US2776256A - Process of making intaglio printing cylinders - Google Patents

Description

K. P. A. EULNER ETAL 2,776,256

PROCESS OF MAKING INTAGLIO PRINTING CYLINDERS 2 Sheets- Sheet l IN VEN TOR. #097196. EUA/VEA? BY dosi/@H M051. if?

A27' Tap/Vey Jan. 1, 1957 Filed March 19. 1953 Jn. 1, 1957 K.' p, A. EULNER ET AL v 2,776,256

PROCESS OF' MAKING INTAGLIO PRINTING CYLINDERS Filed March 19, 1953 2 Sheets-Sheet 2 /lw/E/v 70H. /fa/Hr H62 EUL NER y dosi/DH 77051. Lf@

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47' TaRNfY United States Patent fPROGESS .QF G: INTAGLIO G ,-CYLINDERS -KurtP.,-A.-sEulner-andeJoseph-FsMuellen Louisville, Ky. Application'March 119, 1953,-1Selial -N0.-343;402

'10"Claims. Y(Cl. 204`25) Intaglio 'print-ing rolls or cylinders are -customarily made Iby producing apolshed electroplated coppercoat- `irgg on arbasecylinder and either etching it or forming -a-V polished Ballard shell upon-it and Vthen ,etching the shell. Whiletherpresent invention may be employed with-some advantage in 4producing base cylinders, its 4greatest advantagesare realized when used in producing Bal-lard shells.

'Base -cylindersare conventionally made as follows:

--a-steel or cast iron cylinder of requisiteO. ,'D.` is provvided withga reasonably smooth peripheral surface;.t-his cylinder i-s--plated vin a conventional'copper `cyanidebath Awith la light copper coating approximating .001 in thicklness; the light copper-coated Vcylinder isplated usually under high current density conditions ina conventional copper acid bath with a'heavy coppercoating seldom less than 0.03" -in thickness and usually a little heavier; and the heavy coppercoated -cylinder is ground and polished to the desired O. D. -and itsendsare slightly-beveled or --rounded o. The resulting 'ba-se cylinder may be -etched or prepared for the reception of aBallard shell.

In-the latter event, the copper-surface of-t-he Vbase y'cylinder is cleanedvery carefully. The clean base cyl-inwhich is-now ready to `receive-the'Ballard shell.

YPolished Ballard shells conventionally-range in thickness from f.005-to .008". In producing .a-Ballard shell, the base cylinder, with its oiled blush-nickel coating, is `returned -to the acid-bath and-electroplated, u-nder high -current density conditions, with a -coppershell VAddition-agents are-customarily employed in-thi-s'bath toren- `der the .surface of the shellsrnooth, bright, and Yline grained. While modern vaddition agents effect -.a con .siderable improvement in one or more of :these respects, they do not yet result-in the-production of a surface which is ready to receive the etching. 'invariably the -resulting surface has va mottled appearance whichinterferes-with the layout of the etching'on the cylinder and `a surface roughness-.whicm'while normallyrinvisibleto -thenaked eye,.will nevertheless cause theshelL-When etched,fto print' Idirty, that is to'say, its-.unetched por- -.tions.will retain minute portions of ink and deposit-them gon the surface -being printed. Consequently, in conventionally producinga Ballard shell of say, i006, lit-is Ynecessary to. electroplate the .shell to `a thickness slightly -greater than 10.06", say 1.0.07,andf thenv grind andpolish -that shell y down tto the desired thickness. Normally A.grinding and-polishing is done-with aasuccessionotfour .stones, the first two stones primarily being coarse abrasive --grinding stones of :progressively finer .texture and -the Patented Jan. 11, ..1957

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last two `stones ,primarily being relatively ne rpolishing stones of progressively softer composition. Greatfcare must be exercised during thegrinding Aand-.polishing operation to avoidgrinding marks ,orother imperfections in the nal polished surface because-invisible..scratches willcause the` cylinder to print dir ty.`

The matter to be printed is etched inthe polished shell surface to depthsnormally rangingfrom .0002 -(5 microns), for the'lightest matter to be printed, to .0017" (42;5 microns),'for the darkest ,printed matter. ,In use, the cylinder is .rotationally vmounted -in erpress, the etched and unetched portions of its surface are inked, vthe excessink scraped Off .byiadoctor blade, and .the ink -remainingon the roll is then `deposited 0r ,printed onpaper. After the completion of ,the runf for which that particular shell was made, the cylinder is returnedto the plating room where the "Ballard 'shellis stripped from the polished base cylinder, permittingthe latter to be repeatedly usedin likemanner with a succession of new Ballard shells.

