DE102005024474A1 - Electrolytically etching a cavity in the surface of a workpiece, especially for measuring inherent internal stresses, comprises repeatedly etching and measuring the cavity from beneath - Google Patents

Abstract

Electrolytically etching a cavity in the surface of a workpiece comprises positioning the workpiece in an etching position in which it is flushed with electrolyte from beneath, positioning the workpiece in a measuring position in which a geometric parameter of the cavity is measured from beneath, and performing further etching in dependence on the measurement. An independent claim is also included for apparatus for electrolytically etching a cavity in the surface of a workpiece (1), comprising an etching device (4) in which the workpiece can be positioned for flushing with electrolyte from beneath, a measuring device (5) in which the workpiece can be positioned for measuring a geometric parameter of the cavity from beneath, and a transport device (6) that can be moved between the etching device and the measuring device.

Description

The The invention relates to a method and a device, respectively according to the generic term of the independent Claims.

From the DE 26 51 359 A1 An electrolytic polishing apparatus is known with which a uniform and mirror-smooth surface of a metallic workpiece can be achieved. Furthermore, the electrochemical production of etch pits for the measurement of residual stresses of workpieces is known. The etching pit is generated anodically as a recess by an electrochemical material removal. Since the etching pits are often to have given geometric parameters, in particular a certain depth, a measurement of geometric parameters, for example, the etching depth is required in the production of such etching pits. Usually, for this purpose, the workpiece is masked before etching with an electrochemically resistant material. In this case, an application of the electrochemically resistant material takes place with a brush, wherein an etching spot remains free in the region of the surface of the workpiece intended for the etching pit. This is followed by the electrochemical material removal in the region of the etching spot, wherein the etching pit is formed as a recess in the material. To determine the achieved depth of the etch pit, the masking is removed and the etch pit is measured with a 2D laser topography meter. For example, the etch depth can be determined from the comparison between the unetched workpiece surface and the maximum etch pit depth. To form an etch pit with predetermined geometrical parameters, for example a predetermined setpoint value of the etch depth, the process of masking, etching, mask removal, measurement and comparison is repeated until the desired value is reached.

adversely in the described method is that before each of the Measure the masking away and generally for the rest Material removal must be reapplied. Furthermore, it turns out the use of laser technology in this context consuming because to guarantee a sufficiently accurate 2-D line plot, accurate tracking is required.

outgoing from the cited prior art, it is the object of the present invention Invention, a generic method as well as a generic device to create, with those in a simple way dependent on current readings of at least one geometric parameter a controlled material removal possible is.

The Method and the device according to the invention can be particularly advantageous in the production of recesses in a surface of a workpiece to the so-called non-destructive Measurement of residual stresses by X-ray diffraction, neutron diffraction or ultrasound. Under residual stresses are here Stresses within a workpiece understood without external stress exist and the operating voltages are superimposed.

According to the invention workpiece in at least one etching position positioned and the surface in a for the etching pit provided geodetic area from below by means of a local flushing process with the electrolyte brought in contact with, in this area a material removal of the surface he follows. The workpiece can also successively different etching positions in more than one position be positioned. The use of a local flushing process allows the removal of material without using one on the surface of the workpiece perform applied masking. Therefore, one is unnecessary Removal of such masking from the workpiece when repeated Measurements. In another embodiment becomes an etching window defined by a marking layer. Because the surface of down by means of the local flushing process is brought into contact with the electrolytes, takes place under the influence of gravity in this area some self-cleaning of the Surface, whereby the subsequent Measurement of the or the geometric parameters is facilitated. There the measurement of geodesic below is a simplified, especially automatic Workpiece manipulation during the Method achievable.

Further advantageous embodiments of the invention are dependent claims as well as the description and the drawing.

Advantageous an absolute height measurement takes place the surface in the area of the etching pit, with no reference to unetched Edge areas of the workpiece is taken.

In a preferred embodiment The invention will be a tactile measurement of the or the geometric Parameters of the etching pit performed. This is an information about the relevant parameters by direct contact the interior of the etching pit won. Such a tactile measurement can, for example, with an inductive or piezoelectric sensor.

Furthermore, an optical measurement, for example by means of a laser, can also be carried out become.

Of the local flushing process preferably comprises a rinsing fountain of the electrolyte, in particular in the manner of an etching beam. There are also other forms of flushing conceivable, for example by spray from a nozzle.

