DE102012022844B4 - Method and device for ultra-precise shaping of a surface - Google Patents

Abstract

The present invention relates to a method for the ultra-precise shaping of a surface of at least one workpiece having a dimensional and dimensional stability below 5 μm by means of a tool (7) having at least one diamond (14), comprising the following steps: - first detachable clamping (601) the tool (7) in a first index position on a tool holder (5), wherein the orientation and position of the at least one diamond (14) with respect to the tool holder (5) by the first index position is completely determined, - first machining (603) of a the at least one workpiece with one of the at least one diamond (14), wherein the tool (7) in the first index position on the tool holder (5) is clamped, - releasing (605) of the in the first index position on the tool holder (5) spanned Tool (7), - second detachable clamping (607) of the tool (7) in a second index position on the tool neck ter (5), wherein the relative to the first index position changed orientation and / or position of the at least one diamond (14) with respect to the tool holder (5) is completely determined by the second index position, and - second machining (609) one of the at least one Workpiece with one of the at least one diamond (14), wherein the tool (7) is clamped in the second index position on the tool holder (5).

Description

The present invention relates to a method and a device for ultra-precise shaping of a surface of at least one workpiece with a dimensional and shape retention below 5 microns by means of a tool having at least one diamond.

A machine for the ultra-precise machining of optical workpieces made of plastic with a plurality of arranged on a base plate of a tool holder receptacles for releasably securing a plurality of tools is known from EP 1 916 060 A1 known.

Plastic optics are used today as a disposable item, for example in automotive optical rain sensors, reversing cameras, navigation displays and LED lighting, in photovoltaic in Fresnel lens packages or in medical technology in minimally invasive endoscopes.

There is therefore a great economic interest in producing such plastic optics on the one hand with very high optical quality and on the other hand very cost-efficient and fast. Especially in the miniaturization of plastic optics very complex surface geometries are needed, which can be produced inexpensively via replication processes such as injection molding, injection compression or hot stamping.

By means of diamond cutting, the plastic optics themselves or, for example, an injection mold for the injection molding of a plastic optical system can be formed in an ultra-precise manner, ie. H. with a dimensional and shape retention below 5 microns. However, currently available on the market machine systems for diamond cutting are less productive, only the implementation of highest accuracies in the foreground. Thus, both set-up processes for tool and component as well as changeover processes for different machining strategies are characterized purely by hand. The non-productive times are extremely long compared to conventional machining techniques. In addition, there is a high risk that recurring components can not be implemented reliably due to incorrect operation.

In order to achieve a dimensional and dimensional stability below 5 microns, nowadays the alignment and positioning of the diamond with respect to the workpiece must be performed manually by a skilled person who aligns and positions workpiece and tool by means of a μ-hammers and a dial gauge. Such a manual process can take several hours depending on the experience of the hiring person.

Very often it is necessary for complex surface geometries to use different tools and to change tools between different processing steps or to set a different axis orientation of the tool. Of course, manual alignment / positioning is particularly uneconomical because it has to be repeated after each processing step. However, there is also the danger that an alignment / positioning set in the previous processing step can not be reproduced. In particular, when different people make the manual settings, a dimensional and shape accuracy below 5 μ] m can hardly be achieved because the tool alignment and positioning between the tool changes can not be reproduced accurately enough.

A solution for increasing the reproducibility of the tool alignment and positioning describes the EP 0 922 529 B1 , which describes a palletizing system, in which two coupling elements are clamped together in the direction of a clamping axis and by means of centering spring parts a reproducible relative alignment and positioning of the coupling elements is achieved to each other. The WO 2012/034910 A1 describes a similar system.

However, the prior art does not describe how to make a tool change in diamond cutting as efficient and fast.

It is therefore the object of the present invention to be able to carry out a tool change more efficiently and faster in the diamond cutting with a dimensional and shape accuracy below 5 microns between processing steps.

This object is achieved by a method and a device according to the features of claim 1 or 7. Advantageous embodiments of the invention can be found in the respective subclaims or the description and the figures.

