The effect of tool geometry
The effect of tool geometry
The effect of tool geometry and cutting speed on main cutting force and tool tip temperature
Haci Saglama, Suleyman Yaldiz, a, and Faruk Unsacara
aMechanical Department, Technical Science College, Selcuk University, Konya, Turkey
Received 9 December 2004; accepted 25 May 2005. Available online 11 July 2005.
Abstract
In this paper, the effects of rake angle and entering angle in tool geometry and cutting speed on cutting force components and the temperature generated on the tool tip in turning were investigated. The data used for the investigation derived from experiments conducted on a CNC lathe according to the full factorial design to observe the effect of each factor level on the process performance. As the experiments were designed using an orthogonal arrays, the estimates of the average effects will not be biased. During the tests, the depth of cut and feedrate were kept constant and each test was conducted with a sharp uncoated tool insert. For a comparison, the main cutting force and the temperature generated in secondary shear zone for different cutting parameters and tool geometries were calculated by Kienzle approach and with based on orthogonal cutting mechanism, respectively. The average deviation between measured and calculated force results were found as 0.26%. For statistical analyze the orthogonal arrays L16 was used with a total of 16 tests. Finally, it was found that rake angle was effective on all the cutting force components, while cutting speed was effective on the tool tip temperature. The cutting force signals and temperature values provided extensive data to analyse the orthogonal cutting process.
Keywords: C.Cutting forces; E.Entering angle; E.Rake angle; E.Tool tip temperature; H.Taguchi design
Article Outline
1. Introduction
2. Materials and methods
2.1. Experimental set up
2.2. Test material
2.3. Cutting tool and cutting parameters
3. Empirical approach
4. Temperature generated on the tool rake face
5. Results and discussion
5.1. The effect of entering angle on main cutting force and tool tip temperature
5.2. The effect of rake angle on main cutting force and tool tip temperature
5.3. The effect of cutting speed on main cutting force and tool tip temperature
6. Comparison of empirical and experimental results of cutting forces and temperature
7. Statistical analysis of experimental data
8. Conclusion
Appendix A.
References
1. Introduction
An increase in productivity requires involvement of all production operations, technical possibility for full use or activation of all the available manufacturing facilities. In order to involve all the technological operations, optimum technological processes, optimum tool selection, suitable combination of tool-workpiece material and determination of optimum cutting variables and tool geometry must be considered. The tool geometry has an important factor on cutting forces and cutting forces are essential sources of information about productive machining. Due to more demanding manufacturing systems, the requirements for reliable technological information have increased. This calls for a reliable analysis in cutting in the cutting zone (cutter–workpiece–chip system). As the mechanics of cutting in this area are very complicated, i.e. various laws continuously interact, it is not possible to make any precise statements about their mutual influences [1].
The amplitude and frequency of cutting forces and torque are used in sizing machine tool structures, spindle and feed drive mechanisms, calculating the required power as well optimal planning of individual machining operations based on physical constraints. During cutting process, the cutting tool penetrates into the workpiece due to the relative motion between tool and workpiece. The cutting forces are measured by the dynamometers designed for different working principles [2], [3] and [4] on a measuring plane in the Cartesian coordinate system. Zorev [5] already took into account several influential variables in his study of cutting force. The cutting forces are mainly affected by cutting parameters, tool geometry, cutting conditions and tool wear.
Mechanistic approach has been popular in predicting cutting forces, torque and power for a set of tool geometry and work material. In their investigations, Taylor [6] determined the values of the cutting force components and Victor [7] and [8] and Kienzle [9] reported specific cutting coefficient tables by using different rake angles, feed and speeds and offered applicable practical equations. Ernst and Merchant [10] explained the chip formation process when analysing the cutting process. They claimed that the chip was formed in the shear plane and was shaped in the sliding plane. Therefore, the shear angle is a characteristic variable and depends on cleaving/wedge angle and friction. The cutting forces and temperature contributed in the primary shear, chamfer and sticking, and sliding zones are expressed as a function of unknown shear angle, and known friction constants on the rake face and temperature modified flow stress in each zone [11] and [12].
The cutting process is defined as being a stochastically stationary process so that its prediction cannot be made on the basis of its theoretical analysis. Because the cutting force is known to be very sensitive to even the smallest changes in the cutting process, the attentions were directed to the selection of the conditions of the tests and experimental methodology. Measuring the cutting forces involves three successive stages: pre-process, measuring, and analysis and evaluation of the test results. Therefore, instead of calculating the cutting force theoretically, measuring them in process by dynamometers is preferred.