Procedural is it cheap, if the workpiece positioned before and / or after a measurement in a cleaning position and with a cleaning medium at least in the region of the etching pit is brought into contact with it, thus the measuring accuracy as well as the effectiveness of the material removal elevated becomes.

to Formation of an etching pit with given geometric parameters, it is expedient if the current measured value of the geometric parameter (s) with a Target value compared and the removal of material takes place until the setpoint is reached.

The method according to the invention is preferably used to produce an etching pit which is used to measure a clamping of the workpiece. Such etch pits may have a size of about 1 cm ² and a depth of up to 500 μ.

The inventive device includes an etching device, a Measuring device and a transport device, wherein the workpiece by means of the transport device between the etching device and the measuring device movable is. The workpiece is in an etching position in the area of the etching device positionable or positioned in this area. The surface of the workpiece becomes geodetically in the area of the intended etching pit down by means of a local flushing process brought into contact with the electrolyte, being in this range a material removal is provided. In the area of the measuring device is the workpiece positioned in a measuring position or it is in this area positionable, being geodesic from below at least one geometrical parameter of the etch pit, preferably an etching depth is measurable or measured.

In a preferred embodiment According to the invention, the transport device comprises a stepping motor with the one precise Positioning of the workpiece possible is.

Further advantageous embodiments of the invention are independent from its summary in the claims of the following description and the associated Drawings to take.

in this connection shows

1 schematically the device according to the invention for forming an etching pit.

In the present embodiment, a workpiece 1 in an etching position in the region of an etching device 4 positioned. The workpiece consists of aluminum, iron, stainless steel or any other metallic or semiconductor material in which an electrochemical material removal with an electrolyte is possible. The technique of anodization is used, ie the tool acts as the anode, the electrolyte as the cathode. The etching device 4 includes a tub 2 for receiving an electrolyte 2a , which is suitable for the electrochemical material removal of the relevant workpiece material. The etching device 4 creates a rinse fountain 3 of the electrolyte 2a in which, in the etching position, the surface in the region provided for the etching pit is geodetically brought into contact with the electrolyte from below. The area of the surface intended for the etching pit is defined by an etching window. For a more precise definition of the etching window, it is optionally possible to provide a masking with a resistant lacquer or the like. Preferably, the etching device is with a control module 8th connected, from which a suitable etching voltage is provided. The etching apparatus used is preferably a Struers LectroPol5.

The device according to the invention further comprises a measuring device 5 , The workpiece 1 can be in the range of the measuring device 5 be brought into a measuring position, wherein geodetically from below at least one geometric parameter of the etching pit can be measured. The measuring device preferably has a tactile sensor, for example a sensor based on the induction or piezoelectric effect. In a further embodiment, the measuring device may comprise an optical sensor, for example a laser sensor.

The device according to the invention further comprises a transport device 6 on, wherein the workpiece by means of this transport device 6 between the etching device 4 and the measuring device 5 is movable. The transport device comprises a transport module 6a with a holder into which the workpiece 1 can be clamped. The transport module 6a is along a transport rail 6b movable, with the workpiece 1 can be brought from the etching position to the measuring position.

Optionally, the apparatus further comprises a cleaning station 7 on. Optionally, the workpiece 1 also in the field of Reinigungssta tion 7 by means of the transport device 6 to be brought.

To achieve the most accurate manipulation of the workpiece 1 reach, includes the transport device 6 preferably a stepper motor. The measuring device 5 and optionally the cleaning station 7 are electric with a control unit 9 connected. The control unit 9 can through a PC 10 with a monitor 11 be programmed and monitored. The control unit 9 also allows via the control module 8th the control of the etching device 4 ,

