Taguchi based fuzzy logic optimization of multiple quality characteristics in laser cutting of Duralumin sheet Arun Kumar Pandey, Avanish Kumar Dubey n Mechanical Engineering Department, Motilal Nehru National Institute of Technology, Allahabad 211004, Uttar Pradesh, India article info Article history: Received 25 July 2011 Received in revised form 6 November 2011 Accepted 7 November 2011 Available online 1 December 2011 Keywords: Laser cutting Duralumin sheet Kerf deviation Fuzzy logic Multi-objective optimization abstract Capability of laser cutting mainly depends on optical and thermal properties of work material. Highly reflective and thermally conductive Duralumin sheets are difficult-to-laser-cut. Application of Dur- alumin sheets in aeronautic and automotive industries due to its high strength to weight ratio demand narrow and complex cuts with high geometrical accuracy. The present paper experimentally investigates the laser cutting of Duralumin sheet with the aim to improve geometrical accuracy by simultaneously minimizing the kerf width and kerf deviations at top and bottom sides. A hybrid approach, obtained by combining robust parameter design methodology and Fuzzy logic theory has been applied to compute the fuzzy multi-response performance index. This performance index is further used for multi-objective optimization. The predicted optimum results have been verified by performing the confirmation tests. The confirmation tests show considerable reduction in kerf deviations at top and bottom sides. & 2011 Elsevier Ltd. All rights reserved. 1. Introduction Advanced machining processes are characterized by their advanced machining features such as ability to machine diffi- cult-to-cut materials, generation of complex shapes and intricate profile with stringent design requirements. Advanced machining processes can be classified into three broad categories based on the utilization of energy such as mechanical, chemical and thermal [1]. Laser beam machining (LBM) is a thermal energy based advanced beam machining process in which material is removed by focusing the laser beam on the workpiece surface. Depending upon the prevailing conditions, the material may be removed by different mechanisms such as vaporization, fusion, reactive fusion, ablation and controlled fracture. The melted material is removed with the help of high pressure coaxial assist gas jet [2]. LBM can be used for different purposes such as drilling (1-D), cutting (2-D) and turning or milling (3-D) [3]. Laser cutting is the most widely used LBM process. The schematic of laser cutting process is shown in Fig. 1. The capability of the laser cutting mainly depends on the optical and thermal properties rather than mechanical properties of the material to be cut. The materials which exhibit high degree of hardness or brittleness and passing through favorable thermal and optical properties such as low reflectivity, low thermal conductivity and diffusivity are well suited for laser cutting process [4]. The materials possessing high reflectivity and thermal conductivity such as aluminum and its alloys are known as difficult-to-cut materials with laser cutting process. These mate- rials have wide applications in technologically advanced indus- tries such as aeronautics, automobile, shipbuilding and construction due to the light weight and high strength to weight ratio. These materials are mostly used in different forms and shapes of the sheet, but difficult to cut precisely in complex shapes and intricate profiles with the conventional cutting meth- ods. Laser cutting may be suitable method to fulfill these objectives. Duralumin is a strong, hard, lightweight alloy of aluminum, widely used in aircraft construction, discovered and patented in 1910 by Alfred Wilm, a German metallurgist. Different types of lasers are available in the market such as solid lasers, liquid lasers and gaseous lasers. Among these, solid state Nd:YAG and gaseous CO 2 lasers are mostly used for cutting due to their high powers and other suitable properties required for the cutting of the materials. Due to its poor absorptivity, the use of CO 2 lasers is not common in practice for the cutting of highly reflective and thermally conductive materials such as aluminum and its alloys [5]. High reflectivity of these materials require high laser power when cut with CO 2 laser and there is possibility to damage laser cavity, cavity optics or beam delivery optics due to reflected laser beams. Further, high thermal con- ductivity of aluminum alloys tends to produce large heat affected zone (HAZ), wider kerf and oxides on the molten materials in the cutting front. Although Nd:YAG lasers have low average power but when operated in pulsed mode, give higher peak power and beam intensity. Due to the shorter wavelength (1.06 mm), it can Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/optlaseng Optics and Lasers in Engineering 0143-8166/$ - see front matter & 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.optlaseng.2011.11.005 n Corresponding author. Tel.: þ91 532 2271974; fax: þ91 532 2545341. E-mail address: avanishdubey@yahoo.com (A.K. Dubey). Optics and Lasers in Engineering 50 (2012) 328–335