WO2021255721A1

WO2021255721A1 - Disc saw arrangement for electric discharge machining

Info

Publication number: WO2021255721A1
Application number: PCT/IL2021/050700
Authority: WO
Inventors: Gilad ORR; Gady Golan; Moshe Azoulay
Original assignee: Ariel Scientific Innovations Ltd.
Priority date: 2020-06-14
Filing date: 2021-06-10
Publication date: 2021-12-23

Abstract

An apparatus for electrochemical machining a metallic article comprises: (a) a linearly movable table carrying a metallic article to be machined; (b) an anode electrically connectable to said metallic article; (c) a machining tool positioned such that a gap between said machining tool and said metallic article effective for an electric discharge is formed; (d) means for providing an electrolyte flowing via said gap; and (e) a cathode being in an electric contact with said electrolyte. The machining tool comprises a rotatable dielectric disc having a conductive rim providing a low-resistant electric path within said gap to establish an electric current between said conductive rim and metallic article.

Description

DISC SAW ARRANGEMENT FOR EUECTRIC DISCHARGE MACHINING

FIEUD OF THE INVENTION

The present invention relates to electric discharge machining (EDM) and, more particularly, to disc saw arrangements usable as electrodes for EDM.

SUMMARY OF THE INVENTION

Analysis of known technologies of cutting crystals of soft metals indicates that the aforesaid technologies are associated with risk of damaging these crystals by free dissection. In addition, abrasive cutting, water jet cutting or EDM result in internal defects extending into the bulk of single crystal metals. In the case of a highly repetitive lattice usable for X-ray diffraction, damage to the bulk of the crystal reduces the intensity and broadens the peaks. The common practice for obtaining minimal damage of cut brittle and hard materials is use of a wire saw method including introducing into the cutting area a slurry as the cutting agent or a wire impregnated with fine diamonds with water-based solutions acting as a coolant (Hao Wu. Precision engineering , 43:1-9, 2016).

US 7306508 discloses a multi-wire saw cutting a workpiece while supplying a slurry containing an alkali or mixed acid to a cutting interface between the workpiece and a wire, and includes: a storage tank with a heating mechanism for storing and heating the slurry; a thermal insulating pipe for transporting the slurry sent with a pump from the storage tank with a heating mechanism to a position before a position where the wire is incorporated into the workpiece, while keeping the slurry at a predetermined temperature; a thermostat for keeping a temperature in a vicinity of the workpiece fixed to a stage at the predetermined temperature; and a wire heating mechanism for heating the wire to the predetermined temperature.

Wire cutting of soft metals using slurry suffers from the fact that the many of cutting particles which are considerably harder than the dissected metal get embedded into the metal surface, destroying the crystal lattice and introducing a foreign material.

A chemical etch cutting method using a string saw accurately drawing an acid or base solution over the cut (for example, John Kwadwo Boah, Metallurgical Transactions, 4(5): 1432-1433, 1973). While being successful, the aforesaid method is extremely slow and cannot be used for obtaining defect-free cut specimens. Another known in the art method (Herbert M Einbinder, Review of Scientific Instruments , 41(11): 1660— 1661, 1970; M Metzger, ibid., 29(7):620-621, 1958) of making defect-free cutting is based on electrical etching. Along with the advantage of speed, electrical etching in comparison with over the acid etching environmentally benign and nontoxic solutions.

It should be appreciated that wire and electrical etching methods are unreliable in service. Thus, there is a long-felt and unmet need to provide a reliable, simple-to-use and maintenance-friendly apparatus for electrochemical machining.

SUMMARY OF THE INVENTION

It is hence one object of the invention to disclose an apparatus for electrochemical machining a metallic article comprising: (a) a linearly movable table carrying a metallic article to be machined; (b) an anode electrically connectable to said metallic article; (v) a machining tool positioned such that a gap between said machining tool and said metallic article effective for an electric discharge is formed; (d) means for providing an electrolyte flowing via said gap; and (e) a cathode being in an electric contact with said electrolyte.

It is a core purpose of the invention to provide the machining tool comprising a rotatable dielectric disc having a conductive rim providing a low-resistant electric path within said gap to establish an electric current between said conductive rim and metallic article.

