DE102010032800A1 - Method and device for calibrating a laser processing machine - Google Patents

Abstract

The invention relates to a method and a device for quality assurance of the processing result when processing a workpiece by means of laser, in particular with regard to the positioning and performance control of the amount of energy incident on the workpiece, including self-calibration and drift compensation, which only enables the central administration of decentralized devices. Before processing the workpiece, at least one laser light sensor with a small spatial extent is firmly connected to the machine and its position is determined in the machine coordinate system, which scans at least one laser light sensor with laser light, with the maximum sensor signal the position of the laser beam as corresponding Assumed with the position of the laser light sensor and determined in the laser coordinate system, from the difference between the position of the sensor in the machine coordinate system and the position of the laser beam in the laser coordinate system, at least one point correction value is automatically calculated to adapt the laser coordinate system to the Machine coordinate system and during the subsequent machining of the workpiece, the laser beam is deflected according to the laser coordinate system, taking into account the at least one correction value.

Description

I. Field of application

The invention relates to machines and machining operations in which a workpiece is to be processed by laser, so for example cut, engraved or labeled.

II. Technical background

As with any machining operation, it is also important here that this engraving or marking on the workpiece is carried out at the exact designated target position.

Frequently, however, the processing should not be performed at a fixed position with respect to the workpiece, but depending on the position of a pre-processing, which was previously carried out on the workpiece, and their position on the workpiece production-related may each be another.

In addition, the laser beam between the laser light source and its point of impingement on the workpiece is often deflected by one or more deflecting mirrors, and these deflecting mirrors are movable and driven to move the point of incidence of the laser beam along a desired path.

The precision machining of workpieces by means of laser radiation requires a calibration of the processing system with respect to the adjustment of the laser power density in the focus and the beam deflection unit for laser beam positioning. The state of the art is that for achieving the required accuracies (so-called drift, the above parameters by temperature, wear , Aging, etc.) are carried out prior to a machining trial work, which allow to determine the deviations of set and actual values and to perform a calibration of the system until the required machining precision. Performing the calibration in this way usually requires special knowledge and is associated with high expenditure of time and possibly material consumption. The knowledge goes far beyond the level of expertise that a machine operator needs to perform the actual machining.

The result is only that such laser processing systems are used in central manufacturing centers, where there is the possibility that a specialist cared for several machines, which are then operated by less trained personnel.

A typical application is the personalization of plastic cards, such as credit cards or ID cards, using a laser:
The card blanks are first printed and possibly also embossed, the position of the printing or embossing on the card specifying the position of the subsequent laser inscription.

Thus, for example, under the previously printed word "name", the specific name of the cardholder is to be positioned exactly in the x and y direction.

Since the personalization of such cards very large numbers are processed, these cards are automatically fed into the laser processing machine and ejected and processed in between by means of laser.

• – ungenaue Positionierung der Karte im Kartenhalter der Maschine, bedingt durch Spiel im Einzugs- und Haltemechanismus, insbesondere die Führungsbahnen für den Einzug und die Positionierung des Kartenhalters in der Maschine,
• – Abweichung der Ist-Position der Bedruckung oder Prägung von der Soll-Position relativ zum Kartengrundkörper,
• – Umwelteinflüsse, insbesondere Erschütterungen und Temperatureinflüsse, die die gesamte Maschine beeinflussen und vor allem Temperaturdehnungen im Grundgestell der Maschine bewirken und dadurch die Schwenkachsen der am Grundgestell befestigten Spiegel der Laserstrahlführung verlagern.

Possible sources of deviation of the actual position of the laser marking in terms of their desired position are therefore:

• Inaccurate positioning of the card in the card holder of the machine, due to play in the retraction and holding mechanism, in particular the guideways for the insertion and the positioning of the card holder in the machine,
• Deviation of the actual position of the printing or embossing from the desired position relative to the card main body,
• - Environmental influences, especially vibrations and temperature influences that affect the entire machine and especially cause temperature expansion in the base frame of the machine and thereby shift the pivot axes of the base frame mounted mirror of the laser beam guide.

To make matters worse, if such machines are to be built small, lightweight and compact in order to use them decentrally. This requires on the one hand a lightweight design and thus a supporting base frame of the machine from z. B. plastic instead of steel.

Should such devices be used decentrally, d. H. Distributed over several scattered locations, the task, which can hardly be managed organisationally, is to have these systems calibrated and set up by adequately qualified specialist personnel.

Furthermore, in order to avoid too large structural dimensions of the machine, the laser light source can not be arranged at a great distance and directed perpendicular to the map plane, but instead the laser light source is arranged in or parallel to the map plane and the beam aligned and deflected by multiple deflection perpendicular to the map plane , each one Deflection is fraught with play and represents another source of error by unwanted displacement of its pivot axis.

Another problem is power fluctuations of the laser:
On the one hand, individual diodes of the laser can become defective and as a result the power can decrease, on the other hand, lasers are subject to a natural aging process, which is also accompanied by a loss of power.

However, as decreasing power, with otherwise equal adjustment parameters, causes a declining blackening of the label result, which is detrimental to grayscale images on a card in particular, the laser power impinging on the workpiece should also be subjected to inspection to obtain consistent quality. This can not only by changes to the laser light source, but also by z. As contamination of the mirror in the beam path of the laser light or other factors are affected, such as poor focusing of the laser beam on the surface of the workpiece.

