U.S. patent application number 13/194293 was filed with the patent office on 2012-02-02 for method for producing a metal component.
This patent application is currently assigned to LEISTRITZ TURBOMASCHINEN TECHNIK GMBH. Invention is credited to Martin ROEBLITZ, Georg SCHMIDT.
Application Number | 20120024717 13/194293 |
Document ID | / |
Family ID | 44912121 |
Filed Date | 2012-02-02 |
United States Patent
Application |
20120024717 |
Kind Code |
A1 |
ROEBLITZ; Martin ; et
al. |
February 2, 2012 |
METHOD FOR PRODUCING A METAL COMPONENT
Abstract
Method for machining a metal component which has a
three-dimensional shape produced by removing and/or shaping
material, wherein one or more superior component sections are
electrochemically finish-machined by means of a nozzle-like
cathode, via which an electrolyte is delivered into the working
region, and wherein the cathode or the metal component is moved
freely in space by means of a manipulator element.
Inventors: |
ROEBLITZ; Martin;
(NUERNBERG, DE) ; SCHMIDT; Georg; (SCHWABACH,
DE) |
Assignee: |
LEISTRITZ TURBOMASCHINEN TECHNIK
GMBH
Nuernberg
DE
|
Family ID: |
44912121 |
Appl. No.: |
13/194293 |
Filed: |
July 29, 2011 |
Current U.S.
Class: |
205/645 ;
204/229.8; 204/242; 205/670; 901/41 |
Current CPC
Class: |
B23H 3/00 20130101; B23H
11/00 20130101 |
Class at
Publication: |
205/645 ;
205/670; 204/242; 204/229.8; 901/41 |
International
Class: |
C25F 3/16 20060101
C25F003/16; C25F 7/00 20060101 C25F007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 29, 2010 |
DE |
102010032701.8-34 |
Claims
1. A method for machining a metal component which has a
three-dimensional shape produced by removing and/or shaping
material, the method comprising the steps of: electrochemically
machining at least one superior component section using a
nozzle-like cathode, via which an electrolyte is delivered into a
working region; and moving the cathode or the metal component
freely in space with a manipulator element.
2. The method according to claim 1, wherein the manipulator element
is a robot having a plurality of motion axes.
3. The method according to claim 2, wherein the robot has five or
six motion axes.
4. The method according to claim 1, including also moving the metal
component arranged on a movable work holder in the case of the
cathode being moved by the manipulator element during
machining.
5. The method according to claim 1, including also moving the
cathode arranged on a movable holder in the case of the metal
component being moved by the manipulator element during
machining.
6. The method according to claim 1, including delivering the
electrolyte as a stream of substantially round cross section from a
cathode having a corresponding cross-sectional geometry.
7. The method according to claim 1, wherein a working voltage
applied between the cathode and the metal component or a process
current flowing therebetween is constant or pulsed and/or a
volumetric flow of the electrolyte is between 10 and 100 l/h.
8. The method according to claim 7, including determining a
distance of the cathode from a surface of the metal component from
a ratio of working voltage and process current and/or, as a
function thereof, and controlling a process sequence by varying any
desired process parameter.
9. The method according to claim 6, including blowing out a gas
curtain laterally enclosing the electrolyte stream at least partly
via the cathode.
10. The method according to claim 1, wherein the metal component to
be machined consists of a metallic or intermetallic material.
11. The method according to claim 10, wherein the metal component
is a steel, a titanium alloy or a nickel alloy.
12. The method according to claim 1, wherein the metal component is
a component of a turbomachine.
13. The method according to claim 12, wherein the component of a
turbomachine is a blade component, in particular a guide vane
cluster or a guide vane ring.
14. The method according to claim 13, wherein the superior
component sections machined are edges and surfaces in a region
between two airfoils of the blade component and/or the airfoils of
the blade component themselves.
15. An apparatus for implementing the method according to claim 1,
comprising: a manipulator element formed as a multi-axis robot; an
ECM tool formed as a nozzle-like cathode or a work holder arranged
on the manipulator; an electrolyte feed device for feeding
electrolyte from an electrolyte reservoir to the cathode; a process
energy source connected to the cathode and the metal component; and
a control device controlling operation of the apparatus.
16. The apparatus according to claim 15, wherein the cathode has a
round cross section.
