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Al-Khwarizmi 

Engineering   
Journal 

 
Al-Khwarizmi Engineering Journal, Vol. 15, No. 3, Sptember, (2019) 

P. P. 84- 91 

 
Study the Effects of Machining Parameters on Surface Roughness for 

Free Form Surface Using Taguchi Method 
 

Safaa K. Ghazi*       Mustafa M. Abdulrazaq**    Abdulrahman S. Sultan*** 
Firyal S. Muhi**** 

*,**,***,**** Department of Production Engineering and Metallurgy/ University of Technology/ Baghdad/ Iraq 

*Email: safaa_kadhim1988@yahoo.com 

**Email: mustafaalneame@yahoo.com 
 

(Received 25 November 2018; accepted 19 February 2019) 

https://doi.org/10.22153/kej.2019.02.002 

 
Abstract 
        

The surface finish of the machining part is the mostly important characteristics of products quality and its 

indispensable customers’ requirement. Taguchi robust parameters designs for optimizing for surface finish in turning of 

7025 AL-Alloy using carbide cutting tool has been utilized in this paper. Three machining variables namely; the 

machining speeds (1600, 1900, and 2200) rpm, depth of cut (0.25, 0.50, 0.75) mm and the feed rates (0.12, 0.18, 0.24) 

mm/min utilized in the experiments. The other variables were considered as constants. The mean surface finish was 

utilized as a measuring of surface quality. The results clarified that increasing the speeds reduce the surface roughness, 

while it rises with increasing the depths and feeds. Using the analysis of variance, it found that the most effective 

variable is cutting speed with (53.85%) and the depths has the smallest influence with (20.09%). The data set from the 

experiments was appointed for implementing the optimum procedure, depending on the principle of Taguchi way. The 

result of calculation with the experimental outcome was in good agreement. 

 
Keywords: feeds, surface finish, surface roughness, taguchi. 

 
1. Introduction 
 

Machining technologies case includes size 

components diminishing, enhancement of the 

surface quality, tightest tolerance and manufacture 

accuracies, reduce cost, reduce size of batches and 

diminished weight etc. [1]. The surface finish of 

the machining part is one of the mostly important 

part quality characteristic. The actual profile of 

surface is the superposition of errors for the form, 

roughness and waviness. The deviation is define 

in international standard. The surface finish 

greatly effects on the functional performance of 

mechanical part like as fatigue strength, wear 

resistance, holding a lubricant and ability of 

distributing, transmission and heat generation, 

resistance of corrosion etc [2,3]. The average 

surface roughness (Ra) was select as 

characteristics of surface roughness in operation 

of turning, which is the mostly utilized standard 

variable of surfaces finish. In cutting processes, 

we have two sharps and sometimes contrary 

requirement. The first one with high qualities 

surface while the second one with high 

productions rates. However, more than one 

theoretical model involved approximations and 

simplification in relations with reality machining 

processes and doesn’t take in to accounts any 

imperfection in chips formation and surfaces 

finish. Consequently, the solution of the analytical 

in general wasn’t accurate enough to utilize 

practically [4]. These mathematical (statistical) 

ways and approaches integrated experimentally, 

thus it provides sufficient calculations of precision 

of the reality condition in which the machining 

operation happen. This work demonstrates the 

applications of the Taguchi technique to identify 


 Safaa K. Ghazi                            Al-Khwarizmi Engineering Journal, Vol. 15, No. 3, P.P. 84- 91 (2019)  

85 

 
the optimum turning variables for surfaces finish 

in dry machining of Al-alloy. 
 

2. Theoretical Considerations 
 

This work introduces a mathematical 

representation for the curves mathematical which 

include parametric representations, in addition to 

propose the derivation of the curve. An adopting 

way for generating the tool paths have been 

implemented depending on CAM program 

package. The equations of parametric curves 

describe the dependable and undependable 

variable in term of parameters. The equations can 

convert to nonparametric forms by eliminate the 

dependable and undependable variable from the 

equations. An equation of the Parametric for free-

form surface is constructed by two variables (u), 

and the vector of parametric functions 

representing the coordinate's position of the curve 

[5]. 