III. Presentation of the invention

a) Technical task

It is therefore the object of the invention to provide a method and a device for quality assurance of the machining result in the machining of a workpiece by means of laser, in particular as regards the positioning and power control of the incident on the workpiece amount of energy including self-calibration and drift compensation, which only enables the central administration of decentralized devices.

b) Solution of the task

This object is solved by the features of claims 1 and 12. Advantageous embodiments will be apparent from the dependent claims.

It should be said that there are different laser deflection systems:

single-axis:

• 1. The laser beam is deflected by a movable mirror only in the x direction.
• 2. The card, ie the workpiece, is moved in y-direction during machining.
• a) There is usually no pillow-ton distortion.
• b) A position calibration can only be done in the y direction when the sensor is moved with the card holder.

two-axis system:

• 1. The laser beam is deflected by two movable mirrors in the x and y directions.
• 2. The card is not moved at the label.
• 3. There is always a cushion-ton distortion.
• 4. The sensor can be fixed in place in the machine.

If a light beam of the laser light source deflected in a specific manner in the laser processing machine would reproducibly always impinge exactly on the same point of the workpiece, the problem underlying the invention would not exist at all.

There would be a single laser coordinate system in which the point of impact of the laser beam with respect to the map could be indicated if the map position is known.

In practice, however, this is not the case, since it is expedient to define two different coordinate systems which are not identical:

- First, the laser coordinate system:

The laser light source is fixedly positioned in the laser coordinate system and the point of impact of the laser on the workpiece in this laser coordinate system is caused by the deflections of the laser beam and also the errors and inaccuracies of both the exit position of the laser beam from the laser light source and its direction, as well as the errors in the deflections of the laser beam.

- On the other hand, the machine coordinate system:

This coordinate system is related to the machine as a whole, or to one of its parts, in particular the movable card holder, which then is a coordinate system movable with respect to the overall machine, but which in turn has overall tolerances relative to the fixed part of the machine.

This coordinate system is influenced by thermal expansions and guiding inaccuracies, e.g. As the card slide relative to the base frame of the machine, the vibrations of the base frame of the entire machine and similar factors.

Since positions on the workpiece are to be defined with the machine coordinate system, the machine coordinate system would ideally be a coordinate system, which is fixed with respect to the workpiece itself, which in the However, this case is not possible because of the mobility of the workpiece, so that errors in the positioning of the workpiece in the card holder and its holder coordinate system, especially compared to the machine coordinate system, must be additionally compensated.

• a) Die Ursprünge der beiden Koordinatensysteme – wenn sie analog zueinander festgelegt werden – können differieren, entweder in X-Richtung oder in Y-Richtung, also den beiden Auslenkrichtungen des Laserstrahles, oder in beiden Richtungen,
• b) Die Skalierung der beiden Koordinatensysteme kann differieren, indem ihre Längeneinheiten in einer übereinstimmenden Richtung unterschiedlich lang sind.
• c) Die geometrische Form der Koordinatensysteme kann sich unterscheiden.
• – Das Maschinenkoordinatensystem ist idealerweise ein kartesisches Koordinatensystem, also mit lotrecht aufeinander stehender X- und Y-Richtung.

The mismatch between the laser coordinate system and the machine coordinate system, such as the special holder coordinate system (which is understood in this movable coordinate system, the position of the holder coordinate system in the machining position of the workpiece holder) can be represented in different ways:

• a) The origins of the two coordinate systems - if they are determined analogously to one another - can differ, either in the X direction or in the Y direction, ie the two deflection directions of the laser beam, or in both directions,
• b) The scaling of the two coordinate systems can differ by their length units in a matching direction have different lengths.
• c) The geometric shape of the coordinate systems may differ.
• - The machine coordinate system is ideally a Cartesian coordinate system, so with perpendicular to each other X and Y direction.

In the laser coordinate system, the possible deflection range of the laser (after the last deflection) to the focal point defines a cone or truncated cone with a spherical segment-shaped bottom surface, so that the last lens in the beam path is always a so-called plan field lens, which is the focus points of the laser of this ball segment to distribute in a plane plane.

• – Die Richtung der einander entsprechenden X- oder Y-Richtungen können voneinander abweichen, so dass die Koordinatensysteme relativ um ihre Lotrechte (Z-Richtung) zueinander geringfügig verdreht sein können.
• d) – Die durch die jeweiligen Koordinatensysteme definierten Ebenen, insbesondere die X-Y-Ebenen, sind nicht identisch und auch nicht parallel, sondern bilden einen leichten Winkel zueinander, indem beispielsweise die Ursprünge der beiden Koordinatensysteme miteinander identisch sind, davon abweichende Punkte jedoch einen zunehmenden Versatz in Z-Richtung aufweisen.

However, this unfortunately also causes the laser coordinate system in the plane plane, the map plane, is not an exact Cartesian coordinate system, but has barrel-shaped, indentations or bulges compared to an exact Cartesian as the machine coordinate system.

• - The direction of the mutually corresponding X or Y directions may differ, so that the coordinate systems relative to their perpendicular (Z-direction) to each other may be slightly twisted.
• d) - The planes defined by the respective coordinate systems, in particular the XY planes, are not identical and also not parallel, but form a slight angle to each other, for example by the origins of the two coordinate systems being identical to each other, but deviating points being an increasing offset in the Z direction.

