Solar photovoltaic power generation is a kind of green clean energy, rapid development in recent years. Photovoltaic glass as an essential raw material for manufacturing solar photovoltaic modules, its manufacturing technology and supporting production and processing equipment are also constantly innovating and progressing. Photovoltaic glass is mainly used for photovoltaic module light transmission panel, covering the photovoltaic module on the photovoltaic glass after coating, can ensure a higher light transmission rate, while after the toughening process of photovoltaic glass has a higher strength, which can make the solar cell slices to withstand a greater wind pressure and greater temperature difference between day and night. Therefore, the quality of PV glass and processing technology is an important factor in determining the service life and photoelectric conversion efficiency of PV modules.
With the advantages of double-glass photovoltaic modules in power generation efficiency, service life and other aspects in recent years, its market share gradually increased and began to be widely used in a variety of photovoltaic power generation systems, and objectively also promote the development of photovoltaic glass backsheet perforation technology. Because the conventional photovoltaic cell components only cover using photovoltaic glass, and double-glass components of the cover and back panel are using photovoltaic glass, and the back panel photovoltaic glass must be punched in a specific location in order to photovoltaic cell components of the current lead to the junction box. Therefore, the perforation of PV glass backsheets has become an essential process in the deep-processing production.
Photovoltaic glass perforation process selection
The initial drilling method for photovoltaic glass is the mechanical drilling process, but with the development and progress of technology and the continuous improvement of production efficiency and product quality requirements, laser drilling has gradually become the preferred drilling process in the industry.
Mechanical drilling is the use of special glass drilling machine, the use of upper and lower two special drills at the same time to realize the method. This drilling method is easy to form micro-cracks on the edge of the glass holes, chipping broken and other defects, so that the strength of the cutting edge is reduced, and as the thickness of the glass plate is getting thinner and thinner, the small cracks caused by cutting will also increase, seriously affecting the quality of the perforation. In addition, the mechanical drilling method has serious loss of drill bits, and during normal production, the workload of grinding and repairing drill bits is very large, and the level of experience required for workers to operate is high. Therefore, glass products with low quality requirements for cutting edges can be mechanically drilled.
In the current photovoltaic industry on the glass processing quality requirements are becoming more and more stringent situation, the need for more precise, detailed processing methods. With its high processing quality and mature technology, laser perforation technology has been widely used in continuous production lines for deep processing of photovoltaic glass in recent years.
Laser perforation is a thermophysical process of laser and material interaction, which is determined by the laser beam characteristics (including laser wavelength, pulse width, beam divergence angle, focusing state, etc.) and a number of thermophysical properties of the material. Laser perforation is the earliest practical laser processing technology and one of the main application areas of laser processing. Hardness, high melting point of the material traditional processing methods have been unable to meet certain process requirements. This type of processing tasks with conventional mechanical processing methods is very difficult, sometimes even impossible, and laser perforation is not difficult to realize. Laser beam in space and time is highly concentrated, the use of lens focusing, the spot diameter can be reduced to the micron level so as to obtain a higher laser power density.
Laser perforation machine has the following advantages compared with the traditional perforation process:
- Laser perforation speed, high efficiency, good economic benefits.
- Laser drilling can obtain a large depth-to-diameter ratio.
- Laser drilling can be carried out on hard, brittle, soft and other types of materials.
- Laser drilling has no tool loss.
- Laser drilling is suitable for a large number of high-density group hole processing.
- Laser can process small holes on the inclined surface of difficult-to-machine materials.
- Laser drilling on the workpiece clamping requirements are simple, easy to realize the production line on-line and automation.
- Laser drilling is easy to drill holes for complex shaped parts, and can also be drilled in vacuum.
Because the laser has high energy, high focusing and other characteristics, so that the hardness of the material is also easy to process, high melting point. And laser perforation process through the non-contact method, to avoid the mechanical impact on the photovoltaic glass such as fragile material yield impact, and gradually become the main production tool of the photovoltaic glass industry.
Composition of laser perforation equipment
1.Composition of equipment
Photovoltaic glass online laser perforation equipment is part of the continuous production line for photovoltaic glass deep processing, which is an integrated equipment of light, machine and electricity, and mainly consists of accelerating conveying table, feeding conveying table (including rotating device and liquid coating device), laser perforation machine, and discharging conveying table (including rotating device and hole-breaking device). It can process photovoltaic glass with a thickness of 2～6mm.
Among them, the laser perforator is the core equipment of the process, which generally consists of five major components: laser, electrical control system, optical system, projection system and three-dimensional moving table, which cooperate with each other to complete the perforation task. The laser is responsible for generating the laser light source, the electrical control system is mainly responsible for supplying power to the laser and controlling the laser output, and the optical system is to accurately focus the laser beam onto the processed part of the photovoltaic glass.
2. Process Flow
The process flow of perforation process is as follows: accelerated separation → rotating/coating liquid → feeding → CCD vision positioning → laser perforation → discharging → rotating/broken hole detection.
After the glass is cleaned and dried in the previous process, it is transported to the accelerating conveyor, which accelerates the separation of the glass, widens the distance between the glass, and leaves time interval for the subsequent perforation, and then the glass enters the feeding conveyor after accelerating the conveyor.
In the feeding conveying station, the rotating system below lifts the glass and rotates it by 90 degrees, at the same time, the cylinder drives the positioning mechanism to position the glass at 6 points, at the same time, the liquid coating device coats the glass perforated parts, after the glass is coated with liquid, it is transferred to the laser table perforated position through the belt at high speed.
After the glass is coated with liquid, it will be transferred to the punching position of the laser table through the belt at high speed. The glass will be captured by the CCD vision system at the punching position of the laser table, and judge the position and attitude of the product to complete the accurate positioning, and the laser punching machine will combine with the distance measurement data to punch the glass. After punching is completed, the conveyor belt transports the glass at high speed to the outfeed conveyor station, the rotating system lifts the glass and rotates it by 90 degrees, and at the same time conducts hole-breaking detection and then transports it backward to complete the punching.
With the progress of science and technology and the development of the times, new energy development prospects. China's photovoltaic industry in recent years has experienced a slow - fast - explosive development process, the industry scale is constantly expanding, whether in the core technology, product manufacturing, equipment, or in the market development, installation and service, etc., have certain independent intellectual property rights of the industry chain, and some of them have reached the international leading level, and occupy a pivotal position in the international market. With the growth of market demand for double-glass components and market share, the application of laser perforation technology in photovoltaic glass will continue to upgrade. The continuous development and progress of photovoltaic glass laser perforation equipment and technology is of great significance to the development of photovoltaic industry.