• 1. Das Werkstück 1 wird in die Halterung des Transportmoduls 6a eingespannt. Zur Durchführung einer Nullmessung wird das Werkstück in dem Bereich der Messeinrichtung 5 positioniert und es wird geodätisch von unten zumindest ein geometrischer Parameter der Ätzgrube gemessen. Mit dieser Messung wird ein Referenzwert festgelegt. Vorzugsweise wird eine Referenzhöhe der Oberfläche gemessen; der Fortschritt des Materialabtrags bzw. die Tiefe der Ätzgrube wird dann durch eine absolute Höhenmessung beurteilt. Dies entspricht einer Entfernungsmessung zwischen dem Boden der Ätzgrube und einem Nullwert des Sensors. Eine relative Höhenmessung bei dem die Ätzgrube bzw. die Tiefe der Ätzgrube gegenüber dem ungeätzten Rand der Ätzgrube gemessen wird, kann damit vermieden werden. Es versteht sich, dass in einer weiteren Ausführungsform der Erfindung eine relative Höhenmessung vorgenommen werden kann. In diesem Fall ist es nicht erforderlich, eine Referenzhöhe festzulegen.
• 2. In einem weiteren Schritt wird das Werkstück 1 über der Reinigungseinrichtung 7 positioniert und mit einem Reinigungsmedium, beispielsweise Alkohol zumindest im Bereich der Ätzgrube in Kontakt gebracht bzw. abgespült. Anschließend wird die Oberfläche des Werkstücks 1 zumindest im Bereich der Ätzgrube mit Pressluft trocken geblasen.
• 3. Anschließend wird das Werkstück 1 zum Ätzgerät 4 bewegt. Um einen guten Kontakt zwischen Elektrolyt und Werkstück zu gewährleisten wird ein Spülprozess ohne Ätzspannung für eine vorgegebene Zeit beispielsweise 5 Sekunden eingesetzt. Anschließend wird eine Ätzspannung angelegt und der elektrochemische Materialabtrag gestartet. Die den Materialabtrag bestimmenden Parameter wie Ätzspannung und Ätzstrom werden von dem Steuermodul 8 bestimmt. Die Ätztiefe wird durch die Zeit bestimmt, während der die Spülfontäne den Elektrolyten in Kontakt mit dem Bereich der Oberfläche des Werkstücks bringt, der für die Ätzgrube vorgesehen ist. Die Querschnittfläche der Ätzgrube wird durch den Bereich bestimmt, der von der Spülfontäne erfasst wird. Für eine bessere Festlegung der Ätzgrube kann eine Maskierungsschicht mit einem Ätzfenster auf der Oberfläche des Werkstücks 1 verwendet werden. Es versteht sich, dass statt einer Spülfontäne auch ein anderer lokaler Spülprozess beispielsweise ein Besprühen mit Elektrolyt von der Erfindung umfasst wird.
• 4. Anschließend wird das Werkstück 1 im Bereich der Reinigungseinrichtung 7 positioniert und die Oberfläche mit Alkohol abgespült und anschließend mit Pressluft trocken geblasen.
• 5. Anschließend wird das Werkstück 1 im Bereich der Messeinrichtung 5 in einer Messposition positioniert und geodätisch von unten der oder die geometrischen Parameter der Ätzgrube gemessen. Vorzugsweise wird eine Höhenmessung vorgenommen. Für den Fall, dass eine absolute Höhenmessungen verwendet wird, wird eine Differenz zur Referenzmessung ermittelt. Ein weiterer Materialabtrag erfolgt in Abhängigkeit von dem aktuellen Messwert.
• 6. Zur Bildung einer Ätzgrube mit einer vorbestimmten Ätztiefe wird der aktuelle Messwert der Ätztiefe mit einem entsprechenden Sollwert verglichen und der Materialabtrag solange fortgesetzt bis der Sollwert erreicht wird. Vorzugsweise werden hierzu die Schritte 1 bis 5 wiederholt.

The following procedure is used to form an etching pit.

