DE102018104624B3 - Method and device for determining a surface - Google Patents

Abstract

A method for the optical determination of at least one surface of a moving metal strip, characterized by performing distance measurements at localized measuring points with high frequency perpendicular to the metal strip in Mehrwellenlängeninterferometer method and transverse to the longitudinal extent and to the direction of movement of the metal strip, the measuring site per unit time across the Movement is changed and a device for determining at least one surface of a moving metal strip, wherein the device designed as a Mehrwellenlängeninterferometer scanning unit, a beam steering unit, which has a high frequency periodically adjustable in space reflection plane, and arranged above the metal strip mirror assembly and a Evaluation has.

Description

The invention relates to a method and a device for the optical determination of at least one surface of a moving metal strip.

Such a method of determining band flatness using a prior art optical measuring system is disclosed in U.S.P. DE 10 2015 223 600 A1 disclosed. In this document, a method for producing a metallic strip by endless rolling is described. The DE 10 2015 223 600 A1 provides that, at defined times, measuring cycles for determining the surface properties, in particular the flatness, of the strip are carried out. At the beginning, the tension is reduced by reducing the nominal tension of the belts in the conveyor line. After performing the first step, the degree of flatness of the belt is detected by means of a flatness measuring device and then the reduced tension value is increased back to the nominal tensile stress.

A disadvantage of this known method and the optical measuring system of DE 10 2015 223 600 A1 is that it can be used only at low band pulls from 0 to 15 N / mm ² . For higher band passes the flatness errors are no longer recognizable due to the low resolution. The laser triangulation and / or fringe projection methods in conjunction with the phase-shift technique form the basis of the procedure. The measurement uncertainty of such systems is typically about 10 microns. The measurement uncertainty is the deviation of a displayed measurement result from the true value. The measurement deviations can have systematic or random causes.

A non-contact optical measuring method and apparatus for determining a surface to form lines on the strip surface by means of a light source is known from US Pat DE 197 09 992 C1 known. This method is used for areal scanning of a surface of a hot strip. However, a disadvantage of this measurement method is that the measurement uncertainty here is also approximately 10 μm perpendicular to the strip surface.

From the DE 44 04 663 A1 In addition, a method for the optical measurement of the mutual distance between two mutually substantially parallel measuring surfaces of an object by scattered light interference with light of short coherence length is known.

Furthermore, from the DE 199 50 254 A1 discloses a method and an apparatus for determining a thickness profile and the longitudinal thickness profile of a running web of material.

Ultimately, the shows US 2018/0017499 A1 a method for automatically monitoring the production of a fiber-reinforced polymer composite tape by using an interferometer.

Starting from the DE 197 09 992 C1 It is the object of the invention to provide a method for the optical determination of at least one surface of a moving metal strip, which optically detects surface irregularities and the measurement uncertainty is reduced perpendicular to the strip surface.

• Verfahren zur optischen Bestimmung mindestens einer Oberfläche eines sich bewegenden Metallbandes, gekennzeichnet durch die Durchführung von Abstandsmessungen mit mindestens zwei Laserquellen an örtlich begrenzten Messpunkten mit hoher Frequenz von 20 bis 200 MHz senkrecht zum Metallband im Mehrwellenlängeninterferometer-Verfahren sowie quer zur Längserstreckung und zur Bewegungsrichtung des Metallbandes, wobei der Messort pro Zeiteinheit quer zur Bewegungsrichtung verändert wird.

The solution of the problem arises from the following features of claim 1:

• Method for the optical determination of at least one surface of a moving metal strip, characterized by performing distance measurements with at least two laser sources at localized measuring points with high frequency of 20 to 200 MHz perpendicular to the metal strip in the Mehrwellenlängeninterferometer method and transverse to the longitudinal extent and to the direction of movement of the metal strip , wherein the measuring location per unit time is changed transversely to the direction of movement.

Due to the use of the multi-wavelength interferometric method, the method according to the invention offers a particularly low measurement uncertainty for the surface irregularities of a moving metal strip, wherein the surface unevenness is to be regarded as a geometry error of the metal surface. In a particularly advantageous manner, the measurement uncertainty of the method according to the invention is only 0.1 μm perpendicular to the strip surface of the moving metal strip.

