Analysis and Study the Effects of various Control Factors of CNC-Wire Cut EDM for EN-5 Steel

Analysis and Study the Effects of various Control Factors of CNC-Wire Cut EDM for EN-5 Steel

Analysis and Study the Effects of various Control Factors of CNC-Wire Cut EDM for EN-5 Steel

Er. Ravinder Chaudhary1 , Er. Deepak2, Er. Neeraj Sharma3

1 Assistant Professor in Mechanical at SKIET, Kurukshetra.

2Assistant Professor in Mechanical at GIMT Kanipla.

3Assistant Professor in Mechanical at RPIIT, Karnal.

Abstract: Wire electrical discharge machining (WEDM) is a non traditional machining process which is widely used in machining of conductive materials. The applications of WEDM are in automobiles, aero-space, medical instruments, tool and die industries. in the present study analysis of effect of various control factors like Ton,Toff,Sv,Ip,Wf,Wt on material removal rate, and surface roughness of EN5 steel is studied by using wire cut EDM and one factor time approach.EN5 is a medium strength steel and it have wide applications in making die, shaft pistons etc. the other big advantage of this study is to select the range of significant control factors for final experimentation.

Keywords: Wire Electric discharge machining (WEDM) , OFAT (one factor time approach),EN5 steel, Control Factors (like Pulse On-Time, pulse off time, Peak Current, servo voltage, wire feed and wire tension), Metal Removal Rate (MRR) and Surface Roughness (SR)

1. INTRODUCTION

   Wire Electrical Discharge Machining (Wire-EDM) is an electro thermal production process in which a thin single strand metal wire in conjunction with de-ionized water (used to conduct electricity) allows the wire to cut through metal by the use of heat from electrical sparks. Due to the inherent properties of the process, wire EDM can easily machine complex parts and precision components out of hard conductive materials. Electrical discharge machining is frequently used to make dies and molds conductive.the working principle of wedm is as shown in figure below. Brass wire with

   0.25 mm diameter and SAE 4140 steel with 10 mm thickness were used as tool and work-piece materials in the experiments, respectively. It is found experimentally that the increasing pulse duration, open circuit voltage and wire speed, increase the surface roughness whereas the increasing dielectric fluid pressure decreases the surface roughness.

   Fig 1.1:Mechanisom Of Material Removal In Wedm

   The variation of work-piece surface roughness with machining parameters is modelled by using a power function. The level of importance of the machining parameters on the work-piece surface roughness is determined by using analysis of variance (ANOVA).Yan and huang et al improved the machining accuracy by a closed-loop wire tension control system for a wire-EDM. PI controller and one-step-ahead adaptive controller are employed to investigate the dynamic performance of the closed-loop wire tension control system. In order to reduce the vibration of wire- tension during wire feeding, dynamic absorbers are added to the idle rollers of wire transportation mechanism. Experimental results indicate that the geometrical contour error of corner cutting is reduced with approximately 50% and the vertical straightness of a work-piece can be improved significantly. scott f. Miller et al Studied the WEDM of cross-section with minimum thickness and compliant mechanisms. Effects of EDM process parameters, particularly the spark cycle time and spark on-time on thin cross-section cutting of NdFeB magnetic material, carbon bipolar plate, and titanium are investigated. An envelope of feasible wire EDM process parameters is generated for the commercially pure titanium. The application of such envelope to select suitable EDM process parameters for micro feature generation is demonstrated. Scanning electron microscopy (SEM) analysis of EDM surface, subsurface, and debris are presented.Huang and Chang et al displayed the surface alloying behaviour of tempered martensitic stainless steel

   multi-cut with WEDM. Before machined with

   WEDM, the steel specimens were quenched at

   1050nC and then tempered at 200nC, 400nC, and 600nC, respectively. The microstructure and surface morphology of the multi-cut surfaces were examined with scanning and transmission electron microscopes integrated with an energy-dispersive

