US3285844A - Electrolytic hole forming cathode electrode - Google Patents

Electrolytic hole forming cathode electrode Download PDF

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Publication number
US3285844A
US3285844A US238387A US23838762A US3285844A US 3285844 A US3285844 A US 3285844A US 238387 A US238387 A US 238387A US 23838762 A US23838762 A US 23838762A US 3285844 A US3285844 A US 3285844A
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Prior art keywords
coating
electrode
working tip
cathode electrode
insulating coating
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Expired - Lifetime
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US238387A
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Hallsworth Raymond Thomas
Holroyd Irvin
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Rolls Royce PLC
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Rolls Royce PLC
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Priority claimed from GB2025961A external-priority patent/GB974338A/en
Application filed by Rolls Royce PLC filed Critical Rolls Royce PLC
Priority to US238387A priority Critical patent/US3285844A/en
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Publication of US3285844A publication Critical patent/US3285844A/en
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Expired - Lifetime legal-status Critical Current

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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
    • 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
    • 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
    • B23H9/00—Machining specially adapted for treating particular metal objects or for obtaining special effects or results on metal objects
    • B23H9/14—Making holes
    • B23H9/16—Making holes using an electrolytic jet

Definitions

  • the cathode electrode used to form the hole preferably has an external insulating coating to prevent sideways cutting by the electrode.
  • electrolyte may be supplied through a pasage in the electrode, the electrolyte escaping through a gap between the external surface of the insulating coating and the internal surface of the hole being formed.
  • This gap may be very small, and any pores in the insulating coating will permit sideways cutting by the electrode, the amount of such cutting depending in part on the size of said gap. It is therefore very important that the insulating coating should be as non-porous as possible, and preferably completely non-porous.
  • the pressure and rate of flow of the electrolyte in said gap may be very high, so that the insulating coating must be sufiiciently strong to withstand the resulting physical forces acting on it.
  • a common fault with such electrodes is peeling or separation of the insulating coating adjacent the uninsulated working tip of the electrode. This can be avoided by using a strong durable material for the insulating coating.
  • insulating materials which are strong and durable are generally rather porous, whereas highly non-porous insulating materials are generally not particularly durable and strong. It should be understood that where small holes are to be formed, the maximum thickness of the insulating coating is limited.
  • Such coating may for example comprise a composite coating of plastisol on plastisol primer bonded to the external surface of the electrode.
  • Another object of the invention is to provide an electrode with a first strong durable insulating coating adjacent the working tip of the electrode, and a second highly non-porous insulating coating made of different material from the first coating, the second coating forming a rearward continuation of the first coating.
  • Another object of the invention is to provide an electrode with a forward outwardly projecting flange from whose rearward face the insulating coating extends rearwardly, the insulating coating immediately adjacent said flange having the same transverse external dimensions as the flange, so that the flange affords some protection for the insulating coating.
  • the electrode has a circular transverse cross-section "ice and comprises a hollow stem 81 made of stainless steel.
  • the stem has an annular groove 82, and terminates in an enlarged flange 83 forming an uninsulatedworking tip.
  • a coating 84 of the phenolic epoxy resin Araldite (which is a very strong adhesive) is located in the groove 82, and the stem 81 is provided with a composite coating of plastisol primer 85 and plastisol '86, the layers of which partially extend over the coating 84.
  • the axial length of the uninsulated rim of the working tip 83 is kept as short as possible in order to reduce sideways cutting by the electrode.
  • a satisfactory method of coating the electrode with the plastisol primer and plastisol, i.e. after the coating 84 has been formed on the electrode, is as follows:
  • the ends of the electrode are sealed, and the electrode is degreased.
  • the electrode is then etched, using a solution of 10% Fe(NO 9.H O in concentrated HCl, for 1 /2 minutes at a temperature of 60 C. The etching leaves a black layer on the electrode, which is brushed off and the electrode is washed thoroughly and dried in an oven at C. for about 15 minutes.
  • the electrode is then coated with plastisol primer 219P.X. by partially suspending the electrode in a vessel containing the primer, and then draining the primer from the bottom of the vessel. In order to cure the primer, the electrode is air dried for 20 minutes, and is then further dried at a temperature of C. for 20 minutes.
  • the electrode is then coated with plastisol 218 by slowly withdrawing the electrode from a tank containing the plastisol and in which the electrode is initially partially immersed. The rate of withdrawal of the electrode to obtain the desired uniformity and thickness of the coating, depends on the length and diameter of the electrode.
  • the electrode is then placed in an evacuated chamber in order to remove bubbles in the plastisol coating, and the plastisol is then cured at C. for one hour. In this way a good bond is formed between the plastisol 86, the primer 85 and the coating 84.
  • the finished electrode should be inspected to ensure that the thickness of the composite coating is 0.003 to 0.004", and is free from lumps and does not taper by more than 0.002" from end to end.
  • the coating is then checked for porosity by immersing the electrode and a metal plate in a solution of saturated brine and making the electrode 25 volts negative relative to the metal plate. The presence of even a very small pore in the coating is revealed by a stream of gas bubbles. An optical inspection is also carried out to detect any other imperfections e.g. dust particles in the coating, which may be likely to cause failure during operation.
  • An electrode for use as a cathode electrode in apparauts for forming holes electrolytically in a metallic anode workpiece comprising a hollow elongate metallic member having an uninsulated forward working tip, an intermediate portion adjacent said Working tip, and a rear portion, the intermediate portion having a first external insulating coating extending rearwardly from said working tip, and said rear portion having a second. external insulating coating forming a continuation of said first coating, said second coating comprising a non-porous composite coating of polyvinylchloride bonded to the external surface of said rear portion, and said first coating being made of strong, durable epoxy resin material.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)

Description

Nov. 15, 1966 R. T. HALLSWORTH ETAL 3,235,844
ELECTROLYTIC HOLE FORMING CATHODE ELECTRODE Original Filed May 31, 1962 Attorneys United States Patent 3,285,844 ELECTROLYTIC HOLE FORMING CATHODE ELECTRODE Raymond Thomas Hallsworth, Earby, and Irvin Holroyd,
Barnoldswick, England, assignors to Rolls-Royce Limited, Derby, Derbyshire, England, a company of Great Britain Original application May 31, 1962, Ser. No. 199,092. Divided and this application Nov. 19, 1962, Ser. No. 238,387 Claims priority, application Great Britain, June 5, 1961, 20,259/ 61 3 Claims. (Cl. 204284) This application relates to an electrode for use as a cathode electrode in apparatus for forming holes electrolytically in a metallic anode workpiece, and is a divisional application from our patent application Serial No. 199,092 filed May 31, 1962, now abandoned.
Where it is desired to form holes of accurate dimensions by an electrolytic process, the cathode electrode used to form the hole preferably has an external insulating coating to prevent sideways cutting by the electrode. With such an electrode, electrolyte may be supplied through a pasage in the electrode, the electrolyte escaping through a gap between the external surface of the insulating coating and the internal surface of the hole being formed. This gap may be very small, and any pores in the insulating coating will permit sideways cutting by the electrode, the amount of such cutting depending in part on the size of said gap. It is therefore very important that the insulating coating should be as non-porous as possible, and preferably completely non-porous. Furthermore the pressure and rate of flow of the electrolyte in said gap may be very high, so that the insulating coating must be sufiiciently strong to withstand the resulting physical forces acting on it. A common fault with such electrodes is peeling or separation of the insulating coating adjacent the uninsulated working tip of the electrode. This can be avoided by using a strong durable material for the insulating coating. Unfortunately, however, insulating materials which are strong and durable are generally rather porous, whereas highly non-porous insulating materials are generally not particularly durable and strong. It should be understood that where small holes are to be formed, the maximum thickness of the insulating coating is limited.
It is one object of the invention to provide an electrode having a non-porous polyvinylchloride insulating coating. Such coating may for example comprise a composite coating of plastisol on plastisol primer bonded to the external surface of the electrode.
Another object of the invention is to provide an electrode with a first strong durable insulating coating adjacent the working tip of the electrode, and a second highly non-porous insulating coating made of different material from the first coating, the second coating forming a rearward continuation of the first coating.
Another object of the invention is to provide an electrode with a forward outwardly projecting flange from whose rearward face the insulating coating extends rearwardly, the insulating coating immediately adjacent said flange having the same transverse external dimensions as the flange, so that the flange affords some protection for the insulating coating.
' These and other objects of the invention will be apparent from the following description of a preferred embodiment of the invention, given by way of example, and shown in the accompanying drawing which is a transverse cross-sectional view of an electrode according to the in" vention.
The electrode has a circular transverse cross-section "ice and comprises a hollow stem 81 made of stainless steel. The stem has an annular groove 82, and terminates in an enlarged flange 83 forming an uninsulatedworking tip. A coating 84 of the phenolic epoxy resin Araldite (which is a very strong adhesive) is located in the groove 82, and the stem 81 is provided with a composite coating of plastisol primer 85 and plastisol '86, the layers of which partially extend over the coating 84. The axial length of the uninsulated rim of the working tip 83 is kept as short as possible in order to reduce sideways cutting by the electrode.
