US3883410A

US3883410A - Method of and apparatus for the deburring workpieces

Info

Publication number: US3883410A
Application number: US168173A
Authority: US
Inventors: Kiyoshi Inoue
Original assignee: Individual
Current assignee: Individual
Priority date: 1966-12-01
Filing date: 1971-08-02
Publication date: 1975-05-13
Anticipated expiration: 1992-05-13

Abstract

Apparatus for the electrochemical deburring of metallic workpieces in which a fixture forms a support for the workpieces which, together with carbon particles and/or other abrasive particles, are agitated in an electrolyte.

Description

United States Patent Inoue 1*May 13, 1975 METHOD OF AND APPARATUS FOR THE DEBURRING WORKPIECES [56] References Cited [76] Inventor: Kiyoshi lnoue, 3 Chome, Kamiyoga. UNITED STATES PATENTS Tokyo, Japa 3.521834 8/1970 Hewins .1 148/615 R l Nance: The porticn of the term of this 3,533,928 10/1970 lnoue 204/213 X patent Subsequent to Oct 1988 3.620953 ll/l97l lnoue 204/2l3 X h l as been disc aimed Primary Examiner-Ralph S. Kendall Flled? 1 Attorney, Agent, or Firm-Karl F. Ross; Herbert [21] App]. No: 168,173

US. Cl........ 204/129.46; l48/6.15 R; 204/213;

204/224 R Int. Cl 823p 1/04 Field of Search 148/615 R; 204/143, 2l3,

[57] ABSTRACT Apparatus for the electrochemical deburring of metallic workpieces in which a fixture forms a support for the workpieces which, together with carbon particles and/or other abrasive particles, are agitated in an electrolyte.

1 Claim, 11 Drawing Figures I042 I0I7 I045 I0Ie I023 IoIg I0II lOl9 I030 lOlZ 1023 Iorr' floIa |O4| l r l l I lOl r; IJ 043/ I027 |024a 26 I024b I040 SHEET 2 OF 6 F|G.2A FIG.2B

F l G .4

Kiypshi INOUEI INVENTOR.

(Karl To ATTORNEY PATENTED my I 3 i975 3,883 .41 0

sum 3 or 6 FIG.5

Kiyoshi INOUE INVENTOR.

A '1 TORNE Y LTEMELM 1 SETS 3.883 .410

ShiEi u CF 6 F l G. 6

Kiyoshi INOUE INVENTOR.

BY m-l 'RO ATTORNEY SHEET 8 BF 6 FIG.9

Kiyoshi INOUE INVEN TOR.

BY f arl ATTORNEY METHOD OF AND APPARATUS FOR THE DEBURRING WORKPIECES CROSS-REFERENCE TO COPENDING APPLICATION This application is a continuation-in-part of copending application Ser. No. 714,252, filed Mar. 19, I968, now US. Pat. No. 3,620,953 and a continuation-in-part of copending application Ser. No. 859,532, filed Apr. 21, 1969, now US. Pat. No. 3,533,928, which was in turn a continuation of application Ser. No. 598,391, filed Dec. 1, 1966, which application is now abandoned.

FIELD OF THE INVENTION My present invention relates to a method of and an apparatus for the deburring of metallic and other conductive workpieces whereby surface irregularities of such workpieces are eliminated.

BACKGROUND OF THE INVENTION Deburring apparatus of several types are commonly in use in the metal-working field, primarily for the re moval of surface irregularities in cast, machined and molded metallic workpieces. For the most part, such apparatus includes a tumbling drum provided with agitating means for repeatedly casting the workpieces, generally in a liquid vehicle and sometimes in the presence of an abrasive, into contact with one another, against the walls of the vessel or drum or into contact with other bodies (e.g. of abrasive material) mixed with the Charge in the drum. This tumbling action mechanically dislodges adherent materials while rounding off irregular portions and projections integral with the metallic bodies. These systems, however are relatively slow and even defective when the deburring operation is to remove substantial amounts of material.

OBJECTS OF THE INVENTION It is, therefore, the principal object of the present invention to provide a method of deburring metal workpieces whereby the rate of material removal and the surface finish of the treated objects is significantly increased and improved.

Another object of this invention is to provide relatively simple and inexpensive apparatus for a high rate deburring of metallic workpieces while yielding a relatively high quality surface finish.

Yet another object of this invention is to provide a method of and an apparatus for the deburring of relatively large-dimension workpieces of such nature that tumbling may be impractical.

SUMMARY OF THE INVENTION These objects and others which will become apparent hereinafter are attained, in accordance with the present invention, by a method of deburring metallic workpieces in which the liquid vehicle is agitated in contact with the workpiece to be deburred while mechanical contact between the surface of the latter and at least some other bodies is carried out concurrently with an electrochemical material-removal step.

