(Microsoft Word - \307\323\321\307\301 \332\341\355 \337\307\331\34329 - 37) Al-Khwarizmi Engineering Journal Al-Khwarizmi Engineering Journal, Vol. 15, No. 3, Sptember , (2019) P. P. 29- 37 Optimizing the Parameters of Hot-wire CNC Machine to Enhance the Cutting of Plastic Foam Israa Q. Mohammed* Ali H. Kadhum** *,**Department of Automated Manufacturing Engineering/ Al-Khwarizmi Engineering College/ University of Baghdad * Email: israaqm.90@gmail.com **Email: kadhumali59@yahoo.com (Received 23 October 2018; accepted 28 January 2019) https://doi.org/10.22153/kej.2019.01.006 Abstract Hot-wire cutting is one of the important, non-traditional thermomechanical way to cut polymer, usually expanded foam and extruded foam, in low volume manufacturing. The study and analysis of Hot-Wire cutting parameters play an important role to enhance the quality and accuracy of the process and products. The effects on the surface have been investigated by using experimental tests designed according to the Taguchi orthogonal array (OA). In this study, four parameters with five levels for each parameter have been used: [temperature of wire (A) (100, 120, 130, 150, 160) °C], [diameter of wire (B) (0.3,0.4,0.5,0.7,0.8) mm], [velocity of cutting (C) (200, 300،400,500,600) mm/min], [and density of foam (D) (0.01,0.027,0.029,0.032,0.037) g/cm3]. Statistical software (MINITAB17) used to find the optimum conditions, which they are in Material Removal: 100 ˚C, 0.5 mm, 300mm/min, 0.032 g/cm3. Keywords: Hot-wire cutting, polystyrene, foam cutting, taguchi, MINITAB1, material removal. 1. Introduction Today the products of plastic are an important and integral part of everything in our life. The process of manufacturing the plastic foam is the casting and extruding, so the perfect way to cut these types of foam is hotwire cutting. This cutting can be performed with a source of heat, which is wire that change the physical properties of material until it can be cut with low cutting force [1]. There are several mechanisms for the cutting of plastic foam; they can be divided into three-basic modes or the mixing among them: • Thermal cutting: In this mode, the plastic foam is vaporized or just melting in front of the wire cutter but without touching between them. See Figure 1.a. • Thermo-mechanical cutting: this mode is a mixing between the shearing force and the melting of material to perfume the cutting and the hot-tool in contact with the material. See Figure 1.b. Mechanical cutting: this mode depends on the shearing because it happens when the temperature of tool is below the melting point of the foam [2]. as shown in Figure 1.c Fig. 1. Cutting mechanism [2]. Simply the principle work is an electrical power pass through wire then the wire is heated to desired Israa Q. Mohammed Al-Khwarizmi Engineering Journal, Vol. 15, No. 3, P.P. 29- 37 (2019) 30 temperature degree according to the input voltage through electrical resistance. When the wire contact the surface of foam, it melts the area surrounding it, the heat of the wire vaporises the foam creating a smooth surface Figure 2. shows the wire is moving across the specimen of foam material. Fig. 2. The hot-wire foam cutter. The material to be cut is just soften under the point of melting because it is thermoplastic material, after that the cutting is done. The surface of the cut and kerf-width is affected by the changing of the velocity and the diameter of wire even if it was small [1]. Many researchers have studied the cutting process of polymers and the effective parameters on it. Harmanpreet & Manpreet Singh [3] studied the effect of parameters for the polymer cutting process on material removal rate and kerfwidth also the optimization of the machining process. Ranjeet et al [4] maked investigation in ablation process for the Expanded Polystyrene (EPS) rapid prototyping to predict