This article describes the applications, process capabilities, and limitations and advantages of electrostream and capillary drilling. It describes equipment and. NPTEL provides E-learning through online Web and Video courses various streams. Book Source: Digital Library of India Item : Sridhar ioned.

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Search the history of over billion web pages on the Internet. Most of the industrial applications involve hole making in these electrkstream rials. Bellows and Kohls [1] reported various non-traditional machining methods that can be used to solve the modem hole making problems. They reported de- tailed overview of various non- traditional machining processes, including their capabilities. They suggested guidelines for selecting a particular process. They also reported the cost and drilling capability comparisons of various processes, Fig 1.

It is evident from the fig 1. LBM costs low for very fine hole drilling. They also reported the selection of electrolyte in ESD for machining electrodtream specific kind of workpiece material.

Jain [2] has studied the electro chemical drilling process using bare, coated and bit type electrodes. He found that the use of tool bits in drilling operation can re- sult into a substantial reduction in power consumption and overcut. Tool bits with insulated sides and low operating voltages lead to practically zero over cut.

He performed electro-chemical drilling ECD experiments using NaCl electrolyte to study the electrosstream of voltage on anode profile, and the effect of tool diameter on over cut. Using finite element technique FETanodic profiles for different cases have been obtained and a comparison has been made between experimental and analytical anodic profiles. Sreejith et al [3] reported experimental findings concerning the effects of pro- cess parameters on the profile of a spike obtained during electro-chemical drilling of a blind hole in HSS workpiece.

They concluded that the spike volume is largely governed by the feed rate, hole diameter, and taper angle. The effect of applied voltage on spike volume was not significant. The pump selected for ESD has the following specifications, Head: Ltd Piping The pipes carrying the electrolyte must be acid resistant.

Pipes are clamped at the junctions by wire clamping to avoid the release drillling pipes due to electrolyte pressure. The pipes used in the flow path are of 0.

NPTEL :: Mechanical Engineering – NOC:Advanced Machining Processes

The 3-phase V A. In ESD, the current drawn during the machining is of the order of millie amperes that is very low. Specifications electrkstream the power supply unit used in ESD are, as follows. Values of parameters for different levels 28 References 1.

D Thesis, University of Roorkee, India New York American Elsavier publishing company, Sridhar Sastry, has been carried out under our supervision and that this work has not been submitted elsewhere for a degree. Drilping, Acknowledgement I driloing this opportunity to express the feeling of sincere gratitude tov’. Shekhar for their expert guidance and encouragement which have been the vital factors in successful completion of the present work.

I am thankful to the staff of manufacturing Science Laboratory, Mr. Namdev for their consistent efforts in making the experimental set up. I am specially thankful to Mr. Anil for his cooperation in fabricating the set-up, and his timely help during experimentation.

I am electrostrea thankful to the staff of central glass blowing people for their help in fabricating the glass nozzle. I am very much thankful to Mr.

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Vinod Yadav for their constant encouragement and suggestions in writing the thesis. I would like to express my thanks to all who have helped me, specifically Mr.

It is indeed my great pleasure to express my sincere thanks to Gayatri Prasad, Seshu, Prabhudas, Janardhan Reddy, VenuPhani and all my friends for their timely help drillingg friendly cooperation in sorting out my problems and making my stay at I. I am very much grateful to my parents who always supported me despite many problems in all the circum- stances. Sridhar Sastry Abstract Advances in the field of aerospace, gas turbine, nuclear technologies have pro- duced the need to machine the super alloys and refractory metals.

One such problem is drilling small deep holes in the super alloys. Electro stream drilling ESD dril,ing found to be a potential process for drilling micro holes in these materials. Basic ESD process details were reported by previous researchers. So far, parametric study reported involved the usage of salt electrolytes only. In the present work acidic electrolyte HCl is employed for machining of the work material.

For this purpose experi- mental electro stream drilling machine has been designed and fabricated. eectrostream

Exper- iments have been performed with high speed steel HSS as work material. Few experiments are also conducted on Inconel super alloy. During the course of study an attempt has been made to evaluate the effect of process parameters i.

Geometrical electrosgream such as machined hole profile, hole taper have also been studied. List of Tables 1. This is so because machining has a special status in the whole spectrum of all manufacturing processes. Traditionally shaping of components by selective removal of material has been performed by mechanically operated tools, the inherent principle being that a hard material will cut a elecyrostream one.