In a multi-wavelength interferometry method, a phase shift between an object beam and a reference light beam is measured and used to determine the distance traveled by the object beam between a light source and a surface.

The path length difference between an object beam and the reference light beam is calculated in an evaluation unit. The reference beam always returns a precisely defined distance. The object beam is reflected in a first step by a beam steering unit transversely to the direction of movement of the metal strip and projected in a second step perpendicular to the surface of the metal strip and then reflected back as a reflection beam. The two light beams are brought into interference with each other and then the intensity of a combined light beam measured on a detector. By means of such an interference pattern, very precise relative path length changes can be measured by determining a phase shift between the reference beam and the object beam.

Advantageously, the method also offers the possibility to calculate the surface of the metal strip away from the measuring grid by interpolation of the adjacent distance measurements.

In the interpolation, a continuous function, the so-called interpolant or interpolating, is found mathematically to the measured localized (discrete) measuring points, which maps these measuring points. The interpolation method allows the determination of measured values which were not measured by means of a device but have been calculated from the given measuring points. This mathematical addition to the physical measurement of measuring points enables an accelerated data generation and thus an accelerated statement about the metal strip surface.

According to the invention, it is also provided that determines the surface on both sides of the metal strip and thereby the strip thickness is measured at the same time to the surface irregularities. A thickness measurement related to the area of the measuring tape results from the opposing distance measuring values of the two surfaces of the metal strip.

Advantageously, it is now not only possible to determine the surface unevenness, but additionally also the strip thickness within a method step according to the invention.

• Vorrichtung (10) zur Bestimmung mindestens einer Oberfläche (O) eines sich bewegenden Metallbandes (11), dadurch gekennzeichnet, dass die Vorrichtung (10) eine als Mehrwellenlängeninterferometer (22) ausgebildete Abtasteinheit (21), die mit mindestens zwei Laserquellen versehen ist, eine Strahllenkungseinheit (23), wobei diese eine mit hoher Frequenz von 20 bis 200 MHz periodisch im Raum verstellbare Reflexionsebene (29) aufweist, sowie eine oberhalb des Metallbandes (11) angeordnete Spiegelanordnung (26) und eine Auswerteeinheit (24).

Based on the above-described prior art and the already stated object of the invention, the solution of the problem results from the following features of claim 5:

• Device 10 ) for determining at least one surface ( O ) of a moving metal strip ( 11 ), characterized in that the device ( 10 ) as a multi-wavelength interferometer ( 22 ) trained scanning unit ( 21 ), which is provided with at least two laser sources, a beam steering unit ( 23 ), this one with a high frequency of 20 to 200 MHz periodically adjustable in space reflection plane ( 29 ), and one above the metal strip ( 11 ) arranged mirror arrangement ( 26 ) and an evaluation unit ( 24 ).

With this device, it is now possible to project the object beam generated by the scanning unit by means of a periodically adjustable with high frequency in space reflection plane transversely to the direction of movement of the metal strip on a large number of points of the metal strip arranged above the mirror assembly, wherein the mirror assembly the Object beams are reflected at right angles in the direction of the material band and wherein the resulting reflection on the surface of the metal strip reflection rays are returned by means of the mirror assembly and the beam steering unit to the scanning unit.

In a preferred embodiment, the angle-adjustable reflection plane of the beam steering unit is designed as a rotating polygon wheel. The incident on the reflection plane object beam is reflected in time on the reflection plane offset, resulting in the sequence of a high number of measurement points per unit time.

Furthermore, it is conceivable that the adjustable reflection plane of the radiation unit is designed as a periodically moving mirror.

A further embodiment provides that the angle-adjustable reflection plane of the radiation unit is formed from a combination of a rotatable polygon wheel and at least one periodically movable mirror. The combination of polygon wheel and periodically movable mirror serves, for example, to compensate for a systematic error of the polygon wheel, such as the angular error of the individual surfaces of the polygon wheel.

Advantageously, it is envisaged that the angle-adjustable reflection plane of the beam steering unit is formed from a combination of a rotatable polygonal wheel and a fixed, curved mirror or a combination of a rotatable polygon wheel and at least one optical lens.