The Ballardprocess has come into wide use because ofits many advantages over the old practice of .etching thebase cylinder but it has many objections in common. with the .oldpractice It requires a shell to be electro- ,platedto excess thickness and necessitates the use, during 'the grinding and polishing operation, ofa costlyl grinding machine, relatively expensivegrinding and polishing stones,. expensive highly-skilled labor and an operating time ranging from one to two hours. Quitey often the shellis scratched or scored by unusually hard particles in one or more'of the stones. per, -`ground from 'thesurface itself,becomes embedded in .the polishing stones causing them to scratch or score..

Thus, it is not uncommon to score .a shell, either during;

grinding or polishing, to. such an extent as to render itv unusable; hence ,it can only be stripped and replated.,

VNor is ituncommon to nd a stonewith so many hard' particles in it that it can only be discanded. 'Further-- more-invisible scratches are often left in a shell, evenunder the most careful condition-s ofy operation, and these cause it to print "dirty. Finally, the grinding operation.

may break thebond between the shell and the baseV cyl-- inder and thusV render it unusable.

Heretofore 4attemptshavebeenmade to polish an in `taglio printing cylinder, while it is in the electroplating'` bath and during the electrodepositiomby burnishing itl with an agate, glass or other hard burnishing tool. The- Egli agate roller, described in U. S. 2,372,665, granted"v April 3, 1945, is representative of these attempts. This;

practice, however, tends to roll ridges in the deposit which can Anot very readily be rolled out and appar-- ently ,crushes and flattens ,the copper grains Ysince theV These scales: often'have poor adherence because they sometimes {lakedeposit is usually characterized byscales nover'the-cylinder andthus interfere with the proper de- Vposit ofcopper. 'Needless to say, this practice has not' come intowide use-and, inmany instances where-it has:

been used, it has beenffollowe'dby af grinding and polishing operation.

The'principalobject--of 'this invention is to overcome or avoidthe foregoing objections to `the -Ballard and lthe vburnishing processes without introducing offsetting objections of anyconsequence Morefpart-icularly, it is .ani-in portant objectof "this invention to provide a simple'inexpensive and; highly advantageous process fforso-'poli'shin-g an intaglio printing cylinder kwhile it-is-inthe--electro-f Sometimes cop plating bath and during the electrodeposition as to produce a smooth cylinder of uniform color at the end of the electrodeposition.

Another important object of the invention is to provide a process for producing contemporaneously with the end of the electrodeposition, a polished intaglio cylinder which is substantially ready to receive the etching i. e. ready to receive the etching without further treatment of any substantial character.

Another important object is to provide, contemporaneously with the end of the electroplating operation, a polished intaglio printing cylinder of superior hardness and tensile strength and having an extremely smooth image receiving surface.

A further object is to provide an intaglio printing cylinder characterized by a perfectly smooth or flawless, relatively hard surface having a bright mirror-like nish, this surface being formed by a dense, compact and homogeneous layer of electrodeposited copper.

We have found that when a cylinder is polish-brushed during an electrodeposition interval with a photoengravers plate or brass brush, the copper in the layer electrodeposited during that interval, is harder, denser and more homogeneous and its surface is smoother and of uniform brightness. In fact, under normal operating conditions, all of the foregoing objectives can be attained by brushing the cylinder over a period of time sufficient to produce an improved outermost layer of deposited copper of desired thickness. Thus, if a cylinder is brushed during the last thirty minutes of a two hour deposition period, the last one-fourth of the deposit will form an outer layer having the characteristics above described and the outer surface of that layer will normally be ready to receive the etching because its unetched portions will not print dirty. As a consequence, the cylinder can be plated to its iinal diameter and the use of stones with their attendant objections can be entirely eliminated. The deposit has no scale formation and therefore is not subject to ilaking. If a spot of grease falls on the surface during the polish-brushing operation, it will be removed from the cylinder rather than spread over it and will not interfere with the proper deposit of copper.

