On the use of Copper Tool developed by Atomic Diffusion Additive Manufacturing (ADAM) Process for Electrical Discharge Machining

. This paper highlights the review of work done in the area of 3D printed tools for the spark machining process. In recent times, additive manufacturing has gained wide popularity in different sectors. The additive manufacturing process or 3D printing, is a method for creating three-dimensional objects by layering material. Using the additive manufacturing technique of atomic diffusion, a tool for electrical discharge machining was developed. In this method, a mixture of metal and polymer that are formed into wire was employed and kept in a cartridge. The material mix is deposited in similar to extrusion process. A computer software does all the calculation, costing, weight analysis and printing time assessment. The procedure of the same is discussed. The scanning electron microscopic analysis of the same is done along with porosity measurement using ImageJ software. The surface characteristics of the printed tool was measured with Gwyddion software. Discussion on applicability of printed tool for electrical discharge machining process is done. words.


Introduction
Electrical discharge machining (EDM) is used to machine hard and difficult-to-machine materials.The material is expulsed from the workpiece through melting and vaporization when a spark occurs in a small gap between the work sample and the tool [1].The accuracy of the machined component is greatly influenced by the shape and accuracy of the tool used since, the tool has a shape that corresponds to the intended profile to be formed on the workpiece.Commonly used tool materials include copper, graphite, brass, and graphite.EDM has applications in numerous fields: manufacturing of gear, mould and die making, automobile, aircraft, biotechnology, surgical sectors, etc. [2][3][4].In the manufacture of dies and molds, the machining of tools makes up 25-40 % of the overall lead time and can cost up to 50 % of the entire machining cost [5].A longer lead-time during the mold manufacturing process can delay the product's launch and have an impact on the market.To get the necessary cavities, complex features in die and molds require the use of several tools with precise geometry that are run sequentially.In recent years, the development of the EDM tool using additive manufacturing techniques has demonstrated remarkable possibilities for reducing lead times and lowering the number of tools needed for intricate cavity machining.Thus, the benefits of using 3D printing to manufacture EDM tools are process cost and time.A number of techniques of 3D printing are used for developing EDM tools.A summary of some research in the field of EDM tools is presented in Table 1.
The purpose of this paper is to review the work done in the area of 3D printed EDM tool.A novel technique of atomic diffusion atomic manufacturing to develop EDM tool has been discussed.Necessary steps involved in printing electrode are discussed.In the end, the framework for future research work has been presented.Specification of complete Metal X system is given in Table 2.The photograph of pure Cu EDM tool printed by this process is shown in Fig. 2.

Analysis and Discussion
The dimensions and weight measurements are shown in Fig. 3 while the values of dimensions, weight and, obtained density of developed tool are given in Table 3.The density of tool was calculated using simple equation of density based on weight and volume of the tool.The density of solid copper is nearly 8.9 gm/cm 3 .It can be noted that the EDM tool manufactured by ADAM process has some specific properties one of such property is low density and thus more wear during its use in EDM process.This shows that the printed tool has a good potential to be used in electrical discharge coating process.Number of tool of various density of same material can be printed and tested in EDM under straight and reverse polarity condition.Different analysis of the printed EDM tool were conducted to study surface characteristics and porosity of the tool.The scanning electron microscopy was carried to study the topological features of the surface.A scanning electron microscope of make Joel JSM-IT 100 (available at NITTTR, Chandigarh) was used for this purpose.SEM imaging takes place by scanning the specimen with a high energy beam of electrons.When these electrons strike the specimen they develop secondary electrons, characteristic X-rays, and backscattered electrons.The detectors are employed to collect these signals and form images that can be seen on a computer screen.
SEM image of the printed tool at higher magnification (X100) is shown in Fig. 4. It can be noted that the layers of parent material are clearly visible on the surface.Also, there is significant distance (gap) between the layers which means the porosity of the printed tool is expected to be higher than solid copper tool.It can already have been established that the density of tool is less than solid copper.These properties will result in higher tool wearing with printed tool and hence, bright chances of use in surface coating.Surface roughness is defined as the irregularities which are inherent in the manufacturing process.It is measured by how far an actual surface deviates from its ideal form in the direction of the normal vector.If these variances are considerable, the surface will be rougher and if they are minimal, the surface will be smoother.The variation of surface roughness and waviness is depicted in Fig. 6 and 7 respectively.Surface waviness is the measurement of the more widely spaced portion of surface texture.It is a broader view of roughness because it is more precisely defined as the irregularities with spacing is greater than the roughness sampling length.The value of average roughness and waviness were found to be 4.727 µm and 19.98 µm respectively.While the maximum height of the roughness was recorded to be 95.81 µm, the maximum height of the waviness was detected to be 136.4µm.
The physical property of porosity is crucial in determining the texture and material quality.A porous material has a small amount of empty space between it and the surrounding material.The porosity of the developed EDM tool was determined by using ImageJ software.The value of porosity was found to be 60.67 %.This shows that the EDM tool developed by ADAM process has high porosity.A relationship between the tool wearing rate and porosity need to be established to study the impact of porous tool on surface deposition using reverse sparking machining.The image obtained by ImageJ software for measurement of porosity in shown in Fig. 8.

Conclusions
In the recent times, the 3-D printing has gained wide popularity because of its applicability in various sectors of the industries.The process of 3D printing can be employed for developing tool for EDM process too.Through 3D printing, it is possible to develop tool of different shapes, materials, and properties.The review of literature in the area of 3D printed tool for discharge machining has been presented and the summary of results are highlighted in the tabular form.In this paper, the procedure to develop EDM tool using atomic diffusion additive manufacturing process has been discussed.It was observed that the density of developed EDM tool has low density.The surface characteristics of the printed tool were also determined using Gwyddion software.The results are analysed and discussed.The scanning electron microscopy was conducted to know the surface topography.It was observed that the developed tool has high porosity.The low density and high porosity means that the chances of tool wearing with this tool will be higher.Thus, it has a great potential to be used as tool for electrical discharge coating.
The EDM tool of same material but of different densities can be developed using ADAM process.The influence of tool density as one of the input variable on machining characteristics of EDM can be conducted.The optimal value of tool density for machining as well as coating can be found out.It is also possible to develop too of same density but of different materials.The comparative study of the EDM performance using these tools can be conducted.

Table 1 .
Literature review

Table 2 .
[20]ifications of Metal X system To get the binder off, green parts go through a washing stage.The metal powder is then sintered in a furnace, where it solidifies.5.The final parts are ready for use.No CNC or Wire EDM is required for removal of part from the build plate or to remove the support.A simple wash and support removal needed to make the part usable.[20] 1300°C Fig. 2. EDM tool developed by ADAM process 3 Process of Printing

Table 3 .
Dimensions, weight, and density of tool developed