US 3393141 A
Description (OCR text may contain errors)
y 1968 HANS-DIETER TRENN ETAL 3,393,141
TOOL FOR ELECTROCHEMICAL CONTOURING OF WORKPIECES Filed May 11, 1965 Fig.4 Fig.5
United States Patent 3,393,141 TOOL FOR ELECTROCHEMICAL CONTOURING 0F WORKPIECES Hans-Dieter Trenn and Gerhard Hebold, Mulheim (Ruhr), Germany, assignors to Siemens Aktiengesellschaft, Munich, Germany, a corporation of Germany Filed May 11, 1965, Ser. No. 454,949 Claims priority, application Germany, May 16, 1964,
8 Claims. (Cl. 204-224) Our invention relates to the production of contours or profiles on workpieces by electrochemical processing. Such contouring work is performed by electrolysis with the aid of a template electrode which is shaped in accordance with the desired contour and is moved relative to the workpiece to be shaped.
Electrochemical contouring with such electrolytical template tools, however, becomes difiicult or deficient in cases where precise corners or edges at the workpiece are required. These difiiculties are mainly due to the fact that the corresponding corners of the template contour cause irregularities in the flow of electrolyte so that sludge tends to accumulate in such corners. This interferes with the chemical processing or may cause short circuits and leads to undesired changes in the shape at the corners of the workpiece, so that these corners are no longer sharp but more or less rounded.
It is an object of our invention to improve electrochemical template tools so as to avoid or minimize such difiiculties and trouble. Another, more specific object of the invention is to devise an electrochemical template of a cornered contour shape that reliably secures a troublefree drainage of the sludge-containing electrolyte at the corners of the tool.
According to the invention, we provide the template tool electrode at the corners of the workpiece contour with respective recesses which widen the electrolyte flow path at each corner. Preferably, the recesses are located symmetrically to the respective bisectors of the corner angles.
The recesses may be formed as slits. Their width may be dimensioned in accordance with the particular working conditions of the tool, such as the electric current intensity, voltage, rate of tool feed movement, 01: the particular workpiece material. With proper recess dimensions, any burr formation or accumulation of material at the corners can be readily prevented. Thus, the recess-forming slits in the tool reliably prevent burr formation, if the slit width at each corner amounts to about twice the width of the processing gap at the longitudinal faces of the workpiece being processed.
The invention will be further described with reference to the drawing in which:
FIG. la illustrates schematically a known electrolytic contouring device, and FIG. 1b is a front view of the contouring electrode of the device.
FIG. 2 illustrates the cross section of a workpiece electrolytically produced by means of an electrode according to FIG. 117.
FIG. 3 shows part of a tool electrode according to the invention for producing sharp edges at electrolytically contoured workpieces.
FIGS. 4 to 7 show modified contour shapes of tool electrodes otherwise designed according to FIG. 3.
The contouring device schematically illustrated in FIG. 1a comprises a support a with a holder or chuck b for fastening a workpiece c to be contoured by electrolytical processing. The contour to be produced is determined by an annular template electrode 2d which is fastened to a tubular electrode holder e on a carrier f. The carrier is supported on a slider (not shown) which is displaceable on the machine frame structure by suitable feed means 3,393,141 Patented July 16, 1968 in a direction toward the workpiece. The support a and the holder 3 are connected to the positive and negative leads of a suitable source of electric current. Electrolyte is supplied through inlet and outlet tubes g and h to flow through the inner space of the tubular holder e and between the electrode d and the workpiece c. The electrolytic action, then occurring between the template electrode d and the workpiece c, dissolves material from the workpiece 0 thus shaping its contour in accordance with the template contour of the tool electrode.
According to the front view of the electrode tool 0! shown in FIG. 1b, the template contour is that of a regular hexagon, so that the workpiece, after the tool electrode has longitudinally passed over the entire length of the workpiece, has assumed a corresponding hexagonal shape.
The electrolyte continuously supplied during simultaneous axial displacement of the tool electrode relative to the workpiece may consist, for example, of an aqueous solution of sodium chloride or sodium nitrate. As a rule, the template contour of the tool is given a slightly larger size than required of the workpiece. Despite the sharp corners of the template contour in the electrode tool d according to FIG. 1b, the resulting contour of the workpiece, shown in FIG. 2, does not have sharp edges but is slightly rounded. As mentioned above, this is due to the fact that the sludge-containing electrolyte can not as readily flow through the gap at the contour corners as at the other localities along the perimeter.
