Effects of Various Parameters on CNMG Turning Insert in Machining Ti-6Al-4V Alloy

Transcription

1 International Journal of Engineering & Technology Innovations, Vol. 1 Issue 2, May Effects of Various Parameters on CNMG Turning Insert in Machining Ti-6Al-4V Alloy Eriki Ananda Kumar 1, K. Prahalada Rao 2, G. Naga Malleshwara Rao 3 and A.R. Babu 4 1 Faculty of Mechanical Engineering, Nilai University, Nilai, Negri Sembilan, 71800, Malaysia. 2 Professor, Dept. of Mechanical Engineering, JNTUniversity, Anatapur, , Andhra Pradesh, India. 3 Prof, Shri Shiridi Sai Institute of Science and Engineering, JNTUniversity, Anatapur, , AP, India. 4 Assoc. Prof, Dept. of Mechanical Engineering, SVCET, JNTUniversity, Chittoor, , AP, India. Abstract Now a days titanium materials are difficult to machine. Manufacturers are known that, with proper procedures, titanium can be fabricated using techniques no more difficult than those used for machining SS316. The machining of hard workpiece materials requires significantly harder cutting materials. Advancements in the aerospace, nuclear and other industries require the enhanced in-service performance of engineering components. These requirements have resulted in the large scale development and use of heat-resistant and high-strength materials, such as Ti6A4V alloys, which pose considerable machining problems. In this analysis on machining of titanium alloy using cubic boron nitride (cbn) tools, the machining performance was evaluated in terms of cutting force, specific cutting pressure, cutting temperature, chip strain and surface finish. The studies of turning machinability of titanium alloy using round tee-lock cubic boron nitride (cbn) inserts have been presented. A series of turning experiments were performed with cubic boron nitride (cbn) inserts with the objective: To determining the effect of cutting variable on the tool life. To investigate the effect of cutting speed and feed rate on the surface roughness while using round tee lock inserts. A good surface finish of 0.5 to 1 micron was obtained for cutting speed between m/min, feed of 0.10 to 0.20 mm/rev and depth of cut of 1 mm and also find the Stress intensity in two different axis will be studied. Keywords: CBN, Ti-6Al-4V, Grade2 alloys. 1. Introduction The machining of hard workpiece material requires significantly harder cutting materials. In contrast to diamond, superhard cubic boron nitride (cbn) is outstandingly eligible for the machining of steels. In spite of being a difficult to machine titanium materials and its alloys find wide application in many industries because of their excellent and unique combination of height to weight ratio and high resistance to corrosion. The machinability of titanium and its alloys is impaired by its high chemical reactivity, low modulus of elasticity and low thermal conductivity. Enormous works on machinability of engineering materials have been carried out even though it is difficult to assess machinability index in simple terms. Tool life equation informs that feed and preheating temperature significantly affects the tool life. Induction heating for end milling of titanium alloy Ti-6Al-4V. The results lead to conclusions that workpiece preheating significantly increases the tool life of uncoated WC-Co carbide inserts in end-milling of Ti-6Al-4v. An increase in tool life by 32.5% was achieved while employing preheating at C compared to the experiment at room temperature [1]. The straight cemented carbides (WC-Co) with Co content of 6 wt. % and a WC grain size between 0.8 and 1.4 m gave the optimum performance [2]. This paper presents the results of an investigation of machinability improvement in Titanium Alloy Ti-6Al-4V in machining in lathe and then monitoring the tool condition by the experimental results using ARTIFICIAL NEURAL NETWORK. (ANN), during the machining of titanium alloys, tools wear out rapidly. In this work, tool wear monitoring was accomplished through an approach based on multi-layer neural networks. In comparison with other Artificial Intelligence (AI) approaches (e.g. expert systems), neural networks are relatively easier to develop (a human expert is not needed during the learning and training phases) and require less hardware and software resources. To find the tool wear during machining of titanium in lathe using cubic boron nitride (cbn) as a cutting tool and comparing actual tool wear with estimated tool wear using Artificial Neural Network. Sandvick polycrystalline diamond (PCD) inserts has only one cutting edge [3]. Experimental data were collected during machining of work. For various combinations of the process parameters, the process state variable is measured. The process parameters are cutting speed, axial feed and depth of cut. The process state variable is flank wear land width of the tool and the surface roughness R a of the work piece.