In a particularly preferred embodiment, the mirror arrangement is designed as a parabolic mirror, which is aligned transversely to the direction of movement of the metal strip. The deflection of the object beam via a parabolic mirror ensures that the laser beams always travel almost the same distance regardless of the place of impact on the metal strip. The parabolic mirror is aligned with the metal strip so that the same interference phase (same distance) is measured for a flat metal strip for the respective impact locations on the metal strip. If the metal strip has unevenness, the interference phase changes depending on the location of incidence of the laser beam. From the phase change and the known wavelength of the laser light so the unevenness of the strip surface can be determined.

Alternatively, it is provided that the mirror arrangement is designed as a facet mirror, wherein the facet mirror takes over the task of the parabolic mirror here. The deflection of the object beam takes place in this embodiment at the respective facets of the facet mirror.

A further embodiment provides that the mirror arrangement is designed as a plane mirror, wherein the reflection results are corrected mathematically. The mathematical correction is performed by the evaluation unit.

It is further provided that the device according to the invention operates at a sampling frequency of 20 to 200 MHz.

Preferably, the multi-wavelength interferometer operates at a measurement rate of 100 MHz. In order to obtain a stable measured value, a filtering of the measured values is carried out, whereby the number of output measured values is typically a factor 100 reduced. So there is a net measurement rate of 1 MHz.

A polygon wheel with, for example, 12 areas for beam deflection rotates at a frequency of 50 Hz, which corresponds to 3000 revolutions per minute. The deflection of the object beam over a surface of the polygon wheel typically provides for scanning the full width of the metal strip. Thus, with the parameters mentioned, the metal strip can be scanned 600 times per second (50 Hz * 12 areas).

Taking into account the net measurement rate of 1 MHz, a scan over the metal surface is represented by approximately 1600 points. Here, the 1,000,000 measurement points are divided by the 600 scans per second. This results in 1600 measuring points per scan. A scan describes a measuring process of, for example, 1600 measuring points transverse to the direction of movement of the metal strip. See also description to 4 ,

• 1 eine teilweise schematische Darstellung eines Walzwerkes;
• 2 schematische Darstellung einer Vorrichtung zur Bestimmung mindestens einer Oberfläche eines sich bewegenden Metallbandes entlang der Schnittebene II - II gemäß 1;
• 3 schematische Darstellung einer Strahlquelle und einem Interferometer;
• 4 Draufsicht auf ein sich bewegendes Walzbandes mit einer Messspur;
• 5a Schnittdarstellung zweier Arbeitswalzen mit linksseitiger Walzenverschwenkung;
• 5b Schnittdarstellung zweier Arbeitswalzen mit rechtsseitiger Walzenverschwenkung;
• 5c Schnittdarstellung zweier Arbeitswalzen mit randseitiger Gewichtsbelastung;
• 5d Schnittdarstellung zweier Arbeitswalzen mit mittiger Gewichtsbelastung;
• 6 schematische Darstellung einer Vorrichtung zur Bestimmung mindestens einer Oberfläche eines sich bewegenden Metallbandes entlang der Schnittebene II - II gemäß 1 mit einem ersten profilierten Metallband;
• 7 schematische Darstellung einer Vorrichtung zur Bestimmung mindestens einer Oberfläche eines sich bewegenden Metallbandes entlang der Schnittebene II - II gemäß 1 mit einem zweiten profilierten Metallband.2.

Further advantages of the invention will become apparent from the following description of several embodiments. Show it:

• 1 a partial schematic representation of a rolling mill;
• 2 schematic representation of a device for determining at least one surface of a moving metal strip along the cutting plane II - II according to 1 ;
• 3 schematic representation of a beam source and an interferometer;
• 4 Top view of a moving rolled strip with a measuring track;
• 5a Sectional view of two work rolls with left-side Walzenverschwenkung;
• 5b Sectional view of two work rolls with right-side Walzenverschwenkung;
• 5c Sectional view of two work rolls with edge-side weight loading;
• 5d Sectional view of two work rolls with central weight load;
• 6 schematic representation of a device for determining at least one surface of a moving metal strip along the cutting plane II - II according to 1 with a first profiled metal band;
• 7 schematic representation of a device for determining at least one surface of a moving metal strip along the cutting plane II - II according to 1 with a second profiled metal band.2.

In the drawings, the device according to the invention is indicated overall by the reference numeral 10 Provided.