The two coordinate systems, ie laser coordinate system and machine coordinate system, are not real coordinate systems drawn on the machine, but conceptually defined coordinate systems, for example, also in the control of the machine deposited coordinate systems, although not necessarily both must be stored separately in the control. It can also be deposited only one of two.

Laser coordinate system on the one hand and machine coordinate system on the other hand can therefore also be seen as the desired position and actual position of the desired laser impact points. If only one of them, z. B. the laser coordinate system, in the control physically, ie by defining the zero point and the axial directions, is deposited, the target, so also actual position deposited in the coordinates of this coordinate system.

The laser impact point on the workpiece, z. As the map, is then at the desired target position again, if the deviations of the laser coordinate system, ie the actual position of potential impact points of the machine coordinate system, the desired positions of potential points of incidence of the laser beam is known and the actual position by Taking into account the calculated therefrom correction values can be transferred to the desired position desired.

For this purpose, it is first determined for one or more specific positions in the machining area of the machine how much the actual position (laser coordinate system) deviates from the desired position (machine coordinate system or holder coordinate system).

For this purpose, at these specific positions laser light sensors in the processing area fixed to the machine, or preferably fixed to the movable workpiece holder, arranged so that their position in the machine coordinate system or holder coordinate system is known.

Subsequently, these sensors and thus their position in z. B. holder coordinate system is approached with the laser beam and recorded what position it is at the point of impact, and thus the sensor position measured in the laser coordinate system is.

From this, a point correction value between the two coordinate systems is determined for each of these sensor positions by which the laser coordinate system (actual position) or the point of impact after the laser coordinate system, ie the actual position, must be additionally shifted, to the correct point after the z. B. holder coordinate system (target position) to achieve.

This correction value is taken into account in the subsequent machining of the workpiece for the deflection of the laser beam according to the laser coordinate system.

If only a single sensor is present, only a single point correction value can be determined and its components in the X and Y directions.

Only if the two coordinate systems have no other differences apart from a zero offset can such a single point correction value bring about a correlation of the two coordinate systems.

Since this is not certain, two spaced sensors are used for each of the two deflection directions of the laser beam, ie the X and Y directions, and a point correction value is determined for each sensor.

Under certain circumstances, depending on its design, a sensor can be used to determine the correction value in both of these directions.

From the two point correction values of the same direction can thus be determined automatically whether the scaling of the two coordinate systems in this direction coincides or in addition there is a scaling difference. The two point correction values of the other direction can additionally be used to determine whether there is a rotation of the coordinate systems about their vertical axis (Z axis) relative to one another.

In this way, from these point correction values, a scaling correction value for each of the X and Y directions can be determined, and optionally also a rotation correction value in the presence of a rotation of the two X-Y coordinate systems relative to each other.

In this sense, the arrangement of three or four sensors would preferably each in the corners of a z. B. rectangular processing area, in a rectangular card as a workpiece then just outside the map area in the holding frame, which then represents the workpiece holder, the most meaningful.

If, on the other hand, one wishes to determine the size or the presence of a ton-shaped distortion of the laser coordinate system, one sensor is preferably provided for each direction in the middle of the extension of the edge region and one at the end of the edge region, ie in a corner best a barrel-shaped indentation or bulge in the central region of the edge can be determined and from this in turn a tonnage correction value can be calculated automatically for each deflection direction.

The individual correction values are stored in the control system and, depending on the position of the laser incidence point currently to be calculated in the processing region, ie with respect to the laser coordinate system, calculated and possibly added exactly for this specific impact point, which is based on the type of correction value and the distance of the concrete impingement point mathematical origin of the coordinate system is possible.

To make matters worse, that the laser impingement should not impinge on a fixed position of the workpiece, but in a fixed positioning with respect to an existing on the workpiece visible pre-processing, such as a pre-printing, however, is not always due to production at the exact same card position.

In this case, the pre-processing result, for example the pre-printing, is recorded by a camera permanently installed in the machine and thus determines its position in the holder coordinate system as soon as the workpiece, for example the card, with the workpiece holder is in the processing position and determines a pre-processing correction value which must be taken into account in the subsequent laser processing in addition to the other correction values in the deflection of the laser beam according to the laser coordinate system.

For the laser processing, however, in addition to the exact positioning of the point of impact of the laser beam on the workpiece there, the correct energy input must be effected in the workpiece, because an incorrect amount of energy leads to a wrong processing result, for example when labeling by laser to a high or low degree of blackening or gray scale level.

This may for example be because the laser beam is not on the surface of the workpiece, so the xy plane z. B. the machine coordinate system, is focused. For this reason, with each individual laser light sensor, the laser beam with its focal plane to the height (in the z direction) of the sensor, so the xy plane z. In the machine coordinate system:
For this purpose, after scanning the sensor in the x and / or y direction and determining the exact position of the sensor in the xy direction in the laser coordinate system, the laser is limited to the exact xy direction. Position of the sensor is set, first with Z = 0 for example according to the laser coordinate system.