   X-ray spectrometer for chemical composition

   analysis. N.M. Abbas and bahari et al. studied that EDM process is based on thermoelectric energy between the work piece and an electrode. A pulse discharge occurs in a small gap between the work piece and the electrode and removes the unwanted material from the parent metal through melting and vaporizing. The electrode and the work piece must have electrical conductivity in order to generate the spark. mohammadi and karimi et at. The setting of

   Fig 1.2: pictorial view of wedm machine

   machining parameters relies strongly on the experience of operators and machining parameter tables provided by machine tool builders. It is difficult to utilize the optimal functions of a machine owing to there being too many adjustable machining parameters.H.Singh and Rohit Garg et

   Fig.1.3 shows the arrangement during pilot experimentation.

   of work piece

   al. found that the material removal rate (MRR)

   directly increases with increase in pulse on time and peak current while decreases with increase in

   pulse off time and servo voltage. They used

   ELECTRONICA SPRINTCUT WEDM as a

   machine tool and hot die steel (H-11) as work- piece. Jangra kamal et al presented the optimization of performance characteristics in WEDM using Taguchi Grey relational analysis. Process parameters were investigated using mixed L orthogonal array.GRA was applied to determine optimal L18 process parameters for optimization of

   Fig 1.3: pilot experimentation

   For WEDM, cutting rate is a desired characteristic and it should be as high as possible to give

   multiple performance characteristics

   which were

   minimum machine cycle time leading to increased

   investigated during rough cutting operation in D-3 tool steel. U.Natarajan and yang et al. focuses RSM for the multiple response optimization in micro- endmilling operation to achieve maximum metal removal rate (MRR) and minimum surface

   productivity. In the present study cutting rate and

   surface roughness is mainly measures for a evaluation of job.the cutting which is directly displayed on the screen of the machine and is given units is in mm/min (Figure 1.4). And surface

   roughness. Aluminium block of 60×40×16 mm is

   roughness is measured with the

   help of surface

   used as the workpiece material and carbide endmill

   roughness testor. The figure shown below is the

   cutter of diameter 1 mm as the

   cutting tool.

   arrangement of cutting rate on wire cut electric

   1. harma and R. Sharma et al. optimized the discharge machining process

      process parameters for the cutting speed and

      Display for Cutting Rate

      dimensional deviation for high strength low alloy steel (HSLA) on WEDM. Response surface methodology was used for the modelling and multi- response optimization.

      EXPERIMENTAL DETAIL: WEDM machine (S-

      35, Sparkonix) was used as the experimental

      machine in this study. A Brass Wire with a diameter of 0.025 mm was used as an electrode to erode a work piece of EN-5 (flat plate). The gap between work piece and electrode was flooded with a moving dielectric fluid.

      Figure 1.4: Set Up for Cutting Rate and Measurement

      The purpose of the pilot experiments is to study the various changes of the WEDM cotrol factors on performance measures such as Cutting Rate and Surface Roughness.

      The pilot experiments were performed on ELECTRONICA make SPRINTCUT 734 WEDM

      machine. Various input control factors varied during the experimentation are pulse on time, pulse off time, spark gap voltage, peak current, wire tension, wire feed. Apart from the parameters mentioned above following parameters were kept constant at a fixed value during the experimentation.

      Work piece : EN5 Steel

      Electrode(tool) : 0.25mmØ

      Work piece height : 9mm

      Cutting length : 70 mm Dielectric Conductivity : 20mho Dielectric temperature : 20-240C

2. EXPERIMENTAL SET UP

   The purpose of this study is analysing the effect of WEDM process parameters on response variable such as Cutting Rate and Surface Roughness. Also, it is intended to ascertain the ranges of different parameters required for the experimental design methodology used in this work.

   Observations are made by using one factor at a time approach i.e fixing some parameters and vary individual parameters one by one with the response variable (cutting rate and surface roughness)

   Effect of various control factors are analysed by performing various experiments with variation of input parameters.

