International Journal of Innovative Research in Advanced Engineering (IJIRAE) ISSN: 2349-2163 Volume 1 Issue 8 (September 2014) _________________________________________________________________________________________________ © 2014, IJIRAE- All Rights Reserved
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    International Journal of Innovative Research in Advanced Engineering (IJIRAE) ISSN: 2349-2163   Volume 1 Issue 8 (September 2014 ) _________________________________________________________________________________________________ © 2014, IJIRAE- All Rights Reserved Page -112   OPTIMIZATION OF TiN COATED CARBIDE REAMING PROCESS ON SS 440C USING GREY RELATIONAL ANALYSIS  Abstract— Manufacturing techniques in engineering fields, especially in the aerospace applications and the defence  field are advancing day by day. While considering the manufacturing of any components of aerospace industry it is very important to increase the production quality associated with its manufacturing. The manufacturing of Electro  Hydraulic Servo Valve (EHSV) considered for this work is a two stage electrically operated hydraulic valve, in which  the output flow is proportional to the input current. Here investigated on both theoretical and practical aspects of using different processes involved in the production of EHSV. The material used for EHSV is SS 440 C. This investigation gave me a complete idea about the problems related to different machining processes associated with the  manufacturing of EHSV, especially the problems related to the wire electric discharge machining (WEDM). The  problems associated with WEDM including its high surface roughness value and high cylinricity for manufacturing  cylindrical bores can only be eliminated by replacing the existing WEDM process with suitable process which produce  components with better quality. For this purpose TiN coated carbide reamer is the best option to overcome the above  mentioned problems for the manufacturing of cylindrical bores. In this work the analysis of existing process,  optimization of proposed process, statistical and experimental comparison between the existing and proposed  processes including response comparison are included. This study investigates the effects of various parameters such  as speed, feed and allowance on the surface finish and cylindricity of the EHSV valve body. Grey Relational Analysis is used to optimize the proposed reaming process. Confirmation tests were performed to validate the results. Digital  surface profilometer images were taken in order to investigate the surface characteristics.    Keywords— ANOVA, Cylindrical bores, EHSV, Grey relational analysis, Mean MRPI plot, Taguchi’s design of experiments, TiN coated carbide reamer I.   I NTRODUCTION   The Electro Hydraulic Servo Valves (EHSV) is basically an electrically operated valve in which the output flow is  proportional to input current. The EHSV is a two-stage flow control valve, in which the output flow is proportional to the input current. Different varieties of EHSV are available according to the requirements. The main difference between different EHSV is in its flow rates. The EHSV works in conjunction with an Electro Hydraulic Servo Actuator which is essentially a double acting type actuator. The actuator moves the Fin Tip [5] (controlled elements) with reference to the given command and operates in a closed loop. The material used for manufacturing EHSV is SS 440 C. Figure 1. Cross section of EHSV Figure 1 shows the cross section of an EHSV. There are so many manufacturing techniques used in precision manufacturing of components. Wire EDM is most extensively use techniques in manufacturing components with intricate shapes and profile.    International Journal of Innovative Research in Advanced Engineering (IJIRAE) ISSN: 2349-2163   Volume 1 Issue 8 (September 2014 ) _________________________________________________________________________________________________ © 2014, IJIRAE- All Rights Reserved Page - 113   But this process is not suitable for manufacturing components with cylindrical bores and uniformly tapered bores, as they are time consuming and costly process. Application of advanced reamers like TiN coated carbide reamer can be used to overcome the problems related to manufacturing of cylindrical and tapered bore manufacturing of components in  precision manufacturing. Technological and economical comparison, surface integrity, corner error, crater, corrosion, etc. of WEDM process where studied with the help of literatures [1], [2], [3], [4], [6], [7], [8], [9], [10]. While considering the manufacturing of EHSV, the WEDM is applied for the manufacturing of cylindrical bores in the EHSV valve body. But it is a time consuming and costly process. Also WEDM has several disadvantages as seen from several journals. So advanced process such as special purpose reaming process can be used instead of WEDM process for cylindrical bore manufacturing. Reaming is common machining process for enlarging, smoothing and accurately sizing existing holes to tight tolerances [5]. International manual [14] for special purpose tools gives a complete idea about the type of tools that suitable for different work materials. In that manual the type of reamer suitable for machining SS 440C is found as TiN coated carbide reamer. It was found that the most influencing parameter for reaming process are speed, feed, depth of cut and allowance. In this work, depth of cut is not considered as the variable parameter; as it can only be varied according to the length of spool bore. Reaming was retained for finishing, as a process capable of yielding required results when performed on inexpensive machine tools such as drill press with simple fixtures. Reaming is suitable for batch production typically of job shops, facing the challenges of meeting specifications at competitive costs. Better surface finish and bore geometry can be obtained with the help of reaming process. Apparently minor influences led to enhanced process control and substantially better results at no extra cost. Results supported selection of production  parameters meeting specified quality and cost targets, as well as substantial improvements [11]. From [13] it was found that average surface roughness for reaming range between 0.8 µm and 3.2 µm, but high -accuracy reaming can produce average surface roughness as low as 0.4 µm. The quality of the reamed holes was evaluated in terms of geometrical characteristics (diameter, roundness, cylindricity and surface roughness). Roundness as well as cylindricity was verified to be smaller than the specified tolerance. Higher feed rate leads to lower and more repeatable roughness. MQL in reaming leads to high quality results in terms of hole dimensions and surface finish. [12] The feed and speed are important process parameters to control surface roughness, tool wear, material removal rate and hole diameter error. Thus it is essential to employ suitable combination of cutting speed and feed so as to reduce the variations that can affect the quality of the holes. II.   