• 1. The workpiece 1 gets into the holder of the transport module 6a clamped. To perform a zero measurement, the workpiece is in the area of the measuring device 5 positioned and it is geodetically measured from below at least one geometric parameter of the etching pit. This measurement is used to set a reference value. Preferably, a reference level of the surface is measured; the progress of the material removal or the depth of the etching pit is then assessed by an absolute height measurement. This corresponds to a distance measurement between the bottom of the etching pit and a zero value of the sensor. A relative height measurement in which the etching pit or the depth of the etching pit is measured relative to the unetched edge of the etching pit can thus be avoided. It is understood that in a further embodiment of the invention, a relative height measurement can be made. In this case, it is not necessary to set a reference altitude.
• 2. In a further step, the workpiece 1 over the cleaning device 7 positioned and brought into contact with a cleaning medium, for example alcohol at least in the region of the etching pit or rinsed. Subsequently, the surface of the workpiece 1 blown dry with compressed air, at least in the area of the etching pit.
• 3. Subsequently, the workpiece 1 to the etching device 4 emotional. In order to ensure good contact between the electrolyte and the workpiece, a rinsing process without etching voltage is used for a predetermined time, for example 5 seconds. Subsequently, an etching voltage is applied and the electrochemical material removal is started. The material removal determining parameters such as the etching voltage and the etching current are provided by the control module 8th certainly. The etch depth is determined by the time during which the irrigation fountain brings the electrolyte into contact with the area of the surface of the workpiece intended for the etch pit. The cross-sectional area of the etch pit is determined by the area that is detected by the irrigation fountain. For a better definition of the etching pit, a masking layer with an etching window on the surface of the workpiece 1 be used. It is understood that instead of a rinsing fountain, another local rinsing process, for example, spraying with electrolyte of the invention is included.
• 4. Subsequently, the workpiece 1 in the area of the cleaning device 7 positioned and rinsed the surface with alcohol and then blown dry with compressed air.
• 5. Subsequently, the workpiece 1 in the field of measuring equipment 5 Positioned in a measuring position and geodetically measured from below or the geometrical parameters of the etching pit. Preferably, a height measurement is made. In the event that an absolute height measurement is used, a difference to the reference measurement is determined. Another material removal takes place depending on the current measured value.
• 6. To form an etching pit with a predetermined etch depth, the current measured value of the etch depth is compared with a corresponding desired value and the removal of material continues until the desired value is reached. Preferably, steps 1 to 5 are repeated for this purpose.

1

workpiece

2

tub

2a

electrolyte

3

Spülfontäne

4

etcher

5

measuring device

6

transport means

6a

transport module

6b

transport rail

7

cleaning station

8th

control module

9

control unit

10

PC

11

monitor

Claims (13)

A method for forming an etching pit in a surface of a workpiece by electrochemical removal of material with an electrolyte, characterized in that - the workpiece positioned in at least one etching position and geodetically the surface in an area provided for the etching pit from below by means of a local flushing process with the electrolyte in Contact is brought, wherein in this area a material removal of the surface takes place - the workpiece positioned in a measuring position and geodetically from below at least one geometric Parameters of the etch pit, preferably an etch depth is measured, - depending on the current measurement, a further material removal takes place. Method according to claim 1, characterized in that that for measuring the geometric parameter (s) an absolute altimetry the surface in the area of the etching pit he follows. Method according to claim 1 or 2, characterized that one for the measurement of the geometric parameter or tactile Measurement or optical measurement takes place. Method according to at least one of the preceding Claims, characterized in that the rinsing process is a rinsing fountain of the electrolyte includes. Method according to at least one of the preceding claims, characterized in that a marking layer is used to define an etching window is used. Method according to at least one of the preceding Claims, characterized in that the workpiece in a cleaning position positioned and with a cleaning medium in the etching pit is brought into contact. Method according to at least one of the preceding Claims, characterized in that the current measured value of the or geometric parameter is compared with a setpoint and the Material removal takes place until the setpoint is reached. Method according to at least one of the preceding Claims, characterized in that the etching pit for measuring an internal stress of the workpiece is used. Apparatus for forming an etching pit in a surface of a workpiece by electrochemical material removal with an electrolyte, with an etching device and a Measuring device, characterized in that the workpiece by means of a transport device between the etching device and the measuring device movable is, where - in the Area of the etching device, the workpiece in at least an etching position is positionable or positioned and the surface in the area the proposed etching pit geodesic from below by means of a rinsing process being brought into contact with the electrolyte, being in this range a material removal is provided and - the workpiece in the area the measuring device can be positioned or positioned in a measuring position is and geodesic from below at least one geometrical parameter of the etch pit, preferably an etching depth is measurable or measured. Device according to claim 9, characterized in that that the measuring device has a tactile sensor for measuring the or having the geometric parameter. Device according to claim 9 or 10, characterized that the measuring device is an optical sensor for measuring the or the geometric parameter. Device according to one of claims 9 to 11, characterized the transport device comprises a stepper motor. Device according to one of claims 9 to 12, characterized that a cleaning station is provided and the workpiece by means of the transport device between the etching device, measuring device and cleaning station is movable.