By Christoph Ruettimann, Noémie Dury and Markus Danner
With almost 40 years of experience in precision processing of synthetic crystalline materials, Swiss laser manufacturer ROFIN-LASAG AG has developed a process for cutting sapphire glass, which is now increasingly used in mobile electronic devices and high-quality mechanical watches. Synthetic sapphire is a mono-crystalline aluminum oxide with outstanding technical properties, such as a high thermal conductivity, very high light transmission and complete acid resistance. In addition, it is an outstanding electric insulator and extremely scratch-resistant: With a Mohs’ hardness of 9 sapphire is beaten only by diamond.
Sapphire can be cut with a variety of laser technologies. Ultrashort pulse lasers, such as picosecond lasers, cut the material using very short pulses. The energy of these pulses is transferred so quickly to the electrons that the chemical bonds of the atoms are destroyed. In contrast to that, pulsed fiber lasers with a pulse length in the range of microseconds to milliseconds work with another cutting process, so-called fusion cutting. Continue reading →
Since the advent of commercial fiber and disk laser cutting machines, there has been a lot of controversy about the performance of these devices – particularly in comparison to their more established CO2 counterparts. In the early days, the sales staff promoting fiber technology would often declare that the new lasers would completely take over from CO2 technology very quickly – but this has not happened. Even taking into account the entrenched position of the older technology, fiber and disk lasers have not been as widely accepted as was predicted, although they have been proven to out-perform CO2 lasers in certain important areas.
This paper presents a discussion of the advantages and disadvantages of both types of cutting technology from a commercial point of view – written from the perspective of a laser cutting job shop owner trying to decide between buying a fiber or CO2 laser cutting machine. A quantitative comparison of the two machines is surprisingly difficult – having given several talks on the subject the best analogy we can give is that it’s like comparing a sports car with a family car. Continue reading →
Carbon fiber reinforced polymers (CFRP) are increasingly applied in the aircraft industry as well as the automobile industry. The main reason is the highly mechanical load on one hand and the low density on the other hand. Moreover, the corrosion resistance plus the damping behavior of the material can fully be utilized in highly stressed structures. However, the concept of manufacturing CFRP-parts near- net- shape does not substitute the need of cutting them. The different properties of fiber- and matrix-material constitute an ambitious challenge for the CFRP cutting process with a laser beam. Main influencing parameters are the different thermo-optical characteristics of fiber and matrix. The carbon fibers have a more than 20 times higher sublimation temperature than the decomposition temperature of the resin. Because of a good heat conduction of the fibers, the resin fitting at the fibers will quickly be decomposed, before the carbon fiber itself is cut (Fig.1). The theory to decrease the heat affected zone is to minimize the interaction time between laser radiation and material.
The benefit of the availability of high power and high brilliant laser sources enables ablation and/or cutting processes with high processing speeds. However, the relation between wavelength and absorption on non-isotropic materials on the one hand, the influence of the intensity and the processing speed on the other hand, require fundamental research.
Within the experiments a continuous-wave (cw)-single mode fiber laser was applied in comparison with a Q-switched pulsed laser system (50 W, 100 ns). Using the Remote technology (the laser beam will be deflected by two galvo – driven tilting mirrors) a minimized heat interaction time between material and laser beam can be reached. The setup of the cw-Remote processing is shown in Fig. 2.
The material to be processed was a 3 mm thick consolidated CFRP with epoxy resin. Its fiber volume percentage is about 50% with multidirectional orientation of the long fibers.
As a result two cross sections can be seen:
Fig.3
Cross section of CFRP using cw – laser & Remote processing
Pl = 3 kW, vaverage = 9 m/min, ET = 11 J/mm²
Fig.4
Cross section of CFRP using Q-switched – laser & Remote processing
Pl = 50 W, vaverage = 0,04 m/min, ET = 28 J/mm²
The Remote technology proved to be an excellent tool to cut consolidated CFRP with good cut qualities. Average processing speeds of more than 10 m/min can be reached using high brilliant and high power cw – lasers. The heat affected zone can be minimized by decreasing the interaction time. One possible way is to use Q-switched lasers with short pulse lengths. However, because of the limited overall laser energy, the average processing speed is quite low.
Fig. 1: REM image of CFRP, gas assisted laser cutting
Ultra-slim flexible glass substrates have many potential applications, spanning from photovoltaics to e-paper to touch sensors. Previously, these applications generally incorporated glass substrates in the thickness range of 0.3-1.0 mm and benefited from inherent glass properties including high optical transmission, low surface roughness, high thermal and dimensional stability, and low CTE. Recently, however, there is interest in reducing the thickness of the substrate to ≤200 mm. Glass substrates at this thickness still provide the inherent beneficial properties of glass, but they also enable substrate flexibility and end product devices that are thinner and lighter weight. Continue reading →
Laser cutting technology is a non-conventional machining which being used widely in many industries. However, the application of this technology in textile industry is still new and yet to be explored. Indeed, nowadays many textile industries are preferred to cut the textile by using conventional way such as discs, band blade and reciprocating knives. As compared to traditional cutting methods the laser cutting offers several advantages such as fast cutting speed, reduced the time consumption, a non-contact cutting and no tool wear. Thus, using this technology would be more efficient and productive if the right method of laser cutting process is used to replace the conventional cutting methods.