As set forth in application Ser. No. 598,391, I have found, surprisingly, that electrochemical techniques hitherto used primarily for the electrochemical machining (ECM) and electrochemical grinding (ECG) of metallic bodies, wherein close tolerances are a necessity, can be used effectively in conjunction with a tumbling or agitating operation to debur metallic workpieces or objects having electrolytically soluble surface portions. The surprising nature of this discovery will become all the more apparent when it is recognized that the present method does not require a stationary electrode urged against the workpiece or juxtaposed therewith via a predetermined machining gap.

In accordance with the principal feature of this invention, an electrochemical machining current. which may be direct or periodic (e.g., raw-rectified alternating current, pulsating direct current and ordinary AC) is passed through the liquid vehicle which is constituted as an electrolyte and may contain abrasive particles or merely additional bodies to facilitate mechanical deburring of the workpieces concurrently with the electrochemical action. While, in some cases, the workpiece may be stationary and is connected with a pole of the electrochemical machining sources, I have found that it is not necessary to connect the workpiece directly thereto, and that the mere tumbling of such workpieces in an electrolyte and in a drum having spacedapart contact portions bridged by the electro lyte but not shortcircuited by the drum itself. can effect electrochemical removal of material from the workpiece surfaces.

While I do not wish to be bound by any theory in this regard and the precise reasons why the current flow through the electrolyte is effective to remove material from the surface of the conductive workpieces are not yet clear, it may be hypothesized that each of the work pieces acts as an electrode for the machining of others or as objects undergoing electrolytic erosion against other conductive bodies. Since electrolytic oxydation of the workpiece at its surface is essentially nonreversible in the sense that agitation and mechanical action of the electrolyte carries away the oxide film as soon as it is formed and, even upon electrical (polarity) reversal, metal is not materially redeposited from the oxide onto the machine surface, the electrolytic action is carried out as if a wire were directly connected to each workpiece.

According to a more specific feature of this invention, the agitation of a multiplicity of workpieces is effected in a tumbling drum which may be provided at its base with one electrode portion and with a second contact or electrode, at a location spaced therefrom but in contact with the electrolyte, the electrodes being connected across an AC or DC electrochemicalmachining source (e.g. of the type described and illustrated in any of my applications Ser. No. 512,338 (US. Pat. No. 3,475,312), Ser. No. 535,268 (US. Pat. No. 3,417,006), Ser. No. 562,857 (US. Pat. No. 3,420,759), filed Dec. 8, 1965, .Ian. 19, 1966 and July 5, 1966, respectively and copending application Ser. No. 714,252. The tumbling drum can be upwardly open and rotatable about an axis tilted upwardly at an angle of, say, 30 from the horizontal. In this case, the agitation is effected purely by rotation of the drum.

I have also found it to be possible, in conjunction with such a tumbling drum, or when a stationary vessel is employed, to effect the agitation at least in part by magnetic means. Thus, if the workpieces treated in the deburring operation or the other bodies involved are magnetically permeable, I apply a magnetic field to them so as to effect their displacement in the electrolyte; I also may distribute in the deburring vessel among the workpieces, particles or bodies of a magnetically permeable material. Such bodies may be abrasive or electrically conductive to facilitate electrochemical erosion of the workpieces or produce the friction necessary for the deburring action. In fact, the particles or bodies serving as the agitating means need not be magnetically permeable under some circumstances, since the particles in the electrolyte tend to respond to a rapidly changing magnetic field by rotating about the axis thereof. Thus, agitation may be promoted with the aid of conductive as well as magnetically permeable particles. According to still another feature of this aspect of the invention, the particles which are magnetically or electrically displaceable in the liquid vehicle, can be coated with abrasive material, incorporated in or mixed with abrasive particles which are not influenced by an electromagnetic field.

Preference is given, in accordance with this invention. to pulsating or alternating electromagnetic fields for controlling the movement of particles and inducing electrochemical erosion of the workpiece surfaces since purely direct current has a tendency to produce agglomeration of magnetic particles in the deburring vessel.

According to another aspect of the basic invention, more fully described in application Ser. No. 598,391, the agitation is carried out by rotating an electrode immersed in the electrolyte by, for example, rotating an electrode member in an irregular die cavity to deburr the machined surfaces thereof. Abrasive particles are here included in the deburring vehicle while an electrolytic machining current is applied between the workpiece and this rotating element. Inasmuch as this elec trode member is not closely juxtaposed with the work piece surface and is rotated relatively rapidly, a more or less uniform surfacing is effected. In accordance with this aspect of the invention, I prefer to incorporate in the vehicle a multiplicity of conductive particles which here act as intermediate electrodes and as they are dispersed by the agitation into the rotation of the die surfaces, each particle acts as an individual electrode to facilitate smoothing of the die surface. The to tary electrode member imparts a centrifugal force to the abrasive and conductive particles contained within the electrolyte so that these particles are dynamically urged outwardly and forcefully brought into contact or close juxtaposition with the surfaces to be treated to augment the resulting mechanical deburring action.