In the 1 is partially schematically a rolling mill W shown. It can be seen that during the rolling process, a metal band 11 , in transport direction x is transported. The metal band 11 is due to numerous role arrangements 12 supported and in x Moving direction moves, wherein between the roller assemblies 12 each rolling stands 13 are arranged, which in the transport direction x each a decreasing roll gap 14 respectively.

In transport direction x before and after each rolling stand 13 are on a base frame 15 in each case the devices according to the invention 10 arranged with which the surface (s) of the metal strip 11 be recorded.

In the present case, it is a three-stage rolling process, at the end of the thin Metallbandendprodukt 11 to a coil 16 being rolled up. Ultimately, you recognize the rolling mill 13 with its two outer back-up rollers 17 and two inner work rolls 18 that the nip 14 define.

The change in the geometric properties of the metal strip is determined by means of a control loop using the surface (s) measured by the device according to the invention 11 controlled. These geometric properties may be macro- or microscopic.

The 2 shows the schematic representation of the device 10 based on the cutting line II-II according to 1 , Furthermore, the 2 a beam source 19 , an optical fiber 20 , a scanning unit 21 with the interferometer 22 , a beam steering unit 23 , a mirror arrangement 26 , an evaluation unit 24 and a roller control 25 ,

The mirror arrangement 26 is as a parabolic mirror 26 formed and transverse to the longitudinal extent of the metal strip 11 , on the base frame 15 the device 10 attached. The surfaces of the metal band 11 are with O1 and O2 designated.

In addition, the device 10 two distance sensors 27 on which the distance of the device to a surface T a pulley 28 determine. By guiding the metal band 11 over the pulley 28 becomes the proper movement of the metal band 11 eliminated in the vertical measuring direction. The pulley 28 However, also has concentricity errors whose deviations from the distance sensors 27 can be detected. The distance sensors 27 in this embodiment also operate optically by means of the Mehrwellenlängeninterferometrie method, where they can also operate tactile, capacitive or inductive.

Furthermore, the disclosure 2 a laser beam S , which from the beam source 19 by optical fiber 20 and interferometer 22 in the beam steering unit 23 is directed. In the interferometer 22 becomes the laser beam S split into an object beam L and a reference beam R , The detailed process is below in 3 described.

The object beam L is using the beam steering unit 23 , for example as a rotating polygon wheel 29 , about the parabolic mirror 26 on the metal surface O1 directed. The object beam L is by means of the rotating polygon wheel by way of example in three each a different angle to the parabolic mirror 26 having and staggered measuring beams M1 . M2 and M3 divided up. The measuring beams M1 to M3 meet almost perpendicular to the surface O1 on. These result on the surface O1 the measuring points MP1 to MP3 ,

The multi-wavelength interferometer operates at a measurement rate of typically 100 MHz. In order to obtain a stable measured value, a filtering of the measured values is carried out, whereby the number of the measuring point output frequency by the factor 100 reduced. So there is a net measurement rate of 1 MHz.

After the respective measuring beams M 1 - M3 on the surface O1 . O2 of the metal band 11 These are reflected as reflection rays RL 1 - RL 3 to the parabolic mirror 26 back-projected and via beam steering unit 23 into the interferometer 22 returned and there with the reference beam R superimposed. In the interferometer 22 becomes the phase difference between the reference beam R and the object beam L recorded and then in the evaluation unit 24 further processed. In the evaluation unit 24 , which has a control unit, not shown, with the beam steering unit 23 is related to the distance measurements and the known feed movement of the metal strip 11 an information about the detected surface O1 of the metal band 11 composed.

The information obtained is sent to the roller control 25 transmitted, which in turn the respective work rolls 18 of the rolling stand 13 controls. The rolling surface course or the position of the work rolls 18 each other can be changed according to the detected surface unevenness. The possibilities of work roll control are described below with respect to 5a to 5d described in detail.

With the device according to the invention 10 is next to the determination of the surface O1 also an optical measurement of the unevenness of the surface O2 of the metal band 11 conceivable, wherein a combination of the measurement results additionally the thickness measurement of the metal strip 11 allows. By combining the measurement data of the surfaces O1 and O2 it is also possible the surface unevenness and the strip thickness of the metal strip 11 to be determined in one process step.

In the 3 is schematically the beam source 19 and the scanning unit 21 or the interferometer 22 shown. The beam source 19 exemplifies two laser sources 30 and 31 on, each emit different wavelengths. In this embodiment, the first sends laser source 30 a wavelength λ ₁ = 782 nm and the second laser source 31 a wavelength λ ₂ = 785 nm.

