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Figure from:EFFECT OF CURRENT AND PULSE ON TIME ON MRR AND EWR FOR DIFFERENT INNER ELECTRODE SHAPE OF EDM PROCESS

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In this research, we used the programmed Electric Discharge Machine (CNC EDM) type CHMER CH (323C+50N), as shown in Figure (1) with operational specifications as shown in Table (1). The machine contains of several mechanical and electrical parts to control the movement of axes, especially the work axis z, which is perpendicular to the axis of the workpiece and controlled by the program. For holding the electrode, a special holder has been manufactured, which contains a central hole intended to make the condensation fluid pass through it and shed it on the operating area, as shown in Figure (2).

Figure 1 In this research, we used the programmed Electric Discharge Machine (CNC EDM) type CHMER CH (323C+50N), as shown in Figure (1) with operational specifications as shown in Table (1). The machine contains of several mechanical and electrical parts to control the movement of axes, especially the work axis z, which is perpendicular to the axis of the workpiece and controlled by the program. For holding the electrode, a special holder has been manufactured, which contains a central hole intended to make the condensation fluid pass through it and shed it on the operating area, as shown in Figure (2).

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Table (1): Technical Specifications of CHMER CH 323C.
Table (1): Technical Specifications of CHMER CH 323C.
The workpiece material was chosen from high-speed steel (HSS) due to its high strength, high corrosion and shock resistance, with a hardness of HRC 62 (Kg/mm7?). The HSS workpiece dimensions is (40 x 40) mm of a cross- section and 200 mm length. Table (2) shows the chemical composition of the samples. The samples were cut by (40 x 40) mm in a square and 3 mm thick using the wire EDM and as shown in Figure (3).
The workpiece material was chosen from high-speed steel (HSS) due to its high strength, high corrosion and shock resistance, with a hardness of HRC 62 (Kg/mm7?). The HSS workpiece dimensions is (40 x 40) mm of a cross- section and 200 mm length. Table (2) shows the chemical composition of the samples. The samples were cut by (40 x 40) mm in a square and 3 mm thick using the wire EDM and as shown in Figure (3).
A sample of high speed steel was inspected at the Ministry of Planning/Central Organization for Standardization and Quality Control. The results of this chemical analysis are consistent with the specifications associated with the HSS used in the tests. This is represented by (HS 10-4-3-10) and according to ISO 2002.
A sample of high speed steel was inspected at the Ministry of Planning/Central Organization for Standardization and Quality Control. The results of this chemical analysis are consistent with the specifications associated with the HSS used in the tests. This is represented by (HS 10-4-3-10) and according to ISO 2002.
Table (3): Chemical Composition of Copper Tool Electrode. Four hollow electrode shapes are selected in addition to the solid ones, in order to show their effect on the outputs parameters been mentioned. According to mathematical calculation based on equal cross-section for each electrode shape, the area was selected as (157.524 mm?) as shown in Figure (4).
Table (3): Chemical Composition of Copper Tool Electrode. Four hollow electrode shapes are selected in addition to the solid ones, in order to show their effect on the outputs parameters been mentioned. According to mathematical calculation based on equal cross-section for each electrode shape, the area was selected as (157.524 mm?) as shown in Figure (4).
Fig. (3): the dimensions of workpiecesbefore machining.
Fig. (3): the dimensions of workpiecesbefore machining.
Wire EDM was used for electrode set-up and achieved four hollow geometric shapes (square, triangle, polygon and finally circular) in addition to the basic shape, which is a cylindrical solid and represents the fifth shape as shown in the Figure (5). Which have constant area for all hollow shapes and is estimated at (157,524mm). In order to manufacture the hollow shape which have been selected, a software called (cimco edit) used to generate the required G-code program and transmuted to the wire-ED machine which is used to control the axis.
Wire EDM was used for electrode set-up and achieved four hollow geometric shapes (square, triangle, polygon and finally circular) in addition to the basic shape, which is a cylindrical solid and represents the fifth shape as shown in the Figure (5). Which have constant area for all hollow shapes and is estimated at (157,524mm). In order to manufacture the hollow shape which have been selected, a software called (cimco edit) used to generate the required G-code program and transmuted to the wire-ED machine which is used to control the axis.
Table (4): The machining parameters. In addition, this experiment design is a design for each of the selected shapes, the remaining parameters were selected and are not subject to change. After several tests were made before the final parameters were set. The unchanged machine parameters shown in Table (5).
Table (4): The machining parameters. In addition, this experiment design is a design for each of the selected shapes, the remaining parameters were selected and are not subject to change. After several tests were made before the final parameters were set. The unchanged machine parameters shown in Table (5).
Table (5): the unchanged machine parameters. Below are the part that have been operated using four hollow shape and solid of copper electrode on the electric sparking machine, as shown in the Figure (6).