According to yet another aspect of this invention, de burring is carried out as augmented by a magnetic-field pressure which, when combined with the dynamic flow or rapidly moving particles, with the centrifugal force of tumbling or electrolyte displacement by a stirrer and with gravitational forces, magnetically urges the abrasive bodies against the workpieces and the workpieces against one another. This magnetic-field pressure is, advantageously, supplied by electromagnetic means disposed externally by the deburring vessel and is capable of applying inward magnetic forces to the magnetically permeable particles and workpieces. When the abrasive particles or auxiliary bodies serving to facilitate mechanical removal of irregularities and projections upon the workpieces are magnetically permeable and/or the workpieces are of such permeability, a highfrequency magnetic field applied from without, in accordance with this invention, induces an oscillation and/or a magnetostrictive expansion and contraction of the bodies so that the simple tumbling action is accompanied by a magnetic vibration or pulsation of the body to improve the erosive operation. In this connection it can also be stated that the field may be of such nature that vibration of the individual particles by the magnetic field is coupled with a tumbling action of a rotary drum or a vibration thereof to increase the mechanical abrasion.

Another feature of this invention resides in the use of chemical action in removing surface irregularities in combination with the electrochemical and mechanical deburring action as described above. Thus I have found that surprisingly effective results can be obtained when a chemical mordant or etchant for the workpiece material is incorporated in the electrolyte. For as yet unknown reasons, the surface finish and deburring rate obtained when, for example, ferric chloride is used as the chemical etchant in the electrolyte, is better than that which would be expected with either the etchant or the electrochemical action alone, while the rate of material removal exceeds the sum predictable from the individual actions of the etchant and the electrochemical erosion.

According to a further feature of the present invention, the electrochemical deburring of metallic workpieces is carried out concurrently with agitation of the bodies in an electrically nonconductive tumbling drum rotatable about a recumbant axis (preferably horizontal or near horizontal) containing liquid electrolyte and the conductive (i.e., carbon) particles, together with the workpieces as described therein. A pair of electrodes are in constant contact with the electrolyte during rotation of the drum and are preferably disposed at remote ends of the electrolyte bath and are composed of a material insoluble in the electrolyte and free from electrolytic attack thereby. l have surprisingly found that excellent results can be attained when the conductive electrodes are constituted by the end walls of the drum and rotate therewith, the cylindrical drum wall forming the insulating spacer for these electrodes. At least one but preferably both of these end walls are provided with a passage for circulating the electrolyte through the drum, the axial passage terminating in a fan-like array of bores opening into the drum at the face of the end wall contacting the electrolyte. The drum may further be provided, at least at regions extending above the electrolyte level therein with apertures or vents enabling evacuation of the gaseous products of the electrolytic deburring of the workpieces,

Still another aspect of this invention resides in my discovery that irregular deburring can be avoided by injecting an inert gas into the electrolyte bath with the recirculating electrolyte stream. It appears that the inert gas creates labyrinthian paths for the electric current flowing through the electrolyte, i.e., the ion mobility paths, thereby distributing the electrochemi cal action substantially uniformly. This technique has the additional advantage that the inert gas upon evolution from the electrolyte acts as a diluent for the nascent gases generated by electrolysis and let off through the vents above the electrolyte level. The inert gas may be admixed with the electrolyte in the bath or with the liquid prior to its introduction into the tumbling drum. Furthermore, in accordance with the principles already discussed above in general terms, I provide a magnetic flux radially through the drum, i.e., vertically when the drum is horizontal, preferably at a location intermediate the electrode. to facilitate the agitation of the elec trolyte, the workpieces, and the carbon particles forming intermediate electrodes for the deburring action. These carbon particles have an abrasive or semiabrasive character so that they mechanically co-operate with the workpieces to supplement the electrochemical deburring by mechanical erosion of the rough surfaces. Thus the carbon particles may he carbonaceous materials of relatively high hardness (e.g. synthetic diamond as produced by the system described in my US. Pat. No. 3,207,582 or the nondiamond but high-hardness carbon particles obtained when synthetic diamond is made in accordance with that process).