• – Erstes lösbares Aufspannen des Werkzeugs in einer ersten Indexposition auf einem Werkzeughalter, wobei die Ausrichtung und Position des mindestens einen Diamanten bezüglich des Werkzeughalters durch die erste Indexposition vollständig bestimmt ist,
• – Erstes spanendes Bearbeiten eines des mindestens einen Werkstücks mit einem des mindestens einen Diamanten, wobei das Werkzeug in der ersten Indexposition auf dem Werkzeughalter aufgespannt ist,
• – Lösen (605) des in der ersten Indexposition auf dem Werkzeughalter aufgespannten Werkzeugs,
• – Zweites lösbares Aufspannen des Werkzeugs in einer zweiten Indexposition auf dem Werkzeughalter, wobei die gegenüber der ersten Indexposition veränderte Ausrichtung und/oder Position des mindestens einen Diamanten bezüglich des Werkzeughalters durch die zweite Indexposition vollständig bestimmt ist, und
• – Zweites spanendes Bearbeiten eines des mindestens einen Werkstücks mit einem des mindestens einen Diamanten, wobei das Werkzeug in der zweiten Indexposition auf dem Werkzeughalter aufgespannt ist.

According to a first aspect of the invention, a method is provided for ultra-precise shaping of a surface of at least one workpiece having a dimensional and dimensional stability below 5 μm by means of a tool comprising at least one diamond, comprising the following steps:

• First releasably clamping the tool in a first index position on a tool holder, wherein the orientation and position of the at least one diamond relative to the tool holder is completely determined by the first index position,
• First machining one of the at least one workpiece with one of the at least one diamond, wherein the tool is mounted in the first index position on the tool holder,
• - To solve ( 605 ) of the tool clamped in the first index position on the tool holder,
• Second releasably clamping the tool in a second index position on the tool holder, the orientation and / or position of the at least one diamond relative to the tool holder being completely determined relative to the first index position being determined by the second index position, and
• - Second machining one of the at least one workpiece with one of the at least one diamond, wherein the tool is clamped in the second index position on the tool holder.

The steps of first and second clamping and releasing may each be as in the EP 0 922 529 B1 or the WO 2012/034910 A1 be described described. In this case, the steps of the first and second releasable clamping and loosening can take place manually or automatically. The first and second machining preferably proceeds automatically according to a programmed pattern for ultra-precise shaping of the surface.

The inventive method differs in particular from the prior art by changing the index positions between the first and second machining, so that the same tool can be used in other reproducible positioning of the tool holder and thus the workpiece. Thus, if the tool has multiple diamonds, a second diamond may be substituted for the first diamond in the second index position. The inventive method is also advantageous if the tool has only one diamond, but its alignment and positioning in the second index position is needed. There is no need to fetch and clamp new tools on a new pallet. In addition, the number of required pallets is minimized by the inventive method, whereby a higher reproducibility of the tool alignment and positioning and thus a better dimensional and shape retention is achieved. Preferably, even a dimensional and dimensional stability below 1 μm is achieved with the method according to the invention.

Preferably, the tool has at least two diamonds and the first machining is done with a first of the at least two diamonds and the second machining is done with a second of the at least two diamonds. This has the advantage that for the second diamond no separate tool with its own range must be clamped, but the same tool can be used in another index position. The diamond change is faster. You save yourself a new range and is therefore more efficient. Since a pallet change also brings with it a certain loss of repeatability, changing the index position is also more accurate.

Preferably, the first and second releasable clamping in each case takes place in a clamping axis, wherein the first and second index position differs by a rotation about the clamping axis. This is a particularly reliable and simple way of clamping, which can also be carried out automatically with a robot arm. For this purpose, alternatively or in combination with the rotation, the first and second index positions can also differ by a displacement perpendicular to the clamping axis. Even a translatory transfer of the index positions in the direction of the clamping axis would be conceivable.

Preferably, the first and second machining operations are substantially perpendicular to the clamping axis. Alternatively, the clamping axis can also run parallel to the axis of rotation of the milling or lathe.

Each diamond of the tool is preferably still adjustable in the orientation and positioning with respect to the tool, in particular its position in the direction of the clamping axis. However, with this adjustability, there is a defined reference point, so that at this reference point the orientation and position of each diamond relative to the tool holder is completely determined by the index position.

