Title of Invention

A MACHINE FOR ELECTROCHEMICALLY ASSISTED ARC MACHINING.

Abstract The present invention relates to the development of a machine for electrochemically assisted arc machining useful for fast cutting of billets, rods and sheets of metallic materials of various sections, which are difficult-to-cut by conventional methods. The electrochemically assisted arc machining which comprises a machine tool essentially consisting of endless steel band mounted on a vertical band drive having two end pulleys connected to a prime mover, the said machine tool being mounted on an electrically insulated frame capable of horizontal movement to enable contact of steel band with a job to be machined, the said job being mounted on a vice, which is mounted on the electrically insulated bed, the contact surface of the said steel band and the said job being provided with electrolyte supply through means such as one or more nozzles connected to an electrolyte tank through a conventional chemical pump, the said steel band and said job being electrically connected to negative and positive terminals respectively of a DC power source.
Full Text The present invention relates to a machine for electrochemically assisted arc machining. Electrochemically assisted arc machine is a non conventional cutting machine that can be used for fast cutting of billets, rods and sheets of metallic materials, which are difficult-to-cut by conventional methods. This machine has been developed by combining electrochemical dissolution and arcing processes in a novel electrolyte composition as described and claimed in our copending patent application No: NF-249/02. The machine for electrochemically assisted arc machining (ECAAM) is useful for industrial applications, as conventional methods of cutting cannot be employed for machining difficult to cut super alloy materials such as Inconel, Nimonics, Stainless Steel, Titanium aluminide, tungsten carbide and heat treated high speed steel (HSS).
In mechanical engineering industry there is a need for cutting billets, rods and sheet stock of metallic materials and alloys prior to machining specific components. This operation proves to be time consuming especially with materials like stainless steel, nimonic etc. For cutting these, special alloy steel blades, diamond coated blades or slitting saws are used. This process proves to be costly because of the consumption of expensive tool. Flame cutting is also used for these metals. Disadvantages with flame cutting are a good bit of material is lost since the cut is quite wide and the method is well suited only for plates. Plasma arc or
laser cutting also produce a cut edge with severe undulation. Super alloy materials such as Inconel, nimonics, Titanium aluminide and tungsten carbide cannot be cut easily by conventional methods.
In the light of the above one can see that there is a need for fast cutting of difficult to cut hard metals of various sections.
To the best of our knowledge and belief the very concept of combined arc and electrochemical machining is novel and as such is not known in the art. This has been confirmed as no literature or patents available for such a machine.
The main object of the present invention is to provide a machine for electrochemically assisted arc machining of difficult to cut materials such as billets, rods, sheets of super alloys such as Inconel, Nimonics, Stainless Steels, Titanium aluminide, tungsten carbide and heat treated high speed steel (HSS) material.
Another object of the present invention is to provide a machine for electrochemically assisted arc machining wherein the electrolyte used is as described and claimed in our copending patent application No: N F-249/02,
The machine of the present invention provides electrochemically assisted arc machining wherein electrochemical dissolution and arcing processes are combined to provide machining of metallic billets, rods and sheets which are difficult to cut by conventional methods.
In the drawing accompanying this specification, figure 1 represents the schematic view of the machine of the present invention wherein the various parts are:
1. CNC control panel
2. DC power source
3. Vertical band drive
4. Bed
5. Metal band
6. Horizontal table holding frame
7. Vice for Job mounting
8. Electrolyte tank and pump
Accordingly the present invention provides a machine for electrochemically assisted arc machining which comprises a machine tool essentially consisting of endless steel band mounted on a vertical band drive having two end pulleys connected to a prime mover, the said machine tool being mounted on an electrically insulated frame capable of horizontal movement to enable contact of
