High-precision Helical Cutting Using Ultra-short Laser Pulses

Abstract

The use of a helical optics to drill micro holes in fuel injectors and spinning nozzles has already demonstrated great advantages like high precision and flexibility. Due to the laser beam rotation on a helical path, the hole-geometry is almost independent from the beam shape. By slightly manipulating the beam path inside the optics, positive and negative tapered as well as straight cylindrical holes can be achieved. If the work-piece is moved relatively to the helical-optics, a helical-cutting process is performed. Compared to direct cutting technologies, helical-cutting can meet higher requirements in terms of roughness and taper of the kerf. By using a helical optics with ultra-short laser pulses, micro cutting experiments on metal and sapphire sheets were performed. As a result of the laser beam helical movement, the roughness of the cutting kerf in metal is below 1 µm, and a taper less than 1 degree could be achieved with a cutting speed 10 mm/min. Recast layer and heat affected zone around the exits are negligible.

Research on Optical Path Trajectory Equation Based on Three Optical Wedges

“…In the equation, represents the original normal vector, ' represents the transformed normal vector, and represents the transformation matrix. As can be seen from equation (9), to obtain the transformed normal vector, the transformation matrix must be solved first. For any vector , there is a unit , and the angle between and is .…”

“…Owing to the advantages of high processing efficiency, large depth-to-diameter ratio and wide applicability of materials, laser drilling gradually occupies an important position in this field. At present, laser drilling is mainly divided into single-pulse drilling, multi-pulse drilling, ring drilling and rotary drilling [9][10][11][12]. According to the relevant research, among the four kinds of drilling methods, only rotary drilling can not only ensure higher roundness, but also realize the control of the taper angle of the hole.…”

A Numerical Simulation and Experimental Study on the Ultrafast Double-Laser Precision Cutting of Sapphire Materials

“…Depending on the mechanism, ionization can be divided into linear and nonlinear ionization. Linear ionization occurs when the laser energy density is less than 10 12 W/cm 2 and the photon energy is greater than the bound barrier, which follows the Beer-Lambert law [4]. Laser cutting technology and cutting methods for nonmetallic materials have been studied [5,6].…”

Drilling of micron-scale high aspect ratio holes with ultra-short pulsed lasers: Critical effects of focusing lenses and fluence on the resulting holes’ morphology

“…They are more pronounced in stationary beam drilling methods such as percussion drilling, compared with lower throughput, moving beam methods like trepanning and helical drilling [12]. To address these issues, for both drilling categories, new methods and tools have been developed, in particular changing the focusing position [8,13], the use of assisted gases [14][15][16][17], beam rotation [18,19], drilling under water [20], two-side drilling [21,22], new drilling cycles [12] and also different modelling and optimizing approaches to identify the optimum processing window [23][24][25][26][27]. Furthermore, the effects of process settings were investigated, too, especially peak power and pulse width effects on holes' repeatability in regards to the entry diameters [28] the evolution of shallow craters' diameter and depth in regards to number of pulses (NoP) and fluence [29] and the effect of different laser parameters such as average power on circularity, HAZ and taper angle [30] Other parameters that affect the laser drilling process, especially pulse energy, fluence and intensity, have been investigated, too.…”