The at least one workpiece is preferably an optical element made of plastic or an injection mold for a plastic optical element. The process according to the invention is particularly suitable for processing such surfaces, since a particularly high dimensional and dimensional stability below 5 μm is required there.

• – einem Werkzeug, das mindestens einen Diamanten aufweist, und
• – einem Werkzeughalter,

wobei das Werkzeug in einer ersten und in einer zweiten Indexposition auf dem Werkzeughalter aufspannbar ist, wobei eines des mindestens einen Werkstücks mit einem des mindestens einen Diamanten sowohl dann spanend bearbeitbar ist, wenn das Werkzeug in der ersten Indexposition auf dem Werkzeughalter aufgespannt ist, als auch dann, wenn das Werkzeug in der zweiten Indexposition auf dem Werkzeughalter aufgespannt ist,
wobei die Ausrichtung und Position des mindestens einen Diamanten bezüglich des Werkzeughalters durch die erste Indexposition vollständig bestimmt ist, und wobei die gegenüber der ersten Indexposition unterschiedliche Ausrichtung und/oder Position des mindestens einen Diamanten bezüglich des Werkzeughalters durch die zweite Indexposition vollständig bestimmt ist.According to a second aspect of the invention, there is provided an apparatus for ultra-precise shaping of a surface of at least one workpiece having a dimensional and dimensional stability below 5 μm, comprising:

• A tool comprising at least one diamond, and
• A tool holder,

wherein the tool is clamped in a first and in a second index position on the tool holder, wherein one of the at least one workpiece with one of the at least one diamond is both machinable when the tool is clamped in the first index position on the tool holder, as well when the tool is clamped in the second index position on the tool holder,
wherein the orientation and position of the at least one diamond with respect to the tool holder is completely determined by the first index position, and wherein the relative to the first index position different orientation and / or position of the at least one diamond with respect to the tool holder is completely determined by the second index position.

The device according to the invention differs in particular by the clamping of the tool in different index positions, which completely determines the orientation and / or position of the diamonds, so that the same tool can be used in a different position to the tool holder and thus to the workpiece. Thus, if the tool has multiple diamonds, a second diamond may be substituted for the first diamond in the second index position. The device according to the invention is also advantageous if the tool has only one diamond, but its alignment and positioning in the second index position is needed. There is no need to fetch and clamp new tools on a new pallet. In addition, the number of required pallets is minimized by the inventive device, whereby a higher reproducibility of the tool alignment and positioning and thus a better dimensional and shape retention is achieved. Preferably, even a dimensional and dimensional stability below 1 μm is achieved with the device according to the invention.

Preferably, the tool has at least two diamonds, and a workpiece is machinable with a first of the at least two diamonds when the tool is clamped in the first index position on the tool holder, and wherein one workpiece (same or another) is connected to a second one of the two at least two diamonds machinable when the tool is clamped in the second index position on the tool holder. This has the advantage that for the second diamond no separate tool with its own range must be clamped, but the same tool can be used in another index position. The diamond change is faster. You save yourself a new range and is therefore more efficient. Since a pallet change also brings with it a certain loss of repeatability, changing the index position is also more accurate.

The tool can preferably be clamped both in the first and in the second index position in a clamping axis on the tool holder, wherein the first and second index position differs by a rotation about the clamping axis. This is a particularly reliable and simple way of clamping, which can also be carried out automatically with a robot arm. For this purpose, alternatively or in combination with the rotation, the first and second index positions can differ by a displacement perpendicular to the clamping axis. Even a translatory transfer of the index positions in the direction of the clamping axis would be conceivable.

Preferably, one of the at least one workpiece is substantially machinable both perpendicular to the clamping axis when the tool is clamped in the first index position on the tool holder, as well as when the tool is clamped in the second index position on the tool holder. Alternatively, the clamping axis can also run parallel to the axis of rotation of the milling or lathe.