As is apparent from the foregoing, and as described below in connection with FIG. 7, the method of removing burrs from the workpiece may comprise the steps of attaching the workpiece to a conductive fixture and connecting it to a source of electric current so that the workpiece is the anode in a direct current circuit, submerging the workpiece in a tank containing conductive abrasive media immersed in a conductive solution (i.e., an electrolytic solution), and simultaneously passing a direct electric current through said workpiece and the conductive abrasive media and the conductive solution, and vibrating the tank for providing random contact between the burrs and the conductive abrasive media. It will be apparent that it is inherent in the use of electrolytic solutions and the passage of current in the manner described that atomic oxygen is released on the burr surface to form an oxide coating thereon, whereupon the random contact wipes off the oxidized burrs.

Moreover, the source of electric current can be considered to be a fixed source of electric potential, the conductive abrasive media to have selected percentages of varying size particles providing a fixed range of electrical resistivity, the workpiece to be connected as an anode when oxygen is evolved, and the electric current in the circuit to be regulated by the amplitude and frequency at which the tank is vibrated.

DESCRIPTION OF THE DRAWING The above and other objects, features and advantages of the present invention will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

FIG. 1 is an axial cross-sectional view through a tumbling drum of a deburring apparatus in accordance with this invention;

FIG. 2A is an axial cross-sectional view of an electrode forming an end wall of the drum;

FIG. 2B is an elevational view thereof;

FIG. 3A is a cross-sectional view through a modified electrode;

FIG. 3B is an elevational view of this latter electrode;

FIG. 4 is a diagram of the electrochemical deburring system of the present invention;

FIG. Sis a view similar to FIG. 1 of a modified system for deburring metallic workpieces;

FIG. 6 is an axial cross-sectional view through a tumbling system embodying other principles of this invention;

FIG. 7 is a diagram ofa continuous deburring apparatus in accordance with the principles of this invention;

FIG. 8 is an axial cross-sectional view through a deburring apparatus using a stationary system and diagrammatically showing the electrolyte-circulating means therefor; and

FIG. 9 is a cross-sectional view along the line IX IX of FIG. 8.

SPECIFIC DESCRIPTION AND EXAMPLES In FIG. I, I show a rotary tumbling system for the deburring of metallic workpieces in which a closed drum 1010 has a pair of

end walls

1017 and 1018 forming electrodes and retaining the electrolyte 1011 in the drum. Between the

conductive electrodes

1017 and 1018, the drum is formed as a nonconductive sleeve I041 composed of or lined with electrically insulating material such as a hard rubber or an electrolyteresistant synthetic resin (e.g. a polyacrylate). Electrically insulating rubber gaskets 1042 are provided between the drum body 1041 and the

electrodes

1017 and 1018. The drum may also be formed with a door 1045 to permit the workpieces and intermediate electrodes to be introduced into the interior of the drum.

The

electrodes

1017 and 1018, which are inert to the electrochemical action and to the electrolyte, are com posed of graphite or an insoluble metal (e.g. stainless steel or monel). The drum 1010 is mounted upon a pair of trunnions 1024a and 102411 extending upwardly from a base 1026 and defining for the drum a horizon tal axis. The drum is, in turn, carried by a pair of tubular shafts 1023a and 10231) affixed to the respective

electrode end walls

1017 and 1018 as described in connection with FIGS. 2A, 2B and FIGS. 3A, 3B.

The drive means for the drum comprises a motor 1027 whose output shaft 1028 is connected by a V-belt transmission 1030 with the hollow shaft 10230 to rotate the drum about its horizontal axis. The electric current for the electrochemical deburring operation is pro vided by a power supply 1019 and is applied via a pair ofbrushes 1019a and 1019b to the

electrodes

1017 and 1018 via their shafts 1023a and 1023b. Electrolyte is circulated through the drum by a pump 1039 and a circulating system including an inlet pipe 1040 connected with the tubular shaft 1023b. The tubular shaft 1023a leads electrolyte from the drum to a return tube 1043 ending at a surface 1044.

The

electrodes

1017 and 1018 may be provided with a fanshaped array of bores (FIGS. 2A and 2B) or a central array of mutually parallel bores (FIGS. 3A and 38), while means may be provided for injecting a gas into the liquid-circulating stream (FIG. 5) and a magnetic field may be applied in the radial direction (FIGS. 5 and 6). In the embodiment illustrated in FIG. 1, however, the end walls and

electrodes

1017 and 1018 are provided with axially extending bores 1017' and 1018' communicating with the hollow shafts 1023a and 1023b, respectively.

Within the drum, as described in my application Ser. No. 598,391, copending with application Ser. No. 714,252, I provide, in addition to the electrolyte 1011, a mass of metallic workpieces 1012 (shown as rectangles) accompanied by conductive particles 1013 (hatched circles) and if desired magnetic and abrasive particles as described in application Ser. No. 598,391. The electrolyte may be any of the electrochemical machining solutions described in applications Ser. Nos. 512,338, 535,268 and 562,857, all having been mentioned earlier and having been copending with application Ser. No. 714,252. The particles 1013 are composed of carbon and act as intermediate electrodes.