Subsequently, the Z coordinate is varied at this point and from this a relation between the signal strength of the sensor is determined as a function of the Z position of the focus of the laser beam in the form of a bell curve. When adjusting the focus in the Z direction, a shift of the focus position in the x and y direction should be avoided, as would inevitably be the case, for example, for a change in distance between the plane field lens and workpiece using a non-telecentric f-theta objective. The change in the Z position can be achieved, for example, by a change by beam divergence in front of the plane field lens.

By determining the maximum of this bell curve, which can be done automatically, it is determined at which Z value the signal strength is maximum, which is the Z value at which the focus of the laser beam in the Z direction is exactly at the height of the light sensor located. If this does not agree with Z = 0 according to the laser coordinate system, this results in a Z-correction value for the laser coordinate system.

If this is carried out for all the laser light sensors, Z scale correction values for the scaling of the Z correction value in the X and Y directions, which are additionally taken into account for the subsequent laser processing, can be automatically determined from the individual Z correction values thus obtained. This ensures that the laser is focused on the working plane at each machining point.

Even if this is the case anyway for a point of the coordinate system at Z = 0, for example for the origin of the coordinate system, this does not have to apply to the laser light sensors which are off the origin, since the xy plane of the laser coordinate system may be in one slight angle to the xy plane of the machine coordinate system.

Preferably, the correlation between focus distance and signal strength of the laser light sensor for the respective sensor can also be determined prior to installation of the sensor in the machine in a separate test device, instead of or in addition to the subsequent re-examination in the installed state in the machine.

Another reason why the right laser power is not given off on the workpiece surface during laser processing may be due to the laser light source or the beam path of the laser, for example because each laser light source is producing a different line due to production or the power of the laser light source is decreasing - e.g. B. due to aging - or by one or more of the deflecting mirrors are dirty in the beam path and the laser light is not completely reflected in the desired direction, but partially absorb, partially scatter in undesirable other directions.

For this purpose, a power calibration curve is created for each of the laser light sensors in a test apparatus before it is installed in the processing machine. In this case, the laser light sensor of a similar or ideally identical later laser light source from the subsequent processing machine is applied accurately and without deflecting accurately and with exact focus while the laser power varies gradually, preferably 0-100% of the laser power, and the associated signal strengths, for example Diode voltages recorded by the laser light sensor.

Thus, in the subsequent start-up of the laser light sensors in the installed state in the machine - if the xy positioning and the correct focus is done - be deduced from the then measured signal strengths, which hits power on the workpiece and whether this corresponds to the desired target power ,

In case of deviation of the actual power from the target power at the point of impact, so on the laser light sensor, the control to compensate the recorded power of the laser light source readjust accordingly or - in case of excessive deviation - an error message is issued to the cause of this strong deviation to remedy, for example, a dirty or damaged deflecting mirror or a completely or partially defective laser light source.

For the procedure described above, a suitable laser light sensor is needed in addition to a corresponding control.

c) embodiments

Embodiments according to the invention are described in more detail below by way of example. Show it:

1 : the workpiece, the workpiece holder and the relevant coordinate systems,

2 : the distortion of the laser coordinate system and the position of the laser light sensors in the machine,

3 : setting the focus setting of each laser light sensor,

4 : the power calibration curve of a laser light sensor,

5a : the laser processing machine according to the single-axis system in schematic representation, at which a calibration is to be made,

5b : only one beam deflection according to the two-axis system in schematic representation.

According to 5a is within the laser processing machine shown here in the top view 22 the workpiece holder 3 be moved between a loading position shown in dashed lines and a processing position shown in solid lines, wherein in the workpiece holder 3 an inserted workpiece 4 , usually a plastic card, is located.

In addition, in the machining position, the workpiece holder 3 Controlled in Y-direction movable, while only the X-movement by appropriate deflection of the laser beam 2 he follows. It is therefore a one-axis system of laser deflection.

The possible editing area 7 corresponds to at least the outer dimensions of the workpiece holder 3 ,

The laser beam 2 is from a laser light source 1 in a direction in the XY plane adjacent to the area of the workpiece holder 3 issued.

It is above the workpiece holder 3 to recognize a pentagonal frame, in whose main legs deflecting mirror 20a , b, c are mounted, the z. B. pivotable, controlled by the controller 10 the machine 1 , are.

An analogous same frame with also three deflecting mirrors is in the direction of the 5 aligned under the workpiece holder 3 positioned.

The laser beam 2 meets in the area next to the workpiece holder 3 in height between these two stuck in the frame of the machine 1 mounted frame on a pivoting selection mirror 2 . 4 the laser beam, for example - as in 5 shown - up to the upper pentagonal frame and the local deflection mirror 20a leads, from there to the second deflection mirror 20b and the third deflecting mirror 20c and from there into the plane of the drawing on top of the frame-shaped workpiece holder 3 lying workpiece 4 ,

In the same way can by the pivoting selection mirror 24 the laser beam 2 be deflected to the lower pentagonal frame and the local deflection mirrors, which is a caption of the workpiece 4 caused from the bottom.

Regardless of whether top or bottom of the workpiece 4 To be labeled is with an X-deflecting mirror, which is the last deflecting mirror 20c of the laser beam 2 or a further forward in the beam path, z. B. between laser light source and selection mirror 24 arranged X-deflecting mirror may be deflected controlled in the X direction, while the Y-positioning of the impact point for the laser beam by corresponding movement of the workpiece holder 3 takes place, which is preferably always changed only when a running in the X direction line of the label from the laser beam 2 has ended.