and calculate the kerfwidth and surface roughness (Ra) with mathematical model. Kiril & Jesper [5] proposed a novel thermo- electro-mechanical model for hotwire cutting of EPS foam and predicts the stress, voltage and temperature of wire during cutting of EPS foam. In addition, find relation between kerfwidth and the cutting angle as measured from the horizontal direction. Namrata & Sathyan [6] investigated the factors responsible for the bowing phenomenon via a series of experiments involving variations in current and wire feed rate, build more precise prototypes, kerf width is also examined, Further more finding noval way to predict the influence of gases in bowing has been analyzed and quantified. Luka Ivanovskis [7] developed a 4-axis numerically controlled hot-wire foam cutter suitable for flying aircraft modelling purposes. Numerically controlled foam cutter had to be able to cut intricate shapes out of foam material such as extruded polystyrene by using 3D virtual model, also find novel mathematical model to predict the kerfwidth, and empirical relationship is established to predict the surface roughness (Ra) of the sliced surface by performing regression analysis. Ahn et al [8] studied the Influence of process parameters on the surface Jroughness in hotwire of variable lamination manufacturing (VLM-S) for EPS foam such as cutting angle and compositions of expandable polystyrene EPS, the apparatus is four- axis automatic cutter and the specimen is thin foam. While in my study, parameters differsand the device is 2D axis CNC. with any thickness of foam can be cut. P. Gallina et al [9] studied the hot wire with 2D robotic system to cut polystyrene plates with accurate force control which is delayed reference control (DRC) with time delay: ��(t- T) ,T the time delay calculated online, while my study is about 2D CNC machine and different parameters to reach optimum conditions of cutting without considering of time. The objective of this paper is to obtain the optimum cutting conditions for hotwire cutting process, and study the effects of these parameters on the process. 2. Material and Method 2.1 Foam Used in Hotwire Cutting Extruded Polystyrene (XPS) foam is used in this study with different densities. Foam is a combination of polymer solid phase and gas mixed together in high speed until it become as smooth as desired. The applications are virtually endless, ranging from items as small as a kitchen sponge to a soundproofing systems in cinemas [10]. 2.2 Implementation of Parts of the Machine The machine is very easily adjustable and therefore it is expected to provide a possibility for high accuracy, with specifications as shown in table 1. The two stepper motors as shown in figure 3 make together the movements of the two axes X and Y, which are vertically and horizontally standing. The motors velocity of hotwire CNC machine adjusted by the Universal G code sender software (which is platform of G-code with full featured used to interface between motors of CNC and the computer) as shown in figure4, through the ARDUINO-UNO shown in figure5 [11]. Israa Q. Mohammed Al-Khwarizmi Engineering Journal, Vol. 15, No. 3, P.P. 29- 37 (2019) 31 Table 1, specifications of CNC machine No. of CNC axes 2 a xis Motors Stepper 1.8° , 2A ,12 V Cutting bow Width 170 mm, height 350 mm Fig. 3. The two axis of CNC. The cutter consists of an elbow of aluminium insulated by small ceramic cylinders on both ends to avoid short circuit, and the wire of cut which is Nichrome (Nickel-Chromium alloy). Fig. 4. screenshot of the Gcode universal. Fig. 5. Arduino and CNC shield. 3. Hot-Wire Process Parameters 3.1 Temperature of Wire The five levels of temperature are (100,120,130,150,160) °C which can be adjusted by tunning the power supply. The infrared thermo camera FLIR T335 used to ensure the temperature of wire as shown in Figure 6. Fig. 6. Infrared thermos camera FLIR T335. 