P (u) = [x (u), y (u), z (u)] u from [1, 0]        … (1) 

       In this paper Bezier technique illustrated for 

representing the proposed study curve. Using the 

fifth order degree with six control points to each 

single curve to represent the profile curve of the 

product, and the equation of the proposed Bezier 

curve is 

]1[)(
2345

uuuuuuP =  

            
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−

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000001

000055

000102010

0010303010

052030205

15101051

  
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6

5

4

3

2

1

P

P

P

P

P

P

   
                                                                 … (2) 
 

2.1 Theory of Taguchi Method 
 

The method concept is based on that the 

manufacturing quality should be measure by the 

amount of deviation from the required values 

[6,7]. Taguchi technique is used a statistical 

measuring of performances call signal to noise 

ratio taken from control theory to analyzing the 

result [8]. In this way, the term ‘signal’ refers to 

the desirable values of mean for the outputs 

characteristics and the term ‘noise’ refers to the 

standard deviation. In this paper will be using L9.  

S/N=-10 log[1/n∑ (
�

��
)��	� ] i=1, 2, …..n        … (3) 

Where n are the measurements of input yi 

refers to the measurements value of output. The 

input parameter of nine simple are Design with 

using MINITAB16 program. 

 
3. Implementation the Work 
 

The equipment of the implementations which 

utilized in the work is dividing in two parts: 

 
3.1 Software Requirement 
 

The creation of CAD/CAM modeling has been 

implemented using designing programs package 

for the purpose of constructing and reconstructing 

the surface, transferring the CAD data, beside to 

generating the tool paths and post- processing that 

required to implement the machining process. 

These operations illustrated using MATLAB and 

UG-NX9 program. 

MATLAB software is allowing  matrix  

manipulation, implementation of algorithms and 

plot function. Curve have been modeled using 

Bezier depends on the algorithm includes the 

control point matrices. UG-NX is a program and 

advanced CAD/CAM developing, it is provides 

integrated design management of parametric 

model and machining as shown in Fig. 1. 

 
 Safaa K. Ghazi                            Al-Khwarizmi Engineering Journal, Vol. 15, No. 3, P.P. 84- 91 (2019)  

86 

 
(a)                                                                     (b)    
Fig. 1. Implementing the CAD model: (a) Bezier curves using MATLAB, (b) Achieving the model using UG-NX 

software. 

 
3.2 Hardware Requirements 
 

The Hardware equipment that used in this 

work consists of the computer and CNC turning 

machine. 

 
3.2.1 CNC Turning 
 

The turning process carried out in this work on 

CJK6132 Standard turning machine model 2000 

CE TUV has been utilized that illustrated in Fig. 

2. The machine specification is shown in Table 1. 

The machine is located at University of 

technology/ workshop and training center. 

 
Fig. 2. C-TEK turning (CNC machine). 

 
Table 1, 

Specifications of C-TEK CNC turning machine 

bed over Swing 320mm Φ  
peed(variable)s of Range r/min )2500~100( 

 travel xisa-X Max mm )160(  

 travel xisa-Z Max mm )500( 

rsetrave rapid X m/min )5( 

rsetrave rapid Z 10m/min 

unit input Min 0.001mm 

3.2.2 Cutting Tools  
 

Cemented carbides have high hardness over a 

high thermal conductivity, wide range of 

temperatures, high Young's modulus making them 

die materials and effective tool for a range of 

applications [9]. It is suitable for machining at 

higher speeds than those which can be used for 

tungsten carbide. Typical cutting speeds are: 30 to 

150 (m/min). Carbide cutting tool was used in this 

work as shown in Fig. 3. 

 
Fig. 3. Carbide Cutting tools. 

 
3.2.3 Tester of Surface Roughness  
 

Pocket Surf is instrument that utilized for 

measuring the parts surface roughness after the 

turning illustrated in Fig. 4. It’s a reliable surfaces 

roughness gauge and an economical priced 

device. The specification of the instrument is 

shown in Table 2.  

 
 Safaa K. Ghazi                            Al-Khwarizmi Engineering Journal, Vol. 15, No. 3, P.P. 84- 91 (2019)  

87 

 
Fig. 4. Tester of Pocket Surf. 