EXPERIMENTS   AND   METHODS The main objective of this project work is to find out how various reaming parameters such as speed, feed and allowance influence various output characteristics such as surface finish and cylindricity while considering the manufacturing of cylindrical bores in the EHSV valve body. Figure 2. EHSV valve body  The valve body is the main component of EHSV. Figure 2 shows the EHSV valve body. When consider the valve  body, the spool bore is the most important part of valve body. The spool bore is the only port where spool movement takes place. So while considering the valve body manufacturing, the manufacturing of spool bore was considered specifically and the manufacturing of other ports of valve body generally considered. Figure 3. Bores in EHSV valve body      International Journal of Innovative Research in Advanced Engineering (IJIRAE) ISSN: 2349-2163   Volume 1 Issue 8 (September 2014 ) _________________________________________________________________________________________________ © 2014, IJIRAE- All Rights Reserved Page - 114    A.    Existing Wire EDM Process Wire Electrical Discharge Machining (WEDM) is a widely accepted non-traditional material removal process used to manufacture components with intricate shapes and profile. It is a specialized thermal machining process capable of accurately machining parts with varying hardness or complex shapes that are very difficult to machine by the main stream machining process. The basic features of WEDM are shown in figure 4. The principle of the WEDM process is  based on the conventional EDM sparking phenomenon utilizing the widely accepted non – contact technique of material removal. However, WEDM utilizes a continuously travelling thin wire electrode made of copper, brass, or tungsten of diameter 0.03-0.30 mm, which is capable of achieving very small corner radii. The wire and there is no direct contact  between the work piece and the wire, eliminating the mechanical stresses during machining. In addition, WEDM process is able to machine exotic and high strength and temperature resistive (HSTR) materials and eliminate the geometrical changes occurring in the machining of heat-treated steels. Since the introduction of the process, WEDM has evolved from a simple means of making tools and dies to the best alternative of producing micro-scale parts with the highest degree of dimensional accuracy. WEDM has greatly altered the tooling and manufacturing industry, resulting in dramatic improvements in accuracy, quality, productivity and profit. Over the years, the WEDM process has remained as a competitive machining option fulfilling the demanding machining requirements imposed by the short product development cycles and the growing cost pressures. However, the risk of wire  breakage and bending has undermined the full potential of the process drastically reducing the efficiency and accuracy of the WEDM operation. A significant amount of research has explored the different methodologies of achieving the ultimate WEDM goals of optimizing the numerous process parameters analytically with the total elimination of the wire  breakages and improving the overall machining reliability which are explained in the literature survey. Figure 4. Basic features of WEDM  B.    Experimental details for proposed reaming process The experiment was conducted on vertical milling machine as shown in figure 5. The machine has speed settings up to 15,000 RPM, feed settings up to 30,000 mm/min. The experiments are conducted on stainless steel 440C. Figure 5. Experimental reaming setup Figure 6. TiN coated carbide reamer     International Journal of Innovative Research in Advanced Engineering (IJIRAE) ISSN: 2349-2163   Volume 1 Issue 8 (September 2014 ) _________________________________________________________________________________________________ © 2014, IJIRAE- All Rights Reserved Page - 115   The number of experiments and input levels are decided based on the design of experiments and the input  parameters and their levels are presented in table 1. The responses that needed to be taken into consideration are surface roughness and cylindricity which taken with Taylor Hobson Talysurf & Taylor Hobson Talyrond. In order to achieve the objectives, the experiments were designed based on Taguchi’s design of experiments. Table 1: Reaming Prameters Input Parameters Speed (RPM) Feed (mm/min) Allowance (mm) Level 1 600 80 0.2 Level 2 800 120 0.3 Level 3 1000 160 0.4  Design of Experiments Experimentation can be used for developing new product/processes as well as for improving the quality of existing  product/processes. DOE is a systematic approach to investigation of a system or process. A set of input variables (factors) of a process or system are tested according to the design. In any experimentation the investigator tries to find out the effect of input variables on the output/performance of the product/process. To test the effect of these factors on a response variable, a suitable experiment is designed such that the necessary data for testing the significance of the effects of the factors on the response variable are collected. Identification of the response variable is the first step to be followed for the designing of experiment. Identify the factor affecting response variables, fix the number of levels of each factor, form the skeleton of the experiment and define its components comprises the next step for designing an experiment. Overview of Taguchi Method Taguchi method involves reducing the variation in a process through robust design of experiments. We can produce high quality products with minimum cost to the manufacturer by using Taguchi method. Taguchi developed a method for designing experiments to investigate how different parameters affect the mean and variance of a process performance characteristic that defines how well the process is functioning. The experimental design proposed by Taguchi involves using orthogonal arrays to organize the parameters affecting the process and the levels at which they should be varies. L9 orthogonal array is selected with the help of MINITAB 16 software. Table 2: L9 Orthogonal Array Experiment P1 P2 P3 1 1 1 1 2 1 2 2 3 1 3 3 4 2 1 2 5 2 2 3 6 2 3 1 7 3 1 3 8 3 2 1 9 3 3 2 These data will help to determine the factor which affects the product quality with minimum number of experiments. Instead of having to test all possible combinations like the factorial design, the Taguchi method tests pairs of combinations. This allows for the collection of the necessary data to determine which factors most affect product quality with a minimum amount of experimentation, thus saving time and resources. The Taguchi method is best used when there are an intermediate number of variables (3 to 50), few interactions between variables, and when only a few


Jul 23, 2017
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