AN EXPERIMENTAL STUDY ON ROUNDNESS ERROR IN WIRE EDM FOR FERRO MATERIALS

Transcription

1 AN EXPERIMENTAL STUDY ON ROUNDNESS ERROR IN WIRE EDM FOR FERRO MATERIALS S. Ajaya Kumar Asst. Prof. Department of Mechanical Engineering SVEC, Suryapet TS India ail.com DR.A.PRABHU KUMAR Professor Department of Mechanical Engineering, JNTUH, Hyderabad, TS, India DR.B.BALU NAIK Professor and Principal, JNTUH College of Engineering, Sultanpur, TS, India Abstract: Present industrial phenomenon for production needs mainly in the sector of dies and moulds alloy materials like SS316, EN24 and H13 leads its role for heavy loads. Most of the machining attributes are going with conventional and CNC machining a cost cutting as well as tool wear in machining tends to Wire EDM usage for strengthening alloy material machining. An advantageous factor of Wire EDM in accuracy give a scope of machining cavities, inserts, holes as well as radius. In all these machining cases one important factor is roundness of the object. Now a day s Wire EDM s has been upgraded with pulse deviation auto fixed and the number of cutting repeatability s increased depends on product accuracy. is an important factor in the assembly of inserts present experimental study focuses on the variation of roundness error by increasing number of cuts and by varying nozzle distance. Constant radius and hole accuracy giving good results multiple radius in one profile with insert based observed in the present study with constant thickness. Key words: Wire EDM, circularity error, ferro materials, nozzle distance. Introduction WEDM process with a thin wire as an electrode transforms electrical energy to thermal energy for cutting materials. With this process, alloy steel, conductive ceramics and aerospace materials can be machined irrespective to their hardness and toughness. Furthermore, WEDM is capable of producing a fine, precise, corrosion and wear resistant surface. WEDM is considered as a unique adoption of the conventional EDM process, which uses an electrode to initialize the sparking process. However, WEDM utilizes a continuously travelling wire electrode made of thin copper, brass or tungsten of diameter mm, which is capable of achieving very small corner radii. The wire is kept in tension using a mechanical tensioning device reducing the tendency of producing inaccurate parts. Problem statement Most of the researches focused on the power in put parameters and material removal rate which has been optimized by most of the manufacturers of Wire EDM machines, the output machining objectives study is very less. By considering this aspect nozzle distance variation effects on final accuracy of the product, dimensional accuracy errors also have to rectify with proper study. Optimization of dimensional Page No:1039

2 parameter like roundness which is much needed study in the area of insert failures which is used in dies and molds. Scope of work Accuracy depends on the wire travelling distance that is distance between the nozzles have to optimize effectively for better results, properties of different materials will give different results material consideration also one of the important aspect. The specialization of Wire EDM also sense at present for more dimensional accuracies number of material removal cuts well known as increasing number of finish passes to check the error variation. Researches needed how to minimize the error deviations by increasing number of cuts with cutting stabilization. Materials and methods Material considerations taken as Ferro alloys with and without corrosion with high strength, materials chosen are SS316, EN 24, and H13. The materials chosen for machining with thickness as 6mm and 10mm, nozzle distance taken as 9mm and 29mm where the standard minimum distance 9mm has been changed to 29 to check the radius accuracy error variation. Taguchi method of L12 orthogonal array taken for the experiments with 2 levels with 8 parameter variants, the levels are standard to nozzle distance and 3 cuts as parameters with 3 materials and two thicknesses. Above table shows the TAGUCHI experimental methods of orthogonal array with experimental study. Nozzle height Level 1- Level 2- from top surface 9mm 29mm Thickness variance- work 6mm, 10mm 6mm, 10mm piece Number of cuts 1 cut, 2&3 cuts 1 cut,2&3 cuts Above table shows the variant parameters for experiments Design procedure for experiment of various diameters and profiles has been observed to check the cutting variation in different profiles and thickness. AutoCAD 2017 used to prepare the drawing for Wire EDM process and the program has been generated with wire cam software. The experimental table given below shows the experimental layout of each drawing and profile. Thickness considered as A1, A2 cuts consider as C1, C2, C3 and levels as L1and L2 Expt No Levels (L) Thickness (A) 1 L1 A1 C1 2 L1 A1 C2 3 L1 A1 C3 No of cuts (C) Page No:1040

