US3444069A - Electrolytic shaping apparatus - Google Patents

Description

y 13, 1939 L. A. WILLIAMS 3,444,069

ELECTROLYTIC SHAPING APPARATUS Original Filed Nov. 10, 1958 Sheet of 5 P0 WE? IN VEN TOR.

y 1969 L. A. WILLIAMS 3,444,069

ELECTROLYT I C SHAPING APPARATUS Original Filed Nov. 10, 1958 Sheet 3 of s CONTEOA flMPt #751 INVENTOR.

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May 13, 1969 l L. A. WILLIAMS 3,444,069 v ELECTRQLYT I C SHAP ING APPARATUS Original Filed Nov. 10, 1958 Sheet 31 of s IN V EN TOR.

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Maia l n 3,444,069 ELECTROLYTIC SHAPING APPARATUS Lynn A. Williams, Winnetka, Ill., assignor to Anocut Engineering Company, Chicago, L, a corporation of Illinois Application Dec. 8, 1961, Ser. No. 158,042, which is a division of application Ser. No. 772,960, Nov. 10, 1958, now Patent No. 3,058,895, dated Oct. 16, 1962. Divided and this application July 25, 1966, Ser. No. 567,556 Int. Cl. B23p N14 US. Cl. 204-224 Claims This application is a division of my application Ser. No. 158,042, filed Dec. 8, 1961, now US. Patent 3,276,987, entitled Electrolytic Shaping Apparatus, which in turn is a division of my application Ser. No. 772,960, filed Nov. 10, 1958, entitled Electrolytic Shaping, now issued into Patent No. 3,058,895, dated Oct. 16, 1962.

It has long been known that metal and metalloid materials may be removed by electrolytic attack in a configuration where the metal or metalloid workpiece is the anode in an electrolytic cell. This principle has been used industrially to some degree for the removal of defective plating and the like, and is sometimes referred to as stripping." It has also been used to some extent for electrolytic polishing in which application, however, the principal purpose is to produce a smooth finish with a minimum removal of the work material. Here the purpose is to remove substantial amounts of metal rapidly and with accuracy.

In the present instance, the term metalloid is used somewhat specially in referring to those electrically conductive materials which act like metals when connected as an anode in an electrolytic cell, and are capable of being electrochemically eroded. The term as used here and in the claims includes metals and such similarly acting materials as tungsten carbide, for instance, and distinguished from such conductive nonmetalloids as carbon.

George F. Keeleric has proposed in his Patent No. 2,826,540, issued Mar. 11, 1958, for Method and Apparatus for Electrolytic Cutting, Shaping and Grinding the use of electrolysis in conjunction with a metal bonded, abrasive bearing, moving electrode, and the method and apparatus of this Keeleric patent have found extensive industrial use.

The present invention departs from the teachings of Keeleric in utilizing relatively fixed or slow moving electrodes without abrasive, and is intended for work of a quite different character, as will appear in the detailed description of the invention which follows.

In general, in the present invention an electrode, quite frequently a hollow electrode, is advanced into the work material by mechanical means while electrolyte is pumped through the work gap between the electrode and the work, and at times the hollow portion of the electrode, under substantial pressure. In some circumstances the side walls of the electrode are protected by an insulating material so as to minimize removal of work material except where desired. Various forms of electrodes are used for different kinds of work, and likewise different techniques of advancing the electrode toward and into the work material are used, depending upon the nature of the operation to be performed. An important aspect of the invention lies in providing electrodes in which a flow of electrolyte between the electrode and the work is maintained at high velocity and across a short path between the point of entry and the area of exit regardless of the overall size of the electrode. An electric current is supplied so that current passes from the electrode, which is negative, through the electrolyte to the workpiece, which is positive. For purposes of shaping the electrodes, direct current may be passed in the opposite sense to make the electrode posiatent C tive. In some instances, alternating current may be used.