An important aspect of this invention resides in the fact that the carbon particles are formed of relatively high-hardness carbonaceous material capable of withstanding metallic abrasion in the tumbling of the workpieces. Suitable particles may be made by sintering py' rolytic carbon or by the electric-discharge technique set forth in my US. Pat. No. 3,207,582. In addition, the carbon particles may contain silicon carbide or the like abrasive powder dispersed therein prior to sinteringv As a result, the electrochemical action is augmented by a mechanical smoothing of the workpieces concurrent with electrochemical removal of projecting portions of the workpieces (i.e. burrs). The deburring power supply 1019 may be any electrolysis source as described in application Ser. No. 598,391 and the other applications mentioned earlier. Suitable sources may be alternating current, pulsating direct current or filtered direct current as there described.

EXAMPLE I Using the system of FIG. 1, deburring was carried out in a I592 sodium chloride solution upon a mass of 35% by volume of steel workpieces having a diameter of 10 mm and a length of mm. Conductive particles, i.e., sintered pyrolytic graphite and silicon carbide particles with a diameter of about 5 mm were used in a ratio to the workpiece quantity of about 1.15:1; it was possible to increase the deburring rate over conventional systems using only aluminum oxide abrasive particles and a similar drum (diameter 300 mm, axial length of 7 mm, electrolyte quantity 5 liters, current 80 amp), in terms of the quantity of material removed per unit time, from to 30 times and the yield improved surface finish.

In FIGS. 2A and 28, I show a modified version of the terminal electrode for the drum of FIGS. 1, 5 and 6, the electrodes l l 17 generally comprising a disk 1117a of graphite or other electrochemically inert material attached at a flange lll7b to the tubular shaft 1123. A fanlike array of bores l l 17c is formed in the disk 1117a and open at the inner face 1ll7d in contact with the electrolyte within the drumv From FIG. 28 it is apparent that the bores are distributed in conical arrays about axis of rotation of the drum (represented at 1125) so that a number of these bores open into the drum above the liquid level (see FIG. 1) at each of the

electrodes

1017 and 1018. Thus gas forming above the electrolyte path can pass through the uppermost bores and can be entrained with the liquid stream leaving the drum and flowing to the reservoir 1044. In this reservoir, which is open to the atmosphere, the gases entrained in the liquid can evolve into the atmosphere. The fanlike array of bores has the additional advantage that, at the inlet electrode (e.g. electrode 1018), the bores disperse the liquid and any gases entrained therein (FIGS. 5 and 6) to insure fine distribution of gas bubbles in the electrolyte bath and even deliver some gas above the electrolyte to act as a diluent for the electrolytically evolved gases. The bores 1117c converge axially away from the drum to communicate with the tubular shaft 1123 and thus form a manifold.

Electrode 1217 of FIGS. 3A and 38 represents a modified construction in which the disk 1217a is formed with a plurality of mutually spaced parallel bores 1217c which are located in the region of the cen ter of the disk and communicating with the hollow shaft 1223 which is attached to the disk 1217a at a flange 1217b. This embodiment has the dispersing advantages mentioned in connection with the electrodes of FIGS. 2A and 2B but does not evacuate gases from above the electrolyte level as effectively. Eiether of the electrodes of FIGS. 2A and 2B and of FIGS. 3A and 33 can be used in the drum deburring systems of FIGS. 1, 5 and 6.

In FIG. 4, there is shown a diagram of the principles of the present invention as discussed in greater detail in application Ser. No. 598,391. In this FIGURE, I show the workpieces 1012 as fortuitously located between a pair of carbon particles 1013 and the

electrodes

1017 and 1018. If electrode 1017 is positive as shown for the purposes of the explanation of this electrochemical phenomenon, it will be seen that a proximal carbon particle 1013 received an inducted charge so that its region juxtaposed with surface 1012 in the electrolyte 1011 acts as an electrode to sustain electrochemical machining of this workpiece surface. The random distribution of conductive particles and workpieces between the electrodes is effective to insure practically uniform electrochemical treatment of all workpiece surfaces.

However, burrs or other projections invariably lie at a shorter distance from one of the terminal electrodes or an effective intermediate electrode than the other portions of the surface from which they project. The electrochemical machining current density is substantially higher at these protuberances and machining preferably occurs in these regions. Any mechanical smoothing is cumulative to the electrochemical action. It will be appreciated also that the presence of gas bubbles in the electrolyte augments the machining action and its specific attack upon protuberances and the burrs. It has been found that the gas bubbles tend to adhere to the surface of the workpiece in regions between the burrs and effectively insulate these regions while increasing the current density at the burrs. This too improves the surface fmish and can be controlled by injecting inert gases into the system as will be described in connection with FIG. 5. The term inert, however, must be construed in terms of the activity performed here. When the evolved gases include hydrogen, it will not be advisable to add oxygen and vice versa. Even normally active gases may be considered inert if they are nonexplosive when used in the presence of gases evolved from the deburring bath.