In this study, the influence of tool geometry including rake angle and entering angle and cutting speed on main cutting force component was investigated. The experiments were carried out on a CNC lathe and cutting force components and tool tip temperature were measured in process. Finally, the experimental results of cutting forces and temperature values were compared with calculated results.
2. Materials and methods
2.1. Experimental set up
The experimental planning was prepared by using cutting parameters and test conditions that are advised for a couple of tool-workpiece by the tool manufacturer. In order to measure cutting forces (main cutting force Fc, feed force Ff, and thrust force Ft), a three component turning dynamometer (TeLC DKM2000B1) was used. For temperature measurement on the tool tip an InGaAs radiation sensor (Impact Electronic Seri: 300, 24 VDC, 4–20 mA) focused on the rake face was used. Although most of the heat generated in the cutting process is taken away by the chip (nearly 80% of total heat) from the cutting zone, the important rate of the heat is passed into the tool. Thus, measuring the temperature on crater zone of the tool is a good indicator about the total heat generated. For further evaluation, the force signals and temperature signals obtained are transferred to PC by means of the data acquisition card (PCL-818H).
Four cartridges were used in order to fit the same type of inserts in four different rake angles and entering angles. Force and temperature signals were evaluated by using XKM software by TeLC. The experimental set up is shown in Fig. 1.
(24K)
Fig. 1. Experimental setup.
2.2. Test material
The test samples were selected as to represent the major group of workpiece materials used in industry. For this study, AISI 1040 steel bars were used. Although workpieces were in different microstructures but approximately had the same hardness, thus the cutting force required to fracture the workpiece materials may differ significantly. After the specimens were prepared in required size ( 30 × 200 mm), they were hardened at HRC 40 and then tempered at 200 °C to remove residual stresses in order to obtain a homogeneous structure. The hardness values of the specimens were kept within the limits of ±10%. The chemical composition of the specimens is shown in Table 1.
Table 1.
Chemical composition of the specimens Element C Si Mn Cu Cr Mo Co Al Ni P S Fe
% Value 0.34 0.23 0.7 0.238 0.039 0.026 0.02 0.015 0.012 0.016 0.072 97.8
2.3. Cutting tool and cutting parameters
The cutting tests were carried out on a Leadwell-LTC 20AP CNC lathe equipped with a Fanuc control system. By the four different cartridges designed for different entering angle (45°, 60°, 75°, 90°), the uncoated cemented carbide inserts Komet WCMT 040303 FR ES in grade of P25M having four different rake angles (0°, 6°, 12°, 20°) were used in single-point turning operations. The cutting speed v was assigned four different levels (75; 113; 160; 236 m/min), feed rate f and depth of cut d were kept constant as 0.20 mm/rev and 1.5 mm, respectively. The values of cutting parameters selected are recommended by the tool manufacturer for general purpose and finish turning operations of medium carbon steels. Each experiment was carried out with new sharp tools in order to keep the cutting conditions unchanged. The tests were designed according to full factorial design and conducted in dry cutting conditions. Totally, 64 experiments (43) were performed by the combinations of cutting parameters that are given in Table 2.
Table 2.
Design of experiments Rake angle γ0 Entering angle χ0 Cutting speed v (m/min)
0 45 75
6 60 113
12 75 160
20 90 236
3. Empirical approach
The cutting forces are assumed to be linearly proportional to the uncut chip area Ac The relationship between main cutting force Fc and, uncut chip area Ac and specific cutting force ks is expressed by Kienzle [13] as
Fc=Acks. (1)
The uncut chip area, which is hatched in Fig. 2, is expressed by multiplication of uncut chip width b to uncut chip thickness h.
Ac=bh=df, (2)
where and h=fsinχ.
(15K)
Fig. 2. The area of chip thickness in turning.
Specific cutting force ks for a given chip thickness depends on the factors such as tool-workpiece material, depth of cut, rake angle, metal removing method, inclination angle, etc. Accordingly, specific cutting force can be expressed as
ks=ks11h-zkvkγkT, (3)
where ks11, nominal specific cutting force; h−z, rise in specific cutting force as function of chip thickness; (z, gradient); kv, cutting speed factor; kγ, rake angle factor (; C = 109 for steel); kT, the factor of tool material and metal removal rate.