Among the objects of the invention are the following:

To provide novel apparatus for rapid removal of work material by electrolytic means;

To provide automatic means for advancing electrodes toward and into the work material;

To provide novel mechanism for accomplishing variable feed rates for advancing electrodes toward and into work material for electrolytic removal thereof.

Other objects and advantages will become apparent from the following description taken in conjunction with the accompanying drawings, wherein FIG. 1 is a perspective view of one form of electrolytic shaping apparatus embodying the present invention;

FIG. 2 is a diagrammatic representation of an electrolytesupply system which forms a portion of the apparatus of FIG. 1;

FIG. 3 is a diagrammatic representation of apparatus embodying the present invention, showing one control mechanism therefor including an arrangement for controlling the speed of advance of the electrode;

FIG. 4 is a circuit diagram of a portion of the control system of the apparatus of FIG. 3;

FIG. 5 is a diagrammatic representation of the apparatus of the general character of FIG. 3, but showing an alternative control arrangement therefor; and

FIG. 6 is a diagram of a portion of the apparatus of FIG. 5.

Referring to FIG. 1, the apparatus of this invention includes a frame member 1 which in this instance is the frame member of a conventional and well known arbor press sold under the trade name of Famco. It includes a base section 3, a column 5, and a head 7 which is adapted in the conventional manner to accommodate a ram 9 for vertical reciprocating motion. The detail of the ram mounting is not important to this invention, but it is desirable to provide adjustable gibs or the equivalent in the head so that the ram may move vertically with a smooth action and without lateral play which might introduce undesired side motion. To the bottom end of the ram 9 there is mounted a workplate 11, made of an electrically insulating material which is resistant to the corrosive effect of the electrolyte, and through which a plurality of bolt holes is provided to permit adjustable mounting of a work holding vise 15.

On the base portion 3 there is mounted a metal bottom plate and on top of this a waterproof chemical resistant plastic mounting plate 19. This is provided with a number of threaded bolt holes to permit mounting of an electrode holder 21, which is made of suitable metal and is provided with one or more mounting slots so that it can be adjusted as to its position by selection of the suitable bolt holes in mounting plate 19.

At the working end, the electrode support member 21 is hollow and is adapted to receive an electrolyte feed tube fitting 27 connected to a line leading to a source of electrolyte under pressure.

Extending from the upper surface there is mounted an electrode 31, having a conductive working face, shown here as fastened by brazing to a pipe nipple threaded into the electrode support member 21. Within the hollow support member 21 the electrode is connected by a suitable passage to the feed tube fitting 27. The electrode 31 may take any suitable form, e.g., those shown in Patent No. 3,058,895.

An electric cable 34 is connected to the electrode block or support member 21 and supplies current from the power source. Another electric cable 35 is fastened to work plate 11 to furnish the other (normally positive) connection from the power source.

To move the work plate 11 up and down, a lead screw 37 is secured to and extends upwardly from the upper end of the ram 9. A lead nut 39 is threaded upon the lead screw and is mounted between two horizontal plates 41 which are supported by four column bars 43. The lead nut peripherally is formed as a worm gear so that it may be rotated to move the lead screw 37 up and down. A journal plate 45 is mounted to the plates 41 and carries a bearing bushing 47 which supports the outboard end of a drive shaft 49 which carries worm Sll meshed with the peripheral worm gear of lead nut 39.

The worm drive shaft 49, is in turn, rotated by a variable speed electric motor drive 53 mounted upon a platform 55 attached to the column 5. This drive mechanism has a speed adjusting handle 57 and a reversing handle 59, the latter having a neutral midposition as well as updrive and downdrive positions.

The sizes and proportions of the drive parts are arranged to permit adjustment in the vertical speed of movement of the workplate 11 from zero to one inch per minute. The motion must be smooth, not jerky, and accordingly reasonable accuracy and freedom from excessive friction are an advantage in the moving drive parts. The lead screw 37 may be protected against splatter and corrosion by a plastic enclosure 61 wrapped around the column bars 43.