The invention is illustrated in the accompanying drawing wherein:

Figure l is a somewhat diagrammatical side elevational view of a plating tank apparatus embodying a brush for practicing the invention, this View showing part of the electrodes in dotted lines;

Figure 2 is a sectional view taken along line 2 2 of Figure l; and

Figure 3 is a reproduction of a photomicrograph showing the structure through the thickness of an electrodeposited shell produced in accordance with the present invention.

The apparatus illustrated in the drawings includes a plating tank 1 containing an acid bath of copper sulphate and sulphuric acid in the conventionally required proportions or concentrations. For instance, in a 250 to 300 gallon bath, there will be from 438 to 5 62 pounds of copper sulphate crystals and from 23.4 to 32.8 gallons of sulphuric acid with enough water to bring the bath up to the desired volume. To this solution may be added suitable addition agents which promote smoothness and fine grain, such as phenol sulphonic acid, glue, brighteners and the like. In fact, the use of addition agents, which are conventionally employed to render the shell smooth, bright and fine grained, is recommended. Among these are: a constant composition sold by DuPont under the trademark Dacolyte, which is essentially a ketone-sulphonate mixture; a pair of compositions sold for conjoint use by Standard Process Corporation of Chicago, Illinois, and designated as A and H; and another pair of compositions sold for conjoint use by Electrolytic Laboratories of Augusta, Maine and also designated A and H. Chemicals A and H are of unknown composition but at least one of them in each case includes phenol sulphonic acid. About one-half gallon of chemical A and three-fourths of a gallon of chemical H, as sold by the Electrolytic Laboratories, is recommended for a 250 to 300 gallon bath.

The cylinder 2 to be plated is laid across the tank with its trunnions 3, 4 extending through notches 5 in the sides of the tanks. Suitable bearing supports (not shown) hold the trunnions at an elevation such that the lower half of the cylinder dips several inches into the plating bath. The cylinder is continuously rotated during the plating operation by a suitable belt and pulley drive 6. An anode 7, composed of horizontal bar sections of pure copper, is suitably secured to the anode frame. By means of a sliding brush contact 8, a source of direct current of the proper magnitude and voltage is applied between the anode 7 and the cylinder 2 while the cylinder is continuously rotating.

The apparatus includes a brass brush 9 of the type commonly known as a photoengravers plate brush. The bristles of this brush are composed of iine springy brass or bronze wire or equivalent material. Thus we have obtained excellent results with a series of 3 high grade brushes, each having llexible brass bristles closely arranged in a 1%"x311" mass which is anchored in a wooden base, the bristles approximating .005 in diameter and S in length. Usually we discard a brush when its bristles are worn down to a length approximating Mi. Bristles with the least amount of tin or zinc last longer. Brushing of the cylinder may be done manually but preferably it is performed by a suitable reversing traversing machine of any conventional character. The brush should be conventionally insulated to avoid any current flow between the brush and the cylinder.

While the brushing may be performed over any suitable area of the cylinder, it is preferably performed at the top thereof by causing the brush to reciprocate axially from one end of the cylinder to the other. Preferably the brush should overrun each end from 2" to 3". As the brush moves along the top of the cylinder, the film of electrolyte, which is normally carried by the unsubmerged portion of the cylinder, will pile up against the brush and apparently wash it somewhat. This washing action is believed to lubricate the brush and wash away any irnpurities encountered by the brush. This may account for the failure of a spot of grease to interfere with the proper deposit of copper when that grease is deposited on the cylinder during the brushing action.

The speed of brush travel may vary widely. Good results can be normally obtained with a brush speed approximating 12 to 18 lineal feet per minute but this may be increased or decreased.

The brush pressure may vary widely with flexible brass bristles so long as they remain readily flexible. We normally employ a light pressure barely sufcient to insure uniform contact of the ends of the bristles with the cylinder. This pressure approximates .6 pound per square inch on a new brass-bristle brush and .4 to .5 pound per square inch on a used brush which has worn down to a point where the brush face conforms to the curvature of the cylinder. However, if the brush pressure is substantially increased, no damage will be done so long as the ends of the exible brass bristles remain in contact with the surface of the cylinder. Even where the pressure is so excessive as to flatten the brush bristles, no damage will normally be done unless the curved shoulders formed by the flattened bristles adjacent their anchored ends are forced into the deposited copper. As the hardness and stiffness of the bristle material progressively increases, the allowable maximum brush pressure will progressively decrease and care must be exercised in these regards because a brush having hard sti bristles will scratch and damage the cylinder if the pressure is too great. With such harder or stiier materals, it may be well to reduce the bristle diameter to say .003 more or less toobtain better flexibility.

