Laser beam machining (LBM) is one of the most widely used thermal energy based non-contact type advance machining process which can be applied for almost whole range of materials. Laser beam is focussed for melting and vaporizing the unwanted material from the parent material. It is suitable for geometrically complex profile cutting and making miniature holes in sheetmetal. Among various type of lasers used for machining in industries, CO2 and Nd:YAG lasers are most established. In recent years, researchers have explored a number of ways to improve the LBM process performance by analysing the different factors that affect the quality characteristics. The experimental and theoretical studies show that process performance can be improved considerably by proper selection of laser parameters, material parameters and operating parameters. This paper reviews the research work carried out so far in the area of LBM of different materials and shapes. It reports about the experimental and theoretical studies of LBM to improve the process performance. Several modelling and optimization techniques for the determination of optimum laser beam cutting condition have been critically examined. The last part of this paper discusses the LBM developments and outlines the trend for future research.

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Laser beam machining—A review

Laser beam machining (LBM) is a widely used thermal advance machining process capable of high accuracy machining of almost any material with complex geometries. CO 2 and Nd:YAG lasers are mostly used for industrial purposes. Drilling, cutting, grooving, turning and milling are the applications of LBM with different material removal mechanisms. Modeling and simulation of the LBM process is indispensable for optimization purposes. Modeling can be done by implementing analytical, numerical, experimental and artificial intelligence-based methods. This paper provides a review of the various methods used for modeling and simulation of the laser beam machining process as well as key researches done in this field so far.

A review of modeling and simulation of laser beam machining

Incorporation of material behavior in modeling of metal forming and machining processes: A review

Waterjet guided laser processing is an internationally patented technique based on guiding a laser inside a thin, high-speed waterjet. The process combines the advantages of laser processing with those of waterjet cutting and offers promise as a method for processing thin and heat sensitive materials with a high degree of precision. An improved understanding of the complex interaction between laser, waterjet, and workpiece is required to enable the process to achieve its potential. A model for waterjet guided laser grooving of silicon is presented that treats the energy input of the laser, the cooling effect of the waterjet, and the melting and removal of the silicon. The thermal process is represented in detail in the new method. The model is validated by comparisons of simulation and experimental results, and the simulation provides insight regarding the details of the interactions among laser, waterjet, and workpiece.

https://www.smu.edu/~/media/Site/Lyle/RCAM/Publications/Modeling%20of%20Waterjet%20Guided%20Laser%20Grooving%20of%20Silicon.ashx

Modeling of waterjet guided laser grooving of silicon

Laser cutting is still the most common industrial application of CO 2 laser systems but currently available high-power fibre lasers seem to be an attractive alternative to the established CO 2 laser sources for several cutting tasks. Practical experience has shown that fibre lasers enable significantly increased travel rates in the case of inert-gas fusion cutting. This advantage in achieving higher cutting speeds in comparison to CO 2 laser cutting is however a clear function of the sheet thickness to be cut. In the first part of this article, possible reasons for this experimental fact are derived from a thermodynamic analysis of the process with consideration of the specific beam absorption characteristics under cutting conditions. After that, in the second part, a quite new laser cutting variant, namely the gas-free remote cutting process that considerably benefits from the high beam quality of fibre laser systems, is presented.

Fibre laser cutting: Beam absorption characteristics and gas-free remote cutting

Numerical models of laser cutting are essential for an improved understanding of the process. In order for the models to closely represent real physics the heat lost by conduction during cutting has to be incorporated into them. This paper outlines the details of a mathematical model that is used to estimate heat conduction losses in laser cutting by employing integral methods to solve the three-dimensional, heat-conduction equation. Simple, yet accurate, correlations are presented for the conduction heat loss rate, as well as for characteristic thicknesses of the heat affected zone (HAZ). These variables are functions only of Peclet number (Pe), which may be thought of as a dimensionless cutting speed. The correlations are then used to predict (i) the cutting speed in laser cutting, and (ii) the temperature field in the HAZ. The predictions show an excellent match with experimental results. Cutting speed is predicted using an energy balance at the cutting front. An implicit, nonlinear equation for Pe as a function of Stefan number (Ste) and dimensionless heat of combustion results. Ste gives the ratio of sensible heat to latent heat in the workpiece. Detailed analysis of beam absorptivity, coupled with the dimensionless cutting speed result suggests that the dimensional cutting speed, uo, may be correlated as a unique function of the ratio of incoming laser power to workpiece thickness, Qlas/d. This is corroborated by measured cutting rates over a wide range of sample thicknesses and two beam power settings.

Girish Venkitachalam

Papers

Estimation of heat conduction losses in laser cutting