In principle, it is pointed out that at least two laser sources are required for the measuring method, and it is entirely conceivable to use a larger number of laser sources.

The laser beam S1 the laser source 30 is through a first optical isolator 32 to a deflecting mirror 34 which projects this into a first beam splitter unit 35 passes.

At the same time a laser beam S2 the second laser source 31 through a second optical isolator 33 in the first beam splitter unit 35 directed. Here are the respective laser beams S1 and S2 with the different wavelengths λ ₁ and λ ₂ into a single laser beam S merged.

To a disturbance of the laser sources 30 and 31 through the light emitted by them avoid, are in their beam path, the optical isolators 32 and 33 attached, which prevent optical feedback.

The of the beam splitter unit 35 posted, superimposed laser beam S enters a fiber coupling unit 37 one with the fiber optic cable 20 and a fiber extraction unit 38 connected is.

From the fiber extraction unit 38 becomes the incoming laser beam S in a second beam splitter unit 36 directed and there in an object beam L and a reference beam R divided up. The reference beam R will be at the reference level 39 reflected and in the second semipermeable steel divider 36 with the from the surface O1 reflected reflection rays RL1 to RL3 superimposed and together to the photodetector 40 continued. The object beam L is, however, according to 2 and its description.

Does the distance between the device change? 10 and the surface O1 it changes at the photodetector 40 registered light intensity, which is caused by the change of the interference pattern.

In the 4 is the metal band 11 shown in plan, which has a width a of 250 mm. On the metal band 11 are exemplary measurement points MP shown, with the measuring points MP only as an example on the surface O1 are shown.

The measuring points MP form a measuring track 41 a zigzag arrangement on the surface O1 of the metal band 11 formed by the periodic deflection of the object beam L in the steel steering unit 23 in combination with the movement of the metal band 11 , which moves at a belt speed of 240 m / min, in the transport direction x arises. With the reference number b is the moving distance of the metal band 11 of 4 mm / ms during a measuring process with numerous measuring points MP shown.

The information about the entire surface O1 results from the measuring points MP that go along the measuring lane 41 have been recorded. The gaps c between the measuring points MP are closed by interpolation. Finally, the measured data with the determined data of the distance sensors, not shown 27 corrected.

In the 5a - 5d are the possible roll orientations in the rolling mill W depending on different flatness defects.
In the 5a is an upper and a lower work roll 18A . 18B with the associated longitudinal axes y1 and y2 shown. Unless the surface O of the metal strip, not shown here 11 have no bumps, the two longitudinal axes y1 and y2 aligned parallel to each other and the distance d (Also the width of the roll gap 14 ) of the work rolls 18A . 18B each other is constant over their length.

Once a roughness of the surface O1 . O2 is detected by the method already described, the roller control, not shown occurs 25 in operation, according to the unevenness occurred, the position of the work rolls 18 to each other or their roll surfaces 42 to change.

In the 5a to 5d There are four different ways of adjusting the work rolls 18A and 18B shown on different bumps.

In the 5a and 5 b becomes the respective upper work roll 18A opposite the lower work rolls 18B pivoted. The stripper 18A is right-sided ( 5a) or left-sided ( 5b) pivots and forms either a Verschwenkungswinkel α1 ( 5a) or a pivoting angle α2 ( 5b) between the longitudinal axis y1 and the horizontal. This pivoting changes the distance d the two work rolls 18A and 18B over the length of time ( d1 . d2 ) and thus also the width of the roll gap 14 ,

In the 5c and 5d becomes the roller surface by force 42 the upper stripper 18A adapted to the respective unevenness.

In the 5c act two forces, F ₁ and F ₂ , on the edge of the upper work roll 18A , whereby their to the opposite work roll 18B facing roll surface 42 bent concavely. The nip 14 is in this embodiment centrally formed wider than the edge.

In the 5d however, a force acts F ₃ centered on the upper work roll 18A , whereby their to the opposite work roll 18B facing roll surface 42 convex bends and the nip 14 Consequently, it is narrower in the middle than at the edge.

For a clearer illustration of the work roll drive, the 5 a to 5d shown oversubscribed.