In explaining the operation, we shall assume that a cylinder having an O. D. ofV 46 and an axial length of 76 is to be plated with a plating current capable of depositing ll()k ounces of copper in a 105 minute plating time to form a strippable shell which is .0063" thick. During the plating operation, the bath should be maintained at a temperature of 98 F. to 110 F. With the bath prepared, the oiled nickel-coated base cylinder is lowered until it dips about 4 to 5 inches into the bath. It may be conventionally rotatedV at a speed ranging from 130 to 220 P. M. but the limits of this range may be raised or lowered in accordance with conventional plant practice.

With the cylinder rotating, a clean cheese cloth is used to wipe the entire surface of the cylinder to insure that no foreign material adheres to it. Thereupon the electric current is turned on to institute the plating operation. Once the electrodeposition is begun it should not be interrupted because, when reinstituted, the current should be reversed to deplate for a short interval and since deplating is seldom uniform, it invariably results in a roughening of the surface. Brushing may be instituted at any time after the cylinder has taken on a good copper coloring. If hardness and smoothness are sought only in, say, the outer tenth of the thickness of the shell, the brushing may be deferred until the last tenth of the plating period. However, if the etching is to be` entirely contained within the brushed layer, brushing should be continued over an appropriately longer interval. Under the operating conditions above given, brushing during the last thirty minutes will result in the improved or brushed layer being approximately .0018 thick. If, between the time plating is started and brushing is instituted, an impurity such as` grease is accidentally dropped on the cylinder, brushing may be instituted immediately until that particular impurity is entirely removed. Thereupon brushing may be discontinued until the regular brushing interval begins.

Upon the completion of the plating operation, the apparatus maybe shut down and the cylinder removed from the bath and, carefully washed with water or otherwise treated to'insure the removal of the last traces of the coating solution. Normally the cylinder will now be ready for the etching operation. However, if a brighter finish is desired, two sheets of No. 400 wet and dry rouge or other extremely iine grained finishing paper may be rubbed together and then the cylinder surface lightly rubbed with one of these sheets until the finish is of the desired brightness. This operation seldom requires more than three or four minutes.

Figure 3 is a photomicrograph through the thickness of a Ballard shell having a thickness approximating .006". Here ity will be noted that the structure, through the thickness of the electrodeposited copper shell,` is characterized by two distinctly different portions and 11. The lower or inner portion i0, which was not polishbrushed during the electrodeposition and which is characteristic of conventional deposits, is not dense, compact or homogeneousA but isV believed to be a porous, section characterized by columnar growth or columnar crystals. The upper or outer portion il, which was polishedbrushed during electrodeposition, is quite different in appearance and structure. This portion is dense, compact and homogeneous and is believed to be made up of smallv non-columnar crystals of random orientation; It is characterized by a smooth, flawless, relatively hard surface 12 having a bright mirror-like nish. The copper l1, forming the surface 12, appears to etch faster and will etch more uniformly than the copper 10. The difference in the characteristics and structure of the portion 11 from that of the portion 10 is due solely to the brushing operation.

The surface 12 is smoother than would be the correspending surface of unbrushed copper. As we have previously pointed out, modernl addition agents effect a considerable improvement in smoothness, brightness and tineness ofV texture or grain. The resulting surface however, continues to. be mottled and rough. Usually the roughness is invisible tothe naked eye but it is suicient to cause the cylinder to printv dirty unless it is ground and polished. With the present invention, this invisible roughness is eliminated and the resulting surface is so smooth that it will not print dirty The elimination of this invisible roughness may be due to the fact that polishbrushing prevents columnar growth and promotes random orientation of the particles. Where addition agents are not employed, the roughness of the cylinder'will normally occur to a greater degree and such roughness will not in most instances be eliminated by polish-brushing although the surface will be polished or brightened to a considerable degree.

