The paper presents the research into cutting forces in face milling of three different materials: steel Č 4732 (EN42CrMo4), nodular cast iron NL500 (EN-GJS-500-7) and silumine AlSi10Mg (EN AC-AlSi10Mg). Obtained results show that hardness and tensile strength values of workpiece material have a significant influence on the main cutting force, and thereby on the cutting energy in machining.U radu su prikazana istraživanja sila rezanja pri čeonom glodanju za tri različita materijala: čelik Č 4732 (EN42CrMo4), nodularni lijev NL500 (EN-GJS-500-7) i silumin AlSi10Mg (EN AC-AlSi10Mg). Dobiveni rezultati pokazuju da vrijednosti tvrdoće i vlačne čvrstoće materijala obratka imaju veliki utjecaj na glavnu silu rezanja, a time i na ukupno utrošenu energiju rezanja pri obradi

M. Gostimirović

M. Hadžistević

M. Sekulić

Z. Jurković

English

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M. SEKULI], Z. JURKOVI], M. HAD@ISTEVI], M. GOSTIMIROVI]THE INFLUENCE OF MECHANICALPROPERTIES OF WORKPIECE MATERIALON THE MAIN CUTTING FORCE IN FACE MILLINGReceived – Prispjelo: 2009-10-20Accepted – Prihva}eno: 2009-12-20Preliminary note – Prethodno priop}enjeINTRODUCTIONThere are several criteria for material machinabilityevaluation, and the most frequently used ones are: toollife (influencing the machining time and productioncosts), cutting forces (influencing energy consumption),cutting temperatures (influencing tool wear), machinedsurface quality and chip shape. Based on these criteria,better material machinability is due to: longer cuttingtool life, higher productivity (the amount of removedchip), better machined surface quality, lower cuttingforces, lower cutting temperatures, and more favourablechip shapes, as long as they have been achieved underthe same conditions. In machining diverse materials, un-der constant machining conditions, diverse cuttingforces owe their origin to different physical and chemi-cal properties of the workpiece material. Tensilestrength and hardness are typical material properties in-fluencing the main cutting force. There is, of course, aset of other material properties, like the microstructure,crystal grains size and shape, type and amount of impu-rities and the like, which also exert influence on themain cutting force.The paper presents the researches into cutting forcesin face milling of workpieces made from three differentmaterials (steel for improvement, nodular cast iron, andsilumine). To calculate cutting forces, the Kienzle equa-tion constants are determined by the application of themodel that enables rational use of laboratory time re-sources and small workpiece material consumption 1.From the calculated constants, the main cutting force foradequate cutting conditions may be calculated and thusseparate material machinability compared.MODEL OF CUTTING FORCESIn face milling, the cutting forces exerted by the facemilling cutter tooth on the workpiece are changeable intime and space. Figure 1 presents the cutting forcesscheme in one-tooth face milling (a shaded area is a chipremoved by one tooth per revolution). The paper 1shows that the main cutting force Fv can be calculated onthe basis of measured cutting forces in x and y directionusing the following equation:FFFvxy  	sin cos  (1)where  - angle of cutting point measured from x -axis is anti-clockwise.The equation (1) can be utilized to draw variation di-agrams for the main cutting force Fv during a one-toothcut. For quality implementation of the Kienzle equation:F b h kvmvv  1 1 1. (2)it is necessary to know two constants of theworkpiece material (kv1.1-main specific cutting force re-lated to the cross-sectional area of the cut bxh=1x1=1METALURGIJA 49 (2010) 4, 339-342 339The paper presents the research into cutting forces in face milling of three different materials: steel ^ 4732 (EN42CrMo4), nodular cast iron NL500 (EN-GJS-500-7) and silumine AlSi10Mg (EN AC-AlSi10Mg). Obtained re-sults show that hardness and tensile strength values of workpiece material have a significant influence on themain cutting force, and thereby on the cutting energy in machining.Key words: machinability, main cutting force, face millingUtjecaj mehani~kih karakteristika materijala obratka na glavnu silu rezanja pri ~eonom glodanju.U radu su prikazana istra`ivanja sila rezanja pri ~eonom glodanju za tri razli~ita materijala: ~elik ^ 4732 (EN42CrMo4), nodularni lijev NL500 (EN-GJS-500-7) i silumin AlSi10Mg (EN AC-AlSi10Mg). Dobiveni rezultati po-kazuju da vrijednosti tvrdo}e i vla~ne ~vrsto}e materijala obratka imaju veliki utjecaj na glavnu silu rezanja, atime i na ukupno utro{enu energiju rezanja pri obradi.Klju~ne rije~i:obradivost, glavna sila rezanja, ~eono glodanjeISSN 0543-5846METABK 49(4) 339-342 (2010)UDC – UDK 669.14/15:620.171.70/178:620.18 = 111M. Sekuli}, M. Had`istevi}, M. Gostimirovi}, Faculty of Technical Sci-ences, University of Novi Sad, SerbiaZ. Jurkovi}, Faculty of Engineering, University of Rijeka, Croatiamm2 and exponent 1-mv). The Kienzle equation con-stants are machinability parameters of material itself.The undeformed instantaneous chip thickness and widthof the cut can be derived as follows:h s b ap   1 sin sin / sin   (3)suggesting that there are  - tool cutting edge angle,s1 - feed per tooth and ap - depth of cut.Since the undeformed chip thickness varies accord-ing to the angle of cutting point only one experiment canbe performed to obtain straight line Fi/b=f(h), necessaryfor graphic and analytic determination of the Kienzleequation constants 2.The power requirements of the milling machine isdesigned on the basis of the average value of the maincutting force:F b h kv mmvv  1 1 1. (4)In this equation, hm is an average undeformed chipthickness which can be approximately calculated by thefollowing equation:hBDsms   114 61,sin(5)where are: B - cutting width, D - cutter diameter, s -maximal contact angle between the cutter tooth andworkpiece.EXPERIMENTAL PROCEDUREThe experimental work was carried out at the De-partment of Production Engineering, the Faculty ofTechnical Sciences in Novi Sad. The machining wasconducted on a Vertical-spindle Milling Machine(„Prvomajska“ FSS-GVK-3). A face milling cutter with80 mm diameter („Jugoalat“ G.707.1), with cementedcarbide inserts („Sintal“ type P25 for steel and nodularcast iron and type K10 for silumine) with tool cuttingedge angle =75° and rake angle =0°, was used as atool. All of the experiments were conducted with one in-sert without coolant, except for machining siluminewhen, due to intensive adhesion chip for insert, petro-leum was used. The analysed materials are: steel ^4732,nodular cast iron NL500 and silumine AlSi10Mg.During the experiments, cutting forces were mea-sured using a three-force components Kistler dyna-mometar (the model 9257A) and also sampled using aPC based data acquisition system with LabVIEW soft-ware 3. The experiment conditions and research intomechanical properties of material are summarized inTable 1. The selection of cutting conditions are closelyconnected to the cutting tool and workpiece material.The chemical composition of the investigated materialsis shown in Table 2. Figures from 2 to 4 show theirmicrostructure.The quenched and tempered microstructure of thesteel ^4732 was determined by the metallographic re-search, Figure 2.The microstructure of the nodular cast iron is com-posed of ferrite, perlite and graphite nodule, Figure 3.340 METALURGIJA 49 (2010) 4, 339-342M. SEKULI] et al.: THE INFLUENCE OF MECHANICAL PROPERTIES OF WORKPIECE MATERIAL ON THE MAIN...Figure 1 The scheme of cutting forces 2Table 1 Experiment conditions and