17. The apparatus according to claim 15, wherein the cathode is
designed for delivering gas, fed to the cathode via a gas feed
device, formed as a gas curtain laterally enclosing the electrolyte
stream at least partly, said electrolyte stream discharging from
the cathode.
18. The apparatus according to claim 15, wherein the work holder is
additionally movable when the cathode is arranged on the
manipulator element, or the cathode is additionally movable when
the work holder is arranged on the manipulator element.
19. The apparatus according to claim 15, further comprising means
for detecting a distance of the cathode from a surface of the
component.
20. The apparatus according to claim 19, wherein the means is the
control device, which determines the distance with reference to a
ratio of working voltage and process current and, as a function
thereof, controls a process sequence by varying any desired process
parameter.
21. The apparatus according to claim 19, wherein the means is a
sensor, wherein the control device controls a process sequence by
varying any desired process parameter as a function of a detection
result of the sensor.
Description
[0001] This application claims priority to German Patent
Application No. 1020010032701.8 filed Jul. 29, 2010, the contents
of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] The invention relates to a method for machining a metal
component which has a three-dimensional shape produced by removing
and/or shaping material.
[0003] Metal components are machined or shaped using various
methods in order to obtain a desired three-dimensional geometry.
Material-removing methods such as, for example, drilling, turning,
milling, EDM (electrical-discharge machining) and ECM
(electrochemical machining) or material-shaping methods such as,
for example, stamping, pressing or forging are known. These methods
normally serve for rough contouring, i.e. the three-dimensional
shape is substantially fashioned by these working processes.
Superior component sections, however, still have to be subjected to
finish machining in order for any burrs, projections, edges,
corners and the like to be removed, etc. This finish machining is
effected in most cases by milling. Whereas this is often
straightforwardly possible in the case of large metal components on
account of the accessibility of the superior component sections
which are to be finish-machined, problems often arise in particular
with smaller metal components or with metal components in which the
superior component sections are either very narrow or are difficult
to reach on account of the component geometry, since the tool can
be guided into the desired region only some of the way, if at all.
Further problems are often caused by the material of the metal
component. Special alloys, such as, for example, titanium alloys or
nickel alloys, are often used in particular for special
applications. Whereas components made of titanium alloys still have
sufficient machinability and can therefore, for example, be
satisfactorily milled, components made of nickel alloys have
relatively poor machinability. In conjunction with complex
geometrical relationships, this gives rise to even greater problems
in the course of the finish machining.
SUMMARY OF THE INVENTION
[0004] The problem addressed by the invention is therefore to
specify a method which is intended for machining a metal component
and makes possible finish machining of superior component sections
even in the case of complex component geometry and difficult
machinability of the component material.
[0005] To solve this problem, provision is made in a method of the
type described at the beginning for one or more superior component
sections to be electrochemically finish-machined by means of a
nozzle-like cathode, via which an electrolyte is delivered into the
working region, wherein the cathode or the metal component is moved
freely in space by means of a manipulator element.
[0006] In the method according to the invention, the finish
machining of the superior component region or regions, such as in
the region of edges, surface transitions, burrs and the like, is
effected by electrochemical machining, normally called ECM. For
this purpose, use is made of a nozzle-like cathode, via which the
electrolyte is delivered directly into the working region. That is
to say that the electrolyte is fed to the cathode and, at the tip
of the nozzle-like cathode, flows directly onto the metal component
(workpiece) to be finish-machined. The application of a working
voltage between metal component and cathode produces a process
current which causes material to be removed. The metal component
itself here is anodically polarized. Via the nozzle-like cathode,
material can thus be removed from the workpiece in a precisely
defined region, specifically only in the contact region of the
impinging electrolyte stream. According to a first alternative of
the invention, the cathode itself is arranged on a manipulator
element, preferably a multi-axis robot, preferably one having at
least five motion axes, via which robot, with associated control
device, the cathode can be moved freely (three-dimensionally) in
space. That is to say that the cathode can be moved in any desired
manner and can therefore also traverse any desired geometries.