In contrast thereto, FIG. 3 shows on larger scale a template tool according to the invention. This tool is distinguished by the fact that the electrode body 1 is provided with recess in form of slits 3 at the respective corners 2a of the workpiece contour to be produced. The slits 3 are symmetrical to the bisectors 4 of the angles at the corners of the workpiece contour, and they are given a width equal to 2B, if B denotes the processing gap left between the planar faces of the workpiece 2 and the corresponding template faces of the tool electrode. The gaps provide an enlarged flow space for electrolyte passing through the gap so that any detrimental accumulation of sludge in the region of the corners is avoided. It will be readily apparent, that the electrode slits can be accurately dimensioned, in accordance with the particular operating conditions (current intensity, voltage, rate of feed) to obtain any desired shape at the sharp corners of the workpiece and to avoid burr or bulge formation.
The electrode slits or recesses 3 in the corner regions of the workpiece may be given various other shapes. Some such other shapes are exemplified in FIGS. 4 and 5. According to FIG. 5, the slits are contiguous to the corners of the template contour and each slit extends from the corner in the radial outward direction with parallel slit walls but has a widened cylindrical bore 3a at the outermost end.
In the embodiment of FIG. 5 the walls 3b of the slits extend from the template contour outwardly at an angle in such a manner that the individual slit widens with increasing distance from the workpiece, the radially outward end of the slit being closed by an arcuate wall portion 30 of the template electrode.
The invention is not limited to the processing of pris matic workpieces having a cross section of hexagonal shape, but is applicable, in principle, with any other crosssectional shapes limited by planar, curvilinear, or com posite planar and curvilinear surface portions. For example, FIGS. 6 and 7 show template contours with examples of a suitable design and location of the slits in tool electrodes for workpieces of the latter types. For such composite workpiece contours, the recesses or slits at the corner of the template contour are preferably arranged in symmetrical relation to the bisector of the angle between the tangents of the curved wall portions forming the corner, or symmetrically to the bisector of the angle between the tangent of a curved wall portion on the one hand and an adjacent planar wall portion on the other hand.
However, the invention is not limited to having the electrode slits extend symmetrically to the abovementioned bisectors, and it is sometimes also desirable to give the recesses or slits a width different from the one memtioned in the above-described example.
1. Device for electrochemical contouring of workpieces, comprising a tool electrode having a template contour corresponding to a cornered workpiece contour to be produced and adapted to form with the workpiece a perimetric gap to be traversed by electrolyte for removing material from the workpiece, said electrode having respective recesses located at the corners of the workpiece contour and forming in said electrode a widened flow path for electrolyte through the corner regions of the template contour.
2. In an electrochemical contouring device according to claim 1, said recesses comprising respective slits extending outwardly from the template contour.
3. In an electrochemical contouring device according to claim 2, each of said slits extending substantially in symmetrical relation to the bisector of the angle at the corner of the workpiece contour.
4. In an electrochemical contouring device according to claim 2, said slits adapted to have a width substantially twice as large as the width of said gap.
5. In an electrochemical contouring device according to claim 2, said slits having a shape widening from said template contour in the outward direction.
6. In an electrochemical contouring device according to claim 2, said slits having a straight parallel-wall portion adjacent to said template contour and ending in the outward direction in a cylindrical portion of larger width than said straight portion.
7. In an electrochemical contouring device according to claim 2, said workpiece contour having two curved faces meeting at one of said corners, and said slit ofsaid electrode at said one corner extending in Symmetrical relation to the bisector of the angle between the respective tangents of said two curved faces.
8. In an electrochemical contouring device according to claim 2, said workpiece contour having a curved face and a planar face meeting at one of said corners, and said slit of said electrode at said one corner extending in symmetrical relation to the bisecto'r of the angle between said planar face and the tangent of the curved face at said corner.
References Cited UNITED STATES PATENTS 3,288,699 11/1966 Trageretal. 20 4 22 1 3,324,021 6/1967 Haggerty 204 224 3,324,022 6/1967 Keeleric 204224 JOHN H. MACK, Primary E ruminer.
D. VALENTINE, Assistant Examiner.