In a preferred embodiment of the device according to the invention, the tool and the tool holder have at least two shape-matching pairs of fixing elements,
the male part of each pair of fixing elements being either on the tool or on the tool holder and the female part of each pair of fixing elements being on the other side either on the tool holder or on the tool,
wherein the male part of a first of the at least two pairs of fixing elements engages in the female part of the first pair of fixing elements when the tool is mounted in the first indexing position on the tool holder,
wherein the male part of the first pair of fixing elements engages the female part of a second of the at least two pairs of fixing elements when the tool is mounted in the second indexing position on the tool holder.

Preferably, the pairs of fixing elements are each formed in the form of a conical seat with stop in the clamping direction. Alternatively or in combination, the pairs of fixing elements can also form a Hirth toothing between the tool and the tool holder.

It is also advantageous if the tool can be clamped in N ≥ 2 index positions in a clamping axis on the tool holder,
wherein the tool and the tool holder N have form-matching pairs of fixing elements, and
wherein the pairs of fixing elements are arranged N-fold rotationally symmetrical about the clamping axis.

Preferably, the male part of an n-th pair of fixing elements engages the female part of a k-th of the at least N pairs of fixing elements when the tool is mounted in an m-th index position on the tool holder,
where N ≥ 2 and k, n, m ∈ (1, ..., N) and k = ((n + m - 2) modN) + 1.

For example, in the case of N = 4, there are 4 index positions and 4 pairs of fixation elements.

When the tool is now clamped in the first index position on the tool holder, the male part of a first par engages in the female part of the first pair,
when the tool is clamped in the second index position on the tool holder, the male part of the first pair engages in the female part of the second pair,
when the tool is clamped in the third index position on the tool holder, the male part of the first pair engages in the female part of the third pair,
when the tool is clamped in the fourth index position on the tool holder, the male part of the first pair engages in the female part of the fourth pair.

In such a configuration with 4 index positions and 4 pairs of fixing elements, the four pairs of fixing elements would preferably be offset by 90 ° relative to each other by 90 ° around the clamping axis in a rotationally symmetrical manner. Preferably, therefore, the N ≥ 2 pairs of fixing elements are arranged around the clamping axis around the clamping axis in an N-fold rotationally symmetrical manner about the clamping axis.

For example, if the tool is clamped in the third (m) index position on the toolholder, the male portion of a fourth (n) pair will engage the female portion of the second (k = ((4 + 3-2) mod4) + 1 = 2 ) Pair. For example, in the third (m) index position, the male part of the third (n) pair is in the female part of the first (k = ((3 + 3-2) mod4) + 1 = 1) pair. This is preferably true for all combinations of k, n, m ∈ (1, ..., N), if N> = 2.

In the following the invention will be explained in more detail with reference to the accompanying figures. It shows

1 a perspective view of an embodiment of a device according to the invention together with a workpiece holder;

2 and 3 each a plan view of an embodiment of a device according to the invention, wherein the tool is clamped in different index positions;

4 a perspective view of an embodiment of a device according to the invention, wherein only the clamped on the tool holder pallet of the tool is shown;

5 a perspective view of an embodiment of a tool holder as part of the device according to the invention;

6 a perspective view of an embodiment of a device according to the invention with clamped tool, which has four non-height-adjustable tool stations;

7 a perspective view of an embodiment of a device according to the invention with clamped tool, which has a height-adjustable tool station;

8th a flow chart of the steps of an embodiment of a method according to the invention.

In 1 is a workpiece holder as part of an ultra-precision machine 1 shown without clamped workpiece. The workpiece holder 1 can hold a workpiece for ultra-precise shaping of a surface with a dimensional and shape retention below 5 microns and rotate about a machining axis z. The machining axis z spans a Cartesian coordinate system with a vertical axis y and a transverse axis x, which for better understanding in FIG 1 indicated by arrows.

In z-direction in front of the workpiece holder 1 is an embodiment of the device according to the invention 3 arranged, which has a lower tool holder 5 and a tool mounted thereon in the direction of the vertical axis y 7 having. The vertical axis y is therefore also referred to here as the clamping axis.

