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Laser Machining of Metals
Published in V. K. Jain, Advanced Machining Science, 2023
Laser beam machining is a well-established manufacturing process that has a plethora of applications ranging from micro to meso to macro scales. The ability to machine any metal with great precision and speed makes the laser a very important tool in the machine tool industry. Several different types of lasers exist, both in CW and in pulsed mode, each having its own unique applications. Lasers can be operated in a pulsed mode by using pulsing techniques that include cavity dumping, Q-switching, and mode-locking. The pulse duration can be varied from a few milliseconds to as short as a few femtoseconds. The use of short and ultra-short pulses helps in localizing the heating effects. Besides, the lasers can be focused to narrow spot sizes of a few micrometers using a converging lens. Thus, lasers can generate very high intensities, sufficient to melt and vaporize the material. Pulsed lasers have very high intensities, which can be used to rapidly heat the material even beyond its normal boiling temperature. Material removal in laser beam machining is very complex and is still a subject of intense research. Material removal may occur due to melt expulsion, vaporization, and phase explosion. Phase explosion occurs only when the pulse duration is very short, and the intensities are high, whereas CW lasers do not have sufficient intensity to vaporize the material. Hence, material removal with CW lasers invariably involves melt ejection. Machining processes such as cutting and drilling can easily be performed using both CW lasers and pulsed lasers. CW lasers are usually used along with a high-pressure assist gas to eject the molten material. Lasers are currently routinely used in industry in the cutting of sheet metals, drilling high-aspect-ratio holes for automobile, aerospace, and biomedical applications. Apart from cutting and drilling, lasers are also used for texturing, cleaning, marking, and engraving. Laser texturing can produce sub-micron-sized features for application in tribology and medicine. Lasers are used in industry to clean rust, paints, and grease on metal samples. Lasers have also made marking and engraving very easy to perform with high speed and great accuracy.
Tool path generation for 5-axis engraving in bangles with art patterns
Published in Journal of Industrial and Production Engineering, 2019
Runbo Fan, Yijia Sun, Hu Gong, Jian Zhang, Changya Yan
In the early time, engraving in the bangles was mainly a manual process by the engineer. In recent years, 5-axis machining technology has gradually been applied to the engraving processing technology, which improves the production efficiency to some degree. But, due to the lack of effective tool path method, the potentials of the 5-axis machine tool have not been explored for engraving in bangles. The major reason is that the traditional 5-axis tool path generation method for machining free-form surface is different from that for engraving in bangles. As shown in Figure 1(a), for traditional 5-axis machining, one of the objectives is to machine designed surface accurately [1–4]. These surfaces are usually designed by engineers to meet specific functions. The collision between the designed surfaces and the cutting tools should be avoided [5]. But for engraving in the bangles, the designer usually only provides graphic art design, which consists of many points, lines or curves. A special forming cutter is used to engrave the bangle with variable depth and achieve 3D patterns with artistic effect., as shown in Figure 1(b). Typical forming cutters for the engraving process are shown in Figure 2. Engraving cutter is mainly used for engraving patterns on the surface of the bangles. While balance cutter is mainly used for processing the shading of bangle after the patterns have been engraved, which can enhance the beauty of the bangle. Although the tool path generation method for machining free-form surfaces has been studied extensively, but seldom for 5-axis engraving [6].