5b shows in contrast a schematic representation of an arrangement in which the laser beam successively by two pivotable mirrors whose pivot axes are not identical, but preferably perpendicular to each other, in two spatial directions (x and y) can be deflected, ie a so-called two-axis system.

The rest of the laser processing machine is not shown.

It can be seen that in the beam path of the laser in succession, an X-deflecting mirror and a Y-deflecting mirror, each driven by a Galvomotors controlled by the control of the laser processing machine to be placed tilted about its pivot axis, are arranged.

Between the last deflecting mirror and the workpiece 4 , which is located in the workpiece holder 3 A so-called plan field lens is arranged, which is the barrel-shaped distortion of the coordinate system on the workpiece surface, as by the conically deflected laser beam 2 should balance as well as possible, but this is only possible to a limited extent.

From this basic situation it becomes clear that the laser coordinate system x, y, in which the deflection of the laser beam and thus the necessary movements of the deflection mirror 20a , b, c are set, not always with z. B. the stationary in the machine machine coordinate system X ', Y' coincides due to temperature drift of the mirror suspensions, strains and shrinkages of the base frame of the laser processing machine 22 due to humidity changes, temperature changes or deformations due to vibration or similar reasons.

It is only right that the laser coordinate system x, y does not coincide with the holder coordinate system X, Y, which is stationary with respect to the workpiece holder 3 is set, which is movable in the Y direction and in the X-direction play in its guides, which is despite knowing its nominal positions, especially in the X direction further match error already compared to the machine coordinate system X ', Y', and even more opposite to the laser coordinate system x, y.

In order to eliminate the coincidence errors between the laser coordinate system x, y, in which the deflections of the laser beam are fixed, and especially the holder coordinate system X, Y and thus the laser processing at the correct target position with respect to the workpiece 4 - whereby the machine coordinate system X 'Y' can be used as an intermediate step -, between the individual coordinate systems correction values, especially between the L ... -K ... x, y and the H ...- K ... X, Y, determines what happens as follows:
The correction values determined for the relationship between laser coordinate system x, y and machine coordinate system X ', Y' apply to the (fixed) machine coordinate system X ', Y' in general, while in the determination of correction values between the laser coordinate system x, y and the holder coordinate system X, Y this only for a specific positioning of the workpiece holder 3 in the laser processing machine 22 apply, so these correction values may be for multiple positions of the workpiece holder 3 , At least the initial and final position of the workpiece holder 3 in the processing area of the laser processing machine 22 be determined separately and possibly also a course of these correction values depending on z. B. Y positioning of the workpiece holder 3 must be determined.

The laser beam 2 reachable processing area 7 is related to the laser processing machine 22 only one X-directional line under the deflecting mirror 20c due to the Y-mobility of the workpiece holder 3 however, based on the workpiece holder 3 whose total area including the z. B. central large recess in which the workpiece 4 only rests on a narrow lateral edge.

In 1a are in an enlarged view of only the workpiece holder 3 with inserted workpiece 4 across from 5 the laser coordinate system x, y and the holder coordinate system X, Y drawn, which do not coincide.

Will the laser beam 2 in the laser coordinate system x, y deflecting it, the laser coordinate system x, y represents the actual point of impact of the laser beam on the map, which as a rule does not coincide with the desired position on the workpiece 4 matches, as it results from the specification according to the holder coordinate system X, Y, which stationary with respect to the workpiece holder 3 is defined.

According to 1a is at a defined point of the holder coordinate system X, Y, for example, its zero point, in any case, preferably on the workpiece holder 3 outside the area of the workpiece 4 , a laser light sensor 5.1 mounted, with the controller 10 is coupled, and when hitting laser light 2 in particular emits a quantitative signal.

Because the approximate position of this laser light sensor 5.1 Also known according to the laser coordinate system x, y, the exact position of this sensor in the laser coordinate system x, y can be determined by repeatedly traversing the approximate position range in the x and y directions.

2 B shows how the suspected position of the laser light sensor 5.1 is traversed in a scanning direction, x or y, and thereby laser light pulses are sent at regular time intervals, and the corresponding from the laser light sensor 5.1 thereby emitted sensor signals SS are recorded. The peaks of these sensor signals SS give a bell curve 19 that from the controller 10 is determined automatically, and may have a different amplitude and also a different center position for each scanning direction and certainly for different sensors.

The control 10 is also automatically capable of using known algorithms the highest point of this bell curve 19 to determine what then the exact value in the scanning direction, so x or y, this laser light sensor 5.1 in the laser coordinate system x, y.

If the actual value in the laser coordinate system x, y was the zero point, it is so according to 2 B determined x or y value of the highest point of the bell curve 19 the respective component PKX1 or PKY1, which in total yield the point correction value PK1, by which in this case the zero point of the holder coordinate system X, Y differs from the actual position, the zero point of the laser coordinate system x, y. Of course, this does not only apply to the zero point, but to every point in the processing area.

Around the nominal position with the point of impact of the laser beam 2 on the workpiece 4 In order to achieve this, the point correction value PK1 or an individual, relevant for this point of impact must therefore be used for the previously provided settings of the deflection mirrors in the laser coordinate system x, y Point correction value in the laser coordinate system x, y are added, which is done automatically by the controller.