 
Table 2, 

Specifications of the surface roughness tester  

Measuring Ranges:  Ra (0.03) - (6.35) μm. 
Ry (0.2) - (25.3) μm. 
Rz (0.2) to (25.3) μm. 

Weight:  435 g. 

Totally Dimension 140 x 76 x 25 mm. 

Display Resolution 0.01 μm 
 

3.2.4 Material of the Workpiece 
 

7025 Aluminum alloy is selected to be 

machining with chemically compositions of the 

samples illustrated in Table 3. 

 
Table 3, 

The chemical compositions for Aluminum 7025. 

Si% Mn% Cu% Mg% Pb% Cr% Ni% 

0.16 0.216 2.14 1.55 0.07 0.090 0.012 

Zn% Ti% Ga% V% Fe% Other% AL% 

4.93 0.038 0.01 0.007 0.42 0.132 90.21 

 
This alloy have cut to nine parts. Each 

specimen has a dimension of (Diameter 30 and 

Height 120) mm as shown in Fig. 5. 

 
Fig. 5. Work piece dimension. 

 
3.3 Tool path Generation and Simulations 
 

The process that follows designing and 

representing the CAD models is tool paths 

generation utilizing UG-NX9 program. using 

different values of cutting condition (Speed, 

Depth of cut and feed) as shown in Table 4 and 

makes the simulations for the entire process 

beside to obtaining the G-code of the program that 

created in the paper using UG-NX9 package is 

shown in Fig. 6. 

 
Fig. 6. Generating the tool paths and simulation 

using UG-NX9. 

 
Table 4, 

Parameters level  

Cutting speed (rpm) 1600 1900 2200 

Depth of cut (mm) 0.25 0.50 0.75 

Feed rate(mm/min) 0.12 0.18 0.24 

 
The three machining variables that 

implemented on the experimental work for the (9) 

work pieces i.e. Speeds, Depths of cut and feeds 

clarified with Table 4. The resultant shape of the 

samples after implementing is illustrated in Fig. 7. 

 
Fig. 7.  Final sample shape of turning. 

 
Different conditions for each experiment 

producing the samples, depending on these 

conditions a various values of surface roughness 
have obtained. Fig. 8.  Clarify the measurement of 

surface roughness using the Pocket surf probe. 

120 mm 

D120 


 Safaa K. Ghazi                            Al-Khwarizmi Engineering Journal, Vol. 15, No. 3, P.P. 84- 91 (2019)  

88 

 
Fig. 8. Measuring the Surface roughness 

4. Results and Discussion 
 

This section demonstrates and discuses the 

results values of the surface roughness is depend 

on the three- level parameters depth of cut, speed 

of cutting and feed rate. Analyzing the output 

result carried out utilizing variance analysis 

method for finding the optimal machining factors 

with the aid of Minitab software. After 

implementation the experimental part on the 9 

parts with three parameters are shown in Table 5. 

 
Table 5, 

Reading of Surface Roughness and S/N Ratio 

 
4.1 Effect of Cutting Speeds, Depths of Cut 
and Feed Rates on Surface Roughness  

 
Fig. 9 to 11 clarifies the effects of depths of 

cut, cutting speeds, and feed rates on the resultant 

surface roughness. It is noting that increasing the 

cutting speed decreases the surface roughness; 

this mens that the high cutting speed improving 

the surface roughness. While the rise in the feed 

rates and depths of cut led to increase in surface 

roughness, the cutting speeds influence on the 

friction which is decreased with increasing the 

cutting speeds.  

  
Fig. 9. Cutting speed and feed rate Effect on surface 

roughness. 