steel band with a job to be machined, the said job being mounted on a vice, which is mounted on an electrically insulated bed, the contact surface of the said steel band and the said job being provided with electrolyte supply through means such as one or more nozzles connected to an electrolyte tank through a conventional chemical pump, the said steel band and said job being electrically connected to negative and positive terminals respectively of a DC power source.
In an embodiment of the present invention the endless steel band used may be a steel band loop made by joining the ends of a steel band by conventional methods.
In another embodiment of the present invention the prime mover used may be an electric motor.
In yet another embodiment of the present invention the horizontal movement of the frame mounted with machine tool may be effected by an electric motor.
In still another embodiment of the present invention the horizontal bed is electrically insulated.
In further embodiment of the present invention the electrolyte used may be such as described and claimed in our copending patent application No: N F- 249/02.
In still yet another embodiment of the present invention the steel band is the cathode and the job is the anode.
In the present invention, a novel method of achieving fast cutting of metals and alloys by arcing in a specially formulated electrolyte composition was achieved. In this method, the cutting action is best described as electrochemically assisted arc machining. In other words, electrochemical dissolution and arcing alternatively take place resulting in fast cutting. The electrolyte composition formulated is able to play the dual role of permitting electrolyte dissolution of job as well as formation of arc on the job surface.
The present invention describes a cutting machine that can be used with the specially formulated electrolyte of our copending patent application no. NF-249/02.
The machine for electrochemically assisted arc machining consists of a DC power supply, a machine tool and an electrolyte circulation system. The power supply is a full wave rectifier without any smoothing. A thyristor controlled rectifier may also be used. The power supply has a short circuit protection and also a current limit.
The machine tool consists of an endless steel band which travels between two pulleys. The steel band is formed by butt welding semihard steel strip of appropriate length and annealing the weld seam. The steel band rotates on two pulleys, one of them is provided with a drive. The distance between the pulleys can be adjusted to provide the desired tension on the blade.
Two spring loaded carbon brushes provide the electrical contact to the band. The band may be made to rotate in a vertical, horizontal or inclined plane. However, the preferred one is vertical.
For cutting, the job is mounted on a vice, which is mounted on the horizontal table fixed on the bed which is perpendicular to the moving band. The bed is electrically isolated to prevent shorting. The horizontal table has also a provision to connect the job as anode to the power supply.
The horizontal table is moved by a Programme Logic Controller (PLC), so that cutting may be done automatically. The power supply is connected between the band and the job. The electrolyte composition specified i pumped by a suitable chemical pump on to the steel band and job and the power supply is switched on. To flood the gap between job and band, the electrolyte is delivered through suitable nozzles arranged on either side of the band. Appropriate feed rate and voltage are set. Sparking or arcing starts and job is cut.
The electrolyte is collected in a reservoir kept below the bed and is recirculated. The machine is provided with an enclosure to prevent splashing of electrolyte. The enclosure is provided with an exhaust system.
The experiments have been carried out with steel band at different parameters in the present electrochemically assisted arc machine (ECAAM), to cut various materials.
The electrodes are the workpiece or job, which is connected as anode and the counter electrode, which may be called as tool and acts as a cathode. The ordinary annealed mild steel band is rotated between two wheels while cutting the material with electrolyte. The plain steel band is sufficient, since it is not cutting by abrasive action but only acts as a carrier for the spark / arc current, which cuts the material.
The metal which has to be sliced is clamped in the vice of the machine and the rotating steel band is used as tool. The electrolyte is pumped on to the steel band and job and the power supply is switched on, with appropriate feed rate and voltage. Sparking / arcing starts with electrochemical dissolution and the job is cut.
The following examples are given to illustrate the invention and should not be construed to limit the scope of the present invention.
Example I
The process parameters for cutting tungsten carbide materials