Of course, such a point correction value can be set not only for the zero points of these two coordinate systems, but for any point in the processing area 7 , ie in the area of the workpiece holder 3 , Accordingly, according to 1b not just the laser light sensor 5.1 in the lower right corner of the frame-shaped workpiece holder 3 present, but also laser light sensors 5.2 - 5.4 in the other corners.

For each of these laser light sensors 5.1 - 5.4 Corresponding point correction values PK1-PK4 are determined, each separated according to their components in the x- and y-direction, z. Eg PK2x, PK2y.

The two coordinate systems x, y and X, Y are often not only shifted relative to each other, but also have a non-matching scale, so that a size unit z. B. in the y-direction of the laser coordinate system x, y is another than a Y-unit in the holder coordinate system X, Y and also in the X direction.

wobei der Nenner des Bruches der Abstand in Einheiten des Laserkoordinatensystems in Positionen der beiden benutzten Sensoren 5.1 und 5.2 ist.To determine this, - again separated for the two directions x and y - two spaced apart in this direction laser light sensors, z. B. 5.1 and 5.2 , used and made of z. B. the y-components PK1y and PK2y from the point correction values PK1 and PK2 a scaling correction value for this Y-direction determined in particular according to the formula

where the denominator of the fraction is the distance in units of the laser coordinate system in positions of the two sensors used 5.1 and 5.2 is.

This scaling correction value SKX, SKY is thus a correction value which, depending on the position of the laser beam in the coordinate system per unit length, must be added to the value after the laser coordinate system x, y, which is also in the control 10 automatically done. If already the origins of the coordinate systems according to 1a Of course, this point correction value of the origin of the laser coordinate system x, y is unique.

Another problem is that due to the deflection of the laser beam 2 by two deflecting mirrors, which can be pivoted about an axis, the points of impact of the laser beams 2 in x- and y-direction after the laser coordinate system in the x or y-direction usually no straight lines, but at most in the middle of the processing area, and thus the laser coordinate system x, y is distorted barrel-shaped, which in 2a is exaggerated.

Most two opposite edges are convex convex, the other two spherically concave.

To the deviation of the laser coordinate system x, y, especially with respect to the outermost x and y lines of the machining area 7 To compensate for the Cartesian, rectangular coordinate system X, Y or X ', Y' by means of correction values, barrel correction values TKX and TKY are determined for the two directions x and y, which is done as follows:
According to 2a For this purpose, sensors are spaced in the x and y directions at the edges of the processing area 7 arranged, both at the two corners of the processing area in this direction and in the middle of this edge, so that the deviation from the Cartesian coordinate system is detectable.

So if in the Y direction the sensors 5.1 and 5.4 which occupy positions furthest away from each other along the Y-direction edge, there is another laser light sensor in the middle of this edge therebetween 5.2 arranged.

If there is no additional rotation of the coordinate systems, a Y-line of the X, Y or X ', Y' coordinate system is located through the two remote sensors 5.1 and 5.4 , runs.

The middle sensor 5.2 , on the other hand, is in the laser coordinate system x, y removed by a ton correction value TKYmax from this line.

This can be - taking into account the degree of approach of a specific laser impact position to the upper or lower edge of the processing area 7 in the Y direction - determine a tonal correction value TKY to be determined for this point in each case, and also in the x direction a tonal correction value TKX, calculated based on the sensor centered in the X direction 5.3 determined maximum tonnage correction value TKXmax.

Furthermore, correction values for the adjustment of the focus position in the Z direction are necessary, as in the 3 shown.

So far, it has been spoken of the deviations of the two-dimensional coordinate systems, which in the plane of the 5 and 1 lie.

Perpendicular to this, in the Z-direction, is for the present application, only the focal points of the laser beam 2 of importance, targeted to the machined surface of the workpiece 4 or should also be at a predetermined difference in the depth or above the surface.

However, as it is intended, optimum blackening on the workpiece 4 As a rule, the focus should be precisely on the surface of the workpiece 4 are set, and this is selected as the Z-axis zero point.

To determine if this is true, will - for each of the laser light sensors used in the machine 5.1 to 5.4 and optionally separated for top - the laser beam 2 in the XY direction exactly to the respective sensor z. B. 5.1 aligned and the focus adjustment, so the position in the Z direction of the focal point with respect to the laser coordinate system also several times differently, preferably both sides of Z = 0, set and recorded each resulting sensor signal SS, resulting in a context according to 3a results.

Now finds the maximum sensor signal SS max. not at Z = 0 but at another Z value, such as Z = 1, the difference is the focus correction value ZK by which the adjustment of the height of the focal point in the Z direction must be changed to on the surface of the workpiece 4 to cause optimal blackening.

This focus adjustment ZK is usually performed on the individual sensors, after they are already firmly positioned in the laser processing machine, ie built-in.

Then of course the knowledge of the altitude (Z-direction) of these sensors compared to the zero height (X- / Y-plane) is necessary, to which the focus correction value may have to be added.

In some cases, for structural reasons, this focus adjustment in the machine can not be performed.

In this case, the laser light sensors become in the machine before installation 22 installed in a special test device and there performed this focus adjustment.