3.2 Cutting Velocity of the Process: The velocity levels are (200, 300, 400, 500, and 600) mm / min can be adjusted through the Universal G code sender software. 3.3 The Diameter of Wire The available diameters in the market are:(0.3,0.4,0.5,0.7,0.8) mm. 3.4 The Density of Foams The material of workpiece is XPS foam with different colours and densities (purple 0.037, yellow 0.032, blue0.029, pink 0.027 and white 0.01 g/cm3) as shown in figure 7 to recognize each one according to the density. Fig. 7. Foam colours. Israa Q. Mohammed Al-Khwarizmi Engineering Journal, Vol. 15, No. 3, P.P. 29- 37 (2019) 32 4. Optimizing Parameter with MINITAB17 and Taguchi Technique The MINITAB17 is statistical software using Taguchi method which is technique used to find the optimum values for the parameters and minimize the number of experiments that have to be done. Optimization of process parameters is done to make a great control to the process, It is effective way to improve quality of product at a relatively low cost. In this study Taguchi minimized the total experiments from 625 to 25 effective experiments in orthogonal array as shown in table 2. This orthogonal array has 25 rows and 4 columns, each columns represents specific process parameters while each row represents a trial condition [12,13]. Table 2, the orthogonal array of Taguchi Table 3, the orthogonal array of Taguchi uncoded NO. A (temp.) B (diameter) C (velocity) D (density) 1 100 0.3 200 0.01 2 100 0.4 300 0.027 3 100 0.5 400 0.029 4 100 0.7 500 0.032 5 100 0.8 600 0.037 6 120 0.3 300 0.029 7 120 0.4 400 0.032 8 120 0.5 500 0.037 9 120 0.7 600 0.01 10 120 0.8 200 0.027 11 130 0.3 400 0.037 12 130 0.4 500 0.01 13 130 0.5 600 0.027 14 130 0.7 200 0.029 15 130 0.8 300 0.032 16 150 0.3 500 0.027 17 150 0.4 600 0.029 18 150 0.5 200 0.032 19 150 0.7 300 0.037 20 150 0.8 400 0.01 21 160 0.3 600 0.032 22 160 0.4 200 0.037 23 160 0.5 300 0.01 24 160 0.7 400 0.027 25 160 0.8 500 0.029 The foam cutting process can be outlined as the following steps, which describe the whole process done by the machine and then the results can be processed with the MINITAB software. 1. Fix the hotwire cutting CNC on the table 2. Fix the foam with in the proper place by fixtures. 3. Turn on the power to the WIRE, wait until reach to the required temperature of wire, that can be ensured by the infrared camera 4. Turn on the dc power supply of the shield, then give the order (Gcode of the required shape) to the motors to move, to cut by the arduino program (universal Gcode sender), with the velocity that given. No. A code B code C code D code 1 1 1 1 1 2 1 2 2 2 3 1 3 3 3 4 1 4 4 4 5 1 5 5 5 6 2 1 2 3 7 2 2 3 4 8 2 3 4 5 9 2 4 5 1 10 2 5 1 2 11 3 1 3 5 12 3 2 4 1 13 3 3 5 2 14 3 4 1 3 15 3 5 2 4 16 4 1 4 2 17 4 2 5 3 18 4 3 1 4 19 4 4 2 5 20 4 5 3 1 21 5 1 5 4 22 5 2 1 5 23 5 3 2 1 24 5 4 3 2 25 5 5 4 3 Israa Q. Mohammed Al-Khwarizmi Engineering Journal, Vol. 15, No. 3, P.P. 29- 37 (2019) 33 5. Wait until finishing the cut 6. Take the part to make measurements. 7. Find the material removal MR of the cutting pieces by comparing between the weight before and after the cutting process by using delicate balance. 8. Repeat all steps with changing the parameters according to the Tagauchi array of 25 experiments. 9. Enter the factors (inputs) and results(outputs) in the MINITAB program to find optimization. 