The geometry of cutting tool is defined by certain basic tool angles and thus precise definitions of these angles are essential [14]. The most important factor which determines the chip cross-section is the entering angles of tooling system (Fig. 2).
Although there are many empirical equations proposed for cutting force calculation, experimental measurements are more reliable. In this study, Fc values were calculated by replacing all the related values in Eqs. (1), (2) and (3).
4. Temperature generated on the tool rake face
During metal cutting, the great rate of mechanical energy from cutting forces is converted into heat. Considerable heat is generated, principally in three areas: the shear zone (primary zone), rake face (secondary zone) and at the clearance side of the cutting edge (tertiary zone). The amount of heat generated varies with the type of material being machined and cutting parameters, especially cutting speed plays an important role in heat generation while feedrate plays moderate role. The prediction of temperature distribution is very important in determining maximum cutting speed. The temperature in the cutting zone depends, to a large extent, on the contact between tool and chip, the magnitude of cutting forces and the condition of friction between tool-workpiece materials. Excessive heat will cause undesirable high temperature in the tool which leads to softening of the tool and its accelerated wear and breakage. Although the prediction of the temperature distribution at the tool–chip interface is rather complex, the following simplified analysis is still useful in metal cutting [15]. The average temperature rise in the tool–chip interface ΔTc is computed by Eq. (4).
(4)
where Pu is the friction power spent on the tool face (Pu = FuVc where Fu is the friction force Fu=Fcsinαr+Ffcosαr), mc is metal removal rate, cs is specific coefficient of heat on workpiece. The temperature of tool and chip is increased by the increase of friction force. Boothroyd [11] and Stephenson [16] assumed a constant sticking friction load with a constant rectangular plastic zone at the tool–chip interface. The experimental temperature measurement and assumed plastic deformation zone led to the following empirical relationship [17]:
(5)
where ΔTm is the maximum temperature rise of the chip at rake face, which has a contact length of lt. The nondimensional number δ is the ratio of the plastic layer thickness over the deformed chip thickness hc on the rake face–chip interface. RT is a nondimensional thermal number given by
(6)
where, v is the cutting velocity, h uncut chip thickness, ct is the thermal conductivity of workpiece. From the geometry of orthogonal cutting, the chip–rake face contact length lt can be predicted as
(7)
where c is the shear angle, βa is the friction angle and αr is the rake angle. The average temperature rise (Tint) at the rake face–chip interface is given by Eq. (8).
Tint=Ts+λintΔTm, (8)
where Ts is the average shear plane temperature. Oxley [17] used the following modified equation to predict temperature
(9)
where Tr is the ambient temperature, λh is a factor that considers the plastic work done outside the thin shear zone, and, λs is the proportion of the heat conducted into the workpiece. An average value of λh can be assumed as 0.7 for carbon steels. The heat transferred into workpiece is evaluated with the following empirical equation [18]:
(10)
and λint (≈0.7) is an empirical correction factor that accounts for temperature variations along the tool–chip contact zone.
5. Results and discussion
In orthogonal cutting, the cutting is assumed as to be uniform along the cutting edge; therefore, it is a two-dimensional plane strain deformation without side spreading of the material. Hence, the cutting forces are exerted only in the directions of velocity and uncut chip thickness. In metal cutting theories, it is assumed that the cutting edge is sharp with no chamfer or radius where the deformation takes place. Rake angle is one of the most important parameters, which determines the tool and chip contact area. There is generally an optimum value for rake angle and entering angle. Increasing the rake angle over its optimum value has a negative effect on tool’s performance and accelerates the tool wear. Excessive wear causes large clearance face contact with machined surface, which leads to an increase in cutting forces tool tip temperature. However, increasing rake angle from small values to the optimum value causes reduction in tool/chip contact length; by this, it is expected that the forces will be reduced. Particularly, negative rake angles cause larger contact area and cause also higher chip volume, both of which lead to increased cutting forces and heat generation [2], [19] and [20]. In the experiments, the thickness of plastic layer on the rake face is observed 5–10% of deformed chip thickness (δ/hc ≈ 0.05–0.1).
5.1. The effect of entering angle on main cutting force and tool tip temperature
The main cutting edge approaches the workpiece with entering angle. In large entering angle, the cutting forces are distributed over a shorter section of the cutting edge. Since the main cutting edge enters and leaves the cutting zone suddenly at 90° of entering angle it is subjected to maximum loading and unloading. Therefore, the optimum entering angle has been obtained as 60–75°. At 45° entering angle with the same cutting speed and depth of cut, the effective cutting edge length increased greatly comparing to the 90°. As a result, the chip thickness becomes smaller. The entering angle affects the axial and radial components of the cutting forces. Generally, a large entering angle produces a large feed force and also smaller thrust force. The entering angle also affects the direction of chip flow.
