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US3445372A - Apparatus for electrochemically removing the surface layer from a workpiece - Google Patents

Apparatus for electrochemically removing the surface layer from a workpiece Download PDF

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Publication number
US3445372A
US3445372A US513417A US3445372DA US3445372A US 3445372 A US3445372 A US 3445372A US 513417 A US513417 A US 513417A US 3445372D A US3445372D A US 3445372DA US 3445372 A US3445372 A US 3445372A
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United States
Prior art keywords
electrode
workpiece
electrolyte
deplating
metal
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Expired - Lifetime
Application number
US513417A
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English (en)
Inventor
Robert E Fromson
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CBS Corp
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Westinghouse Electric Corp
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Filing date
Publication date
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
    • B23H3/00—Electrochemical machining, i.e. removing metal by passing current between an electrode and a workpiece in the presence of an electrolyte
    • B23H3/04—Electrodes specially adapted therefor or their manufacture

Definitions

  • This invention relates generally to electrolytic methods and apparatus for removing a surface portion from a metal workpiece, and more particularly it pertains to electrochemical machining of metal.
  • Electrochemical removal of metal obviates those disadvantages; there are no problems of tool wear, burring, overheating, and distortion due to dimensional changes in a finished surface. Other problems, however, do occur with electrochemical machining for various reasons including relative motion between the electrode and the workpiece when operated in a rotational direction. For rotational applications the conventional procedures and electrodes have not proven satisfactory for obtaining surface finishes free of striations and for obtaining uniform stock removal from the surface of the workpiece.
  • Another problem has been the maintenance of electrolyte in the cutting gap between the electrode and the workpiece.
  • Still another problem has been the limitation of feed rates of electrode advance when qualifying, enlarging or reaming holes, such as in precision boring in a workpiece.
  • a plurality of workpieces are mounted on a rotatable worktable in spaced relation with respect to each other.
  • a cathodic electrode is positioned above the path of rotation of the workpieces and spaced therefrom by a distance which is a function of the current density which is used during operation of the apparatus.
  • the cross-section of the electrode is a truncated triangle or sector of a circle, i.e. it is tapered inwardly toward the center of rotation of the workpieces and electrode.
  • Means are provided for circulating an electrolyte between the electrode and each workpiece.
  • Means are also provided for passing an electric current through the electrolyte and between the cathodic electrode and the anodic workpieces as the table is rotated.
  • a circular electrode is provided with an inwardly tapered cutting surface which surface is inclined at an angle to the surface to be removed. This relationship also applies to external surfaces.
  • FIGURE 1 is a diagrammatic representation of one form of apparatus embodying the present invention which is effective for practicing the inventive method
  • FIG. 2 is an enlarged vertical sectional view taken on the line 11-11 of FIG. 1 and having a workpiece in place;
  • FIG. 3 is an enlarged horizontal sectional view taken on the line IIIIII of FIG. 1;
  • FIGS. 4 and 5 are perspective views of various alternate shapes of workpieces which may be used in practicing this invention.
  • FIG. 6 is an enlarged sectional view through adjacent areas of the electrode and workpiece
  • FIG. 7 is a vertical sectional view showing the manner in which an aperture is qualified.
  • FIG. 8 is a horizontal sectional view taken on the line VIII-VIII of FIG. 7.
  • the present invention may be practiced by providing apparatus for electrochemically removing a surface layer from a metal workpiece by a method comprising the steps of placing an anodic workpiece in position for movement in a circular path, positioning a cathodic electrode above the workpiece, moving one of the electrodes and the Workpiece with respect to each other, circulating an electrolyte between the electrode and the workpiece, and passing an electric current through the electrode and between the cathodic electrode and the anodic workpiece as one moves with respect to the other.
  • a device for electrochemically machining a metal surface is generally indicated at 1. It includes an electrode 2, a rotatable worktable 3, means for supporting the electrode and the worktable such as a rigid frame 4, a catch pan 5, means for circulating an electrolyte such as a pump 6 and conduit 7, and means for rotating the worktable including a motor 8 and a shaft 9. There are provided means such as -a source 10 of DC. power and lead wires 11 for passing a current through the electrode 2 and workpieces 12 as the latter move under the electrode 2.
  • the electrode 2 is disposed between a pair of insulating or dielectric elements 13 and 14 which are attached to and depend from the underside of an electrode mounting housing 15.
  • the electrode 2 is metallic and the elements 13 and 14 are of a suitable dielectric material such as a plasticfor instance a phenolic resin laminate.
  • the lower (working) end of the electrode 2 has the shape of a truncated triangle or a truncated sector of a circle with an outer edge 16 wider than an inner edge 17.
  • the electrode 2 also includes forward and hear sides 18 and 19 that extend between the outer and inner edges 16 and 17. The lower end of the sides 18 and 19 are located in planes passing through radii of the circle of rotation of the worktable 3.
  • the dielectric element 13 is preferably composed of plastic and has one side 21 abutting the forward side 18 of the electrode and has another side 22 remote from said forward side.
  • the element 13 is wedge shaped and the sides 21 and 22 converge toward the outer edge 16 of the electrode 2.
  • the side 22 is parallel to the rear side 19 of the electrode 2.
  • a lower end 23 of the element 13 (FIG. 2) is aligned with the lower end 20 of the electrode, whereby a rectangular surface area facing the workpiece is presented by the combined lower ends 20 and 23 of the electrode 2 and the dielectric element 13.