(Table Removed)
Example II
The process parameters for cutting titanium aluminide material
(Table Removed)
Example III
The process parameters for cutting HSS and Nimonic materials
(Table Removed)1With the ECAAM machine, we could cut several difficult-to-cut materials like stainless steel, nickel alloys, titanium alloys, high speed tool steel and tungsten carbide.
Cutting rates obtained with this machine are 3-25 mm/min for SS, 3-5 mm/min for high speed tool steel, 1-2.5 mm/min for Titanium alloy, 3-5 mm/min for Nimonic and 0.5-2 mm/min for Tungsten carbide.
The main advantages of the present invention are : i. The electrochemically assisted arc machining (ECAAM) is very useful for
industrial applications, as conventional methods of cutting cannot be
employed for machining difficult to cut super alloy materials, ii. The ECAAM machine can be used for fast cutting of billets, rods and
sheets of metallic materials of various section, which are difficult-to-cut by
conventional methods, iii. The ECAAM machine can give higher productivity and it is not expensive.
It is cost effective, iv. The electrolyte employed in the ECAAM machine is environmentally
friendly, non-hazardous, non-polluting and safe-to-handle, v. The electrolyte used in the ECAAM machine is versatile, since it can be
used for cutting all the ferrous materials.





We claim:
1. A machine for electrochemically assisted arc machining which
comprises a machine tool essentially consisting of endless steel band
mounted on a vertical band drive having two end pulleys connected
to a prime mover, the said machine tool being mounted on an
electrically insulated frame capable of horizontal movement to
enable contact of steel band with a job to be machined, the said job
being mounted on a vice, which is mounted on an; electrically
insulated bed, the contact surface of the said steel band and the said
job being provided with electrolyte supply through means such as
one or more nozzles connected to an electrolyte tank through a
conventional chemical pump, the said steel band and said job being
electrically connected to negative and positive terminals respectively
of a DC power source.
2. A machine for electrochemically assisted arc machining as claimed
in claim 1 wherein the endless band used is steel band loop made by
joining the ends of a steel band by conventional methods.
3. A machine for electrochemically assisted arc machining as claimed
in claim 1 wherein the prime mover used is an electric motor.
4. A machine for electrochemically assisted arc machining as claimed
in claim 1 wherein the horizontal movement of the frame mounted
with machine tool is effected by an electric motor.
5. A machine for electrochemically assisted arc machining as claimed
in claim 1 wherein the horizontal bed is electrically insulated.
6. A machine for electrochemically assisted arc machining as claimed
in claim 1 wherein the electrolyte used is as described and claimed
hi our copending patent No: NF~-249/02.
7. A machine for electrochemically assisted arc machining as claimed
in claim 1 wherein the steel band is the cathode and job is the anode.
8. A machine for electrochemically assisted arc machining
substantially as herein described with reference to the examples and
drawings accompanying this specification.


Documents:

478-del-2002-abstract.pdf

478-del-2002-claims.pdf

478-del-2002-correspondence-others.pdf

478-del-2002-correspondence-po.pdf

478-del-2002-description (complete).pdf

478-del-2002-drawings.pdf

478-del-2002-form-1.pdf

478-del-2002-form-19.pdf

478-del-2002-form-2.pdf

478-del-2002-form-3.pdf


Patent Number 209238
Indian Patent Application Number 478/DEL/2002
PG Journal Number 41/2007
Publication Date 12-Oct-2007
Grant Date 23-Aug-2007
Date of Filing 22-Apr-2002
Name of Patentee COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH
Applicant Address RAFI MARG, NEW DELHI- 110001, INDIA.
Inventors:
# Inventor's Name Inventor's Address
1 KARAIKUDI SANKARANARAYANA RAJAM NATIONAL ACRORPARE LABORATORIES BANGLORE, INDIA
2 KAPPAM JAYARAM SANTHOSH KUMAR NATIONAL ACRORPARE LABORATORIES BANGLORE, INDIA
3 ANNAMALAI POURASSAMY. NATIONAL ACRORPARE LABORATORIES BANGLORE, INDIA
4 SUNDARAPANDIUM RAMA RAJAGOPALAN NATIONAL ACRORPARE LABORATORIES BANGLORE, INDIA
5 INDIRA RAJAGOPAL NATIONAL ACRORPARE LABORATORIES BANGLORE, INDIA
PCT International Classification Number B23P 21/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA