686 J SCI IND RES VOL 68 AUGUST 2009 Journal of Scientific & Industrial Research Vol. 68, August 2009, pp. 686-695 *Author for correspondence Tel: (+91) 9474112444, Fax: (+91 0343) 2548204,2546745 E-mail: bala_185@yahoo.com Taguchi method and ANOVA: An approach for process parameters optimization of hard machining while machining hardened steel Bala Murugan Gopalsamy 1 *, Biswanath Mondal 1 and Sukamal Ghosh 2 1 Central Mechanical Engineering Research Institute, Durgapur 713 209, India 2 National Institute of Technology, Durgapur 713 209, India Received 02 February 2009; revised 06 May 2009; accepted 11 May 2009 In this paper, Taguchi method is applied to find optimum process parameters for end milling while hard machining of hardened steel. A L 18 array, signal-to-noise ratio and analysis of variance (ANOVA) are applied to study performance characteristics of machining parameters (cutting speed, feed, depth of cut and width of cut) with consideration of surface finish and tool life. Chipping and adhesion are observed to be main causes of wear. Results obtained by Taguchi method match closely with ANOVA and cutting speed is most influencing parameter. Multiple regression equations are formulated for estimating predicted values of surface roughness and tool wear. Keywords: ANOVA, End milling, Hard machining, Regression analysis, Taguchi methods Introduction Taguchi’s parameter design offers a systematic approach for optimization of various parameters with regard to performance, quality and cost 1-4 . Taguchi methodology optimized cutting parameters in end mill- ing when machining hardened steel AISI H13 with TiN- coated P10 carbide insert of high-speed cutting 5 . Fur- ther, design optimization for quality 6 was carried out and signal-to-noise (S/N) ratio and analysis of variance (ANOVA) were employed using experimental results to confirm effectiveness of this approach. Taguchi meth- odology was used to find optimal cutting parameters for surface roughness (SR) in turning operation based on experimental results done on AISI1030 steel bars using TiN-coated tools 7. Experimental study was carried on machined hardened steels AISI 4140(63HRC) with Al 2 O 3 +TiCN mixed ceramic tool for turning process by employing Taguchi’s techniques 8 . Davim et al 9 obtained machinability evaluation of cold work tool steel by hard turning process using S/N ratio and ANOVA by ce- ramic cutting tools and observed cutting speed as most influencing parameter for tool wear. A surface finish (<0.8 μm) was obtained using ceramic tools by select- ing appropriate process parameters. Taguchi method was applied to study dry sliding wear behavior of metal matrix composites 10 . Oktem et al 11 optimized plastic injection mounding parameters to reduce warpage problem by Taguchi technique and compared results with ANOVA. Performances of tool life (TL) and SR were studied on AISI D2 steels (58 HRC) using indexable ball nose end mills employing carbide, cermet tools and solid car- bide ball nose end mills. Wear pattern studies 12 were car- ried out to find tool wear mechanism (chipping, adhesion and attrition). Dutta et al 13 evaluated performance of sil- ver toughened alumina inserts on the basis of progressive flank wear. High speed milling of hardened steel compris- ing of process parameters (TL, SR) has been described 14-20 . Study 14 on machining of AISI D2 steel (hardness, 62 HRC) showed that polycrystalline cubic bo- ron nitride (PCBN) inserts failed by flank wear and fol- lowing observed in feeds (0.08-0.20 mm/rev) and speeds (70-120 m/min). Tool wear studies 15 , conducted on mar- tensitic stainless steel (60 HRC) using alumina based ce- ramic cutting tools, showed that flank wear could affect TL at lower speed, however crater wear could affect TL at high speed (>200 m/min). Attanasio et al 16 used mini- mum quantity lubricant (MQL) for turning process and observed that when MQL applied to flank face, TL increased. High speed end milling of AISI D3 cold-work tool steel hardened to 35 HRC was investigated 17 using coated-