The tool holder 5 has a compressed air connection 9 on. By means of compressed air supply, the tool 7 from the tool holder 5 be solved and by means of compressed air outlet, an internal spring mechanism, the tool 7 true to position with 30,000 N or more on the tool holder 5 tighten.

That on the tool holder 5 clamped tool 7 has four radially projecting and offset by 90 ° tool stations 11 each with a diamond 14 on. The tool stations 11 have item numbers T1, T2, T3 and T4, with the tool station 11 with the Position number T4 is just in the direction of the machining axis z and any in the workpiece holder 1 machining turned workpiece.

In the individual tool stations 11 are the diamonds 14 in position and / or orientation to the tool 7 adjustable. In particular, the position of each diamond 14 in the clamping direction y with respect to the tool 7 adjustable. This setting is initially for each diamond 14 made and only needs to be done with a diamond change again.

In the 2 and 3 the top views show the tool 7 in two of four different index positions where the tool 7 on the tool holder 5 can be stretched. In 2 is the tool 7 in a first index position on the tool holder 5 spanned, which also in 1 you can see. In this first index position has the diamond 14 on the tool station 11 with the position number T4 a completely determined orientation and position with respect to the tool holder 5 , Also the other diamonds 14 on the tool station 11 with the item numbers T1, T2 and T3 have a completely specific orientation and position with respect to the tool holder 5 but are not currently in an active working position when the tool 7 in the first index position on the tool holder 5 is stretched.

In 3 is the tool 7 in a second index position on the tool holder 5 clamped, in which the tool is rotated by 90 ° clockwise about the clamping axis relative to the first index position. Now the tool station 11 with the position number T1 in z-direction in an active working position. All diamonds 14 on the tool stations 11 each have in the second index position a completely specific orientation and position with respect to the tool holder 5 , but now another, namely with respect to the clamping axis rotated by 90 ° clockwise. For a change of index positions, the tool must 7 be released from the clamping and rotated manually or automatically and then clamped again.

4 shows in detail how one at the bottom of the tool 7 located pallet 12 reproducible on a corresponding attachment on the tool holder 5 is aufspannbar. There are four pairs of fixation elements, two of which are in pairs 4 are visible, which set the index position, so the alignment about the clamping axis y reproducible. For the position in the direction of the clamping axis y are four horizontal bearing surfaces 15 provided, of which in 4 only one can be seen in the neckline. For centering the pallet 12 ensure conical surfaces 16 , in the 4 also visible only in the neckline.

In the embodiment shown, the male part is located 17 each of the four pairs of fixing elements 17 . 19 on the tool holder and the female part 19 each of the four pairs of fixing elements 17 . 19 on the pallet 12 of the tool 7 , Here, the pairs are each as a radially extending groove 19 and matching the radially extending spring 17 educated.

In the first index position, it can be arbitrarily determined that the male part 17 a first of the four pairs of fixing elements 17 . 19 in the female part 19 of the first pair of fixing elements 17 . 19 attacks, the male part 17 a second of the four pairs of fixing elements 17 . 19 in the female part 19 of the second pair of fixing elements 17 . 19 attacks, the male part 17 a third of the four pairs of fixing elements 17 . 19 in the female part 19 of the third pair of fixing elements 17 . 19 attacks and the male part 17 a fourth of the four pairs of fixing elements 17 . 19 in the female part 19 of the fourth pair of fixing elements 17 . 19 attacks.

Since the pairs are arranged identically and four times rotationally symmetrically about the clamping axis y, four index positions of the workpiece are possible, and in each index position m, the male part of an n-th pair of fixing elements engages the female part of a k-th of the four Pairs of fusing elements, where k, n, m ∈ (1, ..., 4) and k = ((n + m - 2) mod4) + 1.

In 5 is the tool holder 5 shown alone, so all four male parts 17 the pair of fixing elements 17 . 19 you can see. In addition, the four horizontal bearing surfaces 15 for the position in the direction of the clamping axis y clearly visible. Also for centering the pallet 12 caring conical surfaces 16 are in 5 to recognize.

In 6 is again on the tool holder 5 clamped tool 7 to see on the simplified tool stations 11 are arranged without height adjustment.

In 7 is one on the tool holder 5 clamped tool 7 to see at the only one tool station 11 arranged with height adjustment.