The devices 10 according to 6 and 7 essentially correspond to the device 10 according to 2 , but is instead of a non-profiled metal band 11 either a first profiled metal band 44 ( 6 ) or a second profiled metal band 45 ( 7 ), which are in the design of the surface O1 differ from each other.

To the operation of the device 10 will be on the description to the 2 and 3 directed.

LIST OF REFERENCE NUMBERS

10

inventive device

11

metal band

12

rolling mill

14

nip

15

base frame

16

coil

17

supporting roll

18

Stripper

18A

upper stripper

18B

lower stripper

19

beam source

20

optical fiber

21

scanning

22

interferometer

23

Beam steering unit

24

evaluation

25

roller control

26

Mirror arrangement / parabolic mirror

27

distance sensor

28

idler pulley

29

Reflection plane / Polygon wheel

30

first laser source

31

second laser source

32

first optical isolator

33

second optical isolator

34

deflecting

35

first beam splitter unit

36

second steel divider unit

37

Fasereinkopplungseinheit

38

Fiber extraction unit

39

reference mirror

40

photodetector

41

measuring track

42

roll surfaces

44

first profiled metal band

45

second profiled metal band

a

Width of the metal band

b

Moving distance of the metal band 11

c

Gaps

d

Work roll distance / width of the roll gap 14

F

force

L

object beam

M

measuring beam

MP

measuring point

O

surface

R

reference beam

RL

reflection beam

S

superimposed laser beam

S1

Laser beam from the laser source 30

S2

Laser beam from the laser source 31

T

Surface of the pulley 28

W

rolling mill

x

transport direction

y1

Longitudinal axis of the work roll 18A

y2

Longitudinal axis of the work roll 18B

α1

first pivot angle of the work roll 18A

α2

second pivot angle of the work roll 18A

λ

wavelength

Claims (13)

Method for the optical determination of at least one surface of a moving metal strip, characterized by performing distance measurements with at least two laser sources at localized measuring points with high frequency of 20 to 200 MHz perpendicular to the metal strip in the Mehrwellenlängeninterferometer method and transverse to the longitudinal extent and to the direction of movement of the metal strip , wherein the measuring location per unit time is changed transversely to the direction of movement. Method according to Claim 1 , characterized in that for the determination of the surface of the metal strip away from the measuring grid, an interpolation of the adjacent distance measurements is performed. Method according to Claim 1 or 2 , characterized in that the surface is determined on both sides of the metal strip. Method according to Claim 3 characterized by a thickness measurement related to the area of the metal strip resulting from opposing distance measurements of the two surfaces of the metal strip. Device (10) for determining at least one surface (O) of a moving metal strip (11), characterized in that the device (10) comprises a scanning unit (21) designed as a multi-wavelength interferometer (22) and provided with at least two laser sources Beam deflection unit (23), wherein this has a high frequency of 20 to 200 MHz periodically adjustable in space reflection plane (29), and above the metal strip (11) arranged mirror assembly (26) and an evaluation unit (24). Device (10) according to Claim 5 , characterized in that the with respect to the angle adjustable reflection plane (29) of the beam steering unit (23) as a rotating polygon wheel (29) is formed. Device (10) according to Claim 5 , characterized in that the adjustable with respect to the angle reflection plane (29) of the beam steering unit (23) is designed as a periodically movable mirror. Device (10) according to Claim 6 , characterized in that the angle of reflection adjustable reflection plane (29) of the beam steering unit (23) consists of a combination of a rotating polygon wheel (29) and at least one periodically moving mirror is formed. Device (10) according to Claim 6 , characterized in that the with respect to the angle adjustable reflection plane (29) of the beam steering unit (23) consists of a combination of a rotating polygon wheel (29) and at least one fixed, curved mirror is formed. Device (10) according to Claim 6 , characterized in that the adjustable with respect to the angle reflection plane (29) of the beam steering unit (23) consists of a combination of a rotating polygon wheel (29) and at least one optical lens. Device (10) according to Claim 5 , characterized in that the mirror arrangement (26) as a parabolic mirror (26) is formed. Device (10) according to Claim 5 , characterized in that the mirror arrangement (26) is designed as a facet mirror. Device (10) according to Claim 5 , characterized in that the mirror arrangement (26) is designed as a plane mirror, wherein the reflection results are mathematically corrected.

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