in Engineering Entrance, SI Inter, CA MBA CET, IRMA The melting temperature and thermal conductivity of the work metals may vary from one to another, and EDM operators may need to adjust parameters such as on-time, amperage, and polarity. Copyright 2018 InterviewMania.com - All rights reserved. PG, All To decrease the tool electrode wear novel materials like electrical conductive boron doped CVD diamond (B-CVD) and polycrystalline diamond (PCD) can be used. Electrical discharge machining (EDM), also known as spark machining, spark eroding, die sinking, wire burning or wire erosion, is a metal fabrication process whereby a desired shape is obtained by using electrical discharges (sparks). SAT, CA How to minimise tool wear in EDM? But the thermal conductivity will be 10-15% greater than with a hardened tool steel. During the EDM process, both the tool and the workpiece are subjected to spark erosion, resulting in tool wear in addition to material removal from the workpiece. Tool wear can be minimized by using a tool material that has a high melting point and high thermal conductivity. Interviewmania is the world's largest collection of interview and aptitude questions and provides a comprehensive guide to students appearing for placements in India's most coveted companies. Send OTP again, We Accept all major debit and credit cards, FREE and Unlimited practice for all competitive exams Online Courses, Mock tests and more Learn and Practice, Go Cross section illustrating microcracks in the white layer. 1. Answer 6. Material removal rate ∝ Thermal conductivity of tool ∴  Tool wear ∝ material removal rate, Previous Question These materials are treated as difficulty to machine materials because of low thermal conductivity, high coefficient of thermal expansion, high ductility, and high work-hardening rate, etc. Beryllium copper alloys are readily machinable. This is one of the primary factors that makes it a relatively easy material to EDM. executive, Q In Electrodischarge Machining (EDM), if the thermal conductivity of tools is high and the specific heat of work piece is low, then the tool wear rate and material removal rate are expected to be respectively, Materials Science and Manufacturing Engineering, Materials Science and Manufacturing Engineering Miscellaneous. With the development of (electrical discharge machining) EDM technology, composite tools with special features gradually replace the traditional single-material tools and have become widely used in specific processing conditions. Copper Wirewas the original EDM wire. professional, CS Due to the material’s surprising melting point, graphite is frequently used to make … The thermal conductivity of a material is a measure of its ability to conduct heat.It is commonly denoted by , , or .. Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal conductivity. for A tool is found to be higher than Cu tool and the TRR is also lesser in case of A tool than Cu tool. Melting Point - EDM is a thermal process so the higher the melting point of the electrode material, the better the wear ratio will be between the electrode and work piece. They also found that an increase in the TiB 2 leads to an increase in thermal conductivity. Practice, About Contrary to this, a material with a low conductivity value, such as tool steel can be expected to have a thicker affected layer with more cracking because the spark intensity remains in the spark area longer before the materi-al can dissipate the energy to the surrounding areas. Figure 3. & A Forum, For to Checkout, NEET When EDMing, the materials high thermal conductivity can be a disadvantage when compared to steel. Keeping all other parameters unchanged, the tool wear in electrical discharge machining (EDM) would be less if the total material has, High thermal conductivity and high specific heat, High thermal conductivity and low specific heat, Low thermal conductivity and low specific heat, Low thermal conductivity and high specific heat, Did not receive the code? The spark energy disintegrates the binder and releases the carbide particles into the gap. Presence of ZrB2 particle in Cu matrix increases the wear resistance of A tool, which leads to lesser TRR of A tool during EDM. High Thermal Conductivity and High Wear Resistance Tool Steels for cost-effective Hot Stamping Tools I Valls1, A Hamasaiid1 and A Padré1 1 ROVALMA, S.A., Calle Collita 1-3, 08191 Rubí, SPAIN Abstract. DownloadApp. In Electrodischarge Machining (EDM), if the thermal conductivity of tools is high and the specific heat of work piece is low, then the tool wear rate and material. foundation, CS The amount of worn out materials present between the WP and tool is lesser in case of A tool than Cu tool * Select the material with good thermal conductivity and high melting point as electrode material first. us, Affiliate Then there are options in aluminum and alloys with much greater thermal conductivity that can have a big payback in cycle time. However, tool steels that provide thermal conductivity up to 35 Btu/(hr•ft⋅°F) , commercially known as high thermal conductivity steels (HTCS), should be considered. Two grades of these tool steels, HTCS-1 and HTCS-2, have been used for plastic injection molding. Conversion of electrical energy to thermal energy through repeated occurrence of sparks between the tool and the workpiece in EDM results in the material removal from workpiece as well as tool by melting and evaporation. machining (EDM); due to their unique mechanism of material removal are useful alternatives in such cases [1]. thermal