As shown in Fig. 3(a), in conditions of cutting speed at 160 m/min and constant feedrate (0.20 mm/rev) and rake angle (γ = 0°), the main cutting force decreased by increase of the entering angles, and the greatest decrease was observed at χ = 90°. Nevertheless, the feed force was increased and arrived to its maximum value at χ = 90° as the thrust force was decreased.
(36K)
Fig. 3. The variation of cutting forces and tool tip temperature with entering angle in different rake angles.
Meanwhile, due to the increased chip contact length, the tool tip temperature was obtained maximum at 45° and minimum at 90°. In Fig. 3(b) and (c), for the same cutting speed and rake angle of 6° and 12°, the variation characteristic of cutting forces and temperature were almost the same. If both cutting force and temperature level were considered together, the optimum entering angle could be assumed as 60–75°.
5.2. The effect of rake angle on main cutting force and tool tip temperature
Rake angle has an important effect on all the cutting force components and also on the tool tip temperature. As shown in Fig. 4, the experiments were carried out with tool which has the same entering angle of 60° and at different cutting speeds as 75, 113, 160 and 236 mm/rev. By increasing positive rake angle, the cutting forces were decreased as the tool can plunge into the workpiece easily. But, in contrast, the tool tip temperature was increased in high rake angles due to the increased chip contact length.
(37K)
Fig. 4. The cutting forces and temperature change due to the rake angle in different cutting speeds.
Positive rake angle produces higher shear angle; therefore, it leads to reduction of cutting forces. It also leaves a better surface finish since it assists the chip to flow away from the workpiece. But, excessive rake angle weakens the tool, thus causes to tool breakage. As a result, as the cutting forces and temperature were reduced considerably, the optimum rake angle was obtained as 12°.
5.3. The effect of cutting speed on main cutting force and tool tip temperature
As shown in Fig. 5, the experiments were performed in different cutting speeds with a tool which had a constant rake angle (γ = 6°) and four different entering angles. It was observed that when the cutting speed was raised, all cutting forces were reduced. If the entering angle differs from 90°, the resultant cutting force is mainly directed to the main cutting force and feed force. While the main cutting force was maximum at χ = 45° (Fig. 5(a)) and minimum at χ = 90° (Fig. 5(c)), in contrast, the feed force was obtained minimum at χ = 45° and maximum at χ = 90°. The variation in main cutting force is compensated by feed force. Although the thrust force was lowered by increasing the entering angle, it’s variation was at negligible level. Meanwhile, the tool tip temperature was raised by the increase of cutting speeds and lowered by the increase of entering angle. Evaluating the results of machining conditions in respect to low cutting force and temperature, the optimum cutting speed was obtained for the tool geometry of γ = 6° and χ = 75°.
(39K)
Fig. 5. The cutting forces and temperature change due to the cutting speed in different entering angles.
6. Comparison of empirical and experimental results of cutting forces and temperature
In this study, the effects of cutting speed, entering angle and rake angle on the cutting forces and the temperature on the tool tip were analysed and the cutting force values and the temperature values were obtained experimentally. Then, they were compared with the calculated values. The empirical force values and the temperature values were calculated by using Eqs. (1), (2) and (3) and Eqs. (4), (5), (6), (7), (8), (9) and (10), respectively. In experiments, feed rate f (0.20 mm/rev) and depth of cut d (1.5 mm) were kept constant. In order to determine specific cutting force ks in Eq. (3) for AISI 1040, k11 and m were taken as 990 N/mm2 and 0.18, respectively. However, different k11 values are recommended by different references. The cutting speed factor kv was taken in range of 0.94–1.05 for four cutting speeds. The tool material factor kT was selected as 1 and tool wear factor ka was ignored since each experiment was carried out with a new sharp tool and cutting process took very short time (turning length is 200 mm).