The more familiar machining operations include turning, boring, milling, planing, broaching and grinding. Recent advances electrostrewm science and technology, elcetrostream in areas such as nu- clear and aerospace engineering have imposed a severe demand on the materials requirements.

This aspect led to the development of high strength and temperature resistant, hard and brittle materials, whose machining posed serious problems electrostrewm the manufacturing industries.

Processes for machining such hard and brittle ma- terials are grouped under the common name of Unconventional machining or Non — traditional machining processes. The complex designs associated with the jet engine hardware have posed 1 machining problems which are beyond the capabilities of conventional machin- ing processes.

One such problem is drilling small deep holes in the super al- loys.

Electrostream Drilling Of High Speed Steel

Problems such as tool wear and excessive heat generation at the tool and workpiece interface are encountered while employing conventional mechanical drilling techniques. Additionally, there is some obstruction to the coolant flow since the chip direction is opposite to the direction of drill penetration. It is also considerably difficult to drill holes smaller than micrometer by conventional mechanical drilling.

Rigidity requirements for the tool is another major problem in conventional drilling of small and deep holes. In such cases, non-traditio. Several other situations that favour the application of these advanced machining processes AMPs for drilling are: EDM and LBM are ther- mal processes and therefore cause the formation of heat alfected zones and micro cracks on the work surface, resulting in metallurgical damage of the workpiece surface material.

Typical minimum diameter can be achieved by LBM. Comparison of various non-traditional hole making processes [1] 3 STEM process gives the max machined depth. ECM is considered as an efficient process for machining complicated shapes in any hard and electrically conductive material. Ellectrostream situations that make ECM a prime candidate for machining are as given below. But drilling of small holes with large aspect ratios is beyond the scope of ECM because of over cutting on account of sideway current flow.

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Another problem is the formation of insoluble precipitates during machining which inhibits the ma- electrostrea of small electrkstream holes. This aspect led to the development of specialized EC drilling techniques, the prominent micro drilling techniques being shaped tube electrolytic machining STEMand electro stream drilling ESD.

Shaped tube electrolytic machining is a specialized ECM technique for drilling small, deep holes utilizing acid electrolytes. In STEM, electrode is a carefully straightened acid-resistant metal tube coated with a film of enamel type eldctrostream. The electrode can be shaped to drill drlling cross sections. The voltage used in the process is of the order of V. A thin, electrically charged electrolytic stream electrosyream obtained by pumping electrolyte through a specially drawn non-conducting nozzle glass nozzle of fine outlet diameter.

A Platinum wire inserted in nozzle acts as cathode while work piece is made anode. Platinum is used because of its good electrical conductivity, and elrctrostream inertness to acidic action.

As the charged electrolytic stream impinges on the work piece, material eldctrostream re- electroetream through electrolytic dissolution and is flushed out from the interaction area in the form of elevtrostream ions in the solution. The acidic electrolytes used in ESD dissolves the precipitates thereby avoiding sludge formation during drliling.

The electro chemical reactions which might occur when machining iron with approximately zero pH hydro chlo- ric acid solution are given below. This high voltage requirement in ESD is due to the large gap between platinum wire tip, and electrosrteam piece material. As a result high voltages are essential to over- come the ohmic resistance due to this gap for machining to takes place.

With Elecrtostream holes as small as 0. Insertion of a nozzle with a formed tip permits right angled drilling deep inside the prior hole Fig 1. The po- tential applications of ESD are in fuel injector nozzles of diesel engines, viscosity meters, watches, gas turbine vanes, etc. The general principle of material removal by anodic dissolution was one of the discoveries of Michael Faraday. Faraday in estab- lished the laws of vrilling. Suggestions for the application of metal removal as a metal working technique were proposed by W.

Gussef, a Russian scientist, in and much latter by C. Burgess in a paper for the electro chemical society in To meet the demands of technologically advanced industries like aeronautic, nuclear, gas-turbineautomobile, rapid developments have taken place in the field of material science to develope the materials having better properties in terms of strength, hardness, and toughness at elevated temperatures.

Shaping of these materials by traditional methods is Figure 1. Chryssoluris and Wollowitz [4] developed an electro chemi- cal hole making technique which uses uninsulated tools and passivating XaClOz electrolytes. The method shows advantages over other hole making techniques in terms of the resulting surface quality and process reliability. During machining with bare tools and passivating electrolytes, a transpassive condition would exist at the small frontal gap while passive conditions are obtained along the sides of the holes.