Another object of the invention is to disclose a process of electromachining a metal article comprising steps of: (a) providing an apparatus for electrochemical machining a metallic article further comprising: (i) a linearly movable table carrying a metallic article to be machined; (ii) an anode electrically connectable to said metallic article, (iii) a machining tool positioned such that a gap between said machining tool and said metallic article effective for an electric discharge is formed; (iv) means for providing an electrolyte flowing via said gap; and (v) a cathode being in an electric contact with said electrolyte; the machining tool comprises a conductive member circumferentially disposed at a rim of said dielectric disc; said conductive member providing a low- resistant electric path within said gap to establish an electric current between said conductive rim and metallic article; (b) securing said metal article to said linearly movable table; (c) flowing said electrolyte through said gap; (d) applying a DC voltage between said anode and cathode; (e) passing current through said conductive rim, metal article and electrolyte; and (f) moving said linearly movable table such that said metal article is electrically machined.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be implemented in practice, a plurality of embodiments is adapted to now be described, by way of non limiting example only, with reference to the accompanying drawings, in which

Fig. 1 is a schematic electric diagram of an apparatus for electrochemical machining a metallic article; and

Fig. is a schematic mechanical diagram of an apparatus for electrochemical machining a metallic article.

DETAILED DESCRIPTION OF THE INVENTION

The following description is provided, so as to enable any person skilled in the art to make use of said invention and sets forth the best modes contemplated by the inventor of carrying out this invention. Various modifications, however, are adapted to remain apparent to those skilled in the art, since the generic principles of the present invention have been defined specifically to provide an apparatus for electrochemical machining a metallic article and a method of doing the same.

Reference is now made to Fig. 1 presenting an electric schematic diagram of an electric machining device. Article 10 to be machined is mechanically secured to a linearly movable table (not shown). A machining tool constitutes disc 20 rotatable around axis 25. Disc 20 is made of a dialectic material and provided with conductive member 23 circumferentially disposed at a rim of said dielectric disc. A positive terminal of power supply 40 is connected to article 10 functioning as an anodic electrode. Negative terminal of power supply 40 is connected to metal plate 45 serving as a cathodic electrode. Numeral 35 refers to a trajectory of an electrolyte flow fed from pipe 30. Conductive member 23 is positioned such that a gap between conductive member 23 and metallic article 10 is effective for establishing electric discharge 27. Specifically, conductive member 23 provides a low-resistant electric path within the gap and initiates the electric discharge between conductive member 23 and location 15 to be machined of metallic article 10.

Reference is now made to Fig. 2 showing a mechanical diagram of an electric machining device. Article 10 to be machined is mechanically secured to linearly movable table 50 driven by a step motor drive (not shown). Numeral 55 refers to a direction of linear displacement of movable table 50 during the machining procedure. Disc 20 is rotated by electric motor 29 (for example, a step motor) via shaft (axis) 25.

It should be appreciated that after the specimen when dissected does not need for post-processing. A multi-cut system provided with several disks is also in the scope of the present invention. The conductive disks do not suffer from wire fatigue which results in wire breakage and early termination or failure of the cutting action.

Claims

Claims:

1. An apparatus for electrochemical machining a metallic article comprising: a. a linearly movable table carrying a metallic article to be machined; b. an anode electrically connectable to said metallic article; c. a machining tool positioned such that a gap between said machining tool and said metallic article effective for an electric discharge is formed; d. means for providing an electrolyte flowing via said gap; and e. a cathode being in an electric contact with said electrolyte; wherein said machining tool comprises a rotatable dielectric disc having a conductive member circumferentially disposed at a rim of said dielectric disc; said conductive member provides a low-resistant electric path within said gap to establish an electric discharge between said conductive member and metallic article.

2. A process of electromachining a metal article comprising steps of: a. providing an apparatus for electrochemical machining a metallic article further comprising: i. a linearly movable table carrying a metallic article to be machined; ii. an anode electrically connectable to said metallic article, iii. a machining tool positioned such that a gap between said machining tool and said metallic article effective for an electric discharge is formed; iv. means for providing an electrolyte flowing via said gap; and v. a cathode being in an electric contact with said electrolyte; vi. said machining tool comprises a rotatable dielectric disc having a conductive member circumferentially disposed at a rim of said dielectric disc; said conductive member providing a low-resistant electric path within said gap to establish an electric current between said conductive rim and metallic article. b. securing said metal article to said linearly movable table; c. flowing said electrolyte through said gap; d. applying a DC voltage between said anode and cathode; e. passing current through said conductive rim, metal article and electrolyte; and f. moving said linearly movable table such that said metal article is electrically machined.