Since the cathode itself is a very thin, narrow component having a
diameter of only a few millimeters, it can consequently be moved
even into extremely narrow, constricted component regions, and
displaced there, via the robot. This in turn makes it possible even
for components having a very complex geometry to be machined free
of machining forces in superior, otherwise scarcely accessible
regions. According to a second alternative of the invention, the
metal component can be moved freely (three-dimensionally) in space
by means of the manipulator element, again preferably a multi-axis
robot, preferably one having at least five motion axes; that is to
say that, here, the metal component is moved in any desired manner
relative to the thin cathode. As a result of the free mobility,
even complex geometries can be machined by means of this motion
variant. The invention is therefore based on the idea that there is
spatially free relative mobility between cathode and metal
component, and this relative mobility is realized by means of the
manipulator element.
[0007] The electrochemical working process also enables a wide
variety of different materials to be machined, that is to say that
even materials which are difficult to machine using conventional
working processes, because they are very difficult to cut, can be
readily machined by ECM. In conjunction with the freedom of
movement of the cathode or of the metal component, that is to say
the mobility in any desired manner in space, the method according
to the invention therefore offers the possibility of being able to
finish-machine any desired components or complex geometries
virtually irrespective of the material used.
[0008] As described, the manipulator element provided is a robot
which should have preferably five motion axes, but it can equally
also have six axes, thereby ultimately providing for even more
degrees of freedom of movement. This multi-axis configuration
enables both translational movements in the three space directions
and rotational movements about the space directions.
[0009] According to a development of the invention, the movement is
not restricted only to the cathode according to the first
alternative of the invention or to the metal component according to
the second alternative of the invention. Rather, it is also
possible to move the metal component (with free mobility of the
cathode) or the cathode (with free mobility of the metal component)
in addition, that is to say to permit, for example, a translational
movement, for example along one or more space axes, or to rotate
said metal component or cathode, possibly in addition, about one or
more space axes. That is to say that there are additional degrees
of freedom of movement at the respectively other central working
element, in addition to the movements which are possible via the
manipulator element.
[0010] As stated, the cathode is a thin tube having a diameter of a
few millimeters, provided it is round in cross section and delivers
a round electrolyte stream. Alternatively, an as it were "squeezed"
cathode, which is longer than it is wide, or a hollow cathode
having any other desired cross section can be used. The geometry of
the working region is defined according to the electrolyte stream
geometry, for which reason the corresponding cathode geometry is
selected according to the component section to be machined. In
order for workpiece sections which are difficult to access to be
reached more easily, curved or angled cathode embodiments can be
used.
[0011] The essential process parameters are the distance between
cathode and workpiece, the working voltage or the process current,
the dwell time of the cathode above the location to be machined or
the associated feed rate of the cathode relative to the metal
component, and the composition and the volumetric flow of the
electrolyte. By suitable selection of these parameters, the
material removal can be controlled with regard to removal depth and
removal rate, care always having to be taken when setting the
parameters that as few stray currents as possible occur, which
would possibly lead to material also being removed outside the
actual working region. For example, it is possible for the working
voltage which is applied between cathode and metal component, and
typically between 5V and 200V, or the process current flowing
therebetween to be constant or pulsed and/or for the volumetric
flow of the electrolyte to be between 10 and 1001/h.
[0012] The control of the robot, that is to say the movement of the
cathode for traversing the component geometry to be machined, is
effected via a suitable control device which has a corresponding
control program. The control is based on a model of the component
or of the component geometry, said model being stored in a suitable
program which serves for the control. During operation, then, the
cathode or the metal component (depending on which is moved by the
manipulator element), supported by the program, is moved along the
component section to be machined. Since, as described, the material
removal depends ultimately on the set process parameters and in
particular on the distance of the cathode from the component
surface, an expedient development of the invention provides for the
distance between the cathode and the surface of the metal component
to be determined from the ratio of working voltage and process
current and/or, as a function thereof, for the process sequence to
be controlled by varying any desired abovementioned process
parameter, e.g. the feed rate, it being possible for the feed to be
constant or intermittent.
[0013] The working voltage and the process current are detected,
and the cross-sectional area of the electrolyte stream and thus the
working area are also known. These variables, in first
approximation, have a clearly defined, formal relationship in
accordance with Ohm's law, to the distance between the cathode and
the surface of the metal component. The removal depth and thus the
working progress are therefore clearly linked to the aforesaid
parameters. Any desired parameter, e.g. the dwell time of the
cathode above the metal component surface or the feed rate of the
cathode along the component surface, can therefore be set according
to the continuously determined cathode spacing in such a way that
the desired working result is achieved.