No. Cutting Speed 

(rpm) 

Depth of cut 

(mm) 

Feed rate 

(mm/min) 

Ra1 Ra2 Average of Ra S/N Ratio 

1 1600 0.25 0.12 0.93 1.13 1.030 -3.424 

2 1600 0.50 0.18 1.30 1.21 1.255 -0.965 

3 1600 0.75 0.24 1.12 2.10 1.610 -4.521 

4 1900 0.25 0.18 0.91 0.87 0.890 1.707 

5 1900 0.50 0.24 1.36 0.99 1.175 1.462 

6 1900 0.75 0.12 0.89 0.95 0.920 2.908 

7 2200 0.25 0.24 0.87 0.69 0.780 3.285 

8 2200 0.50 0.12 0.66 0.74 0.700 6.131 

9 2200 0.75 0.18 1.11 0.96 1.035 4.506 


 Safaa K. Ghazi                            Al-Khwarizmi Engineering Journal, Vol. 15, No. 3, P.P. 84- 91 (2019)  

89 

 
Fig. 10. Cutting speed and depth of cut Effect on 

surface roughness. 

 
Fig. 11. Effect of depth of cut and feed rate on 

surface roughness. 

  
4.2 Variance Analysis (ANOVA)  
 

Analyzing the result of experiments have been 

implemented using variance analysis method 

(ANOVA) for finding the influence of turning 

variables on surface finish that depend on cutting 

variables Depths of cut, Speeds and feed rates. 

The results of the analysis of variance for surface 

finish are shown in Table 6. 

 
Table 6, 

Variance analysis of the proposed parameters. 
Source of 

variance 

Degree  Sum of 

squares  

F 

ratio 

P (%) 

Cutting 

Speed(rpm) 

2 0.3282 3.50 53.85 

Depth of 

cut(mm) 

2 0.1247 0.77 20.46 

Feed rate 

(mm/min) 

2 0.1407 0.90 23.09 

Error ,e 2 0.0158  2.75 

Total 8 0.6094  100 

 
The F ratio value of 3.5 for the cutting speed is 

greater than the other variables shown in Table 

(5). Consequently, the most effective variable is 

the cutting speed with (53.85%) which is about 

twice of the feed rate of (23.09%), while the depth 

of cut has a small effect with (20.46%). The 

contribution percent are given in Fig. 12, 

clarifying the most effective variables of the entire 

process among the conditions of machining which 

is cutting speed (rpm). 

 
Fig. 12. Influential effects based on percentage of 

distributions. 

 
4.3 Optimal Condition 
 

The main effect plot is utilized to find out the 

optimum condition of design to give the optimal 

surface roughness through select the best regions 

by use of Minitab software. Fig. 13 Shows the 

main effects plots of the surface finish. That plot 

shows the variations of response (3) variables 

individually, such, depths of cut, cutting speeds 

and feed rates separately. The result are showing 

the optimum condition for surface finish which is: 

cutting speed at level-3 (2200 rpm) depth of cut at 

level-1(0.٥٠ mm) and feed rate at level-1(0.12). 
 

 Safaa K. Ghazi                            Al-Khwarizmi Engineering Journal, Vol. 15, No. 3, P.P. 84- 91 (2019)  

90 

 
Fig. 13. Main Effect Plots for surface roughness.  

 
5. Conclusion 
 

From this work, the following conclusions 

were drawn: 

1. The experimental results show the main effects 
of process parameters on surface roughness for 

7024 AL-alloy. The surface roughness 

decreases with the increasing in cutting speed. 

Surface roughness reduces with decreasing 

feed. The surface roughness increases with 

increase in depth of cut.  

2. The optimal conditions for minimum surface 
roughness were: cutting speed at level-3(2200 

m/min), depth of cut at level-1(0.25 mm), and 

feed at level-3(0.12 mm/min). 

3. From analysis of variance the most effective 
variable is the cutting speed with (53.85%) 

which is almost greatest influential among the 

other parameters, and depth of cut is have a 

small effect with (20.46%).  

4. Analyzing the results by answering the 
following: How the experimenter has set up 

the process such that it is insensitive to the 

uncontrollable factors 

 
6. References 
 

[1] Byrne G, Dornfeld D, Denkena B, “Advancing 
cutting technology”. Ann. CIRP, 52(2): 483-

507, 2003.  

[2] M.M. Ratnam, "Factors Affecting Surface 
Roughness in Finish Turning" Reference 

Module in Materials Science and Materials 

Engineering journal, Vol.1, pp. 1–25, 2017. 

