DE102022205021A1 - Hold-down device for a cutting tool for shear cutting a workpiece - Google Patents

Abstract

A hold-down device (118) for a cutting tool (100) for shear cutting a workpiece (102), in particular a sheet of metal (104), is proposed. The hold-down device (118) comprises at least one contact surface (120) for contact with a workpiece (102), wherein the contact surface (120) is designed to apply a first force (F 1) to the workpiece (102) in a first force direction (122). is. The hold-down device (118) further comprises a hold-down body (124), wherein the hold-down body (124) is designed to be arranged in or on a hold-down holder (110) of the cutting tool (100), wherein the hold-down body (124) is elastically deformable in such a way that Applying the first force (F1) by means of the contact surface (120), a second force (F2) can be applied to the workpiece (102) in a second direction of force (138), the second direction of force (138) being essentially perpendicular to the first direction of force (138). 122).

Description

Technical area

The present invention relates to a hold-down device for a cutting tool for shear cutting a workpiece and to a cutting tool.

Technical background

Cutting tools are used in many technical areas. The forming production of sheet metal components is one of the most economical and efficient processes in production technology. An essential component within these process chains is shear cutting for trimming and punching components or workpieces. During mechanical sheet metal separation using shear cutting, the workpiece is sheared along a defined tool contour between the cutting punch and die. A hold-down device placed next to the cutting punch prevents the sheet metal from lifting during the cutting process and the return stroke of the cutting punch. Each shear-cut component has a characteristic cutting surface, which essentially depends on the cutting parameters of the cutting gap, punch and die radii and the semi-finished material. The transition between elastic deformation after placing the cutting punch, the onset of plastic deformation with the material flowing in the direction of the punch movement and the onset of separation due to crack formation when the material-dependent shear breaking limit is exceeded characterize the cut surface quality and the force requirement of the shear cutting process. In order to optimize the process in terms of force requirements, wear or cut surface quality (edge indentation, smooth cut, fracture surface and burr), a large number of process variants have been established in the past.

In general, a high cut surface quality has low edge indentation, high proportions of smooth cuts, low fracture surface heights and low burr formation. A high proportion of smooth cuts is particularly sought when the cutting surface is a functional surface, such as a gear flank or a fit. Especially when high demands are placed on the quality of the cut surface, for example when the cut surface is used as a functional surface in fits or gears, normal cutting reaches its limits. Today, such high quality requirements can only be met by so-called precision cutting processes such as fine cutting, precise cutting, re-cutting or counter (re-) cutting.

EP 2 208 552 B1 describes, for example, a method and a device for fine cutting of workpieces.

The above-mentioned process variants are characterized in that increased compressive stresses are introduced into the shear zone through a relatively complex tool structure and/or through multi-stage manufacturing processes. These compressive stresses promote the material flow in the shear zone, which in turn allows smaller fracture surfaces and thus higher smooth cut proportions to be achieved.

In addition to high cut surface quality, another important design feature of shear cutting tools is to achieve the longest possible tool life and thus the highest possible productivity of the process. The high mechanical loads on the cutting active elements (punches, matrices) are particularly critical in this regard, which is why cutting edges are usually deliberately broken or rounded before the start of the process. With regard to tool service life, it should be noted that mechanical process vibrations, especially cutting impact, have a negative influence on the service life of active cutting elements. Cutting shock absorbers or a reduction in the (maximum) occurring process forces can help reduce the cutting shock. A well-known solution for reducing cutting forces is to use punch grinds. Compared to conventional, flat cutting punches, the maximum cutting force that occurs in the cutting process can be reduced by around 30% using diagonally ground punches or dies, as only a certain part of the punch always cuts (pulling cut).

Despite the numerous advantages of the cutting tools and hold-down devices known from the prior art, they still have potential for improvement. With the fineblanking process, smooth cuts close to 100% can be produced. These high proportions of smooth cuts are based on the introduction of compressive stresses into the shear zone with the help of a ring prong in the hold-down device along the cutting contour on the top side of the sheet metal. The resulting compressive stresses compensate for the tensile stresses in the shear zone, so that material failure occurs at a later point in the process. The disadvantage of fineblanking, however, is the comparatively complex and therefore cost-intensive tool structure. Attaching the ring serration to the cutting plate and/or the hold-down device is relatively complex and represents a significant cost factor. The ring serration cannot be readjusted or ground, which is why the maintenance keeping is comparatively expensive. Furthermore, the use of multiple-acting presses is usually necessary to apply the counter-holding force required for fine blanking, which prevents plastic deflection of the fine blank part. Further disadvantages of fineblanking are the comparatively low stroke rates and the relatively short tool life. Fine cutting is also limited to very small cutting gaps of around 0.5% of the sheet thickness.

In principle, precise cutting is comparable to fine cutting. With this process, too, the introduction of compressive stresses into the shear zone supports the plastic flow of the material and thus the production of a relatively high proportion of smooth cuts. However, the induction of compressive stress in the lateral direction to the cutting outline does not take place using a ring serration, but rather through small cutting gaps and targeted cutting edge rounding on the cutting punch (punching) or on the die (cutting out). Precise cutting therefore represents a simplification of the fine cutting process. In practice, however, either multiple-acting presses or complex spring-loaded tool concepts have to be used to apply the counter-holding force. Furthermore, due to the lack of ring serrations, higher edge indentations must be expected with precision cutting than with fine cutting. Relatively small cutting gaps of less than 1.5% of the sheet metal thickness are used for precision cutting, which is why higher accuracy requirements are placed on the tool design compared to normal cutting

Re-cutting is used in single-acting presses to trim narrow edges of already pre-punched or pre-cut surfaces (1st process stage) to produce dimensionally stable external and internal shapes with high cut surface quality. Re-cutting therefore represents (at least) a two-stage process. During the actual re-cutting process (2nd process stage), the narrow edge area of the pre-cut contour is separated, which leads to a comparatively high cut surface quality compared to normal cutting. The tool design of the progressive composite tools required for recutting must ensure that the component to be recut is positioned as precisely as possible. With regard to process stability, the relatively complex removal of the chips resulting from recutting must also be taken into account.

Counter cutting is characterized by a multi-stage cutting process and at least one reversal of the cutting direction. This cutting process can be carried out using single-acting progressive tools as well as with the help of multiple-acting presses. In a first (and if necessary second) stage, the sheet metal material is cut with an embossing die only to such an extent that the material is not completely separated. Complete material separation only takes place in the final process stage. The resulting cut surface is characterized in particular by a complete absence of burrs and two smooth cut surfaces with a narrow fracture surface in between. Compared to the structure of normal cutting tools, the structural design of counter cutting tools and the general design of a robust manufacturing process are significantly more complex. The reasons for this lie in the embossing and cutting depths that have to be set specifically for the material as well as the more complex process kinematics.

In summary, it should be noted that with the precision cutting processes mentioned, higher cut surface qualities (higher smooth cuts or freedom from burrs) and higher manufacturing accuracies (IT tolerances) can be achieved than with normal cutting. However, the disadvantage of the precision cutting processes described is that they require significantly more complex and therefore more cost-intensive tool designs. The more complex tool kinematics also limit the stroke rates that can be achieved and the associated output quantities. While conventional normal cutting processes are usually operated at stroke rates between 400 to 800 strokes/min or even sometimes at higher stroke rates of 1500 to 2000 strokes/min, the stroke rates for fine, precision and counter cutting are significantly lower. If punch or die grinding is used to reduce the (maximum) process forces, it should be noted that such active cutting elements can cause undesirable bending moments in the cutting tool. In addition, punches and matrices with special grinds can only be re-sharpened with great effort. Due to their size, cutting shock absorbers often cannot be installed in real series tools due to the available installation space.

Task of the invention

It would therefore be desirable to provide a hold-down device and a cutting tool that at least largely avoid the disadvantages of known hold-down devices and cutting tools. In particular, a technological-economic solution should be provided in the form of a hold-down device and a cutting tool with at least one such hold-down device for influencing the shear cutting process and the quality of the cut surface.

General description of the invention

This task is addressed by a hold-down device and a cutting tool with the features of the independent patent claims. Advantageous further developments, which can be implemented individually or in any combination, are set out in the dependent claims.