Comparing the results of cutting forces, different percentages of deviations were observed. These can be attributed both to the uncertainty of the difficulty of estimating correction factors for the cutting force equations and to the unknown transfer function of the dynamometer. Therefore, in order to obtain the reliable results for each set of cutting parameter, the values of the factors should be re-evaluated. Maximum deviations were obtained mainly for γ = 20°; χ = 90°; v = 160 m/min while the minimum deviations were achieved in γ = 12°; χ = 60°; v = 160 m/min. The average deviation of main cutting force calculations for 64 experiments was found as 0.26%. These closer results can be acceptable if the complexity of cutting process is considered. The deviations of calculated values of main cutting forces Fcc and temperature Tm from the measured values of Fc–m and Tm were shown in Fig. 6. Also, the total measured and calculated cutting forces for various cutting conditions were given in Table 5 in Appendix A.
(38K)
Fig. 6. Deviations of calculated cutting force components from measured values.
In temperature calculation, the utilised values of the parameters are as follows: specific heat coefficient of steel cs = 470 N m/kg °C; thermal conductivity ct = 28.74 W/m °C. The temperature measurements were performed by using the radiation sensor which was inclined in 30° to the axis of workpiece. Since the tool tip was very close to the flowing chip in cutting process some of the heat was conducted to the workpiece. Hence, it was not possible to obtain the real temperature exerted on the tool tip. As a result, great difference was achieved between the measured and calculated values which were higher than the measured ones. The average deviation of the temperature for 64 experiments was found as 54%. In addition to that, the calculated temperature values give a linear trend while the measured values are oscillated depending on material properties and cutting conditions (Fig. 6). The total measured and calculated temperature values were given in Table 6 in Appendix A. Although the prediction of the temperature distribution at the tool–chip interface is rather complex, this temperature measurement can give an idea about the variation characteristics of temperature in different cutting parameters and the effect of cutting parameters on cutting forces; but, for a reliable measurement, a thermocouple should be embedded into the cutting insert.
7. Statistical analysis of experimental data
The experimental data was analyzed using the following statistical tools: (i) to analyze the average effect of each factor level (performed in Section 5), (ii) the percent contribution from an analysis of variance (ANOVA), and (iii) the correlation between the machining parameters and tool geometry and the characteristic of cutting forces and tool tip temperature. The statistical tools are important indicators in order to show which parameters and how they are effective on the product quality or process performance. Therefore, the obtained data were subjected to ANOVA and correlation test.
ANOVA test is an important method used for interpreting experimental data and making essential decisions. According to three factors (γ, χ, v), cutting forces (Fc, Ff, Ft) and tool tip temperature Tm were evaluated. The experiment were designed as to factorial design (as 43 = 64 experiments) to observe the effect of each factor level on the process performance. This design would obviously lead to a large number of tests. As an alternative, the orthogonal arrays (OAs) developed by Taguchi [21] would minimize this number of tests. Owing to reduced number of tests and saved considerable cost and time this technique has been used to in machining processes preferably [22]. However, as the experiments were designed using an OAs, the estimates of the average effects will not be biased [23]. The OAs, which is its equal representation of all factors, was used to statistical analyze. For this analysis, OAs table was extracted from Appendix A, including the experiment number of 1, 64, 24, 41, 36, 29, 53, 12, 58, 7, 47, 18, 27, 38, 14 and 51, respectively, the best fits for this experiment is L16 with a total of 16 tests.
By using data in arranged table according to OAs, the sum of squares of factors (SSF) and the total sum of squares (SST) for observations yi are given by Eq. (11).
(11)
where KF, number of levels for factor F; nFi, number of observations y under level i of factor F (i = 1 ,…, 4); Fi, sum of observations under i level of factor F; T, sum of all observations; N, total number of observations (N = 16).
Sum of square of error SSe is given by Eq. (12),
SSe=SST-SSF, (12)
the variance of error Ve and variance of factors VF are given in Eq. (13);
(13)
where, vF is number of degrees of freedom, and also percent contributions of factors are given in Eq. (14).
(14)
Percent contribution in a variance analysis reflects total variance observed attributed to any factor in an experiment [21]. The percent contributions of error and factors associated with Fc, Ff, Ft and Tm are given in Table 3.
Table 3.
Percent contributions Factors Fc Ff Ft Tm
γ 76.39 56.21 60.07 17.81
χ 6.55 17.03 10.72 17.51
v 11.97 13.66 4.82 60.60
Error 5.08 13.10 24.39 4.08
Table 3 shows that the percent contribution of rake angle has a significant effect on cutting forces but less effect on tool tip temperature. Interestingly, the main cutting force shows excellent sensitivity to the rake angle (76.39%). However, tool tip temperature, feed force and thrust force were more affected respectively by entering angle; its effect on main cutting force is negligible. Although it was shown previously that cutting speed is very important on feed force and main cutting force respectively, its effect on tool tip temperature is considerable (60.6%).