stability, good toughness and thermal conductivity, etc. In electro discharge machining (EDM), if the thermal conductivity of tool is high and the specific heat of work piece is low, then the tool wear rate and material removal rate are expected to be respectively (a) high and high Moreover, a profile on the electrode must be provided based on the desired profile. Since the binder materials of PCD are metals like cobalt and nickel, it is likely to machine PCD by electrical discharge machining (EDM). Electrical Conductivity - Since electric current works as a cutting tool, higher conductivity promotes … At the time it was thought that since Copper wire had high electrical conductivity, it would make the ideal EDM … However, machining of PCD is very challenge especially due to its high wear resistance and extremely high hardness. Program, Privacy In electrodischarge machining (EDM), if the thermal conductivity of tool is high and the specific heat of work piece is low, then the tool wear rate and material removal rate are expected to be low and high respectively. In hot stamping/press hardening, in addition to its shaping function, the tool controls Constable, All Thermal Conductivity affect on EDM Parameters Tool Steel has a low thermal conductivity when compared to other work metals. The tool wear once again depends on the thermal properties of the tool material (e) Though the local temperature rise is rather high, still due to very small pulse on time, there is not enough time for the heat to diffuse and thus almost no increase in bulk temperature takes place. Holds thermal energy where the spark occurs Machines well in positive polarity, longer on-time Allows for electroplating in MBA Entrance, MAH In Electrodischarge Machining (EDM), if the thermal conductivity. has the high conductivity value and is the area that is affected by the EDM process instead of the carbide itself. However, the high thermal conductivity of the copper-based materials will increase the time required for electrical discharge machining (EDM). thermal conductivity and high abrasive wear resist ance tool steels. The thermal conduction of the The thermal conduction of the investigated material was about 66 W/mK at 20 °C [40]. less cracking due to its high thermal conductivity and ductile nature. EDM has a very unique thermo-physical mechanism which involves the conversion of electrical energy to the thermal energy by means of the erosive effect of material from its surface due to the high velocity plasma coming from the tool electrode, the performance parameters like M RR, TWR, Surface finish etc. Pradhan and Biswas (2009) investigated the effect of EDM processes parameter on AISI D2 tool steel with copper electrode. Also by properly configuring the tool design, tool wear can be minimized. term, in the EDM wire business “plain” merely means that the wire consists of a single homogeneous component and does not have a coated or composite construction. policy, Contact The tool electrode should have very good thermal conductivity, because then through the lower energy density in the spark-base point, the energy is more easily dissipated, and … Tutors, Free For experimentation they implemented response surface methodology. B.Tool material (electrode): Engineering materials having higher thermal conductivity and melting point are used as a tool material for Wire EDM process of machining. Copper, graphite, copper-tungsten, silver tungsten, copper graphite, zinc and brass are used as a tool material (electrode) in Wire EDM. EDM has a high capability of machining the accurate cavities of dies and molds. Both materials offer high thermal conductivity and high melting/sublimation point and therewith reduce the wear and enhance the relative removal rate in EDM , . Keeping all other parameters unchanged, the tool wear in electrical discharge machining (EDM) would be less if the total material has High thermal conductivity and high specific heat High thermal conductivity and low specific heat Low thermal conductivity and low specific heat For lower tool wear, the preferred materials have high melting points, high thermal conductivity, high specific heat, and low electrical resistivity. 9. 26 Fig.2.4(a): Relationship between grain size and the cutting rate of carbide material by wire-edm. Electrode wear is dependent of factors like polarity, thermal conductivity, melting point of electrode, duration and intensity of spark discharges, types of power supplies used, the type of work material used in relation to the tool material, dielectric flow in the machining zones. Us. Influence of thermal conductivity on cutting rate: A lower thermal conductivity and a lower melting point result in a higher material removal rate for materials with melting as a main EDM … Next Question. foundation, CA 10. final, CS Please identify the characteristics of an electrode material in order to serve as a good tool. If the same EDM approach is used regardless of the work metal, the result could be vastly different. * It takes into account the factors such as easy to shape the electrode and good machining performance so as to obtain a good EDM effect. Melting Point. These effects can be minimized by performing the bulk of the machining first through conventional means before moving to the EDM process for the finished machining operations. Therefore, die-sinking EDM electrode material should have high electrical and thermal conductivity, good formability and machinability, high melting point and low cost. 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