A conventional dial indicator 63 is shown as mounted to the head 7 of column and has its working tip extended downwardly against the upper surface of workplate 11 so as to indicate relative movement as between these elements.

The entire assembly is mounted in a pan 65 which has an outlet spud adapted to drain electrolyte back into-a supply sump or reservoir 74. The workplate 11 is fitted with plastic curtains 71 which can be tucked down below the level of the pan top to prevent excessive splatter, and to enclose the work area for the workpiece and the electrode 31.

The plumbing system (FIG. 2) comprises a low pressure pump 73 which feeds a suitable conductive electrolyte from the reservoir 74 through a filter 75 into high pressure pump 77, the outlet of which leads to a bypass valve 79 which may be either manually set or of the spring loaded constant pressure type. On the inlet side of the bypass valve 79 a pressure gauge 81 is mounted. Also from the inlet side, a pipe lead is taken through,a needle valve 83 to an electrolyte feed tube 84 leading to the electrode fitting 27. A second gauge 29 is connected to the feed tube 84 so as to indicate the pressure at the electrode.

In operation, a workpiece is positioned in the vise above the electrode 31, and the workplate 11 is then driven down until the workpiece is almost touching electrode 31 as gauged by a piece of paper or shim of known thickness, say .003 inch. The dial indicator 63 is then adjusted to zero minus the known thickness, .003 inch in this example. The curtains 71 are lowered or otherwise closed, the electrolyte pumps 73 and 77 are started, and the valves 79 and 83 are adjusted so that gauge 81 reads about 120 p.s.i., and gauge 29 about 90 p.s.i. This is done while the reversing handle 59 is in neutral position. Then, simultaneously, the reversing handle is moved to down drive position, and the electric power supply is turned on.

As the electrode approaches the workpiece, there will be a rise in pressure at the gauge 29. If the capacity of pumps 73 and 77 is several times the free flow discharge rate through the electrode, the pressure upstream of the needle valve 83 and of bypass valve 79 as readat gauge 81 will change scarcely at all with changes in proximity of the electrode 31 to the work, for most of the flow is passing through bypass valve 79, and it is the adjustment of this which is principally determinative of the pressure at gauge 81. In short, the pumps and pumping system up to needle valve 83 constitute a substantially constant pressure source. The same result may be obtained in many other ways. A constant pressure type pump may be used;

e.g., a centrifugal pump operating near cutoif. Or a pressure regulator may be used. Or a spring loaded relief valve adapted to maintain constant pressure may be used.

Needle valve 83, however, is set so as to constitute a sufiicient restriction to flow so that when the electrode is discharging into the open, the pressure, as read at gauge 29, will be noticeably lower than when its outlet is restricted by being in close proximity to the work.

Thus, if gauge 81 normally reads 120 p.s.i., then when the electrode 31 touches the workpiece so as to shut off the flow, or nearly so, the pressure downstream of needle valve 83, as read at gauge 29, will rise to almost the same value, 120 p.s.i. If, however, the electrode 31 is spaced away by several thousandths of an inch, the pressure at gauge 29 will drop, say to p.s.i.

This change in liquid pressure may be used in adjusting the rate of feed of the work toward the electrode. The initial feed rate may be set at a low level (for an unknown working condition or work material), and then increased by adjustment of the handle 57. Gauge 29 is observed to watch for a pressure rise which approaches that of gauge 81. It takes a little time for the pressure reading to stabilize during actual removal operations, for inasmuch as material is being removed by anodic dissolution, it is necessary for the moving electrode to catch up with the receding work material and to establish an equilibrium spacing distance, for as the electrode comes closer to the work, the removal rate tends to increase. By the exercise of reasonable care, it is possible to make a precise adjustment such that the electrode pressure gauge 29 reads only a few pounds per square inch lower than gauge 81, indicating that the electrode is moving forward at such a rate as to leave only a small gap between the electrode and the work.

