International Journal of Basic & Applied Sciences IJBAS-IJENS Vol:10 No: Sivarao, Fairuz Dimin, T.J.S.Anand, A.Kamely, Kamil

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1 International Journal of Basic & Applied Sciences IJBAS-IJENS Vol:10 No:04 16 Investigation of Tangential Force, Horsepower and Material Removal Rate Associating HAAS CNC Milling, Al6061-T6511 Work Material & TiAlN Coated End Mill Tool Sivarao, Fairuz Dimin, T.J.S.Anand, A.Kamely, Kamil Abstract High speed machining has emerged to become one of the most versatile material removal processes in industries. In gaining optimum cutting conditions, the investigation of the relationship between cutting conditions and technical performance factors such as tangential forces generated during machining is of great importance. This work presents an experimental study on the material removal rate (MRR), horsepower generated at spindle and tangential forces of CNC milling machine tool at 50 mm/min federate by varying depths of cut (DOC). The objective of this research work is to relate the resultant surface roughness measured in arithmetic average mean roughness, Ra to the MRR, horsepower and tangential forces generated by each depth of cut in analyzing their respective behavior / trend. The experiments were carried out using 6 varying depths of cut beginning from 0.5mm with an increment of 0.5mm each depth until the final depth of cut reaches 3.0mm utilizing a new cutting tool at each depth. At each depth of cut, the material removal rate and horsepower were formulated to obtain the cutting forces in the form of tangential forces exerted on the Al 6061-T6511 workpiece. The trend achieved from this work shows MRR, horsepower and tangential forces were all found to be increased with the amplification of cutting depth. The findings are detailed and fully presented latter in this paper. Index Term Milling, tangential force, material removal rate, horsepower, TiAlN, Al6061-T6511. I. INTRODUCTION Today, high-speed machining (HSM) are very common moreover utilizing computer numerical control (CNC) machine tools in manufacturing industries as they provide precision, accuracy, high-repeatability, and a higher production rate compared to conventional milling types. The This work was supported in part by the University Teknikal Malaysia Melaka (UTeM) towards improving engineering materials for future real life structural applications. Ir. Sivarao is a professional engineer, Fairuz Dimin is a certified hazardous ray officer, Assoc. Prof. T.J.S.Anand is a bimetallic material specialist, Dr. Ahmad Kamely is a certified safety officer, together with Kamil are all the academic members of Faculty of Manufacturing Engineering, Universiti Teknikal Malaysia Melaka (UTeM), Hang Tuah Jaya, Durian Tunggal, Melaka, Malaysia who are currently working on improvement of engineered materials for commercial use. The correspondence author can be contacted via kpe_siva@yahoo.com or sivarao@utem.edu.my). most basic function of any CNC machine is to provide automatic, precise, and consistent motion control. Unlike of applying fully or semi manual mechanical motion as required by most conventional machine tools, CNC machines allow motion control in a revolutionary manner. All forms of CNC equipment have two or more directions of motion, called axes. These axes can be precisely and automatically positioned along their lengths of travel. The two most common axis types are; linear (driven along a straight path) and rotary (driven along a circular path). Having such axes however causes the CNC machining process to exert cutting forces in the form of axial and tangential forces onto the workpiece. Tangential cutting force is by far the greater (if translated to the planer this is the force acting on the tool in the direction of the workpiece travel) [1, 2]. Axial cutting force is the force required to keep the cutting edge in contact with the workpiece (perpendicular to the surface of the workpiece on the planer). Tangential cutting force resists the rotation of the work, as relatively high speeds are used the bulk of power consumption lies here. Axial cutting force resists the travel of the tool, however this is a relatively low speed compared with rotation of the work, and therefore, for all practical purposes power consumption may be ignored [3]. That is the reason why the study of tangential forces exerted by the DOC will encompass the MRR and horsepower generated at the spindle at each depth of cut as these parameters are integral in the formulation of tangential forces. Babu et al. [1], presented and validated the fact that, the most influential force during cutting is the tangential force as most of the cutting conditions (given in levels) are responsible in shaping the magnitude of the tangential force. Cutting forces in the tangential direction has also been found to be increased when the depth of cut increases [1,2&4]. Daud et al. [5] determined that at increasing depths of cut the elevated tangential forces causes vibration and chatter. This chatter will inevitably worsen the quality of finished surface. The modeling of cutting forces is often made difficult by the complexity of the tool/workpiece geometry and cutting configuration. Also, analytical cutting force becomes more difficult due to the large number of interrelated machining parameters. The large number of interrelated parameters that influence the cutting forces (cutting speed,