We are not able to explain completely the reason why bra-ss or bronze bristle brushes produce the beneficial results obtainedwith this invention. The action appears to be specific toV springy brasses or bronzes, such as are commonly employed in making wire brushes, for we have been unable to secure any improved surface or deposit by the use of steel ory fibre brushes. The terms brass and bronze are, usedy here interchangeably to designate each other and their equivalents.

Itwill be appreciated that a cylinder treated in accordance withl the present invention may be finished to the final4 dimension desired since it does noty require grinding of; the final platedsurface or other signiiicant treatment to prepare it for the etching operation. lt has a dense, hard, lustrous, surface of a reddish cast as compared to a, conventionally electroplated' cylinder which presents a mat pinky surface or av ground yellowish copper surface. Although an etched cylinder made in accordance with the present invention is more diiiicult to touch up because of the'hardness, this increasedhardness results in a longer life fof theV cylinder in the printing press. ln one instance aV cylinder prepared in accordance with our invention was used to make 650,000y impressions as compared to the usual life of aboutV 350,000 impressions. The hardness of polish-brass-brushed electrodeposited copper and its tensilestrength are substantially higher than unbrushed conventionally electroplated copper. The final improved surface is equally as smooth as, and we believe smoother than, the surface of a conventionally ground and polished cylinder. The surprising feature of our invention is that, when Va deposit is brushed during the end portion of the deposition, there are no scratches in the final surface which can be detected either under the magnification customarily. employed in this art in examining such surfaces or on the printed sheet.

It may be helpful to note that high current' densities are, always employed in electrodepositiug. rotogravure cylinders. It is known that when copper is electrodeposited under high current density conditions and without polish-brushing, the deposit always is made up of columnar crystals, i. e. crystals whose major axes of growth are normal to the plated surface. These crystals form by a process of nucleationand growth. The very iirst crystals to be nucleated have random orientations and grow in random directions. However, before appreciable deposition can occur, those crystals, whose major axes of growth are Aapproximately to the surface, dominate the structure because the other crystals, whose major axes of growth are nearly paralleltothe surface,- soon runinto one another preventing further growth in the parallel direction. In view of this and in further view of the change effected by polish-brushing, it seems correct to say that polish-brushing is substantial or that the polish-brushing time interval is substantial when the brush has been in contact with the cylinder long enough to effect the change and produce an unbroken deposit of the structural character indicated at 11 in Figure 3 but of relatively minute depth, and, under appropriate operating conditions, this may occur within a minute or less.

It will also be appreciated that a polish-brush, having a length substantially equal to that of the cylinder itself, may be employed and either reciprocated over a very short distance or simply lowered into light firm Contact with the rotating cylinder whenever brushing is desired. Other forms of brushes, such as those which rotate, may be employed.

While we have explained this invention in connection with rotogravure cylinders, it will be appreciated that it is equally applicable to other copper depositing operations such as electrotyping. In the manufacture of electrotype, a raised-type printing member is formed by electroplating a copper coating on a cathode mold in a copper depositing acid bath. Here it is desirable, but not essential, to get a perfectly smooth surface on the printing face of the type. It is, however, of importance to make the metal forming the printing face of the type as hard as possible to withstand wear. it becomes possible to produce, contemporaneously with the end of the electrodeposition, a hard polished typeface which reproduces the surface characteristics of the corresponding portion of the mold and which is substantially ready for conventional electrotyping use in that it does not require further surface treatment of substantial character.

The present process produces a very substantial increase in the hardness of the copper deposit. In fact, so far as we know, the hardness of the copper deposited by our process is substantially greater than the hardness of any electrodeposited copper heretofore known. Since exceptional hardness is thus obtainable, this invention is not limited to polish-brushing but should be construed to cover any type of brushing which promotes hardness, particularly since hardness may be desired where a nal smooth surface is not a requisite.

Furthermore, since the brass brushing of a copper deposit clianges the character of that deposit it becomes evident that this process can be used to advantage in the electroplating of other metals from acid baths using, for brushing purposes, a brush having flexible, acid-resistant metal bristles. Preferably the brush employed should be of the type recommended for that particular metal so long as it is acid-resistant. Thus Langbein, in his book entitled Electrodeposition of Metals, 9th edition, published in 1924 by Henry Carey Baird and Company, recommends, on page 267, brass brushes for zinc deposits. For nickel and chromium deposits either a nickel or a stainless steel brush should give good results.