3 4 L1 A2 C1 5 L1 A2 C2 6 L1 A2 C3 7 L2 A1 C1 8 L2 A1 C2 9 L2 A1 C3 10 L2 A2 C1 11 L2 A2 C2 12 L2 A2 C3 Standard parameters considered for experiments of Wire Cut EDM Parameter Unit Name Tension N 6 Feed m/min 12 Flushing Kg/cm 2 4 pressure Current A 100 Figure shows the wire cut work piece set up and CMM machine Equipped with the VAST XXT scanning sensor, ZEISS DuraMax can be used to capture contours. Probe size- 1mm Scanning and single-point measuring CNC-guided stylus change 25 mm adapter plate for optimal reproducibility Axial stylus length: 30 to 150 mm Radial stylus length: 30 to 65 mm Error finding measuring from CMM, the deviation is measured as A standard CMM has three accurate, orthogonal axes and is equipped with a touch-trigger probe. The probe is brought into contact with the component being measured and its position is recorded. A number of points are taken around the component and these are then combined in Page No:1041

4 a computer to calculate the roundness of the component. Typically the number of data points is very small because of the time taken to collect them. As a result the accuracy of such measurements is compromised. Rotational Datum Method The most accurate method for determining roundness of a component is to measure the variation of radius from an accurate rotational datum using a scanning probe (one that remains in contact with the surface and collects a high-density of data points). A circle can then be fitted to this data and the roundness can then be calculated from knowledge of the component centre. There are many dedicated instruments made for the measurement of roundness. The advantages of these instruments are that they can measure roundness extremely accurately in a short measurement time. Figure shows the profile design of work piece for Wire cut EDM Results and discussions The following are the results obtained for the below drawing as observed with cutting related to circularity error s variation of EN24 φ 10mm s variation of EN24 φ 12mm s variation of EN24 φ 14mm male Page No:1042

5 s variation of EN24 profile-1 female s variation of EN24 profile-2 male H13 Material: s variation of H13 φ 10 mm s variation of H13 φ 12 mm s variation of H13 φ 14 mm Page No:1043

6 s variation of H13 profile s variation of H13 profile SS 316 Material: s variation of SS 316 φ 10 mm s variation of SS 316 φ 12 mm s variation of SS 316 φ 14 mm Page No:1044

7 s variation of SS 316Profile1 Expt no s variation of SS 316 Profile Graph shows Vs at 10mm Dia Graph shows Vs at 12mm Dia Page No:1045

8 Graph shows Vs at 14mm Dia Graph shows Vs at Profile 1 Graph shows Vs at Profile 2 Discussions: By observing the statistical data obtained after experiment it is clearly showing that the error in roundness depends on the cutting, as on consider number of cuts increasing the cutting, the material removal rate in the 3 rd cut becomes very low which is always given the low error deviation after machining. The standard of power parameters now embedded in machine controls in advanced Wire EDM operations roundness error decreased by increasing of number of cuts. Conclusion: Most of the experimental study on single radius consideration multiple radiuses in the profiles also have to observe. The experimental results clearly showing that the thickness of work piece decreases the error, nozzle distance also effecting cutting. Multiple radiuses profile also have to observe in further case to conclude the parameters optimization in a sophisticated manner. Maximum observed variation in error dimensionally 0.004, this also have to be checked with different profiles. Page No:1046

9 References 1. Amitesh Goswami, Jatinder Kumar (2014), Investigation of surface integrity, material removal rate and wire wear ratio for WEDM of Nimonic 80A alloy using GRA and Taguchi method, Engineering Science and Technology, an International Journal, ISSN: , Volume No: 17, Issue No: 2, PP: Amitesh Goswami, Jatinder Kumar (2017), Trim cut machining and surface integrity analysis of Nimonic 80A alloy using wire cut EDM, Engineering Science and Technology, an International Journal, ISSN: , Volume No: 20, Issue No: 2, PP: Anand Sharma, Mohinder Pal Garg, Kapil Kumar Goyal (2014), Prediction of optimal conditions for WEDM of Al 6063/ ZrSiO4 (p) MMC, Procedia Materials Science, ISSN: , Volume No: 16, Issue No: 2, PP: Anmol Bhatia, Sanjay Kumar, Praveen Kumar (2014), A Study to achieve minimum surface roughness in wire EDM, Procedia Materials Science, ISSN: , Volume No: 5, Issue No: 2, PP: Antar, M.T., S.L. Soo, D.K. Aspinwall, D. Jones (2011), Productivity and Work piece Surface Integrity When WEDM Aerospace Alloys Using Coated Wires, Proceedings Engineering, ISSN: , Volume No: 19, Issue No: 2, PP: 3-8 Page No:1047