2 International Journal of Basic & Applied Sciences IJBAS-IJENS Vol:10 No:04 17 feed, and depth of cut, cutter geometry, and tool wear, physical and chemical characteristics of the machined part) makes it extremely difficult to develop a sound model. The aim of this research work is to experimentally investigate the metal removal rate besides analyzing the horsepower and tangential force generated on spindle at various depths of cut with cutting speed kept constant with full dry cutting conditions. II. EXPERIMENTAL PROCEDURE The experiment was conducted on Al 6061-T6511 alloy workpiece using 4 flute TiAlN coated carbide cutting tool using 3-axis HAAS CNC mini-mill machining centre as shown in Fig. 1. Machining conditions or control factors for this work is given in Table I. The selected parent workpiece material was cut into six work blocks measuring mm; one for each depth of cut. At each depth of cut, a virgin cutting tool was used to prevent effects of tool wear on overall roughness. Surface roughness was measured in arithmetic mean roughness, Ra as commonly used in surface roughness characterization [6]. COLUMN B row 3, would mean that it denotes the Ra at machining time = 8 minutes. Ra observations were made by SJ 301 Mitutoyo profilometer using 5 cutoff lengths, λc of 2.5mm. Formulation of the material removal rate (MRR) for 0.5 mm DOC is done to further illustrate the significance of depth of cut effects on surface roughness using equation 1. (Eq.1) Where W denotes the width of cut (in.), d is the depth of cut (in) and fm is the feed rate (in/min). MRR is determined in inches to formulate horsepower as the constant used are formulated for inches. Horsepower is given as: (Eq. 2) MRR is the material removal rate (in3/min), Pf is the power constant factor and Es is the spindle efficiency. The spindle efficiency is a reflection of losses from the spindle motor which directly transmits the (Eq. 3) power to the cutter. The spindle efficiency is estimated by the manufacturers to be at least 85%. The power constant factor from this material is 0.95 (alloy steels) as the material hardness is 95Bhn [7]. Subsequently the tangential force, tf is calculated using equation 3. Fig axis HAAS CNC mini-mill machining centre Milling was performed in linear profile for each depth of cut as shown in Fig. 2. Measurements were made chronologically according to the milling profile, in which the profile was segmented into three columns or measuring points beginning from the initial cut as columns A, B and C as illustrated in Fig. 2. The row in which the initial cut is made would be designated as Row 1. Consequently, rows in the milled profile would be numerically denoted from one (1) to ten (10). For each row ranging from line 1 10, three roughness measurements were taken in each column A, B and C. Each column in every row denotes 1 minute of machining time in the tool path respectively. Therefore, identifying the approximated time of machining for certain Ra value, say TABLE I EXPERIMENT CONTROL FACTORS The t f denotes tangential force in pauns (lb), but, the final results will be converted into Newton (N), hp is the horsepower at the spindle, D is the effective diameter of the cutter, in., and rpm is the spindle 1000 rev/minute. The MRR, horsepower and tangential forces for each DOC are tabulated in Table II to interpret the correlation for better relationship study.

3 International Journal of Basic & Applied Sciences IJBAS-IJENS Vol:10 No:04 18 Control Factors Value(s) Unit Comments Feed Rate 50 ft/min Spindle speed 1000 revs/min Cutting Tool 6 mm (dia). Depth(s) of cut 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, mm Low feed is selected to determine MRR, horsepower, and tangential forces at varying depth Standard spindle speed for machining aluminium IPG Four Flute Short Carbide TiAlN-Coated, 30 Helix angle, ± milling tolerance An increment of 0.5mm per iteration. Fig. 2. Linear Profile used in the experiment depicting R a measurement schematic Machining III. RESULTS AND DISCUSSION The experimentally observed data sets are presented in Table II. Table II shows the horsepower, tangential force and average surface roughness, Ra for each performed depth of cut. The correlation between depth of cut, horsepower, tangential force and surface roughness can be seen. Figure 3 shows the required horsepower by the spindle at each increasing depths of cut, where the relationship could be defined as directly proportional. This can be attributed to the increasing depth of cut necessitating the need of more horsepower in order to facilitate the movement of the tool under increased cutting load. As the depth of cut increases, the tool is further penetrated into the work material which not only increases the cutting force exertion on the tool, but also proportionally increases the material removal rate. Table II numerically witnesses that, increasing depth of cut the material removal rates also proportionally increases which in return rises the need of more horsepower as also shown in Fig. 3. In short, the increasing depth of cut precipitates the need for increased horsepower. TABLE II HORSEPOWER, TANGENTIAL FORCE AND AVERAGE RA FOR EACH DOC