In 8th shows a flow chart, the individual steps of an advantageous embodiment of the method according to the invention for ultra-precise shaping of a surface of at least one workpiece with a dimensional and shape retention below 5 microns by means of at least one diamond 14 having tool 7 ,

The first step is a first releasable clamping 601 of the tool 7 in a first index position on a tool holder 5 where the orientation and position of the at least one diamond 14 with respect to the tool holder 5 is completely determined by the first index position.

A second step involves a first machining 603 a workpiece with the diamond 14 , wherein the tool in the first index position on the tool holder 5 is stretched.

A third step is solving 605 in the first index position on the tool holder 5 clamped tool 7 , Then in the fourth step, a second releasable clamping follows 607 of the tool in a second index position on the tool holder 5 , wherein the relative to the first index position changed orientation and / or position of the at least one diamond 14 with respect to the tool holder is completely determined by the second index position.

Finally, a second machining follows 609 one (same or another) workpiece with one (same or another) diamond 14 , where the tool 7 in the second index position on the tool holder 5 is stretched.

The invention described above by means of embodiments has the following advantages: When the tool 7 several diamonds 14 may have another diamond in another index position 14 in place of the first diamond 14 move. The device according to the invention is also advantageous when the tool 7 only a diamond 14 but its orientation and positioning in the second index position is needed. There is no need for a new tool 7 on a new palette 12 be brought and spanned. In addition, by the device according to the invention, the number of required pallets 12 minimized, whereby a higher reproducibility of the tool alignment and positioning and thus a better dimensional and shape retention is achieved below 5 microns.

LIST OF REFERENCE NUMBERS

1

Workpiece holder

3

contraption

5

toolholder

7

Tool

9

Compressed air connection

11

Tool stations)

12

Palette on the tool

14

diamonds

15

support surfaces

16

conical surfaces

17

male part of the fixing elements

19

female part of the fixing elements

Claims (16)

