Glass, as an important industrial material, is used in many industries of the national economy, such as home appliances, sanitary ware, decoration, electronics, crafts, optics, construction, automotive, photovoltaic industry, etc. It is as small as a few micrometers of small optical filters, laptop flat panel displays, and as large as large-sized glass panels used in large-scale manufacturing fields such as automotive, photovoltaic, and construction industries.
Glass, as a typically brittle material, presents significant difficulties during processing. Traditionally, glass is cut using carbide or diamond tools, and the cutting process is divided into two steps. First, a diamond tip or carbide grinding wheel is used to create a crack in the glass surface; afterwards, mechanical means are used to split the glass along the crack line.
Scribing and cutting using this method has a number of drawbacks; the removal of material results in the creation of chips, fragments, and microcracks that degrade the strength of the cut edges, necessitating an additional cleaning process. Deep cracks from the process are usually not perpendicular to the glass surface because the parting lines created by mechanical forces are generally non-perpendicular, and the loss of yield due to the application of mechanical forces to thin glass is also a negative factor.
These shortcomings can be improved by using stress-free glass and further optimizing the process used for splitting. However, it is still not possible to completely avoid the systematic contradiction between vertical cutting lines and the prevention of edge chips/cracks. The development of laser technology offers a solution to these quality problems.
Unlike conventional mechanical cutting tools, the energy of a laser beam cuts glass in a non-contact manner. The energy heats up a specified part of the workpiece to a predefined temperature. This rapid heating process is immediately followed by rapid cooling, which creates a vertically oriented stress band within the glass, resulting in a crack in that direction with no chips or cracks. Since the crack is caused only by heat and not by mechanical reasons, no chips or microcracks appear.
Laser cut edges are stronger than conventional scoring and splitting methods, and the need for finishing is reduced or eliminated. In addition, the occurrence of broken glass can be avoided completely.
In the case of laser cutting, the surface of the glass is scored by the heating and subsequent cooling of the laser beam by approximately 10 mm and the glass can then be split in the direction of the scoring. Since the laser technology does not produce any glass fragments, the common burrs and low strength of the cut edges are avoided, and subsequent polishing and sanding processes are no longer necessary. What's more, the glass processed by this means is up to three times more shatter-resistant than glass split by conventional methods. For glass thicknesses of up to 20 mm, it is possible to cut the entire piece in just one step. Splitting and subsequent polishing, grinding and rinsing are no longer necessary. The strength of the cut edges can be measured by means of the standardized four-point bending test from DIN-EN 843-1. A piece of glass is fixed on two rollers, and on the upper surface of the glass two additional rollers are used to generate the required bending force, under which the glass can be split into two parts. The test was repeated approximately 100 times to obtain suitable and reliable statistical values for the possibility of splitting.
In most cases, laser cutting is the choice for high-volume glass cutting processes. The advantages are high speed and precision, as well as simple parameterization. However, where many different lines are to be cut and the processing time is sufficient, monolithic cutting is a more attractive method due to its dry cooling and the absence of additional cutting steps. In both cases a high quality cut edge is produced. It can be seen that laser cutting of glass is perfectly suited to save time and at the same time bring about an increase in processing quality.
Transferring a new and proven technology into a high-volume production line for high-tech products is not an easy task. From the customer's point of view, before implementation, the technology must be an automated, reliable solution that is not only well proven, but also considered economical. In practice, the application of innovative technologies is only effective in two situations: the launch of a new product requires new means of production to realize the innovative features or to reduce production costs by reducing the number of processing steps, or the existing production encounters economic pressures that need to be alleviated by a huge improvement in production methods.
In the flat panel display industry, it took five years for the rollout of laser cutting technology to find its place in the production line, provided that it had undergone thousands of hours of application verification on many processing lines. It is now often considered for the production of new products where there is a risk of glass breakage, or in the electronics industry for the manufacture of communication mobile products containing glass, or other products where there are fragile parts containing thin glass, such as sensors, touch panels, or glass housings.
Processing is often carried out in dust-free environments, as in the biochemical industry, as these are very sensitive to particles generated by conventional cutting or grinding steps. For example, substrate materials covered with DNA codes (biochemical barcodes) or materials that have been laser cut into sheets are used for product testing. For laser cutting technology, the most promising application sectors are currently the household appliance industry, the sanitary ware industry, the solar industry and the automotive industry.
Just as laser technology has developed over the years in the metal processing industry, laser cutting technology for glass processing will continue to evolve; the technology will be used in a wide range of applications for different products, replacing traditional means.
As an innovative technology, laser cutting will be used more in the future in many glass industries such as home appliances, sanitary ware, decoration, electronics, crafts, optics, construction, automotive, photovoltaic and many others. In addition to laser cutting glass, there are many other technologies for laser processing of glass that are already being promoted and applied, such as drilling and chamfering, as well as coating removal.