In FIG. 5, there is shown a horizontal drum 1310 with a central body 1341 held between a pair of gaskets 1342 and

electrodes

1317 and 1318 of the type shown in FIGS. 2A and 2B. The electrodes are carried between the tubular shafts 1323a and 1323b whose slip rings are in contact with brushes 1319b and 1319a of the electrochemical machining power supply 1319. A motor 1327 drives the drum about its horizontal axis while electrolyte is circulated through the drum via a pump 1339 from the reservoir 1344 and a line 1340 communicating with hollow shaft 1323b. The electrolyte from the drum is returned via line 1343' to the reservoir.

In accordance with the principles of the present invention, gas is injected into the electrolyte prior to its passage into the drum, the gas-supply source being shown at 1350 in FIG. 5. The source is a tank of air, argon, carbon dioxide, nitrogen or the like which is connected via a valve 1350a and a line 13501) with the hollow shaft 1323b of electrode 1318. When the gas is forced under high pressure into the electrolyte which, in turn, is under pressure of pump 1339, the liquid/gas mixture entering the drum through the electrode I318 expands to evolve the gas in the form of bubbles and, in part, to induce some of the gas into the drum above the electrolyte, thereby diluting the nascent gases released by electrolysis. The gas bubbles within the electrolyte adhere to the workpiece surfaces and augment the deburring action. An electromagnet 1315, whose flux can be represented by arrow I is provided beneath the drum 1310 and is effective to increase the electrochemical machining action.

As described in application Ser. No. 598,391, the magnetic field may be of unidirectional or alternating type while the magnet itself may be stationary or reciprocating. The magnet may be energized by a high frequency a.c. source in addition to a low-frequency vibrating or oscillating source. The high-frequency source preferably operates at 400 kHz to 50 kHz and ends above sonic frequencies while the low-frequency source operates at, say, 30 to 40 Hz. It appears that the magnetic field has a two-fold action whereby it induces a dynamic flow of liquid electrolyte and secondly, imparts magnetically attractive or repulsive motions to the workpieces when they are permeable.

In the system of FIG. 6, the drum 1410 has a cylindrical body 1441 which is preferred to evolve gases and permit electrolyte to enter the drum as the latter is rotated in a bath 1435. A hood 1451 overlies the bath 1435 and collects the evolved gases. Here too, the tumbling drum 1410 has a pair of disk-shaped

electrodes

1417 and 1418 which are insulated from each one another by the gaskets 1442 although the electrodes are here not perforated. Nontubular shaft 1423a and 1423b rotatably support the drum 1410 into a pair of trunnions 1424a and 1424b. The drive means is constituted by a motor 1427 and a V-belt transmission 1430 connecting this motor with shaft 1423a. An electrolysis power supply 1419 applies electric current to the

electrodes

1417 and 1418 by the brushes 1419a and 1419b. A magnetic field is applied, as previously described, by the coil 1415 in the vessel 1435.

FIG. 7 shows a continuous system for the deburring of metallic workpieces wherein a succession of workpieces is deposited from a hopper 1552 upon a belt 1553 which directs these workpieces to a perforated endless belt 1510 which functions similarly to the drum of the preceding embodiments. The endless belt 1510, which has horizontal stretch 1510a receiving the workpieces 1512 from the conveyor 1553, passes over an idler pulley 1510b into the electrolyte bath 1511 in a vessel 1535 of funnel-shaped construction prior to emerging from the bath over a further pulley 1510c. Within, the vessel 1535, I provide agitating means in the forming electromagnet 1537 which vertically displaces an armature 1530 against a pair of compression springs 1538a to jumble the workpiece and carbon particles contained on the stretch 1510d of the belt passing through the electrolyte bath. The armature 1538 carries a number of rollers 1538b which supports the belt in this region without frictionally impeding its movement.

Upon leaving the electrolyte bath 1511, the conveyor 1510 has a horizontal stretch 1510c overhanging a collecting receptacle 1554 in which the deburring workpieces are caught, the band being then returned to the horizontal stretch 1510a by downward stretch 1510f, a

horizontal stretch l5l0g and a vertical stretch 1510/1.