   First observation is made to check the Effect of Pulse on Time on Response Variable as:

3. RESULT AND DISCUSSION

   In the first set of experiment :- The pulse on time (Ton) is varied from 105 machine units to 125 machine units. The values of the other control factors are given as Toff = 31 unit; IP= 115 A SV

   Pulse on Time (µs)	Cutting Rate (mm/min)	Surface Roughness (µ m)
   105	1.09	1.25
   110	1.88	1.56
   116	2.91	1.99

   =50V WT = 8 machine units; WF = 8 m/min; and SF = 2100 unit. The experimentally observed values of the response variables for different values of pulse on time are given in Table 1.1 The scatter plots of pulse on time versus response variables are shown in Figure 1.5.

   120	2.9	2.39
   125	4.4	2.40

   Table 1.1 Experimental value of Ton vs CR and

   S

   PULSE ON TIME vs CR & SR

   5

   4.5

   4

   3.5

   3

   R

   &2.5 CUTTING RATE (mm/min)

   C

   R 2

   SURFACE ROUGHNESS

   1.5 (µm)

   1

   0.5

   0

   100 105 110 115 120 125 130

   PULSEON TIME

   Figure 1.5: Effect of Pulse on Time on Cutting Rate and Surface Roughness.

   The cutting rate and surface roughness increases with the increase in the pulse on time. This is due to the fact that with the increase in pulse on time the discharge energy increases, due to which CS and SR increases also with the increase of Ton machining time increase. These findings are in agreement with some of researchers [Tarng, Y. S., Ma, S. C., Chung, L. K. (1995)].

   In the second set of experiments: the pulse off time (Toff) is varied from 20 machine units to 60 machine units. The values of the other control factors are given as Ton = 116 unit; IP= 115 A SV

   =50V WT = 8 machine units; WF = 8 m/min; and SF = 2100 unit. The experimentally observed values of the response variables for different values of pulse off time are given in Table 1.2 The scatter plots of pulse off time versus response variables are shown in Figure 1.6.

   Pulse off Time (µs)	Cutting Rate (mm/min)	Surface Roughness (µm)
   20	2.99	2.62
   25	2.97	2.42
   31	2.85	2.25
   50	1.65	2.32
   60	0.95	2.29

   Table 1.2:Effect of Pulse OFF Time on CR & SR

   PEAKCURRENTvsCR&SR

   4

   3.5

   3

   S R2.5

   & 2 CUTTINGRATE

   C (mm/min)

   R1.5

   1 SURFACEROUGHNESS

   0.5 (µm)

   0

   0 50 100 150 200

   PEAK CURRENT

   C R and SR

   4

   3

   2

   1

   0

   0 20 40 60 80

   Toff

   Figure 1.6: Effect of Pulse off Time on Cutting Rate and Surface Roughness.

   With the increase in pulse off time, the cutting rate and surface roughness decreases. Due to decrease in spark energy. These findings are in agreement with some of researchers [Gwo-LianqChern and Ying-JengEngin in 2007].

   .In the third set of experiments: Effect of peak Current on Response Variable is calculated by considering following values:

   The Peak Current is varied from 50 units to 180 units. The values of the other control factors are given as Ton=116 unit; Toff=31 unit, SV =50 V, WF=8 m/min, WT=8 machine unit and SF=2100 unit. The experimentally observed values of the response variables for different values of peak current are given in Table 1.3 The scatter plots of Peak Current versus response variables are shown in Figure 1.7

   Peak Current	Cutting Rate (mm/min)	Surface Roughness (µm)
   50	1.76	1.86
   90	2.58	2.19
   110	3.07	2.39
   150	3.41	2.62
   180	3.45	2.78

   Table 1.4: Effect of Peak Current on CR & SR

   Figure 1.7: Effect of Peak current on Cutting Rate and Surface Roughness.

   It has been observed that as the Peak current increases the value of cutting rate and surface roughness. This is in line with one of the researcher [Gwo-LianqChern and Ying-JengEngin IN 2007]. in the fourth set of experiments : In the fourth set of experiments, the servo voltage is varied from 20 units to 80 units. The values of the other control factors are given as Ton = 116 unit; Toff = 31 A Ip

   = 115 A ;Wt = 8 machine unit ,Wf = 8 machine unit, SF = 2100 unit. The experimentally observed values of the response variables for different values of Servo voltage are given in Table 1.4 The scatter plots of pulse on time versus response variables are shown in Figure 1.8.

