Thermal drift in laser cutting of metallic mesh structures

产品复杂性越来越高的趋势要求扩大对制造技术的理解，以应对研究和工业生产中的挑战。这种趋势在音频系统领域（如声换能器）或表面分析领域（如电子光谱学）中观察到。对于字母，中心组件是一个网状帽，它被用作电子光学透镜来聚焦电子束。这些部件是通过激光加工和附加深冲压制造的网状结构。网状结构由薄网组成，其显示出低刚度并且在热传递方面受到限制。不合适的激光扫描策略会导致热量积聚，从而导致材料的热膨胀。这导致幅材宽度的偏差，并且使这种网状结构的质量劣化。因此，薄金属板的激光加工需要新的技术和方法来解决这些挑战。到目前为止，激光加工中只有局部方面得到了解决。对于激光加工，例如表面完整性高度依赖于环境介质和激光的扫描速度，而材料中的加热取决于脉冲持续时间、能量密度和重复率。很少有人注意到薄金属板在激光加工过程中的整体热漂移。特别是当在大的薄金属板上产生许多凹口和微结构时。从自己的初步研究中可以得出，特别是全局激光扫描策略对热积累有显著影响。到目前为止，还没有一种方法能够描述网格结构中的热漂移依赖于激光扫描策略，从而能够利用这种行为。假设合适的扫描策略导致金属板中的低温度偏差，这导致均匀的热漂移，并因此导致更规则的腹板宽度和凹口。

The trend towards higher product complexity requires to broaden the understanding of manufacturing technologies to rise to challenges in research and industrial production. This trend is among others observed in the field of audio systems like sound transducer or in the field of surface analysis like electron spectroscopy. For the letter, the central component is a mesh calotte, which is used as an electron-optical lens to focus electron beams. Such components are formed mesh structures, which are manufactured by laser machining and additional deep drawing. The mesh structures consist of thin webs, which show low stiffness and are limited in heat transfer. Unsuitable laser scan strategies lead to heat accumulation and consequently to thermal expansion of the material. This results in a deviation in web widths and deteriorates the quality of such mesh structures. Therefore, laser machining of thin metal sheets needs new techniques and methods to solve those challenges. So far, only local aspects in laser machining were addressed. It was shown for laser machining that e.g. surface integrity highly depends on ambient medium and scan speed of the laser, whereas heating in the material depends on pulse duration, fluence and repetition rate. Little notice has been given to the global thermal drift of thin metal sheets during laser machining. Particularly, when many notches and microstructures are produced on large thin metal sheets. It can be derived from the own preliminary studies that especially the global laser scan strategy has a significant effect on heat accumulation. So far, no methodology exists, which describes the thermal drift in mesh structures in dependence of the laser scan strategy to be able to take advantage of this behaviour. It is assumed that a suitable scan strategy leads to a low temperature deviation in the metal sheet, which results in an even thermal drift and accordingly to more regular web widths and notches.