Intermediate electrodes are formed by a mass of carbon particles 1513 as previously described. The carbon particles are retained in a supply trough 1555 and are carried by a bucket conveyor 1556 to the vessel 1511 where they are deposited upon the mass of workpieces entering the bath. The band 1510 is, as previously indicated, perforated and has openings through which the carbon particles may pass as they settle from the electrolysis zone. Thus carbon particles which settle through the belt 1510 are discharged at an outlet 1543 of the vessel and are collected upon a sieve conveyor 1557 which carries them to the trough 1555. The electrolyte passing through the sieve conveyor 1557 is collected in the reservoir 1544 and recirculated by a pump 1539 and a line 1540 to the bath 1511.

The electrodes may, as described in application Ser. No. 598,39l, comprise vertical rods 1518a, 1518b and 1518c which can be angularly oscillated about respective vertical axes and vertically reciprocated by the mechanism shown for similar electrodes in the lastmentioned application. I have found, moreover, that improved power utilization can be obtained when a polyphase power supply is available and the number of electrodes is equal n X P where P is the number of phases (usually three) available as the supply and n is an integer. In this system, each phase is applied between one pair of electrodes or the corresponding electrodes of a pair of sets, each set having n electrodes. In the simplified system of FIG. 7, the power supply comprises a three-phase source 15190 which supplied a conventional Y or A transformer diagrammatically represented at 151% each of the output faces of which is applied across a pair of the electrodes 15180 through 1518c. The connections to these electrodes are shown both for Y and A systems although it will be understood that only one of these systems may be in use at any time. In the Y system, the neutral pole may be grounded at the transformer. This arrangement permits each phase ofa three-phase current to be effective and provides a greater effectiveness of the supply power without the expense rectifier systems which would be necessary to produce direct current and the complex circuitry which would be necessary to convert the three-phase force current to single'phase balanced current is operating the deburring device. It has been found that the system is particularly desirable when a large number of workpieces with a relatively large total volume is to be deburred at one time.

In FIGS. 8 and 9, I show another embodiment of the present invention in which no continuously displaceable endless surface is provided and the agitation of the electrolyte, carbon particles and workpieces, is carried out by means of pulsed jets or high-velocity streams of electrolyte directed tangentially into the vessel at the deburring region. This system, while affording some mechanical smoothing by contact of the workpieces with the carbon particles and the electrodes and wall of the vessel, primarily is effective to promote electrochemical removal of material from the workpiece surfaces without any movable apparatus members. The freedom of this system from vibrational and rotational movement of the electrodes, containers and the like eliminates the need for drive motors journaling assemblies and the like, thereby making the entire apparatus more practical and less expensive, especially where small quantities of workpieces are to be treated.

In accordance with the principles of the present invention, the apparatus comprises a stationary vessel 1610 of electrically insulating material having an upwardly open potshaped chamber 1643 with an arcuately concave bottom 1643a. A pair of

electrodes

1617 and 1618 disposed at diametrically opposite locations along the inner wall of the chamber and energized by an electrochemical machining deburring powcr supply 1619 of the character previously described. The vessel contains an electrolyte 1611 in which the workpieces 1612 (diagrammatically shown as circles) are distributed. The carbon particles 1613 are composed of sintered carbon to which abrasive powder has been added and may be used in conjunction with abrasive particles which contain no conductive materials, When a number of pairs of electrodes are provided in this system, the considerations discussed in connection with FIG. 7 apply and the power supply may include a polyphasecurrent source each phase of which is connected across a respective pair of electrodes or a respective pair of electrode sets.

In the present embodiment, the agitation of the electrolyte, workpieces and carbon particles is carried out by a fluid stream and the bottom 1643a of the vessel may thus be provided with a plurality of liquid inlets 1623a. 1623b 1623c, l623n forming electrolyte jets oriented generally tangentially to an imaginary circle C centered upon the vertical axis of the chamber and tangential as well to the curvature of the floor of the vessel as will be apparent from FIGS. 8 and 9. These inlets individually extend through the vessel 1610 and communicate via lines 1640a... etc. with a pump 1639 drawing electrolyte from the reservoir 1644. Electrolyte is returned to the reservoir via a line 1643'. Each of these lines is provided with a respective electromagnetically operable valve 1659a, etc. which successively pulse the electrolyte jets introduced into the vessel. Consequently, a vortex agitation ofthe electrolyte is provided which dynamically coacts with gravitational force to produce the desired turbulence. When more turbulence is desired, the jets can be pulsed in random sequence rather than in succession as indicated. The deburring electrolyte may be admixed with inert gas (see FIG. from a cylinder 1650 and a valve 16500 which may be injected into the electrolyte stream or may be added exclusively through one of the inlet passages (ie, passage 16230 in the system of FIGS. 8 and 9).