In effect, this hydraulic system constitutes a flow meter, and the same result may be obtained by using a more formal flow meter to sense the How rate through the gap between the electrode and work. Such flow meters may be of any suitable sort, as, for instance, of the orifice type (which, in effect, uses the principle of the system just described), or of some other type, for example, that in which a moving bob is supported by upward flow in a conical glass vessel (e.g., the Fischer & Porter type).

It is not easy to measure this gap with accuracy, as apparently it is not always uniform at every point, but as measured in a practical way, by turning off the current and advancing the electrode until it seems to bottom, the distance may be as small as .001 inch or less, to as much as .010 inch, with satisfactory results, although it is preferred to work with the shortest spacing distance which can be managed without causing occasional contact and arcing between the electrode and the work, and I have found that about .002 inch to .005 inch is usually a safe distance while still permitting rapid removal of work material.

In general, low voltages and close spacing, of the order of .001 inch to .005 inch, give high removal rates and low electric power costs and a higher degree of accuracy, but less striation is produced upon the side wall of the work cavity when greater spacing, of the order of .010 inch, is used. The greater spacing results in a lower work removal rate unless the voltage is raised, however, since removal rate is a function of current. As a practical matter in most applications, I prefer to use about 4 to 15 volts and from to 3000 amperes per square inch of active electrode area.

It should be noted that work material is removed by electrolytic action, not by spark or are erosion, as with the so-called electrodischarge method. This is important for several reasons, among them the fact that damaging thermal metallurgical efiects on the work material are avoided and that there is virtually no erosion of the electrode. The fact that the electrode is not eroded is of great importance where the cavity is to be accurately shaped, for accurate shaping is rendered very difficult when the electrode is being eaten away at a rate rapid enough to alter its dimensions during the operation.

Thus, it is important to avoid too fast a feed rate which may cause arcing between the electrode and the work.

Another method of gauging the feed rate is by reference to an ammeter in the electrolytic power supply circuit. Once the penetration of the electrode into the work has been well established, the rate of feed is gradually increased until an arc is observed. Usually this will be of short duration. The reading of the ammeter is observed and read just prior to the first arc, and the' speed is then adjusted downwardly until the ammeter shows a reading of little below the critical point where the first arc occurred.

A transducer sensitive to either the electrolyte liquid flow rate or the electrolytic electric current may be used as the signal generating element in an automatic feed control system.

FIG. 3 is a schematic illustration of one type of apparatus for automatic control of the feed rate of the electrode. Motor 101 is of the direct current shunt wound type, and serves to advance the electrode 31 toward the work W (or the work W toward the electrode) by a screw drive, all in the general manner shown in FIG. 1, except that the speed of motor 101 is varied electrically and automatically rather than manually. Other suitable mechanical configurations will be self-suggesting.

The electric supply system and amplifier 103 include rectifier circuits to provide a relatively fixed direct current voltage for the field of motor 101 and an automatically adjusted voltage for the armature so that the motor speed is automatically varied with a variation in armature voltage. The amplifier 103 derives a signal from a pressure responsive transducer 105 (FIG. 4), arranged to respond to the pressure differential across the needle valve at 107 which is in the line between the pump 108 and the electrode 31. As one example, a diaphragm device or other pressure responsive sensing element may be mounted so that the liquid pressure differential thereacross causes a variation in pressure upon a carbon pile variable resistor 109 connected in a bridge circuit as in FIG. 4. For this purpose, however, I prefer to use a variable impedance, for example, a pressure actuated variable capacitor, in an oscillator circuit feeding the output to a discriminator to derive a control signal. As the value of the capacitor changes, it alters the oscillator frequency, and this affects the signal. All this is conventional and well known, and needs no detailed description.

