ELECTROSTREAM DRILLING 

INTRODUCTION:

Electro stream drilling (ESD) could be a special version of electrochemical machining adapted for drilling tiny holes (usually but one mm) by mistreatment of high voltages and acid electrolytes. ESD was initially developed within the middle Sixties by the overall power service, Aircraft Engine cluster. The method was fabricated to resolve the issues related to drilling thousands of tiny cooling holes in rotary engine blades. It uses acid solution rather than the salt electrolytes that are usually employed in an Electrochemical machine to drill tiny holes. Electro stream drilling (ESD) method is gaining prominence within the machining of small holes in tough to machine materials employed in the house, aviation, physical science and

computers, medical, and automobile industries. This method employs a jet of the charged acid solution for the anodic dissolution of work material. Because the trend towards making smaller or fewer continues, this method has shown its superiority over different up-to-date non-standard small and micro hole drilling processes. The key advantage of this method is to drill tiny holes having diameter vary from 0.125 to 0.2 millimeter with a giant ratio.

Fig. Electro stream Drilling

SPECIFICATIONS & METHOD PRINCIPLES:

With a high rate Electro stream of the solution is flowing through the nozzle. The nozzle diameter is formed as tiny as attainable. it's conjointly given a feed towards the workpiece. And Acidic solution once natural events on the surface can dissolve it and material removal can occur. To vent out the gas bubbles created throughout the method fan is employed. solution temperature maintained through the employment of heater. The filter is employed to strain antimonial hydroxide particles from the solution.

Also, there are a few method principles that are listed below.

1. This method differs from standard chemical science Drilling.

2. High rate charged solution is employed.

3. detritus of Metal hydroxides generated during this method is dissolved by acidic solution.

4. Thus, you'll be able to generate any kind of hole.

5. Conjoint Holes of size 0.127-0.89 millimeters are often generated.

6. The voltage of 150-850 V is applied.

7. The nozzle is formed of glass.

TYPES OF ELECTRO STREAM DRILLING:

There are 2 styles of Electro stream drilling. i.e., Dwell Drilling & Penetration Drilling.

1) Dwell Drilling –

1. Zero feed rate provided

2. For shallow and fewer correct holes

3. Depth of hole and accuracy restricted

4. most Depth of five millimeters is often achieved

2) Penetration Drilling

1. Deep & correct drilling.

2. mistreatment finite feed rate constant gap is maintained.

3. There's a continuing gap maintained through gap sensing devices.

4. most Depth nineteen millimeters.

5. Machining rate 1.5mm/min.

Equipment and Tooling:

The Electro stream drilling method could be a high voltage method during which a voltage is applied between the work and a cathode wire sometimes made from Ti placed in a glass nozzle. The voltage (250-650 V) applied drives this through the Associate in Nursing electrolyte column. This method conjointly needs an additional tank within the solution system. From one tank once the acid electrolyte is pumped up and so once traveling through the machine, overflows in a separate tank, that is at first electrically insulated. Therefore, this is prevented from creating a complete circuit around the system. It's vital that To forestall the voltage issue machine ought to be guarded. Electro stream drilling uses a nozzle formed glass tube as a cathode. A platinum wire is inserted within the tube to relinquish the acid solution. Electro stream drilling machines have one feed axis that is capable of constant feed rates between 0.125 to 0.25 mm/min similarly to cardiopulmonary exercise movement. Multi-axis machine units permit rotation of the half or permit an Associate in Nursing array of tubes to be indexed across the half. Feed rates and voltages are programmed by employing pc numerical management.

PROCESS PARAMETERS:

The key method parameters for Electro stream Drilling embody 

Voltage: 250 to 650V

Electrolyte Type:

a) Type – Acid- vitriol, acid, or acid

b) Concentration of fifteen to five hundredth by volume

c) Pressure: 0.275 to 0.40 N/mm2

d) Temperature: 40°C for vitriol and 20°C for others

e) Feed rate: 0.75 to 2.5mm/min.

PROCESS CAPABILITIES:

Material removal rates and tolerances - Penetration rates 1.5 to 3.0 mm/min are typical for the super alloys. The electrolytic dissolution follows Faraday's law and current density is proscribed by the boiling of solution within the nozzle from the resistive heating. Diameter tolerances are usually +1- 0.025 millimeter or and or -5 for sizes on top of 0.5mm.

ADVANTAGES:

The advantages of electro stream drilling embody the subsequent

1) No heat-affected zone.

2) No burrs are created.

3) No induced stress within the work.

4) Not laid low with the hardness of the metal.

5) Blind and decussate holes are often trained.

6) No recast layer.

7) No Burr generation, no residual stresses induced, and No tool wear.

Limitations:

Electro stream drilling is often solely used on corrosion-resistant metals (stainless steel cobalt, and nickel base rotary engine alloys) and electrically semiconducting work. Generally, this method can't drill commercially pure Ti and refractory metal.

Other limitations are as follows

• The method is slow once drilling a single hole.

• costly electrodes.

• Special geographic points and environmental precautions ought to be taken to handle acid.

• possibilities of nozzle breakage since glass could be a fragile material.

• Bell-mouth hole entrance.

• High preventive maintenance value.

Applications:

Applications of electron stream drilling embody

• Drilling rows of cooling holes in turbine blades and vanes.

• Machining of oil passages.

• Machining of fuel nozzles.

• In EDM drilling oil passages within the bearings can cause cracks.

• Drilling regular arrays of holes in corrosion-resistant metals of low machine

(for example, strainers and dies).

References:

1. Jia Jixin,Qu Ningsong,Fang Xiaolong,Zeng Yongbin(Nanjing University of Aeronautics & Astronautics,Nanjing 210016,China)  - Investigation on Electrostream Drilling of Micro-holes.

2. S.V. RamaRao, P.K. Mishra, Hole drilling by electrojet. In Proceedings of the Fifth International

Conference on Production Engineering, Tokyo (1984)

3. G. Bellows, Drilling Without Drills (American Machining, 1982)

Metals Handbook, Vol. 16, Machining (ASM International, Materials Park, OH, 1989)