FR2468435A1 - PROCESS FOR THE ELECTRO-EROSION MACHINING OF A METAL PIECE - Google Patents

Abstract

Process for machining a metal part by spark or electro-erosion. The machining electrode It moves on the part I, in a plane passing through this part, along a line of intersection of this plane with an outer wall of the part, removing the material as desired. along this line of intersection by spark. Production of contours of any shape, as well as indentations and openings on parts, for example strips of hard material.

Description

The subject of the present invention is a method for machining by electromechanical

  erosion or sparking of a piece

  metal on a spark machine controlled by a computer

  which includes a table of posi-

  movable in a plane along two co-ordinates and a machining electrode movable relative to this plane along a third coordinate, in which the movements of the workpiece and the movements of the electrode

  machining are controlled via the computer

  following pre-given programs.

  Processes of this kind are known which make it possible to carry out automated machining operations on the part held fixed in the machine. Thus, for example, the part is positioned appropriately to

  using a perforated band and a vertical mobile electrode

  hold went down into the room to make an opening

  ture. Such work operations are repeatable at

  the same, with a constant aperture diameter, in use

  reading the same machining electrode, possibly after changing the position of the part. In case of change of

  opening diameter, the machining electrodes are replaced

  possibly automatically, the exchange operation

  being controlled by the perforated band.

  It is also possible and common to produce external contours on parts which can have as complicated shapes as one wants by automatically penetrating into the workpiece of the machining electrodes.

appropriate form.

  The disadvantage of the known methods is that the elec-

  machining trodes used must be adapted to the shape

  material to be made and to be chosen in a similar way.

  This is why the manufacture of such machining electrodes is a relatively complicated operation entailing corresponding tooling expenses. If the machining operations are performed in large series, the wear suffered

  machining electrodes makes it necessary to maintain a supply of

  important dimensioning of these electrodes.

  The object of the invention is to improve the known processes of the type indicated at the beginning and to make it possible to produce even complicated contours on metal parts by electro-erosion without being obliged to use machining electrodes of corresponding shape. The electrodes used must have a shape essentially independent of the shape of the surface to be machined by electro-erosion and must

  can be easily replaced when worn.

  This result is obtained by the invention with a

  of the type indicated at the beginning due to the fact that the machining electrode is guided on the workpiece in a plane passing through the workpiece, along the line of intersection of this plane with an outer wall or an inner wall of the piece, so as to flash-remove the material of the piece on

  along this intersection line.-

  This method makes it possible to produce contours of any shape in this plane. By properly programming the computer controlling the machine, it is possible to

  to make parts of any shape with the possibility of

  a number of superimposed machining planes, or

  angularly offset from each other. The

  shape of the machining electrode whose active surface exerts

  the sparking effect may be of a generally linear

  area, or spread on the surface, must be adapted to the conditions

  space available on the article dealt with, and possibly

  the width of the surface to be machined.

  The characteristics and advantages of the invention

  will emerge, moreover, from the following description,

  for example, with reference to the accompanying drawing in which

  Figures 1, 2 and 3 represent three

  my different machining according to the invention of a band of

hard metal.

  In FIG. 1, there is shown in FIG.

  tangular hard metal that one wants to machine smooth by

  electro-erosion or sparkle along its straight edges

  2, 3 and 4, which are also to be electro-

  erosion, in zones 5 and 6, of notches 7 and 8 of form

  for example circular, by removal of the corresponding material

  laying. The sheet metal strip 1 is mounted on the moving table

  cross-sections of the spark-erosion machine so that, under the control of a computer, it can move in a horizontal plane along the X and Y axes of rectangular coordinates, and a working electrode 11, with a section

  transverse circular, also controlled by a computer

  tor, is mounted in the upright of the machine and can move perpendicular to this horizontal plane along the Y axis. To machine the sheet 1, the electrode 11 is moved along the Z axis, bringing it into the plane of the sheet 1 along the edges thereof, the electrode 11 being disposed by its center, for example, at such a distance from the edge 3 as it is formed between the surface of the machining electrode 11

  and the edge 3 a gap of appropriate size. Through

  the width of this gap is subjected to the usual process of adjustment of gap width, so that this gap width is kept constant in a manner known per se. Then, the machining electrode 11 is moved parallel to the edge 3, along the latter, in the plane of the sheet metal strip 1 in the direction of the arrows 12 and 13, and the edge 3 is thus machined smooth by spark. We proceed in the same way with edges 2 and 4. When short circuits occur

  between the machining electrode 11 and the sheet 1, it is advantageous

  giously arranged to adjust the position of the electrode of

  float by increasing the interval between this electrode and the contour during machining. For this purpose, it is, for example, advantageous to move the sheet 1 in the direction opposite to the machining electrode 11. In order to reduce the wear that the machining electrode 11 undergoes, this electrode about its axis so that each location of the periphery of the machining electrode 11 participates in the machining process in a manner corresponding to the speed

rotating said electrode.