[0014] In a development of the invention, a gas curtain, preferably
an air curtain, laterally enclosing the electrolyte stream at least
partly, preferably completely, is blown out via the cathode. That
is to say that not only is the electrolyte stream delivered via the
cathode but so too is a gas stream, which encloses the electrolyte
stream preferably completely. The result of this is that the
electrolyte stream is delivered onto the component surface in a
concentrated manner and is kept away from the vicinity of the
working region by being "blown out". This avoids the situation
where adjacent surfaces are undesirably affected and therefore
stray currents lead to undesirable removal in adjacent regions. The
nozzle itself is therefore of double-walled design, with an inner
electrolyte passage and an outer air passage, which are connected
to corresponding supply lines. In addition to air, some other gas,
e.g. inert gas such as nitrogen or helium, can also be used for
forming the gas curtain.
[0015] As already described, the method according to the invention
is suitable in particular for machining components made of special
(metallic and intermetallic, high-temperature) materials; it is
primarily useful for the machining of metal components made of
steels, titanium alloys and in particular nickel alloys, which are
extremely difficult to cut.
[0016] A metal component which is in particular preferably to be
machined with the method according to the invention is a component
of a turbomachine, for example a casing component, but in
particular a blade component. Blade components which are especially
difficult to machine and have a very complex geometry are integral
rotors ("blisks"), guide vane clusters or guide vane rings, as are
used, for example, in high-pressure compressors of a gas turbine.
Such integral rotors, guide vane clusters or guide vane rings are
subject to stringent requirements, for which reason they consist
either of a titanium alloy or high-temperature steel, but
preferably of a nickel alloy. In particular the guide vane clusters
and the guide vane rings have a very complex geometry, normally
consisting of two shrouds, between which the twisted guide airfoils
extend. The distances between the airfoils go from a few
millimeters up into the centimeter range. As a result, the
accessibility of the regions between the airfoils is greatly
restricted. Nonetheless, in particular the edges/corners or the
transition surfaces in these regions require the finish machining
according to the invention. If such a guide vane cluster or a guide
vane ring is produced from solid material by cutting or other
removal processes, this inevitably results in the finish machining,
in particular in the region between the airfoils, involving
considerable outlay. It is precisely in the production of blade
components, in particular of the guide vane clusters or guide vane
rings, that the method according to the invention can be used in an
especially advantageous manner, in particular if there are very
small airfoil and shroud spacings. This is because, with the method
according to the invention, the edges and surfaces present there in
the region between two airfoils and/or the airfoils themselves can
be readily machined, since the very thin, narrow cathode can be
moved even into these extremely narrow regions, and positioned
there with high precision, via the robot moving it in any desired
manner in space.
[0017] In addition to the method, the invention also relates to an
apparatus for implementing the method, comprising a manipulator
element in the form of a multi-axis, preferably five- or six-axis,
robot, on which an ECM tool in the form of a nozzle-like cathode or
a work holder holding the metal component is arranged, an
electrolyte feed device for feeding the electrolyte from an
electrolyte reservoir to the cathode, a process energy source
connected to the cathode and the metal component, and a control
device controlling the operation of the apparatus. The cathode,
which of course is interchangeably arranged on a corresponding
cathode holder on the robot, has a round, elongated or any other
desired cross section; the desired cathode shape is dictated by the
machining task. In order to be able to more easily reach workpiece
sections where access is difficult, curved or angled cathode
embodiments are possible.
[0018] In a development of the invention, the cathode can be
designed for delivering gas, in particular air, fed to it via a gas
feed device, in the form of an air curtain laterally enclosing the
electrolyte stream at least partly, preferably completely, said
electrolyte stream discharging from the cathode. The material
removal is thereby concentrated on the working region, and the
effect on adjacent zones can thereby be reduced. The nozzle itself
is therefore, for example, of double-walled design, with an inner
electrolyte passage and an outer gas passage enclosing said
electrolyte passage, said passages being connected to corresponding
supply lines.
[0019] In an advantageous development, the work holder is
additionally movable, preferably along or about a plurality of
space axes, when the cathode is arranged on the manipulator
element, or the cathode is additionally movable, preferably
likewise along or about a plurality of space axes, when the work
holder is arranged on the manipulator element. That is to say that
two movement modalities are provided in the apparatus according to
the invention, namely, firstly, the robot for moving the cathode or
the work holder together with metal component and, secondly, also
the work holder or the cathode, such that an adapted relative
motion sequence between cathode (tool) and metal component
(workpiece) can be set for the respective application.