5. Results and Discussion The results have been analysed by using (MINIITAB17) in the following steps: 5.1 Signal to Noise Ratio (S/N) The (S/N) ratio is defined as standard approach where the result used for the average of the result is run with the main parameter. The optimum with S/N ratio is studying, the main effect of the parameters and giving the optimum result which effect on the process. In the hotwire cutting process, the S/N ratio is used to measure the sensitivity of the quality surface characteristic with the parameters [14]. There are three categories of the quality characteristics: smaller is better, normal is better and larger is better, the aim of any experiment is always to determine the highest possible (S/N) for the result. In this study selecting the smaller is better which means the maximum response of the material removal with the smallest lost of material [15]. The mean squared deviation (MSD), (S/N) ratio and prediction are determined by the equations (smaller is better) below: MSD=( � � � (y � ��� … (1) (S/N)ratio=- 10 log10 ( � � � (y � ��� ) … (2) Where: n: is the number of the trial i: is trial number The analysis of material removal is explained with the parameters by using (S/N) ratio, describes the quality of the surface in the hotwire cutting process. The results have been analysed by using S/N ratio to obtain the optimal level for each process parameter that has larger effect of the surface quality. The main effect of each parameter with four level on the S/N ratio and mean for material removal are calculated in the tables (3&4), the plot of the S/N ratio and mean is shown in the figure (8&9). Note: there are 4 experiments failed through cutting, so they neglected in all calculations. Table 4, The main effect of the S/N ratio for MR s/n ratio for response level A B C D level 1 59.21 48.98 46.19 44.26 1 2 41.81 45.20 46.35 44.26 2 3 43.37 51.21 45.38 38.99 3 4 45.29 37.76 44.05 45.25 4 5 45.99 45.84 45.63 39.96 5 Delta 17.39 13.46 2.30 17.17 Delta Rank 1 3 4 2 Rank S/N ratio optimization Table 5, The main effect of the mean for MR Means for response level A B C D 1 0.001700 0.005620 0.007940 0.002860 2 0.008225 0.006120 0.007020 0.007160 3 0.008020 0.003767 0.007750 0.011575 4 0.007120 0.013275 0.007133 0.005975 5 0.007800 0.006975 0.005950 0.010233 Delta 0.006525 0.009508 0.001990 0.008715 Rank 3 1 4 2 Mean optimization From the tables (3 and 4), the effect of each factor (Rank) can be seen which mean the effect degree of each factor on the MR. In addition, the optimal level of the parameters with MR is calculated according to the larger value of the mean and S/N ratio, so in this case the rank of optimal parameters which effected on the MR is: wire temperature (A), followed by density (D), then the wire diameter(B) and velocity of cut (C) , and It noticed that the optimal condition is : A1 , B3 , C2 , D4 for s/n ratio, and A2, B4 , C1 , D3 for means . Figures ( 8&9) show the plots of SN ratio and Mean of the MR for the material. Israa Q. Mohammed Al-Khwarizmi Engineering Journal, Vol. 15, No. 3, P.P. 29- 37 (2019) 34 Fig. 8. Main effects plot S/N ratio plot for MR. Fig. 9. Main effects plot of means for MR. For this situation, we need to make a prediction. This can be used to predict the optimum level of S/N ratio and mean, then choosing the optimum level which depends on the large value of the S/N ratio [ 16] as shown in table 8. Table 6, The prediction of the mean and S/N ratio of MR S/N ratio mean A B C D A B C D 1 3 2 4 2 4 1 3 S/N Ratio Mean S/N ratio mean 63.3489 -0.00066 38.4977 0.01147 From the table 5 the optimum predict value for S/N ratio is 63.3489 which is the larger, that mean in the conditions of: A1(100 C), B3(0.5mm), C2(300mm/min), D4(0.032 gm/cm3) the material removal is in the smallest removed amount which is the optimum result. 