Index of content:
Volume 28, Issue 1, February 2016
Picosecond laser processing of polycrystalline cubic boron nitride — A method to examine the ablation behavior of a high cubic boron nitride content grade material28(2016); http://dx.doi.org/10.2351/1.4931930View Description Hide Description
Chipping of hardened steel is often performed by the use of polycrystalline cubic boron nitride (PCBN). Moreover, PCBN tools are also suitable for many machining tasks with a lower degree of specialization, due to their excellent mechanical properties. Despite the significantly higher lifetime and the associated process reliability plus the reduction of nonproductive times, tools from PCBN cannot yet prevail over competing cutting materials. The reason for this can be seen in high tool costs, which especially arise from an expensive, mechanical final preparation process that is subject to a high tool wear. Laser material processing with ultrashort pulsed laser sources can be regarded as an alternative to the conventional preparation of PCBN cutting tools. However, the multitude of laser process parameters in combination with different material properties by a variety of available PCBN-types requires an each individual setup and review of the process. This represents a barrier for introducing laser processes into industrial applications. Therefore, the objective of this research is to establish an efficient method for a global parameter determination which is performed by varying the parameters power, repetition rate, scan speed, and track-distance of the laser process. Investigations are carried out by use of picosecond pulsed laser radiation on a PCBN grade with a high cubic boron nitride content and a titanium-based binder to gain a basic understanding of the ablation behavior of PCBN. The results of the experimental investigations show that processing of PCBN cutting tools by laser ablation is feasible. Due to the achieved volume ablation rates of QA > 18 mm3/min and an overall minimal surface quality of Sa = 1.52 μm, this process shows potential as an alternative to the conventional preparation method. Therefore, also the processing of enhanced tool geometries in PCBN by use of laser technology becomes possible.
28(2016); http://dx.doi.org/10.2351/1.4932619View Description Hide Description
The interaction process between pulsed CO2 laser radiation and glass was studied systematically. The concept of the structuring process is related to an absorption-controlled ablation of small elementary material volumes with reduced melt formation, the so-called elementary volume ablation (EVA). For this purpose, suitable pulse parameters were predicted on the basis of the optical and thermal materials properties. These pulses with durations as low as 10 μs and a peak power of up to 600 W were generated using a specific arrangement consisting of a commercially available continuous CO2 laser of high beam quality and a cascade of two interference laser beam modulators. Optical microscopy, scanning electron microscopy, white light interferometry, and tactile profilometry were used to investigate the influence of the CO2 laser pulse parameters on the processing quality. The results obtained from the ablation of borosilicate glass (Borofloat33) and 100 μm thick sheets of cerium doped borosilicate glass demonstrate that the EVA method is a suitable approach to select an appropriate range of processing parameters for a high precision thermal ablation of glass without microcrack formation.