[0020] Finally, a means for detecting the distance of the cathode
from the component surface is provided. This nozzle distance is a
measure of the removal capacity and the removal depth and is
clearly linked, in first approximation, in accordance with Ohm's
law, to the process parameters working voltage, process current and
cross-sectional area of the electrolyte stream, for which reason
the detection of the distance is advantageous for the continuous
monitoring of the working result. The means in this respect is
expediently the control device, which determines the distance. It
is possible for any desired parameter, e.g. the dwell time of the
cathode above the workpiece surface or the feed rate of the cathode
along the component surface, to be set with reference to the
detected distance in such a way that the desired working result is
achieved. However, the distance can also be determined by means of
one or more distance sensors, the control device again controlling
the operation, that is to say the relevant process parameters, in
accordance with the measuring results from the sensor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Further advantages, features and details of the invention
can be gathered from the exemplary embodiment described below and
with reference to the drawings, in which:
[0022] FIG. 1 shows a diagrammatic illustration, as a perspective
view, of a guide vane cluster to be machined with the method
according to the invention and the apparatus according to the
invention,
[0023] FIG. 2 shows a diagrammatic illustration of the apparatus
according to the invention,
[0024] FIG. 3 shows a diagrammatic illustration of the
cathode/metal component working region.
[0025] FIG. 4 shows a diagrammatic illustration of the cathode
movement, and
[0026] FIG. 5 shows a diagrammatic illustration of a cathode with a
gas curtain laterally defining the electrolyte stream.
DETAILED DESCRIPTION OF THE INVENTION
[0027] FIG. 1 shows, in the form of a perspective view, a metal
component 1 in the form of a guide vane cluster 2 which for the
purpose of forming a complete ring, is assembled with a plurality
of such clusters to give a ring shape. Such a guide vane cluster
consists of two shrouds 3, 4 and a multiplicity of airfoils 5
extending between said shrouds 3, 4. The shrouds 3, 4 and the
airfoils 5 are fashioned from solid material by cutting and/or
other removal processes. The airfoils 5 have a complexly twisted
geometry and are very closely spaced apart, i.e. there are only
very narrow spaces 6 between the individual airfoils 5. The complex
geometry consequently results in curved edge regions and curved
surfaces in the transition between the airfoils 5 and the shrouds
3, 4 or at the surfaces of the shrouds 3, 4 and at the surfaces of
the airfoils 5 themselves, which, after the metal component 1 or
its sections (shrouds 3, 4, airfoils 5) have been pre-machined
using appropriate working processes, have to be finish-machined
using the method according to the invention.
[0028] An apparatus as shown in FIG. 2 as a diagrammatic
illustration is used for this purpose. The apparatus comprises a
manipulator element 7 in the form of a multi-axis, preferably at
least five-axis, robot 8 which carries a cathode 9 which serves for
the ECM of the metal component 1, which is arranged on a
corresponding work holder 10. The cathode 9 is a nozzle-like,
narrow tube which can be moved in any desired manner in space via
the robot 8, such that any desired three-dimensional structures can
therefore be traversed and machined. In addition to the mobility of
the cathode 9, it is also possible for the work holder 10 to be
movable, either translationally along one or more space axes or
rotationally about one or more space axes, or both translationally
and rotationally, as indicated by the motion arrows.
[0029] A liquid electrolyte, for example an NaCl solution, is
delivered via the cathode 9 directly into the working region, for
which reason the electrode 9 is embodied, as described, as a nozzle
or tube. Provided for this purpose is an electrolyte reservoir 11,
from which the electrolyte 12 is directed to the cathode 9 via a
controlled pump 13 and a suitable electrolyte feed line 14.
Provided at the robot 8 is a corresponding connection box 15, at
which the line opens out and at which the cathode 9 is also
interchangeably accommodated. The volumetric flow of the
electrolyte can be monitored via a flow meter 16, and the fluid
pressure can be monitored via a pressure gage 17. Furthermore, a
temperature measuring device 18, a heating controller 19 and a pH
measuring instrument 20 and a conductivity measuring instrument 21
are provided in the electrolyte reservoir 11 in order to be able to
correspondingly set or monitor the electrolyte properties.