The change in pressure is thus used to provide signals to the grid of a vacuum tube amplifier which terminates in one circuit where I have used in a pair of 807 power tubes. The output tubes may be fed with alternating current from a transformer split secondary, and they thus serve as rectifiers as well as amplifiers and provide a variable direct current supply to the motor armature. The amplifier circuit is so arranged that an increase in pressure differential across the transducer element 105, which reflects an increase in the electrode to work spacing, causes an increase in power output, thus causing the motor speed to increase, which in turn causes the electrode to catch to the receding work face.

Accordingly, the system serves to maintain a feed rate which is held at a level to maintain constant liquid flow in the electrolyte feed line as sensed by a constant differential pressure across adjustable orifice or valve 107. This assures substantially constant spacing between the electrode 31 and the work W. In some situations there will be a tendency for the circuit to hunt, and antihunting circuit techniques may be required. Thus, the gain of the amplifier may be made adjustable as by the knob 11 1; capacitance with a slow bleed and a resistance feed may be connected across one of the grid circuits, etc. These techniques do not relate to the novelty of this invention and are, therefore, not described in detail, for

riate variable impedance) in circuit with transducer element 109 in such manner as to vary the level at which signal response occurs. In FIG. 4, resistors 109 and 117 are balanced against each other in a simple bridge circuit, and should be regarded as representative of any variable impedance, whether resistive, capacitive, or inductive. The cam will be shaped to alter the feed rate as desired to produce the variations in width of cavity which are wanted. It should be understood that where the transducer element 109 is not of the resistance type, then element 117 need not be a resistor. If, for example, transducer is a variable capacitor, then element 117 may be a vari able capacitor; or if 105 is a variable inductor.

The system just described constitutes a flow meter for a sensing and control device in which the flow rate range may be set for the desired response level, depending upon the area of the electrode. Other types of flow meters capable of providing an electrical control signal may be used; for example, a magnetic flow meter in which an AC magnetic field is impressed across a nonconductive section of electrolyte feed line and two electrodes set in a plane transverse to the field. The electrolyte acts as a moving conductor in the field, and its velocity determines the voltage generated. The directly induced AC is canceled out electrically, and thus a signal is derived whose voltage is linearly proportional to flow rate.

The reversing switch at 11 9 enables the motor 101 to run in either direction so as to extend or retract the electrode 31 as desired.

FIGS. 5 and 6 show an alternative arrangement to that of FIGS. 3 and 4. All parts are similar and bear like reference numerals except that the automatic feed control is responsive to the electric current passing between the electrode 31 and the work W. Variation in the current in series coil 121 affects the saturation of the iron core 123 which in turn is reflected in a change in inductance of coil 125. This mechanism, therefore, acts as a variable inductance which can be used to modulate the output of the amplifier 103. When the electrolytic current rises above a predetermined level, the voltage to the armature of motor 101 is reduced to slow the speed of advance.

Variable speed is accomplished by the same type of cam system used in the apparatus of FIG. 3. One form of interconnecting bridge circuitry which may be housed principally within the amplifier box at 103 is shown in FIG. 6.

Variable inductor 125 responsive to current value is balanced against variable inductor 127 actuated by cam 113 in a circuit with fixed resistors 129 such that the level of amplifier response is varied in accordance with the electrolytic current in the circuit and the position of the electrode. Variable inductor 127 may be of any suitable type such as a coil 131 having a movable core 133 attached to the follower of cam plate 113.

From the foregoing it will be appreciated that the objectives which were claimed for this invention at the outset of the description are fully attained by the apparatus described and shown.

Also, from the above description of my invention, it will be appreciated that many changes may be made in the apparatus without departing from the scope or spirit of the invention, and that the scope of the invention is to be determined from the scope of the accompanying claims.

Iclaim:

1. In an apparatus for electrolytically shaping an electrically conductive and electrochemically erodible workpiece, the combination including, mounting means for the workpiece, an electrode having a conductive working face adapted to be brought into close spacing relationship with the workpiece to define a work gap of predetermined narrow spacing between the workpiece and said electrode working face, means connected for pumping an electrolyte to and through the work gap, electric circuit means connected for supplying an electrolyzing current between the workpiece and said electrode working face, power means connected to said workpiece mounting means and to said electrode for positively moving the workpiece and said electrode working face relatively toward each other as material is removed from the workpiece, and control means for said power means for automatically adjusting the rate of relative advance of the workpiece and said electrode working face.

