has not only the complex mechatronic features of conventional numerical control equipment, but also its unique structural features such as optical system, high pressure system and cooling system.
To minimize processing time and reduce costs, it is essential to maintain equipment to ensure the highest processing speed of the machine tool. This will increase the mean time between failures and improve the equipment utilization rate.
1. CO2 laser cutting machine from Bystronic laser AG
Fig. 1 Optical structure diagram of Bystronic laser cutting machine
1.1 Design structure of Bystronic laser cutting machine
Bystronic's laser machine consists of several components, including bed, changing table, electrical control cabinet, laser generator, laser control cabinet, loading and unloading device and more. The cutting tool used by the machine is a laser beam.
To ensure the stability of the light path from the laser generator to the cutting head, a floating optical system is used, with a reflector group fixed to the machine's moving coordinate axis. This technology has now become a widely used standard across the world.
The laser activation medium used in the machine is a mixture of carbon dioxide, nitrogen and helium. The direction of gas flow is consistent with the cavity axis, enabling effective cooling of axial-flow gas and optimizing the energy conversion process in the cavity.
1.2 Processing principle of Bystronic laser cutting machine
The cutting process involves the interaction of the laser beam, the cutting assist gas and the workpiece. The laser beam acts on the surface of the material, heating it to a high temperature and causing it to melt. The molten material is then burned or blown by the auxiliary gas to form a crack.
To obtain the best cutting effect, laser cutting parameters such as power and pressure can be adjusted accordingly.
2. Maintenance of Bystronic CO2 laser cutting machine
Based on the structure and processing principle of the equipment, maintenance can be divided into four parts: peripheral equipment maintenance, machine bed and control maintenance, laser generator and high-pressure parts maintenance, and process control maintenance .
2.1 Maintenance of peripheral equipment
Most equipment users often only focus on the maintenance of the equipment itself and ignore the maintenance of peripheral equipment. However, it is important to note that peripheral equipment maintenance is also crucial to ensure optimal equipment performance.
2.1.1 Power quality
Due to the high voltage system used in laser cutting machines, a high quality power supply is generally required. The permitted mains voltage range is normally -10% to +5% of the nominal value. Large voltage fluctuations, three-phase imbalances, or high-frequency interference can cause machine tool malfunctions and damage high-voltage components. Therefore, it is crucial to frequently monitor the quality of the main power supply.
For areas with poor quality of the electrical network, it is recommended to install voltage regulators and use special lines to ensure the proper functioning of the equipment. The Bystronic laser machine also requires independent equipment grounding for safety design and to ensure the stability of cutting nozzle distance detection during cutting. Therefore, regular measurement of the earthing resistance of the equipment is necessary.
2.1.2 Compressed air quality
In addition to the requirements of a conventional pneumatic system, the outer lens of the optical path of a laser cutting machine is typically protected by compressed air. The cutting machine from Bystronic laser AG is equipped with multi-stage air filters in the gas unit and laser generator, including oil-water separators and activated carbon filters. The protective gas source for the lens is filtered through an ultrapac filter for secondary filtration to ensure dry, clean gas, with a clearly limited filter element replacement cycle.
It should be noted, however, that although the equipment has its own filtering device, there are still requirements regarding the user's source of compressed air. If the compressed air contains a lot of water and oil, the life of the filter element will be greatly reduced. Once the lens is polluted, its service life will be reduced, the laser power will decrease, the cutting speed will be reduced, and maintenance costs will increase. Therefore, the maintenance of the laser cutting machine should not neglect the maintenance of the air compressor and dryer.
2.1.3 Laser gas purity
The laser gases of CO 2 laser cutting machine are CO 2 He and N 2 .
All manufacturers have strict gas purity standards, as shown in Table 1:
Table 1 Gas purity index of laser cutting machine
| Types of gas | Note |
Purity
(%Vol.) |
(H 2 O) Content
(ppm) |
(O 2 ) Content
(ppm) |
Gas mixing percentage (%) |
| He | 4.6 | ≥99,996 | ≤5 | ≤5 | 63.1 |
| CO2 | 4.5 | ≥99,995 | ≤5 | ≤10 | 3.4 |
| N 2 | 5.0 | ≥99,999 | ≤5 | ≤3 | 33.5 |
| Sum | 100 |
Ensuring the purity of the laser gas is crucial to obtain the best discharge E/N (electron characteristic energy) value after mixing and to produce a stable laser.
If the gas content exceeds the standard, especially if the water content exceeds the standard, the laser beam energy will be weakened and the aging of internal components such as the discharge tube and discharge electrode will be accelerated.
In addition, the service life of the resonator's internal lens will be reduced.
2.1.4 Vacuum cleaner maintenance
During the laser cutting process, a significant amount of industrial dust is produced.
The job of a vacuum cleaner is to remove dust and odors and keep equipment and the environment clean.
Regular cleaning and maintenance of dust removal equipment must be carried out in strict accordance with regulations to ensure effective dust removal.
