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Single frames of two X-ray videos showing the piercing process in a 30 mm thick sheet of stainless steel. Red, yellow and white coloured areas show the shape and the width of the produced hole (Multimedia view in appendix A, Video S1); P Peak = 6 kW, τ on = 0.8 ms, s = 30 mm a) f = 350 Hz, b) f = 588 Hz.
Source publication
An in-process analysis of the piercing process at the beginning of a laser cut using high-speed X-ray imaging is presented for the first time. Sheets of stainless steel with thicknesses ranging from 10 mm to 30 mm were pierced by laser pulses at a wavelength of 1 μm with a peak power of 6 kW. With a constant pulse length and a constant peak power,...
Contexts in source publication
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... order to investigate the reason for the observed limitation, the difference of the geometry of the formed piercing holes between the successful and unsuccessful piercing process was analyzed by means of high-speed X-ray imaging. Fig. 3 shows single frames from two X-ray videos of the piercing process in a 30 mm thick sheet of stainless steel. Since the bottom side of the ROI was aligned with the bottom surface of the sample, the images show the lower 22 mm of the 30 mm thick sample. The position of the ROI is indicated by the black dashed rectangle in Fig. 4. The red ...
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... frames from two X-ray videos of the piercing process in a 30 mm thick sheet of stainless steel. Since the bottom side of the ROI was aligned with the bottom surface of the sample, the images show the lower 22 mm of the 30 mm thick sample. The position of the ROI is indicated by the black dashed rectangle in Fig. 4. The red dashdotted line in Fig. 3 represents the axis of the laser beam. The pictures show the colour-coded transmittance of the X-ray radiation through the samples. The shape and width of the piercing holes can be recognized from the red, yellow and white coloured areas. Fig. 3a) shows that with a pulse repetition rate of 350 Hz the sheet was pierced successfully ...
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... position of the ROI is indicated by the black dashed rectangle in Fig. 4. The red dashdotted line in Fig. 3 represents the axis of the laser beam. The pictures show the colour-coded transmittance of the X-ray radiation through the samples. The shape and width of the piercing holes can be recognized from the red, yellow and white coloured areas. Fig. 3a) shows that with a pulse repetition rate of 350 Hz the sheet was pierced successfully within a time of slightly less than 3.3 s. With a repetition rate of 588 Hz, Fig. 3b), the limit indicated in Fig. 2 is already exceeded and the 30 mm thick sample cannot by pierced all the way through. In this case, the piercing depth increases during ...
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... colour-coded transmittance of the X-ray radiation through the samples. The shape and width of the piercing holes can be recognized from the red, yellow and white coloured areas. Fig. 3a) shows that with a pulse repetition rate of 350 Hz the sheet was pierced successfully within a time of slightly less than 3.3 s. With a repetition rate of 588 Hz, Fig. 3b), the limit indicated in Fig. 2 is already exceeded and the 30 mm thick sample cannot by pierced all the way through. In this case, the piercing depth increases during the first 0,6 s and then starts to fluctuate, indicating that melt re-fills the bottom of the piercing hole instead of being ejected. At the same time, the diameter of ...
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... result obtained with a repetition rate of 588 Hz. Large recast layers are located at the bottom of the pierced hole as well as on the lower part of the walls. It can be concluded from this picture, that with a repetition rate of 588 Hz, sheets can only be pierced up to a maximum thickness of approximately 25 mm as marked by the dashed red line in Figs. 3 and ...
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... shown in Fig. 3b), a fluctuation of the piercing depth occurs once the limit is reached. To investigate the stagnation of the piercing progress in more detail, the distribution of the absorbed irradiance I abs inside the developing piercing hole formed at a repetition rate of 666 Hz into a 20 mm thick stainless steel sheet was analyzed by means of a ...
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Citations
... The power of the laser, the spot size of the laser beam, the speed of the laser movement, the material being pierced, and the thickness of the material are all factors in the LBP process. The equation for laser beam piercing can be quite complex and is dependent on a variety of variables, including the laser's particular characteristics and the material being pierced [31]. ...
This chapter provides an overview of the fundamental physical processes that are involved in laser machining, with a particular emphasis on laser cutting, drilling, and piercing processes. In this chapter, the process of laser machining can be segmented into one-dimensional, two-dimensional, and three-dimensional processes depending on the movement of the erosion front that occurs when the beam strikes the item. It also demonstrates how melting and vaporization play a crucial role in all operations involving laser machining. This chapter provides a comprehensive discussion on the myriad of configurations that are possible for laser machining processes, including but not limited to drilling, cutting, and piercing.
In addition to that, it investigates techniques associated with 3D laser machining,
such as milling and turning. The information presented in this section serves as
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can get some suggestions and pointers from this book.
... Depending on energy input and interaction time, lasers can do ablation, welding and cutting [3] [4]. If the penetration depth exceeds the thickness of the base metal, the melt pool falls from the spot, which is called drop-through or piercing [5]. For in-situ observation of the laser welding process, the X-ray phase contrast method can be used for identifying keyhole and melt pool [6] [7]. ...
As digital manufacturing is being implemented across industries, the automation of the laser welding process is a crucial step to enhance production efficiency. To monitor the in-situ welding process, there are several approaches to detect the electromagnetic and mechanical waves on various frequencies for comprehending laser beam-material interaction. Five sensing techniques, namely the optical microphone, welding camera, inline coherent imaging, infrared camera, and heat flux sensor, can be employed to identify distinct features in the laser welding process. These features include pore formation, melt pool geometry, weld bead topography, keyhole depth, and thermal distribution. The discussion of a proposed welding system designed with compatibility for multisensory data fusion is included, both on its capabilities and potential challenges, to offer guidance of welding monitoring.
... Visualization of machining phenomena is an important technical issue for analyzing phenomena and leading to its development as in the case of wood machining by cutting tool. Visualization technologies in laser metal processing have been established to understand the behavior of the molten metal [22]. In the processing of wood, Content courtesy of Springer Nature, terms of use apply. ...
A short-pulsed laser with an ultraviolet wavelength is used for laser micro incisions of wood. In order to solve the technical issue of processing efficiency, the laser oscillation conditions were investigated. The output of this pulsed laser is the product of the pulse energy and the pulse repetition rate, and the output is represented by their two-dimensional planes. For the purpose of understanding the characteristics of processing on wood by this laser, drilling was performed on wood under each condition of this two-dimensional plane. As a result, the hole depth showed an asymptotic tendency with respect to the output increase, and the heat effect and the hole diameter tended to increase. Therefore, it was presumed that both machining quality and its efficiency could be achieved by beam splitting that disperses the output of the beam. In an application example of drilling hundreds of holes per square centimeter at a depth of a few millimeters, it was predicted that the machining time would be halved by applying such a beam splitting device. Moreover, it was considered that the shortening rate could be increased as improving the output of the oscillator. On the other hand, further shortening of pulse width by using the pico-second laser was not considered to be beneficial in the processing of wood. In-process monitoring of the processing phenomenon was examined and the progress of laser drilling was observed.