mechanical properties of materials used during machinability testWorkpiece material Tensile strengthRm /MPaHardness /HBCutting toolmaterialv / m/min s1 / mm/tooth ap /mmCode in JUS Code in DIN^4732 42CrMo4 975 265 HM P25 89,17 0,281 1NL500 GGG-50 495 170 HM P25 89,17 0,281 1AlSi10Mg G-AlSi10Mg 85 49 HM K10 281,48 0,281 1Table 2 The chemical composition of materials used during machinability testMaterialChemical composition / wt. %C Si Mn S P Cr Mo Ni Cu V Fe Mg^4732 0,40 0,427 0,497 0,042 0,039 0,914 0,183 0,35 0,17 0,01 - -NL500 3,50 2,67 0,40 0,012 - 0,05 - - - - - -AlSi10Mg - 9,03 0,282 - - - - - 0,069 - 0,46 0,104Figure 2 The microstructure of steel ^4732There are also micro-cavities of irregular shapes, as wellas non-homogenity in perlite amount (micro-cavitiescan be observed in perlite as well).Figure 4 presents modified silumine comprising of solid solution and granular eutectic. Micro-cavities andthe dendrite orientation of the microstructure can be ob-served.EXPERIMENTAL RESULTSFigures 5 to 7 present diagrams of variations in or-thogonal cutting forces and main cutting force, derivedfrom the equation (1) for face milling of the tested mate-rials.Determined values of the main specific cutting forcekv1.1 and exponent of the Kienzle equation 1-mv areshown in Figure 8.Based on the constants from Figure 8 and the condi-tions from Figure 1 (B=D, s=), the average value ofthe main cutting force for different feed per tooth can becalculated by utilizing the equation (4), Figure 9.The average value of the main cutting force with ref-erence to hardness of analysed materials (e.g. for feedper tooth s1=0,281 mm/tooth, accordingly for averageundeformed chip thickness hm=0,173 mm and width ofthe cut b=1,035 mm), is presented in Figure 10. It is ob-vious that the hardness value of workpiece material hasa significant influence on the value of the main cuttingforce in face milling.METALURGIJA 49 (2010) 4, 339-342 341M. SEKULI] et al.: THE INFLUENCE OF MECHANICAL PROPERTIES OF WORKPIECE MATERIAL ON THE MAIN...Figure 3 The microstructure of nodular cast iron NL500Figure 4 The microstructure of silumine AlSi10MgFigure 5 Cutting forces variation vs. tooth positionFigure 6 Cutting forces variation vs. tooth positionFigure 7 Cutting forces variation vs. tooth positionFigure 8 Empirically determined Kienzle constantsFigure 9 Variation Fvm vs. feed per toothCONCLUSIONMechanical properties of workpiece material are im-portant factors affecting machining conditions. Regard-ing low cutting forces, low values of hardness and ten-sile strength usually provide better machinability. Thisinvestigation has shown that hardness and tensilestrength of the workpiece material have a significant in-fluence on the main cutting force in face milling, andthereby on the cutting energy in machining.REFERENCES1 H. Q. Zheng, X. P. Li, Y. S. Wong, A. Y. C. Nee, Internatio-nal Journal of Machine Tools&Manufacture 39 (1999), pp.2003-2018.2 M. Sekuli}, M. Gostimirovi}, Z. Jurkovi}, P. Kova~, Proce-edings, 7th International Scientific Conference on Produc-tion Engineering, Kairo, 2009, pp. 17-183 F. Mocellin, E. Melleras, W. L. Guesser, L. Boehs, J. of theBraz. Soc. of Mech. Sci&Eng, XXVI (2004) 1, pp. 22-274 R. T. Coelho, A. Braghini Jr., C. M. O. Valente, G. C. Me-dalha, J. of the Braz. Soc. of Mech. Sci&Eng, XXV (2003)3, pp. 22-27Note: The responsible translator for the English language is KsenijaMance, Senior Lecturer at the Faculty of Engineering, Rijeka, Croatia.342 METALURGIJA 49 (2010) 4, 339-342M. SEKULI] et al.: THE INFLUENCE OF MECHANICAL PROPERTIES OF WORKPIECE MATERIAL ON THE MAIN...Figure 10 Variation Fvm vs. hardness HB

Utjecaj mehaničkih karakteristika materijala obratka na glavnu silu rezanja pri čeonom glodanju

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