If cutting dust cannot be removed effectively, it will adhere to mechanical and electrical components, accelerating wear on mechanical components and increasing the risk of short circuits and electrical failures.
Excessive dust accumulation in the cutting head will result in inaccurate detection of nozzle distance, making it difficult to ensure cutting quality, especially when cutting stainless steel, aluminum alloys and other materials with high focus power requirements.
For cooling device maintenance, the main focus is to regularly replace the standard cooling water and clean the water filter, condenser and air filter. For devices with a long service life, it is necessary to check the amount of refrigerant when the refrigeration effect decreases.
Relevant details should be found in the equipment data and, when necessary, the manufacturer's technical assistance departments should be contacted.
2.1.5 Chiller maintenance
The efficiency of CO2 lasers is typically 10% to 20%, with most of the input power being used to heat the gas. As a result, the gas temperature increases rapidly. When the working gas temperature reaches 300 °C, the particle inversion of the upper laser level no longer exists, resulting in no laser output. In fact, the photoelectric conversion efficiency has already decreased significantly when the temperature exceeds 150 °C. As a result, laser cutting machines have a cooling system to maintain a constant temperature for the laser gas and to cool the laser lens and other heating components.
Typically, if the chiller malfunctions and triggers an alarm, such as a temperature or flow alarm, the high voltage will automatically cut off and the laser will shut down. The laser cutting machine cannot be started until the chiller problem is resolved, making chiller stability crucial to the overall health of the equipment.
2.2 Maintenance of the machine base and control part
Machine transmission parts such as chains, racks and guide rails should be cleaned and lubricated regularly. The oil must be changed at regular intervals, especially the turbine oil and the vacuum pump oil.
It is important to note that irregular replacement of turbine oil can significantly reduce the life of the turbine, resulting in significant economic losses.
Furthermore, the cooling and ventilation system of the CNC device should be cleaned regularly based on the production environment. Check that the cooling fans are working properly and that there are no water or air leaks.
Due to the large amount of dust in the laser cutting environment, attention should also be paid to prevent dust from entering the electrical cabinet. The door of the electrical cabinet should be opened as little as possible, as dust and metal powder present in the air can fall on the printed circuit board or electrical connector, causing the insulation resistance between the components to drop, causing failures or even damage. .
Furthermore, it is essential to keep random data, installation software and parameter backup disk. If possible, use cloning software to back up your hard drive data.
2.3 Maintenance of laser generator and high voltage part
Maintenance of the laser generator and high-voltage parts is normally carried out by the manufacturer's professional technical personnel. This may include tasks such as cleaning and adjusting the high voltage module, cleaning the optical path lens on the laser, and adjusting the laser power and mode.
Bystronic Laser AG provides tracking service for each laser cutting machine, and when signing a maintenance contract with customers, the company will carry out comprehensive maintenance and debugging of the equipment according to the “maintenance inspection list”. This helps to identify and resolve any hidden problems in a timely manner and effectively ensure the stability and integrity of the equipment.
2.4 Control of the machining process
The control range of the machining process is quite broad, covering the optimization of cutting sequences and layouts, as well as the optimization of cutting parameters and much more.
It is essential to highlight aspects that may go unnoticed in daily maintenance:
2.4.1 Purity of auxiliary gas cutting and gas pipeline cleaning
Over time, impurities in the gas or piping can cause the gas pressure reducing valve to become blocked. As a result, the pressure of the gas used for cutting becomes unstable, which can lead to a decline in processing quality.
2.4.2 Cutting head maintenance
Regularly check the condition of the shaving head lens and shaving nozzle and clean or replace them immediately. If internal leakage is detected, replace the sealing ring immediately. Establishing an effective preventive maintenance system is crucial to preventing equipment accidents and strictly controlling accidents caused by poor equipment lubrication.
Operators must strictly follow operating procedures to avoid equipment failures and reduced accuracy caused by operational errors or violations of operating procedures. Record fault repairs and maintenance work, including the fault phenomenon, troubleshooting method and maintenance performed. This helps with tracking management and provides convenience for future maintenance.
For laser cutting machines, it is necessary to keep spare parts such as lenses, nozzles, ceramic rings and other wearing parts in stock according to the actual situation. Following the manufacturer's suggestions, it is also advisable to keep high-power circuit boards and modules that can fail in stock. This makes on-site maintenance more convenient and avoids equipment shutdowns and prolonged maintenance cycles due to lack of spare parts.
Many users currently implement the Total Productive Maintenance (TPM) management system, which effectively improves overall equipment efficiency. It's a system worth promoting.
3 . Conclusion
Maintenance of a laser cutting machine is a necessary measure to ensure long-term maintenance or full recovery of the equipment's processing capacity (efficiency and precision) and to maintain its use value. It is an effective means of reducing the operating cost of the laser cutting machine and improving the equipment utilization rate.