Further, for the laser light sensors spaced apart in the X- and Y-direction and the focus correction values ZK1, ZK2, ZK3 detected therefrom, it is possible to read in one direction, e.g. B. the Y direction, spaced sensors and focus correction values ZK1 and ZK2 turn a focus scale correction value ZSKY for the Y direction and ZSKX analog for the X direction are determined, if in the z in this z. B. Y-direction spaced sensors 5.1 and 5.2 the corresponding Z correction values ZK1 and ZK2 were not the same size.

Because this means that the xy plane in the laser coordinate system xy is not parallel but at an angle to the xy plane in the holder coordinate system X, Y or machine coordinate system X ', Y', which can be compensated with this focus scale correction value ZSKX, ZSKY ,

In contrast, always outside the machine - in 4 shown - the relationship between the at the laser 1 adjusted power and the resulting signal level of the sensor signal SS as a power calibration curve 8th recorded.

This is necessary in order later to be able to reverse the signal level of the sensor signal SS to the power arriving on the workpiece, which despite the unchanged power setting - the laser calibration curve 8th is carried out with the new laser light source - does not remain the same, but has a drop as an aging phenomenon or due to a mirror contamination.

This aging phenomenon can be compensated for by means of control, so that the same value of the sensor signal SS and thus the line impinging there is always present at a desired processing location.

LIST OF REFERENCE NUMBERS

• x, y laser coordinate system
• X, Y holder coordinate system
• X ', Y' machine coordinate system
• VK1 pre-processing correction value
• TKX, TKY tons correction value
• K1 correction value
• PK1, PK2 point correction value, deviation
• VK1 pre-processing correction value
• SKX, SKY Scaling correction value
• ZK1 focus correction value
• ZSKX, ZSKY focus scale correction value
• Z focus adjustment
• SS sensor signal
• 
  Values in the coordinate system

LIST OF REFERENCE NUMBERS

1

Laser light source

2

Laser light, laser beam

3

Workpiece holder

4

workpiece

5.1, 5.1 ', 5.2, 5.3, 5.4

Laser light sensor

6

Vorbearbeitungsresultat

6 '

target position

7

editing area

8th

Power calibration curve

9

Focus calibration curve

10

control

11

glass fiber

11a

free end

12

Fiber Cover

13

photodiode

14

cover

15

Light diffuser

16

Amplifier circuit

18

Laser light pulse

19

bell curve

20a, b, c

Deflection mirror

22

Laser processing machine

23

electrical line

24

selection mirror

Claims (15)