  • the element 14 is preferably rectangular in horizontal cross section and includes a side 24 which is spaced from the rear side 19 of the electrode 2.
  • the side 24 includes a flange 25 at each vertical edge, which flanges rfit snugly against the rear side '19 (FIG. 3) of the electrode.
  • a slot 26 is provided between the electrode 2 and the element 14 and between the flanges 25 which slot extends from the upper end of the electrode where it communicates with an aperture 27 in the underside of the housing 15.
  • the housing 15 is mounted on the lower end of a tube 28 that is attached to the upper portion of the frame 4.
  • the tube 28 is connected to the conduit 7. Accordingly, electrolyte is pumped through the conduit 7 and through the tube 28 into a. plenum chamber 29 of the housing 15. From there the electrolyte flows through the slot 27 as shown by arrows 30 to the lower end of the electrode 2 where it is directed through a clearance or gap 31 between the workpiece 12 and the lower ends 20 and 23 of the electrode 2 and the element 13.
  • a sealing wiper bar 32 is affixed to the lower end of the element which bar is composed of dielectric material and has a low coefficient of friction and suflicient resilence for sealing and wiping the surface of the workpiece.
  • the worktable 3 is mounted for rotation on the shaft 9 which is driven by the motor 8.
  • the worktable 3 is preferably composed of metal and is faced with a layer 40 of dielectric material.
  • the worktable 3 has a series of spaced workpiece rnounting means such as recesses 41 which are adapted to clamp the workpieces 12 in place.
  • the metal shaft 9 is connected to the lead wire "11 leading from the direct current power source or battery 10.
  • the worktable 3 and the shaft 9 provide an electrical conducting path to the lead wire 11.
  • the lead wire 11 leading from the direct current power source or battery 10.
  • the catch pan 5 is mounted on the frame 4 and includes a bottom wall 42 and a side wall 43 the upper end of which extends above the top of the table 3.
  • the purpose of the catch pan 5 is to collect electrolyte as it drains off of the periphery of the worktable 4 and return the electrolyte to the circulatory system through an electrolyte outlet 44 which communicates with the conduit 7 and the pump 6.
  • the workpieces 12 are electrochemically machined or deplated by rotating the worktable 3 while passing an electric current through the electrolyte in the gap 31 between the workpieces and the electrode.
  • the worktable 3 is rotated at a speed of from 0.5 to 50 inches per minute.
  • FIG. 1 shows a rotatable worktable with a workpiece mounted thereon, it is understood that the apparatus may be modified by holding the workpiece stationary and moving the electrode with respect thereto.
  • the pump 6 circulates the electrolyte downwardly through the conduit 6, the plenum chamber 29, and the slot 26 from where the electrolyte flows through the gap 31 between the lower end of the electrode and the workpiece.
  • the gap 31 may vary from 0.003 to 0.030 inch and preferably between 0.010 and 0.020 inch.
  • the electrolyte flows through the gap 31 in the direction of the arrows 30; that is, in the direction ahead of the relative movement of the electrode and the workpiece.
  • the wiper bar 32 prevents the electrolyte from flowing backwardly or under the element '14 and effecting post-etching of the deplated surface.
  • the electrolyte must flow at a predetermined rate that is dependent upon the type of metal involved. If the how rate is too slow, heat develops in the gap 31 which causes the electrolyte to boil. Gas bubbles are thereby created which create an insulated portion and cause sparking due to incurred voltage variations. On the other hand, if the electrolyte flows too fast a passive oxide film may be formed on the metal surface. Such film is insulating and greatly reduces or stops flow of electrical current.
  • the current density for performing the electrochemical machining may vary from to 8,000 amperes per square inch (a.s.i.) with the preferred range being from 500 to 1,500 a.s.i.
  • the current density being a function of the electrolyte conductivity and voltage and is inversely proportional to the spacing or gap between the electrode and the workpiece so that the greater the spacing the lower the current density at a given voltage.
  • the current density is a function of the gap dimensions.
  • the pressure of the electrolyte as it enters the gap 31 may be as high as about 500 p.s.i. and the preferred pressure is from 40 to 50 p.s.i. Moreover, the pressure must be maintained at a relatively constant high level to provide a highly reflective metallic finish free of striations.
  • a top layer 45 is removed by deplating to provide a finished surface 46. The deplating commences at the forward corner 47 and continues as long as the lower end 20 of the electrode is located over any area of the workpiece. In other words, deplating occurs primarily within the gap 31. Deplating also occurs in the zones just ahead of and behind the electrode, because the electrolyte in those zones provides a path for the current, though at a lower density.
  • sufiicient pressure must be maintained on the electrolyte to not only sustain a continuous flow but to maintain the pressure of from 40 to 500 p.s.i. at the rear corner.
  • the electrolyte must flow ahead of the electrode or toward the workpiece surface to be deplated.
  • Equal electrolyte pressure from one edge 16 to the other edge 17 is maintained by the wedge shaped end 23 of the element 13 which together with the undersurface 20 of the electrode 2 provide a gap 31 or restrictive passage of equal length for the electrolyte. Thus striations are avoided.
  • the electrolyte is preferably an aqueous solution of a neutral salt, such as sodium chloride (NaCl) or potassium nitrate (KNO which may have a specific gravity of about 1.08 when one pound of salt is mixed for each gallon of water.
  • a neutral salt such as sodium chloride (NaCl) or potassium nitrate (KNO which may have a specific gravity of about 1.08 when one pound of salt is mixed for each gallon of water.
  • the surface of the workpiece is deplated.
  • a hydroxide of the removed metal is formed and carried away by the electrolyte which is unafiected by the presence of the hydroxide until the viscosity of the electrolyte is high enough to reduce its flow.
