Nowadays, the reduction of production costs is one of the critical factors to survive within the global market. This also applies to the glass industry. A helpful means for achieving this target is to increase the degree of automation at the production and to reduce the labour costs respectively. At this point, the laser, successfully been used in the automotive and metal industries for decades, can also be used in the glass industry.
One of the important advantages is the flexibility of laser light. By focusing the laser beam it is possible to cut quartz glass or to scratch borosilicate glass for a subsequent cracking-off process. A glass heating used for forming or joining processes can be realized by the adjustment of larger laser beam diameters on the glass. Each kind of glass, from quartz glass to AR-glass, can be processed with a laser source.
The advantages of the laser can be seen at the following summary:
■ Fully automated processes
■ Multiple processes with „one tool“
--- focused cutting - defocused heating
--- possibility of production from the tube directly, not only from tube sections
--- low maintenance
■ Temperature control during heating processes
--- freely adjustable temperature profile, adjusted to the working process
--- high reproducibility: „constant process parameters – constant process results“
■ No chemical influence on the glass during the process
--- no water condensation or soot
--- no remaining residual stresses
■ no flame pressure
■ no heating of the machine periphery
--- no spreading flame
--- efficient energy introduction to the glass
--- less temperature load of the production environment
■ adjustable intensity distribution of the laser beam
--- the heating zone at the glass can be adjusted
--- line focus, focus point, elliptical beam geometries etc.
■ beam guidance by mirrors
--- one laser can be used at several stations
--- during loading / unloading of one station the laser beam can be used at another station
■ integration of the laser into existing production lines
■ high cost efficiency due to flexibility, short processing times and possible multiple use at several machines
■ low variable costs, because of low maintenance, no gas consumption etc.
Possible glass working processes by using a laser are cutting (sublimation cutting, hot cutting, thermal shock cutting, scratching), joining of similar and dissimilar materials, forming, drilling, structuring, labelling or polishing.
During a three-year research project Arnold has together with further partners provided the basis for the industrial use of a laser especially for glass tube processing. Based on the following two examples we like to describe the advantages of using a laser in comparison to currently available manufacturing processes.
Example for laboratory equipment manufacturing
In the field of glass tubes processing often several steps are necessary to get to the final product. In addition to forming and joining processes also cutting steps are needed. Since these steps can currently not be integrated directly into the process chain, ready-made tubing often has to be used. However, it would be ideal to start working directly from the glass tube. Due to the traditionally manual production processes and the material properties of the glass considerable variations of the product quality can be recognised. At this point the advantages of a laser as an automatable tool can be used. Hence, at hot glass processes the glass temperature can be measured by means of a pyrometer and be processed within a closed control loop. The laser gets continuously new performance data via the control. Like that, it is possible to reach (without glass breakage) processing temperatures of glasses within seconds, which significantly reduces the overall process times.
The machine operator is able to determine the temperature profiles in testing series, which leads then to reproducible production processes. Since the glass temperature essentially follows the determined temperature due to the closed loop, the use of a temperature control is an excellent tool for stabilization of the production process and also establishes completely new possibilities. For example, the processing of thin-walled glass becomes possible because no flame pressure causes any deformation of the low viscosity glass.
The above mentioned intermediate steps in terms of cutting processes are possible inline between forming and joining processes due to the flexible tool laser, which allows the processing of not pre-conditioned tubes.
The advantages of the laser:
■ fully automated production processes
■ short process times
■ reproducible process results
Application Example for cutting of quartz tube
Nowadays the cutting of quartz glass is typically carried out with mechanical saws. At this process a water-cooled saw blade is operated through the quartz glass tube. Due to the tool related force application chipping appears. Depending on further processing the cutting edge has to be reworked, which includes grinding, fire polishing etc.
In any case, washing and drying of the tubes is required to remove the chips. In contrast, no additional process steps are required at laser cutting of quartz tubes.
Depending on the wall thickness the laser beam is focused and is used to evaporate the irradiated material. The cutting width is about 100 microns. The contamination of the glass tube due to occurring quartz smoke can be avoided by an efficient suction. The cutting time for tubes with outside diameters up to 50 mm and wall thickness up to 3mm takes only a few seconds. The separated quartz tubes can be directly taken out after the laser cut. Post-processing steps, such as at the current production, are not necessary.
The advantages are as follows:
■ one-step process
■ fully automatable
■ short process times
■ no need of machines for cleaning and drying
■ no need of water treatment
■ no tool wear, compared to cutting blades
■ constant cutting results
■ automatic process adjustment to different tube geometries
In order to perform customer inquiries, applications tests resp. and for carrying out complete test series two modifiable glass working lathes for tube diameters from 3 mm up to 160 mm are available. These systems are coupled with lasers in the power range from 60 W to 2500 W. The installation of new test equipment (also for flat glass, plastics, etc.) is possible. In addition, we work closely together with well-known research institutes in order to develop optimal solutions for our customers.
In case you need additional information, you are interested in a demonstration of glass processing with laser radiation or you are already thinking about concrete applications within your product portfolio, please feel welcome to visit us in Weilburg. We are looking forward to perform some tests with your components.
Dipl.-Ing. (FH) Hendrik Gebauer, +49 (0)6471 9394 225, hendrik.gebauer(at)arnold-gruppe.de