(xy Positioning) Method for Calibrating a Laser Processing Machine ( 22 ), with - a laser light source ( 1 ), - a laser beam ( 2 ), which is deflectable in the two deflection directions (x and y) of the laser coordinate system (x, y), - a workpiece holder ( 3 ), in which a laser light ( 2 ) workpiece to be machined ( 4 ), characterized in that before machining the workpiece ( 4 ) - at least one laser light sensor ( 5 ) with a small spatial extent with the machine, in particular the workpiece holder ( 3 ), and its position in the machine coordinate system (X ', Y'), better in the holder coordinate system (X, Y), is determined, - the at least one laser light sensor ( 5 ) with laser light ( 2 ) is sampled, - at the maximum sensor signal (SS) of the sensor ( 5 ) the impact position of the laser beam ( 2 ) as coincident with the position of the laser light sensor ( 5 ) and in the laser coordinate system (x, y) is determined, in particular including the necessary deflection of the laser beam ( 2 ), - from the difference of the position of the sensor ( 5 ) in the machine coordinate system (X ', Y'), better in the holder coordinate system (X, Y), and the impact position of the laser beam ( 2 ) in the laser coordinate system (x, y) at least one point correction value (PK1) is automatically calculated to adapt the laser coordinate system (x, y) to the machine coordinate system (X ', Y'), better the holder coordinate system (X, Y), and - in the subsequent processing of the workpiece ( 4 ) the laser beam ( 2 ) is deflected after the laser coordinate system (x, y) taking into account the at least one correction value (PK1). A method according to claim 1, characterized in that for scanning the laser light sensor ( 5 ) with the laser beam ( 2 ) is overrun in the direction (x or y) in which the deviation (PK1X, PK1Y) or between the sensor position and the impact position is to be determined. Method according to one of the preceding claims, characterized in that in the direction (x or y), in which the deviation (PK1X, PK1Y) or between the sensor position and the impact position is to be determined, spaced apart two laser light sensors ( 5.1 and 5.2 or 5.1 and 5.3 ) and a respective point correction value (PK1 and PK2 or PK1 and PK3) is determined, and from the two point correction values (PK1, PK2) of one direction, a scaling correction value (SKX, SKY) for this direction is automatically determined from which additional point correction values can be automatically determined for any point in this direction. Method according to one of the preceding claims, characterized in that for each deflection direction (X, Y) of the laser beam ( 2 ) two spaced laser light sensors (( 5.1 and 5.2 . 5.1 and 5.3 )), of which at least one laser light sensor ( 5.1 ) is used for both directions. (Laser-focusing) Method according to one of the preceding claims, characterized in that before the machining of the workpiece ( 4 ) on at least one of the sensors installed in the machine ( 5.1 ), especially for all sensors ( 5.1 - 5.4 ), the laser beam ( 2 ) with the focus setting Z = 0 in the laser coordinate system (x, y) to the xy position of the maximum sensor signal (SS) of the sensor ( 5.1 ) and in this position the focus setting (Z) of the laser beam ( 2 ) and the resulting values of the sensor signal (SS) are recorded and stored in the controller ( 10 ) are stored. Method according to one of the preceding claims, characterized in that from the focus adjustment (Zmax), in which a maximum sensor signal (SSmax) of the sensor ( 5.1 ) results in a focus correction value (ZK1) for this sensor compared to the focus setting Z = 0 ( 5.1 ) is determined. Method according to one of the preceding claims, characterized in that from the focus correction values (ZK1, ZK2, ...) of all sensors ( 5.1 - 5.4 ) Focus scale correction values (ZSKX, ZSKY) are automatically determined for the X and Y directions representing the deviation from the parallelism between machine coordinate system (X ', Y') and laser coordinate system (x, y) and from which a focus correction value is automatically calculated automatically for each point of the machining area and 2 ) is taken into account. (Pre-printed) Method according to one of the preceding claims, characterized in that - before processing, the position of the pre-processing results ( 6 ), in particular pre-printing or pre-embossing, of the workpiece ( 4 ) in the machine coordinate system (X ', Y'), in particular in the holder coordinate system (X, Y) as well as in the laser coordinate system (x, y) is determined and from a Vorbearbeitungs correction value (VK1) is determined and - in the subsequent Machining the workpiece ( 3 ) the laser processing in the desired local relation to the pre-processing result ( 6 ) is applied by the position of the pre-processing results ( 6 ) in the machine coordinate system (X ', Y') as well as a preprocessing correction value (VK1) for this position between the laser coordinate system (x, y) and the machine coordinate system (X ', Y'). (Tons correction) Method according to one of the preceding claims, characterized in that by arrangement of the two in one direction (x or y) spaced laser light sensors ( 5.1 and 5.2 . 5.1 and 5.3 ) at the edge of the processing area, on the one hand in the middle of the edge ( 5.2 ) and at one end of the edge ( 5.1 ), from the two point correction values (eg PK1, PK2) an additional ton correction value (TKX, TKY) for each direction is automatically calculated for the shape deviation of the barrel-shaped distorted laser coordinate system (x, y) in this direction in comparison to the Cartesian machine coordinate system (X ', Y'), in particular holder coordinate system (X, Y). (Power determination) Method according to one of the preceding claims, characterized in that each of the laser light sensor (eg. 5.1 ) before installation in the machine with the light of a laser light source ( 1 ) of the same type, in particular the identical laser light source ( 1 ), precisely and centrally with focus adjustment (Z = 0) is applied and by varying the power of the laser light source ( 1 ) and the associated strengths of the sensor signal (SS) of the laser light sensor ( 1 ) a power calibration curve ( 8th ) and especially in the controller ( 10 ) of the machine is deposited. (Focus error) Method according to one of the preceding claims, characterized in that the laser light sensor ( 5 ) before installation in the machine with the light of a laser light source ( 1 ) of the same type, in particular the identical laser light source ( 1 ) is precisely applied centrally and by varying the focus setting (Z) of the focal point of the laser beam ( 2 ) from the laser light sensor ( 5 ) and the associated sensor signal (SS) of the laser light sensor ( 5 ) a focus calibration curve ( 9 ) and especially in the controller ( 10 ) of the machine is deposited. Device for calibrating a laser processing machine ( 22 ) comprising a machine coordinate system (X ', Y') comprising - a laser light source ( 1 ), which - a laser light beam ( 2 ), which has movable deflection mirrors ( 20 ) in the two deflection directions (X and Y) of the laser coordinate system (x, y) is deflectable, - a workpiece holder ( 3 ), in which a laser light ( 2 ) workpiece to be machined ( 4 ), and that in the editing area ( 7 ) of the laser beam ( 2 ), - a controller ( 10 ), in which both the laser coordinate system (x, y) and the machine coordinate system (X ', Y'), in particular its holder coordinate system (X, Y) is deposited and which comprises a computing unit and the position of the movable deflecting mirror ( 20 ), characterized by at least one laser light sensor ( 5.1 ), whose position in the machine coordinate system (X ', Y'), in particular in the holder coordinate system (X, Y) is known. Device according to one of the preceding device claims, characterized in that between the diaphragm ( 14 ) and the photodiode ( 13 ) a scattered light disc ( 15 ) is arranged. Device according to one of the preceding device claims, characterized by an optical sensor, in particular a CCD sensor, for determining the at least one pre-processing result ( 6 ) on the in the processing area ( 7 ) workpiece ( 4 ) in the machine coordinate system (X ', Y'), in particular in the holder coordinate system (X, Y), wherein the optical sensor signal-wise with the controller ( 10 ) connected is. Device according to one of the preceding device claims, characterized in that the device has a test stand outside the laser processing machine ( 22 ) for laser light sensors ( 5.1 ff.) comprising a laser light source ( 1 ), in particular the same laser light source ( 1 ) like the laser processing machine ( 22 ), and in which the laser beam ( 2 ) of the laser light source ( 1 ) exactly on the protruding free end of the optical fiber ( 11 ) or the aperture ( 14 ) of the laser light sensor ( 5.1 ) and the power of the laser light source ( 1 ) and / or the focus setting (Z) of the laser beam ( 2 ) and the signal strengths (SS) of the laser light sensor ( 5 ) a control, which also comprises a computing unit, in particular the controller ( 10 ).

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