  • the electrolyte may be replaced in whole or in part or filtered to remove the hydroxide which is of a fine suspension or gelatinous nature.
  • the electrode 2 is composed of metal such as copper.
  • the electrode For rotational machining the electrode has a configuration of a truncated triangle or sector of a circle, the sides of which diverge on spaced radii of the path of rotation of the workpiece. The angular velocity of any point in the workpiece increases proportionally with the distance of the point from the center of rotation.
  • all areas of the workpiece are subjected to equal time exposure to the electrode by providing an electrode having the described configuration, i.e. a truncated triangle or sector of a circle.
  • the thickness of the surface layer removed varies with the speed of rotation and the current density and can be appropriately adjusted to meet production requirements.
  • a single or multiple electrode may be used.
  • the amount of surface metal removed is proportional to the width of the electrode.
  • the workpiece 12 is shown as having the shape of a truncated sector of a circle or truncated triangle, the workpiece may have any shape, such as workpieces 48 and 49 in FIGS. 4 and 5.
  • the lower end 20 of the electrode 2 is shown as being parallel to the upper surface of the workpiece 12.
  • the electrode may advance at any speed (feed rate) and deplate a surface layer having a thickness which is a function of the width of the electrode and of the current density.
  • the lower end or face of the electrode may be inclined at an angle to the horizontal plane (FIG. 6).
  • a surface layer 50 is deplated to a greater depth as the electrode 51 advances in the direction of the arrow 52 and/or the workpiece 12 moves in the direction of the arrow 53.
  • the principle of the inclined angle of the face or lower end of the electrode is applicable not only to electrochemical machining where the relative movement between the electrode and workpiece surface is rotational, but it is also applicable to linear movement. It is applicable to metal removal both from plane or contoured surfaces as well as plunge type machining such as qualifying a hole in a metal plate.
  • a hole 61 in a metal plate 62 may be reamed by an electrode 63 at the lower end of a shaft 64.
  • the electrode 63 has the shape of a truncated cone with a peripheral surface 65 inclined downwardly and inwardly at an angle to the vertical axis.
  • the hole 61 may be round or any other shape, but for such a hole the electrode must have an appropriate configuration.
  • a forward portion or toe 66 of the electrode 63 is maintained outside of the deplating zone 67 between the original bore surface 61 and the finished surface 68.
  • the heel or rear portion 69 of the electrode 63 is maintained in a zone between the finished and original surfaces, whereby an inclined surface 70 is formed during deplating which advances from the upper to the lower sides of the plate 62 as viewed in FIG. 7.
  • a shield 74 is mounted around the shaft 64 and over the bore 61 to retain the proper electrolyte pressure within the gap 73. Seals 75 and 76 are provided on the shield 74 where it contacts the shaft 64 and plate 62.
  • the method and apparatus of the present invention provides for the electrochemical removal or deplating of a metal surface without the disadvantages frequently incurred in mechanical machining such as face cutting on a lathe, grinding and the like where tool wear requires resharpening from time to time and the workpiece is frequently overheated which results in a change of metallurgical structure of the workpiece near the removed surface.
  • each metal has a penetration rate at a given current density that could not be exceeded by prior known methods, the apparatus and methods of this invention permit greater machining or deplating speeds while obtaining removal of metal layers of specified thickness.
  • Apparatus for electrochemically removing a surface layer from a metal workpiece to provide a finished surface comprising means for holding a workpiece, means for moving one of the electrodes and workpiece relative to the other, a cathodic electrode mounted above the workpiece and having a deplating surface with forward and rear edges with respect to the direction of relative movement, the electrode also having forward and rear side surfaces extending upwardly from the forward and rear edges, a first imperforate dielectric element mounted in spaced relation to the rear side surface and forming therewith slot means for delivering an electrolyte at the rear edge of the deplating surface, sealing means at the lower end of the first dielectric element engageable with the surface of a workpiece and for directing the electrolyte in the direction of movement bewteen the deplating surface and workpiece, and means for passing an electric current through the electrolyte and between the cathodic electrode and the anodic workpiece, whereby the electrolyte flows only forwardly with the sealing means preventing the electrolyte from flowing
  • a second dielectric element is mounted on the forward side surface of the electrode and having a lower end surface in substantial alignment with the deplating surface, the lower end surface having one edge adjacent to the forward edge of the deplating surface, and the lower end surface also having another edge remote from said forward edge and substantially parallel to the rear edge of the deplating surface, whereby a clearance space between the workpiece and the surface including the aligned deplating surface and the lower end surface of the second dielectric element provides a restrictive passage of equal length for the electrolyte between the rear edge of the deplating surface and said other edge of the second dielectric element.
  • a second dielectric element is mounted on the forward side surface of the electrode and having a lower end surface in substantial alignment with the deplating surface and the second dielectric element having a lower edge remote from said forward edge and substantially equally distant UNITED STATES PATENTS 3,102,090 8/1963 Bassr 204-217 3,243,365 3/ 1966 Aikin 204290 3,255,097 6/1966 Williams 204143 3,287,245 11/1966 Williams 204224 3,293,162 12/1966 Sullivan 204-4405 3,324,021 6/1967 Haggerty 204224 ROBERT K. MIHALEK, Primary Examiner.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Mechanical Engineering (AREA)
  • Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
US513417A 1965-12-13 1965-12-13 Apparatus for electrochemically removing the surface layer from a workpiece Expired - Lifetime US3445372A (en)