Finally, the evaluation of the results has shown that the cutting forces can be determined by rake angle mainly, while tool tip temperature can be controlled by cutting speed. Therefore, for minimum cutting force and temperature, the rake angle and the cutting speed must be determined strictly. For this purpose, the selection of tool geometry and cutting parameters should be selected as optimum in a certain range among the values recommended by tool manufacturers instead of random selection [24].
As shown in Table 4, the comments stated above about percent contributions of the factors were verified by the correlation coefficients of the factors. It was observed that rake angle is correlated to cutting force components Fc, Ff, Ft by 87%, 72% and 61%, respectively, and cutting speed to tool tip temperature by 78%. Accordingly, it is assumed that cutting force components can be controlled by the rake angle, while Tm can be controlled by mainly the cutting speed and partly by the entering angle. Additionally, Table 4 shows that the highest cumulative correlation values are associated with the rake angle.
Table 4.
Correlation coefficients of factors Factors Fc Ff Ft Tm Fc + Ff Fc + Ft Fc + Tm Ff + Ft Ff + Tm Ft + Tm
γ 0.87 0.72 0.61 0.42 1.59 1.48 1.29 1.33 1.14 1.03
χ 0.24 0.39 0.37 0.40 0.63 0.61 0.64 0.76 0.79 0.77
v 0.36 0.38 0.27 0.78 0.74 0.63 1.14 0.65 1.16 1.05
8. Conclusion
In the course of this study, the cutting forces and averaged tool tip temperature were measured in turning and the measured results were also compared with their calculated values. On the other hand, the effects of cutting speeds and tool geometry including entering angles and rake angles on cutting forces were evaluated. The following conclusions and observations can be drawn from these investigations.
1. Although some theoretical methods and empirical approach have been developed, the measurement of cutting forces is an essential requirement. Since metal cutting mechanic is quite complicated, it is very difficult to develop a comprehensive model which involves all cutting parameters affecting cutting forces. Under the cutting conditions used in this investigation, the cutting forces and the averaged temperature on the tool tip were measured and also compared with the calculated results. It was found that the average deviation between calculated and measured values of main cutting force was 0.26% in 64 number of experiments, while the deviation in temperature was 54% for the same experiments. Due to the confusing chip flow, the radiation sensor was not able to penetrate into the rake surface and, therefore, it could not be taken as real temperature. But, these temperature results were used to analyze the effects of cutting parameters.
2. In main cutting force calculations, Kienzle approach was used. The success of this approach depends on determining the factors (such as cutting speed factor kv workpiece constant m, the unit of specific cutting force ks11, etc.) distinctly for different couples of tool–workpiece. When ks11 was taken as 990 N/mm2 for an uncoated tool insert and hardened workpiece of AISI 1040, the calculated force values were found consistent with the measured results. The empirical equations derived from orthogonal cutting mechanic were used for temperature calculations. Therefore, in order to obtain reliable results, the factors for each set of cutting parameters should be re-evaluated. In comparison with the measured and calculated values of main cutting force, the maximum deviations were obtained mainly for γ = 20°; χ = 90°; v = 160 m/min while the minimum deviations were achieved in γ = 12°; χ = 60°; v = 160 m/min.
3. Since the main cutting edge enters and leaves the cutting zone suddenly at 90° of entering angle, it is subjected to maximum loading and unloading. If the cutting tool has an entering angle different then 90°, the cutting edge enters and leaves the workpiece gradually, thus the impact of load is not exerted on it. Therefore, the optimum entering angle was obtained at 60–70°. The great entering angle produces greater feed force but less thrust force.
4. When the cutting speed was raised, the cutting forces were reduced but the temperature was increased. For the increased positive rake angle, the cutting forces were decreased, which means less force/power is required. When the results of cutting forces and temperature were evaluated together, the optimum rake angle was found as 12°.
5. When the results of analysis of variance were evaluated, it was observed that the rake angle had a significant effect on cutting forces components, while the cutting speed was effective on tool tip temperature. These conclusions were verified by the correlation coefficients.