5.2 Analysis of the Variance (ANOVA) The optimum of the work accomplished by determine the percentage of each parameter on the results of the experiments. The ANOVA is a statistical treatment analysis which is used for this purpose for the MR [16]. In this part, ANOVA is used to determine the influence of the parameters on the material removal as shown in the table 6. Israa Q. Mohammed Al-Khwarizmi Engineering Journal, Vol. 15, No. 3, P.P. 29- 37 (2019) 35 Table 7, ANOVA for MR Source Df Adj SS F-Value P-Value Contributed (%) Temp. A 4 0.000033 0.65 0.655 3.4 Diameter B 4 0.000160 8.58 0.030 46.8 Velocity C 4 0.000039 1.04 0.484 5.5 Density D 4 0.000136 7.04 0.043 38.6 Error 4 0.000038 5.5 Total 20 0.000406 100 From table 6, it is noticed that the significant effect of the parameter is the diameter (B 46.8%) then the density (D 38.6%) followed by the velocity (C 5.5%), and temperature (A 3.4%) as shown in figure 10. Fig. 10. The contributed percentage of the factor for MR. 5.3 Regression equations for MR Regression is a statistical measure used to find and calculate the mathematical relationship between the independent variables and the dependant variables or in other word the input and output parameters which is linear [17]. The general form of multiple regression is: = � + ���� + � � + ���� + ⋯ + �� �� … (3) t = 1,2,3, ……n While: y: the output or the predicted variable x: the input or the variable which is needed to find y value a: constant b: slope By using MINITAB software, the regression equation for estimating the MR used to find the comparison between the experimentally and numerically results of them, that has been obtained as the following: Y= - 0.00551+0.01008B + 0.2759 D ... (4) Where: B: the wire diameter D: the density of foam Y: Material Removal 6. Conclusions From analysing the results of experiments, which they are physical and mechanical tests by using Minitab17 we obtained some conclusions and summarized as: 1. The Signal to Noise Ratio (S/N) for hotwire cutting process, found that: The optimum condition for MR are: the temperature is 100˚C, diameter of wire is 0.5 mm, velocity of cut is 300mm/min and density of foam is 0.032 gm/cm3. 2. This research agreed with the previous researches, that the Diameter of wire B has larger percent of effect on the MR (46.8%), (because increasing the diameter cause to increase the MR), followed by the density of foam D (38.6%),(because of increasing the shear force), then the velocity of cutting C (5.8%), and temperature of wire A (3.4%) , because the melting of materials. Fig. 10 show the plot of the material that, increasing the diameter cause to increase MR. 7. Aknowledgment Thanks a lot to God who helped me and gave me the strength to complete this research. I would like to offer my thanks and appreciation to my supervisors al-Khwarizmi College of Engineering for continual inspiration and gave me all support during the research period. Thanks to my family that I always find beside me to give full support in my life. Special thanks are due to my husband who was the source of my power in the Moments of weakness. Finally, I would like to express my thanks to my friends and everyone who gave me any type of assistance throughout the course of research A B C D Error Category Error 5.5% D 38.6% C 5.8% B 46.8% A 3.4% Pie Chart of MR Israa Q. Mohammed Al-Khwarizmi Engineering Journal, Vol. 15, No. 3, P.P. 29- 37 (2019) 36 List of Abbreviations ANOVA Analysis of Variance CNC Computer Numerical Control EPS Expanded Polystyrene MR Material Removal OA Orthogonal Array Ra Surface roughness SMPS Switched-Mode Power Supply S/N Signal to Noise Ratio XPS Extruded Polystyrene 8. References [1] Aitchison, D., Brooks, H., Bain., J., Pons, D. “An Investigation into the Prediction of optimal Machining Conditions for Polystyrene Foam Cut with a Taut Hot-Wire”. The Annals of “Dunarea de Jos” University of Galati, Fascicle V, Technologies in Machine Building, ISSN 1221- 4566, 2009 [2] H. Brooks, “Plastic Foam Cutting Mechanics for Rapid Prototyping and Manufacturing Purposes” (Ph.DThesis), Mechanical Engineeringat the University of Canterbury , Christ church , New Zealand , 2009 [3] Harmanpreet & Manpreet Singh, “Influence on Kerf Width in Machining Polystyrene by Heating Element Profile Maker using