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Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3514390A (en) * 1965-11-16 1970-05-26 Siemens Ag Electrode device for electrochemical forming of unobstructed recesses in metallic workpieces
US3627664A (en) * 1967-09-06 1971-12-14 Centro Speriment Metallurg Apparatus for electrochemically treating and testing surface areas
US3910832A (en) * 1970-08-27 1975-10-07 Secr Defence Brit Tool for drilling cooling passages in turbine blades
US3928154A (en) * 1973-04-12 1975-12-23 Trw Inc Electrochemical radius generation
US3933615A (en) * 1969-06-09 1976-01-20 The United States Of America As Represented By The Secretary Of The Air Force Fluid flow stripping and plating system
US4046662A (en) * 1974-11-06 1977-09-06 Rolls-Royce (1971) Limited Electro-chemical machine tools
US4098664A (en) * 1977-07-25 1978-07-04 Butler Richard E Rotating vertical plating table
US4541909A (en) * 1984-07-20 1985-09-17 Westinghouse Electric Corp. Controlled metal removal by parallel-to-face electrochemical machining
US4752366A (en) * 1985-11-12 1988-06-21 Ex-Cell-O Corporation Partially conductive cathode for electrochemical machining
US5071525A (en) * 1989-07-06 1991-12-10 Olympus Optical Co. Ltd. Method of grinding lenses and apparatus therefor
US20150273603A1 (en) * 2012-11-08 2015-10-01 Hoden Seimitsu Kako Kenkyusho Co., Ltd. Electrode, electrochemical machining apparatus using the electrode, electrochemical machining method, and product machined by the method