4 International Journal of Basic & Applied Sciences IJBAS-IJENS Vol:10 No:04 19 DOC (mm) MRR (in 3 /min) Horsepower (hp) Tangential force (N) Average R a (µm) Fig. 3. of DOC (mm) versus Horsepower (hp) Required at Spindle for DOC mm Graph

5 International Journal of Basic & Applied Sciences IJBAS-IJENS Vol:10 No:04 20 Fig. 4. of DOC (mm) versus Tangential Forces (N) for DOC of mm Graph The histogram in Fig. 4 represents the depth of cut with the corresponding tangential force. As evident in Figure 4, tangential forces are amplified while machining with grater depth of cuts. This is because, when the depth of cut increases, flute engagement of the cutting tool with the work material also increases, where, the flute engagement in the milling process is considered critical and important as it directly influences the tangential force [2]. Not only that, the tangential force is also influenced by the radial and axial depths of cut as they affect the width and length of the cutting tool contact area in the feed and rotational directions, respectively. Thus, the deeper the radial or axial depths of the cut, the more flutes will be engaged, where, the radial depth of cut plays an important role in milling forces because when the radial depth of cut is increased, the contact area increases in the rotational direction, and the forces immediately become larger. Axial depth of cut is another factor influencing the contact area since it affects the axial cutting length of the machined area. That is, when the axial depth of cut is increased, the length of engaged flutes increases, and the milling forces also increase. Fig. 5 illustrates the effective vector of the tangential force. It is studied that, increasing the number of flutes or teeth engaged in the cut will increase the tangential forces and increases surface roughness [1]. Fig. 5. Tangential and Radial Forces The combined histogram plot as shown in Figure 6 clearly indicates that, the tangential force and horse power increases as the depth of cut is increased. This agrees well with the work validated by [2] who works with different sets of experimental parameters.

6 International Journal of Basic & Applied Sciences IJBAS-IJENS Vol:10 No:04 21 Fig. 6. IV. CONCLUSION The following conclusions can be drawn from the investigations carried out: The increase of horsepower is directly proportionate with the increase of depth of cut. Increase in horsepower to overcome the forces by indulging the depth of cut actually increases the material removal rate. Cutting forces in the form of tangential forces increases when depth of cut is increased. An increase in tangential forces induces a detrimental effect on the surface finish. Surface roughness increases with increasing tangential force. The coating material of the cutting tool and the work material applied in this research do not give significant change to the fundamental statements relating tangential force, material removal rate and horse power with respect to depth of cut as commented by other researchers. Chart illustration of the DOC, Horsepower and Tangential Force Relationship. of Machine Tools and Manufacture, 2004 Vol. 44, pp [4] Ekanayake, R.A. and Mathew, P. An Experimental Investigation of High Speed End-Milling. 5th Australasian Congress on Applied Mechanics (August 2007 Sydney), 2007 pp [5] Daud, R., Hasfa, N.K., Tomadi, S.H., Hassan, M.A., Kadirgama, K., Noor, M.M., and Rejab, M.R.M. Prediction of Chatter in CNC Machining based on Dynamic Cutting Force for Ball End-Milling. International MultiConference of Engineers and Computer Scientists (March 18-20, 2009, Hong Kong), 2009 Vol. II IMECS [6] Bhushan, B. Modern Tribology: Principles of Tribology Handbook Vol. 1 Ohio: CRC Press, 2001 pp , pp [7] Walsh, R.A. and Cormier, D. Machining and Metalworking Handbook, Third Edition. New York: McGraw-Hill, 2006 pp Bar REFERENCES [1] Babu, G.B., Selladurai, V., Shanmugam, R. Analytical Modeling of Cutting Forces in End Milling Operation on Aluminum Silicon Carbide Particulate Metal Matrix Composite Material Using Response Surface Methodology. ARPN Journal of Engineering and Applied Science, 2008 Vol. 3, pp [2] Lai, H.L. Modelling Cutting Forces in End Milling Operations. Tamkang Journal of Science and Engineering, 2000 Vol. 3 pp [3] Raksiri, C. and Parnichkun, M. Geometric and Force Errors Compensation in A 3-axis CNC milling machine. International Journal