   Servo voltage (SV)	Cutting Rate (mm/min)	Surface Roughness (µ m)
   20	3.36	3.50
   40	3.13	2.82
   50	3.16	2.30
   60	2.69	2.29
   80	1.86	2.32

   SERVOVOLTAGEvs CR&SR

   4

   3.5

   3

   S2.5 R

   & 2

   C CUTTING RATE (mm/min)

   R1.5

   SURFACEROUGHNESS (µm)

   1

   0.5

   0

   0 20 40 60 80 100

   SERVOVOLTAGE

   Table 1.5: Effect of Serco voltage on CR & SR

   Figure 1.8: Effect of servo voltage on Cutting Rate and Surface Roughness.

   It is observed that as the value of servo voltage increases, the value of cutting rate and increases and surface roughness decreases.[Tarang et al (1994)].

   In fifth set of experiments: the wire feed is varied from 6 units to 15 units. The values of the other control factors are given as Ton = 116 unit; Toff = 31,Ip= 115 A: SV =50V; WF= 8 machine unit and SF = 2100 unit. The experimentally observed values of the response variables for different values of Wire Feed are given in Table 1.6 The scatter plots of pulse on time versus response variables are shown in Figure 1.9

   Wire Feed	Cutting Rate (mm/min)	Surface Roughness (µm)
   6	2.68	2.39
   8	2.68	2.39
   10	2.68	2.39
   12	2.68	2.39
   15	2.68	2.39

   WFvsCR&SR

   2.7

   2.65

   2.6

   S R2.55

   &

   C CUTTINGRATE(mm/min)

   R 2.5

   2.45 SURFACEROUGHNESS (µm)

   2.4

   2.35

   0 5 10 15 20

   WIREFEED

   Table 1.6 : Effect of wire feed on CR & SR

   Figure 1.9: Effect of Wire Feed on Cutting Rate and Surface Roughness.

   The cutting rate and surface roughness remains practically constant with the increase in wire feed, while the surface roughness decreases with increase in wire feed.These finding are in line with a researcher [Hascalyk, A. and Caydas and U. (2004)]

   In the sixth set of experiments

   the wire tension is varied from 6 units to 15 units. The values of the other control factors are given as Ton = 116 unit; Tofff = 31 ,Ip= 115 A: Sv =50V; Wf= 8 machine unit and Sf = 2100 unit. The experimentally observed values of the response variables for different values of Wire Tension are

   given in Table 1.7 The scatter plots of Wire Tension versus response variables are shown in Figure 1.11.

   Wire Feed	Cutting Rate (mm/min)	Surface Roughness (µ m)
   6	2.68	2.39
   8	2.68	2.39
   10	2.68	2.39
   12	2.68	2.39
   15	2.68	2.39

   WTvsCR&SR

   2.6

   2.55

   S2.5 R

   &

   C CUTTINGRATE(mm/min)

   R2.45

   SURFACEROUGHNESS(µm)

   2.4

   2.35

   0 2 4 6 8 10 12 14 16

   WIRETENSION

   Table 1.7: Effect of wire feed on CR & SR

4. CONCLUSION From the above study is concluded that :

1. Cutting Rate is increase with the increase in pulse on time upto a certain amount of range beyond this limit of pulse on time MRR start decrease. And surface roughness increase with increase.

2. CR is decreased with increase of pulse duration because discharge energy reduced which reduced cutting rate and surface roughness

3. CR is increased with increase of peak current because increase in discharge energy and at the same time surface roughness is reduced to minimu value.

4. CR and SR decreased with increase of servo gap voltage

5. The effect of Wire feed and Wire Tension is almost contant on cr and surface roughness.

6. Finaly the ranges of control factors on are selected

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