[0030] The electrolyte collected after delivery via the cathode 9
is fed back into the electrolyte reservoir 11 by an electrolyte
feed line 23, i.e. a circuit is established. The robot 8 and the
work holder 10 are provided in an enclosure 24, i.e. the apparatus
is closed to this extent with regard to the working region.
[0031] Furthermore, the apparatus comprises a process energy source
26, via which the working voltage and the process current can be
applied. The parameters are correspondingly monitored via an
ammeter 27 and a voltmeter 28. A supply line 29 runs, once again,
to the connection box 15; it makes contact with the cathode 9. The
supply return line 22 leads from the metal component 1 back to the
process energy source 26. In the process, the circuit is closed by
the electrolyte stream.
[0032] Finally, a gas supply, in this case shown embodied as a
compressed air supply, for example in the form of a compressor 30,
is provided, from which an air feed line 31 runs likewise to the
connection box 15. This air feed line is connected in turn to the
cathode, which is embodied as a double-walled tube. The electrolyte
is fed in the central passage; in the outer passage, an air curtain
which encloses the electrolyte can be blown out via the fed
compressed air. A controlled restrictor valve 32 and a flow meter
33, via which the air flow can be measured, are provided in the air
feed line 31.
[0033] Three roughly distinguishable regions are therefore
provided, namely the "process energy" region A, the "electrolyte
supply" region B and the "compressed air supply" region C.
[0034] Finally, a control device 34 is provided. The control device
controls the operation of the robot 8, that is to say the free
movement in space of the cathode 9 and the movement of the work
holder 10, if provided. It is of course also possible to control
and monitor all the sub-components of the apparatus in FIG. 2 for
the electrolyte and gas supply and the process energy source 26
(that is to say the regions A, B and C) via the control device
34.
[0035] FIG. 3 shows, as a diagrammatic illustration, the tip of the
cathode 9 in a sectional view. The electrolyte 12 flows through the
tubular, nozzle-like cathode 9. The anodically polarized metal
component 1, for example the guide vane cluster 2 known from FIG.
1, is at a distance from the cathode 9. As illustrated by the arrow
diagram, the cathode 9 can be moved translationally in the three
directions in space, just as it can also be moved rotationally
about each of the three directions in space. The robot 8 is
accordingly activated for this purpose via the control device 34.
Control is based here on a stored model of the metal component 1,
which defines the surface along which the electrode 9 is to be
moved.
[0036] It can be seen that the electrolyte 12 is conveyed through
the nozzle-like or tubular cathode 9 and delivered to the metal
component 1. An electric flow field 36 forms in the electrolyte
stream 12. Electrochemical, locally limited metal removal takes
place in the region 37, i.e. a cavity forms in the metal component
1. The corresponding removal depth is obtained in accordance with
the process parameters selected.
[0037] FIG. 4 shows, as a diagrammatic illustration, the movement
of the cathode 9, which, for example in the case of a round
cross-sectional geometry, has a diameter of three millimeters and
is at a distance of, for example, one millimeter from the original
workpiece surface. It can be seen that a linear region 37 can be
removed by a horizontal movement of the cathode 9, as shown by the
arrow P. Whereas only a movement along one space coordinate is
shown in FIG. 4, it is possible, as described, for the cathode 9 to
be moved in any desired manner in space, i.e. the round edge
regions of the guide vane cluster 2 shown in FIG. 1 or the
three-dimensionally twisted airfoils 5, etc., can be readily
traversed in order to remove material there to the desired
extent.
[0038] Finally, FIG. 5 shows a further embodiment of the cathode 9,
which is embodied as a double-walled tube. The electrolyte 12 is
directed in the central passage 38. The compressed air fed via the
gas feed device, shown in FIG. 2 as air feed device 31, is
discharged in the outer passage 39. As FIG. 5 shows, a gas curtain
40 enclosing the electrolyte stream 12 all around is formed. This
reduces the effect on adjacent metal component surfaces.
[0039] Even though a cathode 9 of round cross section is shown by
way of example in the figures, the cathode can of course also have
an elongated cross section or any other desired cross section. It
can have, for example, in the electrolyte passage, a length of 10
mm and a width of 3 mm, such that a long, but narrow, zone can be
machined, which is expedient in particular for machining relatively
large areas. If a gas curtain is present, the corresponding air
passage has, of course, a corresponding geometry.
* * * * *