2 International Journal of Engineering & Technology Innovations, Vol. 1 Issue 2, May The principal problems in machining are high cutting temperature and the rapid tool wear. Most of the tool materials are wear rapidly even at moderate cutting speeds. To minimize the tool wear, currently the machining of the cutting speed is less than 60m/min. The machining characteristics of titanium and its alloys are summarized as: Titanium and its alloys are poor thermal conductors. As a result, the heat generated when machining the titanium cannot dissipate quickly; the heat is concentrated on the cutting edge and tool face. Titanium has a strong alloying tendency of chemical reactivity with the cutting tool material at tool operation temperatures. This causes galling, welding and smearing along with rapid wear or cutting tool failure. During machining, titanium alloys exhibit thermal plastic instability which leads to unique characteristics of chip formation. The shear strains in the chip are not uniform but they are localized in an arrow band that forms serrated chips. The contact length between the chip and the tool is extremely short; this implies that the high cutting temperature and the high stress are simultaneously concentrated near the cutting edge. Serrated chips create fluctuations in the cutting force. This situation is further promoted when alpha-beta alloys like Ti-6A1-4V are machined. The vibration force together with the high temperature exerts a micro fatigue loading on the cutting tool, which is believed to be partially responsible for several flank wear [5]. To predict the flow stress behavior of the Ti6Al-4V alloy at various temperature and strain rates, the experimental data has been collected by conducting isothermal uniaxial tensile tests at elevated temperatures ( K) and constant strain rates (10-5, 10-4, 10-3, and 10-2 s -1 ), stress-strain data are the employed to derive the constitutive equation related flow stress, strain, strain rate and temperature [6]. Friction coefficients of chip-tool-work based on Shaw s orthogonal cutting force model by incorporating 2-D forces and chip morphology. [7].FEA is very important tool for stress and strain analysis, plastic material flow approaches Eulerian technique and Lagrangian technique to prediction of high cutting speed is very effective in the machining cutting parameters [8]. 2. Experimental Setup The straight tungsten carbide (WC) cutting tools, C-2 carbides are used extensively in engine and airframe manufacturing for turning and face milling operations. In recent years, in the United Sates as well as in Europe, solid C-2 end mills and end mills with replaceable C-2 carbides are finding applications, particularly in aerospace plants. Now a day, the M7 and, more frequently, the M42 and M33 high-speed steels are recommended for end milling, drilling, and tapping of titanium alloys. According to that the data were collected and shown in the Table 1. Table 1: Composition of work material O N C H Fe Residuals The Experimental has been conducted on a CNC Lathe with cubic boron nitride (cbn) inserts for various sets of cutting conditions, i.e. speed, feed and depth of cut. Flank wear measurements have made at different predetermined time of intervals, the machining was stopped depending on the stipulated time and flank wear land width (V b ) of the tool, and surface roughness (R a ) of the work piece has been measured. The tool life has been fixed of flank wear land width of the tool life period. The sets of measurements immediately prior to a wear measurement have been used for training the neural network. During reinsertion of tool inserts after every wear measurement, inserts were alleged into the slot made out in the tool holder, so that there is no change in the tool overhang. 3. Experimental work 3.1 Tables and Figures The Experiment was carried out on a Lathe machine with tool cubic boron nitride (cbn) insert. Machining was carried out on Titanium alloy of different cutting parameters like cutting speed, depth of cut and feed. The various cutting parameters were considered and given in experimental conditions. Specification of work material: ASTM B348-02, Grade 2 (commercial pure titanium), as shown in Fig.1. Fig. 1 Titanium material The tool is modeled with the assumption that it is mechanically rigid. Rake angle-6 0 and clearance angle-21 0 used to design the cutting tool geometry as shown in Fig.2, tool material: Shank size-12.5mm 12.5mm, Tool material- CBN, Insert shape-cnmg, and cutting condition: Speed (60, 90,120 m/min), Feed (0.1, 0.3 mm/rev), Depth of cut (0.05, 0.15, 0.3mm) with dry environment as shown in Fig.3., Fig. 4 shows the orthogonal (2-D) turning test setup with cutting force, thrust force and feed motion of cutting tool with Ti-6Al-4V workpiece material.