Process for the ultra-precise shaping of a surface of at least one workpiece with a dimensional and dimensional stability below 5 μm by means of at least one diamond ( 14 ) tool ( 7 ), comprising the following steps: - first releasable clamping ( 601 ) of the tool ( 7 ) in a first index position on a tool holder ( 5 ), wherein the orientation and position of the at least one diamond ( 14 ) with respect to the tool holder ( 5 ) is completely determined by the first index position, - first machining ( 603 ) of one of the at least one workpiece with one of the at least one diamond ( 14 ), the tool ( 7 ) in the first index position on the tool holder ( 5 ), - releasing ( 605 ) in the first index position on the tool holder ( 5 ) clamped tool ( 7 ), - second detachable clamping ( 607 ) of the tool ( 7 ) in a second index position on the tool holder ( 5 ), wherein the orientation and / or position of the at least one diamond changed relative to the first index position ( 14 ) with respect to the tool holder ( 5 ) is completely determined by the second index position, and - second machining ( 609 ) of one of the at least one workpiece with one of the at least one diamond ( 14 ), the tool ( 7 ) in the second index position on the tool holder ( 5 ) is stretched. Method according to claim 1, wherein the tool ( 7 ) at least two diamonds ( 14 ) and the first machining ( 603 ) with a first diamond ( 14 ) of at least two diamonds ( 14 ) and the second machining ( 609 ) with a second diamond ( 14 ) of at least two diamonds ( 14 ) he follows. The method of claim 1 or 2, wherein the first and second releasable clamping ( 601 . 607 ) takes place in each case in a clamping axis (y), wherein the first and second index positions differ by a rotation about the clamping axis (y). Method according to one of the preceding claims, wherein the first and second detachable clamping ( 601 . 607 ) takes place in each case in a clamping axis (y), wherein the first and second index positions differ by a displacement perpendicular to the clamping axis (y). Method according to claim 3 or 4, wherein the first and second machining ( 603 . 609 ) takes place substantially perpendicular to the clamping axis (y). Method according to one of the preceding claims, wherein the at least one workpiece is an optical element made of plastic or an injection mold for a plastic optical element. Device for the ultra-precise shaping of a surface of at least one workpiece with a dimensional and dimensional stability below 5 μm, comprising: - a tool ( 7 ) that has at least one diamond ( 14 ), - a tool holder ( 5 ), the tool ( 7 ) in a first and in a second index position on the tool holder ( 5 ), wherein one of the at least one workpiece ( 7 ) with one of the at least one diamond ( 14 ) is both machinable when the tool ( 7 ) in the first index position on the tool holder ( 5 ), as well as when the tool ( 7 ) in the second index position on the tool holder ( 5 ), wherein the orientation and position of the at least one diamond ( 14 ) with respect to the tool holder ( 5 ) is completely determined by the first index position, and wherein the relative to the first index position different orientation and / or position of the at least one diamond ( 14 ) with respect to the tool holder ( 5 ) is completely determined by the second index position. Apparatus according to claim 7, wherein the tool ( 7 ) at least two diamonds ( 14 ) and wherein one of the at least one workpiece with a first of the at least two diamonds ( 14 ) is machinable when the tool ( 7 ) is clamped in the first index position on the tool holder, and wherein one of the at least one workpiece with a second of the at least two diamonds ( 14 ) is machinable when the tool ( 7 ) in the second index position on the tool holder ( 5 ) is stretched. Apparatus according to claim 7 or 8, wherein the tool ( 7 ) in both the first and the second index position in a clamping axis (y) on the tool holder ( 5 ), wherein the first and second index positions differ by a rotation about the clamping axis (y). Device according to one of claims 7 to 9, wherein the tool in both the first and in the second index position in a clamping axis (y) on the tool holder ( 5 ), wherein the first and second index positions differ by a displacement perpendicular to the clamping axis (y). Apparatus according to claim 9 or 10, wherein one of the at least one workpiece ( 7 ) substantially perpendicular to the clamping axis (y) is both machinable when the tool ( 7 ) in the first index position on the tool holder ( 5 ), as well as when the tool ( 7 ) in the second index position on the tool holder ( 5 ) is stretched. Device according to one of claims 7 to 11, wherein the tool ( 7 ) and the tool holder ( 5 ) at least two shape-matching pairs of fixing elements ( 17 . 19 ), wherein a male part ( 17 ) of each pair of fixing elements ( 17 . 19 ) either on the tool ( 7 ) or on the tool holder ( 5 ) and a female part ( 19 ) of each pair of fixing elements ( 17 . 19 ) vice versa either on the tool holder ( 5 ) or on the tool ( 7 ), the male part ( 17 ) of a first of the at least two pairs of fixing elements ( 17 . 19 ) in the female part ( 19 ) of the first pair of fixing elements ( 17 . 19 ) engages when the tool ( 7 ) in the first index position on the tool holder ( 5 ), the male part ( 17 ) of the first pair of fixing elements ( 17 . 19 ) in the female part ( 19 ) a second of the at least two pairs of fixing elements ( 17 . 19 ) engages when the tool in the second index position on the tool holder ( 5 ) is stretched. Device according to claim 12, wherein the pairs of fixing elements ( 17 . 19 ) are each formed in the form of a conical seat with stop in the clamping direction. Device according to claim 12, wherein the pairs of fixing elements ( 17 . 19 ) form a Hirth toothing between the tool and the tool holder. Device according to one of claims 12 to 14, wherein the tool ( 7 ) in N ≥ 2 index positions in a clamping axis (y) on the tool holder ( 5 ) is clamped, wherein the tool ( 7 ) and the tool holder ( 5 ) N shape-matching pairs of fixing elements ( 17 . 19 ), and wherein the pairs of fixing elements ( 17 . 19 ) N-count rotationally symmetrical about the clamping axis (y) are arranged. Device according to claim 15, wherein the male part ( 17 ) of an n-th pair of fixing elements ( 17 . 19 ) in the female part ( 19 ) a k-th of the at least N pairs of fixing elements ( 17 . 19 ) engages when the tool ( 7 ) in an m-th index position on the tool holder ( 5 ), where k, n, m ∈ {1, ..., N) and k = ((n + m - 2) modN) + 1.

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