[3] H. H. Shahabi, M. M. Ratnam "Simulation and 
measurement of surface roughness via grey 

scale image of tool in finish turning", Precision 

Engineering jurnal Vol 43, pp.146-153, 2016.   

[4] Davim JP, “A note on the determination of 
optimal cutting conditions for surface finish 

obtained in turning using design of 

experiments” J. Mater. Process. Technol., 

116(2-3): 305-308, 2001. 

[5] R. B. Agarwal, "Computer Aided Design in 
Mechanical Engineering", Lecture Notes, 

chapter four, 2013. 

[6] Tzeng Yih- fong," Parameter design 
optimization of computerized numerical 

control turning tool steel for high dimensional 

precision and accuracy", Material and Design. 

27, p.p 665-675, 2006. 

[7] W. K. Hamdan, “Feasibility Development of 
Incremental Sheet Metal Forming Process 

Based on CNC Milling Machine”, Eng. & 

Tech. Journal, Vol. 27, Part (A), No. 15, 2009. 

[8] Maan A. Tawfiq, Shukry H. Aghdeab and 
Ahmed B. Abdulwahhab, “Studying The effect 

of Current on (MRR) and (EW) in Electrical 

Discharge Machining (EDM)”, Eng. & Tech. 

Journal, Vol. 31, Part (A), No. 17, 2013. 

[9] Jose M. Tarragóab, Selassie D. Joan Esteved 
and Luis Llanes “Influence of the 

microstructure on the thermal shock behavior 

of cemented carbides” Ceramics International 

journal, Vol 42, Issue 11, pp. 12701-12708, 

2013. 

 
 )2019( 84- 91، صفحة 3، العدد15دجلة الخوارزمي الهندسية المجلم                          صفاء كاظم غازي                                  

91 

 
  دراسة تأثير متغيرات التشغيل على الخشونة السطحية للسطوح الحرة باستخدام طريقة تاكوشي
  

    ***سلطان الرحمن شاكر عبد          **مصطفى محمد عبد الرزاق         *صفاء كاظم غازي

  ****فريال صباح محي
  العراق / الجامعة التكنولوجية/ االنتاج والمعادنقسم هندسة *،**،***،****

  yahoo.com1988safaa_kadhim@: البريد االلكتروني*
  mustafaalneame@yahoo.comالبريد االلكتروني: **

  
  الخالصة
   

م االنهاء السطحي لألجزاء المشغلة يعد من اهم الخواص لجودة المنتجات المصنعة واالكثر تطلبا للمستهلك. تم استخدام طريقة تاكوشي لتصميان 
لتي تم بواسطة عدد قطع كاربيدية وا ٧٠٢٤التجارب للحصول على افضل خشونة سطحية في عملية الخراطة باستخدام المكائن المبرمجة لسبيكة المنيوم نوع 

) ملم و معدل ٠٫٧٥ ،٠٫٥٠ ،٠٫٢٥دقيقة، عمق القطع ( ) دورة/٢٢٠٠ ،١٩٠٠ ،١٦٠٠استخدامها لهذا البحث. ثالثة متغيرات للتشغيل وهي: سرعة القطع (
اخذ معدل االنهاء السطحي ) ملم/دقيقة تم استخدامها للتجارب العملية. فيما تم تثبيت باقي المتغيرات التشغيلية االخرى. تم ٠٫٢٤، ٠٫١٨، ٠٫١٢التغذية (

بينما تزداد الخشونة بزيادة كل من عمق القطع ومعدل  ،كمؤشر لجودة السطح. اظهرت النتائج ان زيادة سرعة القطع تعمل على تقليل الخشونة السطحية
) بينما عمق القطع هو  االقل تأثير %٥٣٬٨٥التغذية. تم استخدام تقنية تحليل تباين العناصر(انوفا) وجد ان اكثر المتغيرات تأثيرا هو سرعة القطع بنسبة (

 مقبولية حيث اظهرت النتائج ،خشونة سطحية باالعتماد على طريقة تاكوشيمن خالل التجارب تم تحديد افضل ظروف لتحديد افضل  ،)%٢٠٬٠٩بنسبة (
  للعملية.  جيدة