Table (5): the unchanged machine parameters. Below are the part that have been operated using four hollow shape and solid of copper electrode on the electric sparking machine, as shown in the Figure (6).
Fig. (6): five hollow shape of HSS workpiece: a- circular shape produced by hollow electrode, b- polygon shape produced by hollow electrode, c- Square shape produced by hollow electrode, d- triangle shape produced by hollow electrode and e- circular shape produced by hollow tube electrode. For the purpose of measuring output response, there are several tools used to define and find the purpose of this objective. The rate of removal of the metal or (MRR) is measured by the weighting of each workpieces before the machining, and then operate the workpiece on the electric sparking machine or (EDM), after that the part is cleaned, dielectric liquid removed, the dirt is quitted and dried, and then the workpiece is weighed again. Sensitive weights device (Denver Instrument) is used which have the accuracy of (+ 0.001) gm, and the mathematical formula for MRR (mm?/min) were used to calculate as showing in the relation (1) [22].
Fig. (6): five hollow shape of HSS workpiece: a- circular shape produced by hollow electrode, b- polygon shape produced by hollow electrode, c- Square shape produced by hollow electrode, d- triangle shape produced by hollow electrode and e- circular shape produced by hollow tube electrode. For the purpose of measuring output response, there are several tools used to define and find the purpose of this objective. The rate of removal of the metal or (MRR) is measured by the weighting of each workpieces before the machining, and then operate the workpiece on the electric sparking machine or (EDM), after that the part is cleaned, dielectric liquid removed, the dirt is quitted and dried, and then the workpiece is weighed again. Sensitive weights device (Denver Instrument) is used which have the accuracy of (+ 0.001) gm, and the mathematical formula for MRR (mm?/min) were used to calculate as showing in the relation (1) [22].
Fig. (7): The influence of current on material removal rate (MRR) within 50 us for five shapes. A high current generates a high-intensity spark and as has been inferred in the results, thus increasing the thermal flux of the internal cavity. As a result, the heat of the spark area increases sharply, which leads to a frequent melting of the contact area of the workpiece, this difference is estimated by a percentage of (12.971 %).
Fig. (7): The influence of current on material removal rate (MRR) within 50 us for five shapes. A high current generates a high-intensity spark and as has been inferred in the results, thus increasing the thermal flux of the internal cavity. As a result, the heat of the spark area increases sharply, which leads to a frequent melting of the contact area of the workpiece, this difference is estimated by a percentage of (12.971 %).
Fig. (8): The influence of current on Material Removal Rate (MRR) at 100 us for five shapes.
Fig. (8): The influence of current on Material Removal Rate (MRR) at 100 us for five shapes.
As for figure (9), what mentioned above is applied here, but the difference is in pulse-on time, which is (150us). Hence it is obvious that the increase of current will increase the MRR significantly.
As for figure (9), what mentioned above is applied here, but the difference is in pulse-on time, which is (150us). Hence it is obvious that the increase of current will increase the MRR significantly.
Fig. (11): The influence of current on electrode wear ratio (EWR) at 100 ys for five shapes At a pulse-on time of (100 us), it is also observed in Figure (11) that the hollow electrodes are preferred on the solid electrode. For example, at the current of (4A) it is noticed that there is a huge difference between the electrodes with a rate up to 91% and the hollow square shape is of the least electrode wear ratio by 0.04295.
Fig. (11): The influence of current on electrode wear ratio (EWR) at 100 ys for five shapes At a pulse-on time of (100 us), it is also observed in Figure (11) that the hollow electrodes are preferred on the solid electrode. For example, at the current of (4A) it is noticed that there is a huge difference between the electrodes with a rate up to 91% and the hollow square shape is of the least electrode wear ratio by 0.04295.
AS arising in current value of (10A), it has been noticed that there is a great difference between the lowest readings of the electrode wear ratio for the hollow square shape up to (92.5%) with the solid electrode. For the (16A) current, it is also noticed that the square shape has the lowest wear ratio of (79.61%) compared to the solid shape, followed by the triangle (69.72%), the polygon (54.2%) and finally the circular shape which is less than the solid in about (41.76%). It is observed that (Figure 12) behaves in the same manner as in the previous figures (10) and (11) where the relationship is exponential, the only difference here is the use of pulse-on time (150us).
AS arising in current value of (10A), it has been noticed that there is a great difference between the lowest readings of the electrode wear ratio for the hollow square shape up to (92.5%) with the solid electrode. For the (16A) current, it is also noticed that the square shape has the lowest wear ratio of (79.61%) compared to the solid shape, followed by the triangle (69.72%), the polygon (54.2%) and finally the circular shape which is less than the solid in about (41.76%). It is observed that (Figure 12) behaves in the same manner as in the previous figures (10) and (11) where the relationship is exponential, the only difference here is the use of pulse-on time (150us).