  To machine the indentations 5 and 6, the machining electrode 11 is lowered in the plane of the sheet metal strip 1 by making it penetrate into the plane of the edge A. According to the ratio between the size of the indentation and the diameter of the machining electrode, this operation can be performed either in a single workpass or in several successive work passes, each of which removes a quantity

  partial of the material of the recess of the sheet metal strip 1.

  It can be seen that the method described can be adapted to the thickness of the sheet metal strip 1 by appropriately choosing the dimension in the direction of the Z axis of the electrode 11, that is to say the dimension of this electrode perpendicular to the plane of the drawing. The stretched action surface in which the machining sparks are produced between the machining electrode 11 and the sheet metal strip 1 is thus adaptable to the thickness of the strip of

sheet.

  As can be seen also, it is not neces-

  that the sheet metal strip 1 coincides with the plane of the X and Y axes of the spark-off machine. The plane of the sheet metal strip 1 may have any angular position with respect to the plane passing through the X and Y axes, and for this purpose the machining electrode 11 must be inclined correspondingly. By appropriately controlling the three axes of movement of the machine, the tracking movement of the machining electrode is determined in a desired manner in the edge of the plane of the sheet metal strip 1. It is thus possible to realize in 'imported

  which plane of section of a part any external contour

  inside and out, these outlines being made by guiding

  the machining electrode along this machining contour.

  In FIG. 2, a strip of hard sheet has been shown on the outer side of which it is desired to make a sawtooth contour 21. To achieve this contour, a machining electrode 22, elongated in shape, is used. the plane of the drawing and provided with a tip whose dimension in the direction perpendicular to the plane of the drawing substantially corresponds to the thickness of the sheet 20. For the machining of

  accuracy of the contour, this electrode is guided parallel-

  audit contour so that it forms between the tip

  of the machining electrode and the contour the usual gap.

  The electrode 22 is guided parallel to the contour and the latter is subjected, in a manner known per se, to the smooth machining process by flashing. It is advantageously provided that the machining electrode 22 is mounted so as to be able, like the electrode 11 of FIG. 1, to rotate around its main axis of displacement and to pivot at certain angles. This possibility of pivoting

  the machining electrode also allows, as shown in FIG.

  re 2, to produce discontinuous contours.

  FIG. 3 shows a strip of hard metal which is provided with a recess 31. The inner edge of the recess is machined by electroerosion by means of a

  machining electrode 32 which moves in the direction of the arrows

  represented. The active surface of the machining electrode

  used for spark machining present in this

  example of a particularly simple embodiment, dimensions

  important and has a rectangular shape.

  It is not mandatory that the contours to be made according to the invention are, with the inclination of the surface to be treated, placed perpendicular to the workpiece mounting plane which is taken as a basis for machining. Thus, for example, the edge contours 7 and 8 of the example

  embodiment shown in FIG. 1 can be inclined

  born at an angle other than 90 from the plane of the drawing. To achieve the contour, it is necessary to incline the sheet 1 correspondingly, or to give the electrode

  machining a corresponding inclination.

  The process according to the invention is distinguished essentially

  by the fact that the machining electrode that presents itself

  in the form of a unitary electrode has a surface area of

  which may possibly take a linear shape, and which, along the edge to be machined, along which it is guided in the direction of the edge, has a dimension corresponding to the width of the edge to be machined. This dimension can not be given a greater value than along edges which, in the sense of this surface, have no accumulations of material or do not have any troublesome. However, on the other hand, it is possible to give the spark-acting surface a dimension smaller than the width of the edge to be machined. In such cases, it is necessary that the electrode passes several times on this edge. Another advantage of the process according to the invention is

  that, however complicated the form of outward contours,

  in the working plane of the workpiece,

  Geometrically shaped machining electrodes can be used.

  as simple, for example round, angled, triangular or other. The cost price of the treatment of obtaining by

  electro-erosion of different room shapes is noted.

  lowered. The corresponding expenditure for the programming of the control of the machine tool is reduced in a comparable way.

24684-35

Claims (3)

REVENDI CATIONS   1. A method for machining by electro-erosion or sparkling of a metal part on a computer-controlled sparking machine, which comprises for mounting and fixing the workpiece a mobile positioning table in a plane along two coordinates , and a machining electrode   able to move in relation to this plane following a third   coordinate, a process in which the movements of the   piece and the movements of the machining electrode are controlled   through the computer following   my pre-established, characterized in that the machining electrode is guided on the workpiece in a plane passing through the workpiece, along the line of intersection of this plane with an outer wall or an inner wall of the workpiece , so as to flash off the material of the piece along this line of intersection.   2. Method according to claim 1, characterized in that, for machining the outer contour, a   machining electrode having in section with the plane of machining   a symmetrical form of revolution, and that electricity   machining trode can rotate and rotate around its axis of symmetry.   3. Process according to claim 1 or 2, characterized   in that in the event of a short-circuit occurring between the machining electrode and the machined part, the gap formed between the machining electrode and the contour to be produced is increased by increasing the interval between the machining electrode and the machined part. machining electrode and the   machined part, measured perpendicular to the contour.