This application is a continuation-in-part of our copending application Serial No. 11,604, filed February 27, 1948, and now abandoned.

We claim as our invention:

1. An improvement in the art of manufacturing an intaglio printing cylinder wherein a copper coating is electroplated on the smooth polished periphery of a base cylinder while it is rotating in a copper depositing bath comprising: polish-brushing the copper coating on the periphery of the rotating cylinder with a flexible brassbristle brush for a substantial time during the end portion of the deposition period and while copper is being deposited on the cylinder to produce a smooth polished cylinder substantially ready for the etching operation.

2. The improvement of claim 1 wherein: said polishbrushing operation is performed by reciprocating said brass brush axially relatively to said rotating cylinder,

With the present invention 3. The improvement of claim 1 wherein: substantially continuous brushing occurs during the deposition of an outermost copper layer having a thickness not substantially less than the depth to which said cylinder is to be etched.

4. An improvement in the art of manufacturing an intaglio printing cylinder wherein a strippable copper shell is electroplated on the smooth polished periphery of a rotating base cylinder while it is partially submerged in a tine-grain copper-depositing acid bath comprising: polish-brushing the unsubmerged portion of the copper coating on the periphery of the rotating cylinder with a brush, having flexible brass bristles pressed against said coating for a substantial time during the end portion of the deposition and while shell-forming copper is being deposited on the cylinder to produce a smooth polished cylinder substantially ready for the etching operation.

5. The improvement of claim 4 wherein: the polishbrushing operation is performed by reciprocating said brass brush axially relatively to said rotating cylinder.

6. The improvement of claim 4 wherein: substantially continuous brushing occurs during the deposition of an outermost copper layer having a thickness not substantially less than the depth of the etching it is intended to receive.

7. An improvement in the art of manufacturing an intaglio printing cylinder of desired nal diameter comprising: electroplating a strippable copper shell on the smooth polished periphery of a rotating base cylinder of smaller diameter while said cylinder is partially submerged in a tine-grain copper depositing acid bath, said electroplating operation being continuously performed until the outside diameter of said shell equals the desired nal diameter; and polish-brushing the unsubmerged portion of the shell-forming deposit on the rotating cylinder with a flexible brass-bristle brush for a substantial time during the end portion of the deposition and while shellforming copper is being deposited on the cylinder to produce a smooth polished cylinder of desired inal diameter substantially ready for the etching operation.

8. The improvement of claim 7 wherein: said brushing operation is performed by reciprocating said brass brush axially relatively to said rotating cylinder.

9. An improvement in the art of manufacturing a printing member wherein a copper coating is electroplated on a cathode in a copper depositing acid bath comprising: polish-brushing the copper coating on the cathode -with a relatively moving flexible brass-bristle brush for a substantial time during the end portion of the deposition period and while copper is being deposited on the cathode to produce a hard polished surface substantially ready for conventional use without further surface treatment.

10. An improvement in the art of electrodepositing metal comprising: electrodepositing metal on an electrode in an acid bath; and preventing columnar growth, while metal is being electrodeposited, by simultaneously brushing the deposit with flexible, acid-resistant metal bristles.

References Cited in the ille of this patent UNITED STATES PATENTS FOREIGN PATENTS 702 Great Britain 469,689

1889 Great Britain July 30, 1937

Claims (1)

1. AN IMPROVEMENT IN THE ART OF MANUFACTURING AN INTAGLIO PRINTING CYLINDER WHEREIN A COPPER COATING IS ELECTROPLATED ON THE SMOOTH POLISHED PERIPHERY OF A BASE CYLINDER WHILE IT IS ROTATING IN A COPPER DEPOSITING BATH COMPRISING: POLISH-BRUSHING THE COPPER COATING ON THE PERIPHERY OF THE ROTATING CYLINDER WITH A FLEXIBLE BRASSBRISTLE BRUSH FOR A SUBSTANTIAL TIME DURING THE END PORTION OF THE DEPOSITION PERIOD AND WHILE COPPER IS BEING DEPOSITED ON THE CYLINDER TO PRODUCE A SMOOTH POLISHED CYLINDER SUBSTANTIALLY READY FOR THE ETCHING OPERATION.

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