3 International Journal of Engineering & Technology Innovations, Vol. 1 Issue 2, May Table 2: Experimental Design and its response Fig. 2 Cutting tool geometry Expt. No. Speed (V c) (m/min) Depth of Cut (D c) (mm) Feed (F) (mm/rev) Time (min) Surface roughness (R a) (µm) Tool Wear (V b) (mm) A surface roughness cut off optimum value was used, measurement values used in the result are the average of five readings taken at equal intervals around the workpiece.the cutting tool and chip formations were studied under scanning electron microscopy (SEM). The level of cutting parameter ranges and the initial parameter ranges and the initial parameter values were chosen from the handbook recommended for the tested material. 3.2 Experimental Measurements Fig. 3 2D orthogonal dry cutting Ti-6Al-4V The work setup is show in Fig 5. The experimental work was carried out on a CNC lathe. The turning operation was carried out on Commercial pure titanium. The composition of the work material, details of the cutting tools used and the cutting conditions are given. Data collected include flank wear, surface roughness and cutting time for various combinations of feed (f), depth of cut (DOC). Tool wear land (V b ) was measured using a tool maker s microscope. Surface roughness (R a ) has been measured using perthometer. About 18 pairs (patterns) have been collected. Fig. 4 Schematic of orthogonal turning Fig. 5 Experimental set-up of Ti-6Al-4V turning test

4 International Journal of Engineering & Technology Innovations, Vol. 1 Issue 2, May Titanium alloys are very sensitive to changes in feed, as show in Fig.6. powder form. Wear get increase as depth of cut increases. Fig. 7, shows variation of Flank wear with machining time for the depth of cut = 0.05mm and feed = 0.1mm/rev. Fig. 7 Variations of flank wears with machining time 4. Conclusions Fig. 6 Effects of cutting speed&feed control life when turning Ti-6Al-4V Tool-life data have been developed experimentally for a wide variety of titanium alloys where tool life (as time) is plotted against cutting speed (rpm) for a given cutting tool material at a constant feed and depth in relation of Ti-6Al- 4V. It can be seen that at a high cutting speed, tool life is extremely short. As the cutting speed decreases, tool life dramatically increases. In industry generally operates at cutting speeds providing long tool life. Analysis of the cutting and thrust force data shows a considerable improvement in the amount of force required to an uncoated, FGD and NCD coated inserts [4]. The forces in machining can be determined with a tool dynamometer. In turning, the tool dynamometer usually measures 3 components: Tangential (cutting) Thrust (separation) and feed forces. 4. Results and Discussion An oblique turning test was conducted to see the effect of input parameters are speed, feed, Depth of cut. Surface roughness (Ra) on output parameter flank wear is analyzed. As the speed and feed increase the flank wear increases due to more rubbing action of the tool with work. The greater flank wear were observed at increasing cutting speed and feed. When depth of cut increases the chips flow out is lengthy and for lower depth of cut the chips are in The suitability of CNMG insert in turning of the titanium alloy (Ti-6Al-4V) was investigated in this study. The following conclusions were arrived based on the series of experiments and analysis of the results: Titanium alloy (Ti-6Al-4V) was identified and the specimen was checked for composition of its constituent elements. The composition confirmed to ASTM grade B-348 grade-2 for bars and forged sections. The experiments were conducted by varying the cutting speed, feed and depth of cut and surface roughness was measured for different cutting conditions. A good surface finish of micron was achieved for cutting speed between m/min, feed of 0.1 to 0.2 mm/rev and depth of cut of 1mm and finding stress intensity in two different axis will be studied. Cutting stiffness of thrust forces remained almost constant against variation of cutting speed and with of tool flank wear. Coefficients of velocity component of thrust force rose linearly with increase of width of flank wear normalized by cutting speed. Cubic boron nitride (cbn) tools can generate all kinds of wear like common wear resistance coatings: crater wear at high cutting velocities, plastic deformation at high velocities and high feeds, tool fracture at high feeds, the built-up edge effect at low cutting parameters, and uniform and continuously growing flank wear in safe zone. Substantially increasing tool life during turning Ti-6Al- 4V (gr2) using round tee-lock cubic boron nitride inserts.