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3102090A (en) * 1960-08-11 1963-08-27 Ct Informazioni Studi Esperien System and universal apparatus for the complete preparing of metallographic samples
US3243365A (en) * 1962-05-07 1966-03-29 Ex Cell O Corp Elecrode for electrolytic hole drilling
US3255097A (en) * 1962-06-12 1966-06-07 Anocut Eng Co Method and apparatus for clarifying electrolyte
US3287245A (en) * 1961-06-19 1966-11-22 Anocut Eng Co Method and apparatus for use in electrolytic machining
US3293162A (en) * 1964-06-30 1966-12-20 Bell Telephone Labor Inc Process for electropolishing both sides of a semiconductor simultaneously
US3324021A (en) * 1962-10-23 1967-06-06 Cincinnati Milling Machine Co Electrochemical machining apparatus and tool therefor

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3102090A (en) * 1960-08-11 1963-08-27 Ct Informazioni Studi Esperien System and universal apparatus for the complete preparing of metallographic samples
US3287245A (en) * 1961-06-19 1966-11-22 Anocut Eng Co Method and apparatus for use in electrolytic machining
US3243365A (en) * 1962-05-07 1966-03-29 Ex Cell O Corp Elecrode for electrolytic hole drilling
US3255097A (en) * 1962-06-12 1966-06-07 Anocut Eng Co Method and apparatus for clarifying electrolyte
US3324021A (en) * 1962-10-23 1967-06-06 Cincinnati Milling Machine Co Electrochemical machining apparatus and tool therefor
US3293162A (en) * 1964-06-30 1966-12-20 Bell Telephone Labor Inc Process for electropolishing both sides of a semiconductor simultaneously

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3514390A (en) * 1965-11-16 1970-05-26 Siemens Ag Electrode device for electrochemical forming of unobstructed recesses in metallic workpieces
US3627664A (en) * 1967-09-06 1971-12-14 Centro Speriment Metallurg Apparatus for electrochemically treating and testing surface areas
US3933615A (en) * 1969-06-09 1976-01-20 The United States Of America As Represented By The Secretary Of The Air Force Fluid flow stripping and plating system
US3910832A (en) * 1970-08-27 1975-10-07 Secr Defence Brit Tool for drilling cooling passages in turbine blades
US3928154A (en) * 1973-04-12 1975-12-23 Trw Inc Electrochemical radius generation
US4046662A (en) * 1974-11-06 1977-09-06 Rolls-Royce (1971) Limited Electro-chemical machine tools
US4098664A (en) * 1977-07-25 1978-07-04 Butler Richard E Rotating vertical plating table
US4541909A (en) * 1984-07-20 1985-09-17 Westinghouse Electric Corp. Controlled metal removal by parallel-to-face electrochemical machining
US4752366A (en) * 1985-11-12 1988-06-21 Ex-Cell-O Corporation Partially conductive cathode for electrochemical machining
US5071525A (en) * 1989-07-06 1991-12-10 Olympus Optical Co. Ltd. Method of grinding lenses and apparatus therefor
US20150273603A1 (en) * 2012-11-08 2015-10-01 Hoden Seimitsu Kako Kenkyusho Co., Ltd. Electrode, electrochemical machining apparatus using the electrode, electrochemical machining method, and product machined by the method
US10369646B2 (en) * 2012-11-08 2019-08-06 Hoden Seimitsu Kako Kenkyusho Co., Ltd. Electrode, electrochemical machining apparatus using the electrode, electrochemical machining method, and product machined by the method

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DE1565934A1 (de) 1970-06-18
CH468239A (de) 1969-02-15

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