EXAMPLE I] A series of comparative tests were carried out with the stationary vessel arrangements of H65. 8 and 9, with a rotary vessel system with a vibratory vessel system as described below. The electrolyte was an aque ous solution of by weight of potassium nitrite and the workpieces were hexagonal nuts composed of iron and of 8 mm diameter. The nuts were of first grade .llS standard, black. class 4 M8SS4lB-D with a total volume of 500cc. The deburring elements added to the system were carbon particles of l5 mm diameter or abrasive particles of alumnia or silica, each of IS mm diameter. When particles were added, a total quantity of 2,000 cc of such particles were used. The rotary system involved 55 drum revolutions per minute, the vibratory system applied drum-vibrations of 1,500 cycles per minute and the jet system made use ofa electrolyte pressure of 5 and 15 kg per cm Four jets were employed in each case and the following Tables give the total quantity of material removed in the deburring process, the voltage and amperage provided for the electrochemical action and the particle wear in percents by weight. The deburring operation for each case was carried out equally for 10 minutes.

Particle wear Deburred Particles Voltage Amper- (72 by weight) quantity 8 (grams) l. Rotary System (a) Carbon only 37 88 3 48 (b) Carbon 50 vol.'/( 72 35 4 N 0,, 50 vol.% (C) Al Ct 50 V0l. 7r 90 0| 20 SK); 50 Vol.7;

2. Vibratory System (a) Carbon only 30 80 5 42 (b) Carbon 50 Vol.9? 65 6 25 M 0 50 Vol.7? (c) [M 0 S0 volfil B5 40 0] 22 SiO 5O VOl.%

3. Jet System with S kg/cm electrolyte pressure (a) Carbon only 18 90 4 52 (b) Carbon 50 vol/Z Al O 50 vol.7 60 3.6 38 (0) M 0, vol?! 62 45 0.2 26 SiO 50 volf/i 4. Jet System with 15 kg/cm electrolyte pressure (a) Carbon only l5 l0() 3 56 (b) Carbon 50 vol/7r N 0 50 volfir 43 62 4 39 (c) M 0 S0 vol.7r

in addition, an electromagnet 1615 may be provided below the vessel as shown in FIG. 8 to augment the dynamic movement produced by the liquid jets by electromagnetically induced movements. it will also be understood that various combinations of the several systems may be provided as well. Thus, the systems of FIGS. 1, and 6 may provide pulsed electrolyte jets to increase agitation while similar jets may be provided in the system of FIG. 7. A conveyor belt may be passed through the vessel of FIG. 8. The vessel of H6. 8 may also be vibrated by electromagnetic means as shown in FIG. 7 or may co-operate with angularly oscillatable and vertically reciprocable electrodes as there shown.

I claim:

1. The method of removing burrs from a workpiece, comprising the steps of:

supporting said workpiece in conducting relationship with a source of electric current. said workpiece being the anode in a direct current circuit;

submcrging said workpiece in a tank containing conductive abrasive media immersed in a conductive solution, said solution being an electrolyte solution; and simultaneously passing a direct electric current through said workpiece and said conductive abrasive media and conductive solution, to release atomic oxygen on the burr surface and to form an oxide coating on the surface of the burrs, and

vibrating said workpiece relative to said solution and said abrasive conductive media for providing ran dom contact between said burrs and said conductive abrasive media to wipe off said burrs.

Claims

1. THE METHOD FOR REMOVING BURNS FROM A WORKPIECE, COMPRISING THE STEPS OF: SUPPORTING SAID WORKPIECE IN CONDUCTING RELATIONSHIP WITH A SOURCE OF ELECTRIC CURRENT, SAID WORKPIECE BEING THE ANODE IN A DIRECT CURRENT CIRCUIT, SUBMERGING SAID WORKPIECE IN A TANK CONTAINING CONDUCTIVE ABRASIVE MEDIA IMMERSED IN A CONDUCTIVE ABRASIVE MD2EDIA AND CO SOLUTION BEING AN ELECTROLYTE SOLUTION, AND SIMULTANEOUSLY PASSING A DIRCT ELECTRIC CURRENT THROUGH SAID WORKPIECE AND SAID CONDUCTIVE ABRASIVE MEDIA AND CONDUCTIVE SOLUTION, TO RELEASE ATOMIC OXYGEN ON THE BURR SURFACE AND TO FORM AND OXIDE COATING ON THE SURFACE OF THE BURNS, AND VIBRATING SAID WORKPIECE RELATIVE TO SAID SOLUTION AND SAID ABRASIVE CONDUCTIVE MEDIA FOR PROVIDING RANDOM CONTACT BETWEEN SAID BURNS AND SAID CONDUCTIVE ABRASIVE MEDIA TO WIPE OFF SAID BURRS.