Since chip flow is directed by entering angle and rake angle, by the optimum design of these angles, not only the cutting forces but also tool tip temperature can be controlled. Less pressure is advantageous as regards the stresses imposed on the edge and, for this reason, smaller entering angles are often applied to heavy duty and intermittent cuts. Thicker chip will improve the contact between chip and edge and can thus be advantageous as regards tool-life. Also, some materials (hard) cut better when a thicker chip is taken off. A too small entering angle may reduce tool-life in some cases if the chip is too thin.
References
[1] F. Cus, The inclusion of geometrical shape of the cutter into the optimization of milling process, Int J Advance Manufacturing Tech 16 (2000), pp. 392–403. Abstract-INSPEC | Abstract-Compendex | Abstract + References in Scopus | Cited By in Scopus
[2] M.C. Shaw, Mechanics of Orthogonal Cutting, Metal Cutting Principles, Oxford University Press, London (1984).
[3] H. Saglam and A. Unuvar, Three-component strain gauge based milling dynamometer design and manufacturing, Trans SDPS J Integrated Design Process Science 5 (2001), pp. 95–109. Abstract + References in Scopus | Cited By in Scopus
[4] X. Dai and G.H. Gautschi, Next generation of cutting force dynamometers, International Symposium on Test and Measurement, International Academic Publishers, Beijing, China (1997), pp. 615–616. Abstract-Compendex | Abstract + References in Scopus | Cited By in Scopus
[5] N.N. Zorev, Metal cutting mechanics, Pergamon Press, New York (1966).
[6] F.W. Taylor, On the art of cutting metals, Trans ASME 28 (1907).
[7] H. Victor, Beitrag zur Kenntnis der Schnittkraft beim Drehen, Hobeln und Bohren Diss TH Hannover 39 (1956).
[8] H. Victor, Schnittkraftberechnung für das Abspanen von Metallen, Wt.-Z ind Fert 59 (1969), pp. 317–327.
[9] O. Kienzle, Die Bestimmung von Kräften und Leistungen an spänenden Werkzeugen und Werkzeugmaschinen, Z VDI 94 (1951) (11/12), pp. 299–305.
[10] H. Ernst and M.E. Merchant, Chip formation, friction and high quality machined surfaces, Trans ASME 29 (1941), pp. 299–328.
[11] G. Boothroyd, Temperatures in orthogonal metal cutting, Proc Inst Mech Engng 177 (1963), pp. 623–654.
[12] I. Lazoglu and Y. Altintas, Prediction of tool and chip temperature in continuous and interrupted machining, Int J Mach Tools Manufact 42 (2002), pp. 1011–1022. SummaryPlus | Full Text + Links | PDF (303 K) | Abstract + References in Scopus | Cited By in Scopus
[13] O. Kienzle, VDI Verein Deutsch Ingenieure 94 (1952), pp. 299–305.
[14] A.R. Watson, Geometry of drill elements, Int J Mach Tool Des Res 25 (1985) (3), p. 209. Abstract-Compendex | Abstract + References in Scopus | Cited By in Scopus
[15] Y. Altintas, Manufacturing Automation: Metal Cutting Mechanics, Machine Tool Vibrations, and CNC Design, Cambridge University Press, Cambridge, MA (2000).
[16] D.A. Stephenson, Material characterization for metal cutting, J Eng Mater Technol 111 (1989), pp. 210–219.
[17] P.L.B. Oxley, The mechanics of machining, Ellis Horwood Limited, Chichester (1989).
[18] A.O. Tay, M.G. Stevenson, G.D.E. Vahl Davis and P.L.B. Oxley, A numerical method for calculating temperature distributions in machining, from force and shear angle measurements, Int J Mach Tool Des Res 16 (1976), pp. 335–349. Abstract-Compendex | Abstract + References in Scopus | Cited By in Scopus
[19] Jaspers SPFC. Metal cutting mechanic and material behaviour. PhD Thesis, Eindhoven Technical University, 1999.
[20] L. Huang, J.C. Chen and T. Chang, Effect of tool–chip contact length on orthogonal turning performance, J Industrial Technol 15 (1999) (2).
[21] P.J. Ross, Taguchi Techniques for Quality Engineering, McGraw-Hill, New York (1988).