Nichrome Wire”, International Journal of Engineering and Technical Research V4 (04), April 2015 [4] Ranjeet K. B., Sajan K., Pushkar K. &K. P. Karunakaran , “ Investigation of ablation studies of EPS pattern produced by rapid prototyping” ,Virtual and Physical Prototyping, Volume 13, Issue 4, 2018. [5] Kiril P.Petkov, Jesper H.Hattel” A thermo- electro-mechanical simulation model for hot wire cutting of EPS foam” International Journal of Machine Tools and Manufacture Volume 107, Pages 50-59,2016. [6] Namrata Karmakar , Sathyan Subbiah , “Investigating Bowing of Hot Wire during cutting of EPS” Procedia Manufacturing Volume 26, Pages 671-680, 2018 [7] Luka Ivanovskis, “Four Axis Hot-Wire Foam Cutter Controlled by Mindstorms EV3 “, Saimaa University of Applied Sciences, Faculty of Technology, Lappeenranta Degree Programme in Mechanical Engineering and Production Technology, Thesis 2017 [8] Dong-Gyu Ahn, Sang-Ho Lee, Dong- Yol Yang ,“Influence of process parameters on the surface roughness in hotwire cutting of EPS foam sheet for VLM-S rapid prototyping process”, Journal of Materials Science 40(21):5699-5702, 2005 [9] P. Gallina, R. Mosca, P. Pascutto, “Optimized Hotwire Cutting Robotic System for Expandable Polystyrene Foam”, AMST’05 Advanced Manufacturing Systems and Technology. CISM International Centre for Mechanical Sciences, vol 486. Springer, Vienna, 2005 [10] Katrine Sivertsen, polymer foams,3.063 Polymer Physics, Spring2007 [11] https://libraries.io/github/winder/Universal- G-Code-Sender [12] R. K. Roy,” Aprimer on the Taguchi method”,1ST Edition (New york: Van Nostrand Reinhold ,1990) [13] BalaRaju.J, Anup Kumar.J, Dayal Saran.P, Dr.C.S.Krishna Prasad Rao"Application of Taguchi Technique for Identifying Optimum Surface Roughness in CNC end Milling Process", International Journal of Engineering Trends and Technology (IJETT), V21(2),103- 110 March 2015. [14] M.Vishnu Vardhan, G. Sankaraiah, M. Yohan , H. Jeevan Rao , ”Optimization of Parameters in CNC milling of P20 steel using Response Surface methodology and Taguchi Method” ,Science Direct ,Volume 4, Issue 8, , Pages 9163-9169 ,2017. [15] Shouvik Ghosh, Prasanta Sahoo, and Goutam Sutradhar, “Tribological Performance Optimization of Al-7.5% SiCp Composites Using the Taguchi Method and Grey Relational Analysis”, Journal of Composites, Volume, Article ID 274527, 2013 [16] Hanan H. Murad, “Parametric Investigation of the Magnetic Abrasive Finishing Method” (MS.c Thesis), Al-Khwarizmi College of Engineering of University of Baghdad, 2017 [17] Marwa K. Qate’a, Ali H. kadhum , Faiz F. Mustafa, “The Influence of the Magnetic Abrasive Finishing System for Cylindrical Surfaces on the Surface Roughness and MRR “ , Al-Khwarizmi Engineering Journal ,Vol 11 No 3 , 2015 )2019( 29- 37، صفحة 3، العدد15دجلة الخوارزمي الهندسية المجلم اسراء قاسم محمد 37 إيجاد المثالية لمتغيرات عملية القطع بالسلك الحراري لتحسين خواص فوم البولسترين **علي حسين كاظم *اسراء قاسم محمد كلية الهندسة الخوارزمي / جامعة بغداد /قسم هندسة التصنيع المؤتمت **،* kadhumali59@yahoo.com :البريد االلكتروني* israaqm.90@gmail.com :البريد االلكتروني ** الخالصة الحرارية لقطع البوليمر عادة اما الفوم التمددي او الفوم االنبثاقي في اإلنتاج ذو ق غير التقليدية الميكانيكية ائالقطع بالسلك الكهربائي هو احدى الطر للمنتوجات. التأثيرات على السطح تم ودقتها م في تحسين جودة العمليةالدور المه ؤديالحجم القليل. الدراسة والتحليل لعوامل القطع بالسلك الحراري ت مستويات لكل متغير (حرارة ةطبقا الى مصفوفة تا كوشي. في هذه الدراسة تم استخدام أربعة متغيرات مع خمس ايجادها باستخدام تصميم التجارب العملية ) ٦٠٠ ٥٠٠ ٤٠٠ ٣٠٠ ٢٠٠ mm/min) و(سرعه القطعmm 0.3,0.4,0.5,0.7,0.8و(قطرالسلك )١٠٠،١٢٠،١٣٠،١٥٠،١٦٠ C° السلك على وفق لظروف القطع وكانت نتيجتها ةاليجاد المثالي 17MINITAB وتم استخدام برنامج )3g/cm0.01,0.027,0.029,0.032,0.037 ةو(كثاف :النحو االتي 3g/cm 0.032mm/min, 300 mm, 0.5C, ˚100 : MR .وكذلك نسبه تأثير كل عامل على العملية تم ايجادها