5 International Journal of Engineering & Technology Innovations, Vol. 1 Issue 2, May References [1] Turnad, L.G and Amin, AKMN: Cutting Force and Tool Life Model in End Milling Titanium Alloy Ti-6Al-4V with Thermally-Assisted Machining, International Journal of Mechanical Computational and Manufacturing Research, Vol. 1, No.1, (2012), pp. 1-5, ISSN: [2] S. Ramesh, L. Karunamoorthy and K. Palanikumar: Measurement and analysis of surface roughness in turning of aerospace titanium alloy (gr5), Measurement 45 (2012) [3] Turnad, L.G and Amin, AKMN: Improved Tool Life in End Milling Ti-6Al-4V through workpiece preheating European Journal of Scientific Research, Vol. 27, No.3, (2009), pp , ISSN X. [4] C.D. Torres, P.J.H and A.V. Sumant: Analyzing the performance of diamond coated micro end mills. International Journal of Machine Tools & Manufacture; doi: /j.ijmachtools [5] Hong, H., Riga, A.T., Cahoon, J.M., Scott, C.G., Wear, (1993) p34-39 [6] Nitin.K, Hansoge N.K., Pavan. P, and A.K. Gupta: Microstructure study and constitute modeling of Ti-6Al-4V alloy at elevated temperature. Material and Design, 54 (2014) [7] Anil.K.S., Z. Xueping, Tim Bell and C.Steve, Investigations on turning Ti-6Al-4V titanium alloy using super-finished tool edge geometry generated by micro-machining process (MMP), Pennsylvania, USA. [8] Moaz H. Basim A, K. M. Bashir and A.A. Oshkour: Prediction of High Cutting Speed parameters for Ti-6Al-4V by using Finite Element Modeling International Journal of Modeling and Optimization, Vol. 2, No., (2012), pp Eriki Ananda Kumar is a Senior Lecturer in department of mechanical engineering in Nilai University, Malaysia. He has 9 years of experience in teaching and industry. He has published 10 papers in various Journals and Conferences. He obtained his B.Tech degree in Mechanical Engineering from Sri Venkateswara College of Engineering and Technology, Chittoor and M.E Degree from Sathyabama University in the specialization of CAD. He has 1 year of industrial experience in CNC, Chennai. His interested areas in research are Titanium alloys, Material and Manufacturing, CAD/CAM and Industrial Engineering Prof. K. Prahalada Rao has 31 years in teaching and about 20 years of research experience. He has published many papers in different journals in the field of design and manufacturing Dr. G. NagaMalleshwara Rao is Professor and Principal of the SSSS at Vadiyampeta, Anantapur. He has published many papers in different journals in the field of manufacturing and metal cutting. His areas of specializations: Design and Manufacturing, Material and Mangement. A.R. Babu is an Associate professor in the Mechanical Engineering in Sri Venketeswara College of Engineering and Technology, Chittoor, India. He has 10 years of experience in teaching and industry. He obtained his B.Tech and M.Tech, degrees in REC-warangal, India. His research area of interest is IC engines, Bio-fuels and Industrial Engineering.