[22] H. Saglam and A. Unuvar, Tool condition monitoring in milling based on cutting forces by a neural network, Int J Production Res 41 (2003) (7), pp. 1519–1532. Abstract-Compendex | Abstract-INSPEC | Full Text via CrossRef | Abstract + References in Scopus | Cited By in Scopus
[23] R. Azouzi and M. Guillot, On-line prediction of surface finish and dimensional deviation in turning using neural network based sensor fusion, Int J Mach Tools Manufact 37 (1997) (9), pp. 1201–1217. Abstract | Full Text + Links | PDF (963 K) | Abstract + References in Scopus | Cited By in Scopus
[24] H. Saglam, F. Unsacar and S. Yaldiz, An experimental investigation as to the effect of cutting parameters on roundness error and surface roughness in cylindrical grinding, Int J Production Res 43 (2005), pp. 2309–2322. Abstract-INSPEC | Abstract + References in Scopus | Cited By in Scopus
Appendix A.
See Table 5 and Table 6.
Table 5.
The measured and calculated cutting forces for various cutting conditions Exp No. γ χ v, m/min Fc–m (N) Ff (N) Ft (N) Fc–c (N)
1 0 45 75 520 267 372 508
2 113 491 252 341 483
3 160 481 194 306 474
4 236 456 159 216 454
5 0 60 75 497 279 239 489
6 113 480 247 210 471
7 160 453 217 185 452
8 236 423 172 111 438
9 0 75 75 490 344 190 480
10 113 475 258 176 462
11 160 448 233 150 443
12 236 417 203 144 430
13 0 90 75 481 379 172 477
14 113 474 341 163 459
15 160 433 269 138 441
16 236 410 271 118 427
17 6 45 75 456 194 132 456
18 113 437 107 95 443
19 160 419 95 78 430
20 236 406 60 58 416
21 6 60 75 423 225 106 440
22 113 411 147 82 427
23 160 405 117 76 414
24 236 398 111 48 402
25 6 75 75 422 252 69 431
26 113 409 177 56 419
27 160 400 124 48 406
28 236 395 69 44 394
29 6 90 75 416 288 57 429
30 113 406 168 45 416
31 160 400 144 43 404
32 236 388 111 37 391
33 12 45 75 403 138 118 414
34 113 398 118 105 402
35 160 386 105 94 390
36 236 379 94 90 378
37 12 60 75 396 150 92 399
38 113 382 136 78 388
39 160 376 118 72 376
40 236 369 92 50 364
41 12 75 75 393 164 56 391
42 113 381 149 53 380
43 160 372 142 49 369
44 236 368 130 44 357
45 12 90 75 386 168 46 389
46 113 378 156 37 378
47 160 371 154 33 366
48 236 367 136 29 355
49 20 45 75 368 104 93 357
50 113 363 80 74 346
51 160 362 74 59 336
52 236 347 60 53 326
53 20 60 75 363 107 83 344
54 113 352 88 66 334
55 160 342 83 63 324
56 236 324 71 58 314
57 20 75 75 362 123 77 337
58 113 351 115 69 328
59 160 342 107 49 318
60 236 319 82 41 308
61 20 90 75 358 154 50 335
62 113 345 144 44 325
63 160 341 125 29 316
64 236 302 98 24 306
Table 6.
The measured and calculated temperature values Exp No. Tm (°C) Tc (°C)
1 356 662
2 384 798
3 405 935
4 452 1110
5 338 584
6 367 700
7 387 816
8 421 962
9 333 544
10 347 650
11 380 754
12 393 884
13 322 531
14 344 634
15 378 735
16 392 860
17 380 745
18 394 899
19 443 1053
20 474 1250
21 353 657
22 383 788
23 399 918
24 448 1082
25 340 612
26 374 731
27 389 849
28 431 995
29 339 598
30 373 714
31 387 827
32 425 968
33 384 803
34 428 969
35 455 1136
36 494 1349
37 368 709
38 389 851
39 428 991
40 459 1169
41 354 660
42 384 790
43 397 917
44 447 1075
45 344 645
46 382 771
47 394 893
48 441 1046
49 388 838
50 432 1012
51 461 1187
52 495 1411
53 378 740
54 393 889
55 437 1038
56 473 1226
57 360 690
58 388 827
59 413 961
60 453 1130
61 357 675
62 386 807
63 408 937
64 451 1100
Corresponding author.
این پايگاه توسط جمعی از فارغ التحصيلان مهندسی ساخت و تولید پشتیبانی می شود. در این پايگاه اينترنتي سعی ما بر این است که مجموعه کامل و مفیدی از مقالات مرتبط با مهندسی مکانیک, ساخت و تولید و موضوعات وابسته را گرد آوری کنیم.