A satisfactory method of coating the electrode with the plastisol primer and plastisol, i.e. after the coating 84 has been formed on the electrode, is as follows:
Firstly, the ends of the electrode are sealed, and the electrode is degreased. The electrode is then etched, using a solution of 10% Fe(NO 9.H O in concentrated HCl, for 1 /2 minutes at a temperature of 60 C. The etching leaves a black layer on the electrode, which is brushed off and the electrode is washed thoroughly and dried in an oven at C. for about 15 minutes. The electrode is then coated with plastisol primer 219P.X. by partially suspending the electrode in a vessel containing the primer, and then draining the primer from the bottom of the vessel. In order to cure the primer, the electrode is air dried for 20 minutes, and is then further dried at a temperature of C. for 20 minutes. In this way a good bond is formed between the primer 85, the coating 84 and the stem 81. The electrode is then coated with plastisol 218 by slowly withdrawing the electrode from a tank containing the plastisol and in which the electrode is initially partially immersed. The rate of withdrawal of the electrode to obtain the desired uniformity and thickness of the coating, depends on the length and diameter of the electrode. The electrode is then placed in an evacuated chamber in order to remove bubbles in the plastisol coating, and the plastisol is then cured at C. for one hour. In this way a good bond is formed between the plastisol 86, the primer 85 and the coating 84.
The finished electrode should be inspected to ensure that the thickness of the composite coating is 0.003 to 0.004", and is free from lumps and does not taper by more than 0.002" from end to end. The coating is then checked for porosity by immersing the electrode and a metal plate in a solution of saturated brine and making the electrode 25 volts negative relative to the metal plate. The presence of even a very small pore in the coating is revealed by a stream of gas bubbles. An optical inspection is also carried out to detect any other imperfections e.g. dust particles in the coating, which may be likely to cause failure during operation.
We claim:
1. An electrode for use as a cathode electrode in apparauts for forming holes electrolytically in a metallic anode workpiece, comprising a hollow elongate metallic member having an uninsulated forward working tip, an intermediate portion adjacent said Working tip, and a rear portion, the intermediate portion having a first external insulating coating extending rearwardly from said working tip, and said rear portion having a second. external insulating coating forming a continuation of said first coating, said second coating comprising a non-porous composite coating of polyvinylchloride bonded to the external surface of said rear portion, and said first coating being made of strong, durable epoxy resin material.
2. An electrode as claimed in claim 1 in which both the rear portion and the intermediate portion have smaller external transverse dimensions than the working tip and the external transverse dimensions of the first coating at the forward end thereof are the same as those of the working tip.
References Cited by the Examiner UNITED STATES PATENTS 2/1964 Williams 204224 7/1965 Williams 204-143 JOHN H. MACK, Primary Examiner.
D. R. JORDAN, Assistant Examiner.

Claims (1)

1. AN ELECTRODE FOR USE AS A CATHODE ELECTRODE IN APPARATUS FOR FORMING HOLES ELECTROLYTICALLY IN A METALLIC ANODE WORKPIECE, COMPRISING A HOLLOW ELONGATE METALLIC MEMBER HAVING AN UNINSULATED FORWARD WORKING TIP, AN INTERMEDIATE PORTION ADJACENT SAID WORKING TIP, AND A REAR PORTION, THE INTERMEDIATE PORTION HAVING A FIRST EXTERNAL INSULATING COATING EXTENDING REARWARDLY FROM SAID WORKING TIP, AND SAID REAR PORTION HAVING A SECOND EXTERNAL INSULATING COATING FORMING A CONTINUATION OF SAID FIRST COATING, SAID SECOND COATING COMPRISING A NON-POROUS COMPOSITE COATING OF POLYVINYLCHLORIDE BONDED TO THE EXTERNAL SURFACE OF SAID REAR PORTION, AND SAID FIRST COATING BEING MADE OF STRONG, DURABLE EPOXY RESIN MATERIAL.
US238387A 1961-06-05 1962-11-19 Electrolytic hole forming cathode electrode Expired - Lifetime US3285844A (en)