2. Apparatus as claimed in claim 1, wherein said control means is sensitive to an operating variable in the apparatus.

3. Apparatus as claimed in claim 1, including actuating means being sensitive to the rate of flow of the electrolyte to and through the work gap.

4. Apparatus as claimed in claim 3, including means sensitive to the position of said electrode for additionally actuating said control means.

5. Apparatus as claimed in claim 3, including means sensitive to an operating variable other than the electrolyte flow rate for additionally actuating said control means.

6. Apparatus as claimed in claim 1, including actuating means for said control means, said actuating means being sensitive to the electrolyzing current in said electric circuit.

7. Apparatus as claimed in claim 1, including means sensitive to the position of said electrode for additionally actuating said control means.

8. Apparatus as claimed in claim 1, wherein said power means includes an electric motor, and said control means includes an electric circuit for said motor to control the speed of the latter.

9. Apparatus as claimed in claim 8, wherein said electric circuit includes an amplifier connected to sense the rate of electrolyte flow to and through the Work gap.

10: Apparatus as claimed in claim 8, wherein said electric control circuit includes an amplifier connected to sense the electrolyzing current passing between the workpiece and said electrode working face.

References Cited UNITED STATES PATENTS 3,219,564 11/1965 Wilkinson 204224 XR 3,228,863 1/1966 Wanttaja et a1. 204-224 XR 3,288,693 11/ 1966 Livshits 204143 3,338,808 8/1967 Johnson 204-143 3,365,381 1/1968 Fromson 204143 HOWARD S. WILLIAMS, Primary Examiner.

D. R. VALENTINE, Assistant Exmm'ner.

US. Cl. X.R. 204-143, 225

22x3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,444,069 D d May 13, 1969 Inventor( Lynn A. Williams It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 6, line 20, after "variable inductor" insert --,then element 117 will be a variable inductor SIGNED AND SEALED SEP 2 1959 (SEAL) Attest:

Edward M'Flemhcr'h WILLIAM E. SCIHUYLER, JR- Attesting Officer Commissioner of Pat n

Claims (1)

1. IN AN APPARATUS FOR ELECTROLYTICALLY SHAPING AN ELECTRICALLY CONDUCTIVE AND ELECTROCHEMICALLY ERODIBLE WORKPIECE, THE COMBNATION INCLUDING, MOUNTING MEANS FOR THE WORKPIECE, AN ELECTRODE HAVING A CONDUCTIVE WORKING FACE ADAPTED TO BE BROUGHT INTO CLOSE SPACING RELATIONSHIP WITH THE WORKPIECE TO DEFINE A WORK GAP OF PREDETERMINED NARROW SPACING BETWEEN THE WORKPIECE AND SAID ELECTRODE WORKING FACE, MEANS CONNECTED FOR PUMPING AN ELECTROLYTE TO AND THROUGH THE WORK GAP, ELECTRIC CIRCUIT MEANS CONNECTED FOR SUPPLYING AN ELECTROLYZING CURRENT BETWEEN THE WORKPIECE AND SAID ELECTRODE WORKING FACE, POWER MEANS CONNECTED TO SAID WORKPIECE MOUNTING MEANS AND TO SAID ELECTRODE FOR POSITIVELY MOVING THE WORKPIECE AND SAID ELECTRODE WORKING FACE RELATIVELY TOWARD EACH OTHER AS MATERIAL IS REMOVED FROM THE WORKPIECE, AND CONTROL MEANS FOR SAID POWER MEANS FOR AUTOMATICALLY ADJUSTING THE RATE OF RELATIVE ADVANCE OF THE WORKPIECE AND SAID ELECTRODE WORKING FACE.

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