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Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB2025961A GB974338A (en) 1961-06-05 1961-06-05 Apparatus suitable for forming holes electrolytically in a metallic workpiece
US19909262A 1962-05-31 1962-05-31
US238387A US3285844A (en) 1961-06-05 1962-11-19 Electrolytic hole forming cathode electrode

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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3436331A (en) * 1965-09-03 1969-04-01 Heppenstall Co Electro-chemical machining electrode
US3547798A (en) * 1967-03-29 1970-12-15 Cincinnati Milacron Inc Electrochemical machining tool
US3547797A (en) * 1967-03-29 1970-12-15 Cincinnati Milacron Inc Apparatus for simultaneously electrochemically machining a plurality of previously formed surfaces of a workpiece
US3857776A (en) * 1973-06-14 1974-12-31 Electro Petroleum Deep submersible power electrode assembly for ground conduction of electricity
US3880745A (en) * 1974-03-28 1975-04-29 United Aircraft Corp Helically fluted deep hole cathode and method of making same
US4394238A (en) * 1979-04-07 1983-07-19 Kernforschungsanlage Julich Gmbh Method of making a measuring electrode assembly and electrode made thereby
US4696103A (en) * 1986-12-04 1987-09-29 The United States Of America As Represented By The Secretary Of The Army Method of making a rotating disk electrode
DE19854793A1 (en) * 1998-11-27 2000-06-08 Univ Stuttgart Inst Fuer Ferti Electrodes for electrochemical machining of metallic part, have metal body coated with ceramic or polymer
CN110170713A (en) * 2019-05-10 2019-08-27 中国航发南方工业有限公司 Radial diffuser inter-leaf flow channel forming and machining method
EP3766618A1 (en) * 2019-07-19 2021-01-20 MTU Aero Engines GmbH Cathode for electrochemical machining with optimized flow parameters

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3120482A (en) * 1959-11-16 1964-02-04 Anocut Eng Co Apparatus for electrolytic hole sinking
US3196093A (en) * 1960-06-13 1965-07-20 Anocut Eng Co Electrolytic cavity sinking apparatus and method for non-parallel workpiece surfaces

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3120482A (en) * 1959-11-16 1964-02-04 Anocut Eng Co Apparatus for electrolytic hole sinking
US3196093A (en) * 1960-06-13 1965-07-20 Anocut Eng Co Electrolytic cavity sinking apparatus and method for non-parallel workpiece surfaces

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3436331A (en) * 1965-09-03 1969-04-01 Heppenstall Co Electro-chemical machining electrode
US3547798A (en) * 1967-03-29 1970-12-15 Cincinnati Milacron Inc Electrochemical machining tool
US3547797A (en) * 1967-03-29 1970-12-15 Cincinnati Milacron Inc Apparatus for simultaneously electrochemically machining a plurality of previously formed surfaces of a workpiece
US3857776A (en) * 1973-06-14 1974-12-31 Electro Petroleum Deep submersible power electrode assembly for ground conduction of electricity
US3880745A (en) * 1974-03-28 1975-04-29 United Aircraft Corp Helically fluted deep hole cathode and method of making same
US4394238A (en) * 1979-04-07 1983-07-19 Kernforschungsanlage Julich Gmbh Method of making a measuring electrode assembly and electrode made thereby
US4696103A (en) * 1986-12-04 1987-09-29 The United States Of America As Represented By The Secretary Of The Army Method of making a rotating disk electrode
DE19854793A1 (en) * 1998-11-27 2000-06-08 Univ Stuttgart Inst Fuer Ferti Electrodes for electrochemical machining of metallic part, have metal body coated with ceramic or polymer
DE19854793B4 (en) * 1998-11-27 2004-04-01 Universität Stuttgart Institut für Fertigungstechnologie keramischer Bauteile Electrode for the electrochemical processing of a metallic workpiece and method for producing such
CN110170713A (en) * 2019-05-10 2019-08-27 中国航发南方工业有限公司 Radial diffuser inter-leaf flow channel forming and machining method
EP3766618A1 (en) * 2019-07-19 2021-01-20 MTU Aero Engines GmbH Cathode for electrochemical machining with optimized flow parameters

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