Below, the terms “have,” “have,” “comprise,” or “include,” or any grammatical variations thereof, are used in a non-exclusive manner. Accordingly, these terms can refer both to situations in which, in addition to the features introduced by these terms, no further features are present, or to situations in which one or more further features are present. For example, the expression "A has B", "A has B", "A includes B" or "A includes B" can refer to the situation in which, apart from B, no other element is present in A (i.e. to a situation in which A consists exclusively of B), as well as to the situation in which, in addition to B, one or more other elements are present in A, for example element C, elements C and D or even other elements .

Furthermore, it should be noted that the terms “at least one” and “one or more” as well as grammatical variations of these terms when used in connection with one or more elements or features and are intended to express that the element or feature is provided single or multiple times can usually only be used once, for example when the feature or element is introduced for the first time. If the feature or element is subsequently mentioned again, the corresponding term “at least one” or “one or more” is generally no longer used, without limiting the possibility that the feature or element can be provided once or multiple times.

Furthermore, the terms “preferably”, “in particular”, “for example” or similar terms are used below in connection with optional features, without this limiting alternative embodiments. Thus, features introduced by these terms are optional features and these features are not intended to limit the scope of protection of the claims and in particular the independent claims. Thus, as those skilled in the art will recognize, the invention can also be carried out using other embodiments. Similarly, features introduced by “in an embodiment of the invention” or by “in an embodiment of the invention” are understood to be optional features, without this being intended to limit alternative embodiments or the scope of protection of the independent claims. Furthermore, these introductory expressions should remain unaffected by all possibilities of combining the features introduced here with other features, be they optional or non-optional features.

In a first aspect of the present invention, a hold-down device for a cutting tool for shear cutting a workpiece is proposed. The workpiece can in particular be a sheet metal. The hold-down device includes at least one contact surface for contact with a workpiece. The contact surface is designed to apply a first force to the workpiece in a first force direction. The hold-down device further comprises a hold-down body. The hold-down body is designed to be arranged in or on a hold-down holder of the cutting tool. The hold-down body is elastically deformable in such a way that when the first force is applied by means of the contact surface, a second force can be applied to the workpiece in a second direction of force. The second direction of force is essentially perpendicular to the first direction of force.

The present invention therefore provides a transversely elastic hold-down device that enables targeted influence on the state of stress during the cutting process in the shear zone. The hold-down device is subjected to a first, such as vertical, force via a hold-down holder and thereby fixes the workpiece between the cutting punch and the die before, during and after the cutting process. Due to its geometric design, the uniaxial application of force leads, in addition to the first force, to a second, such as horizontal, transverse deformation of the hold-down device. An additional horizontal thrust force is thus transmitted to the workpiece via the frictional contact surface with the workpiece. Depending on the orientation of the transversely elastic hold-down device, this means that compressive forces can be superimposed in the shear zone, which lead to a later onset of the breaking process and thus to a higher proportion of smooth cuts during shear cutting. On the other hand, in the opposite orientation, a tensile force can be induced in the shear zone and thus lead to a significant reduction in the required cutting force. In order to influence the cutting process, there is only a ring serration in fine cutting, which is impressed into the sheet metal and only causes compressive stresses in the shear zone. It goes without saying that, alternatively or additionally, a positive lateral force transmission between hold-down devices and sheet metal, such as using ring serrations as in fine cutting, can be achieved. A basic idea of the present invention lies in the topology-optimized hold-down geometry, which experiences a vertical transverse deformation in the horizontal direction through a vertical introduction of force. Overall, this novel approach differs in that the stress state can be adapted to the cutting process and the respective optimization size depending on the geometry and the hold-down force. This does not require any formative or surface-destroying form elements or other complex assemblies, such as force redirection through slides.

When the first force is applied, the hold-down body can be elastically deformable in a first direction parallel to the first direction of force and in a second direction parallel to the second direction of force. Thus, a topology-optimized hold-down geometry is provided, which experiences a vertical transverse contraction or transverse expansion in the horizontal direction through a vertical introduction of force. Overall, this novel approach differs in that the stress state can be adapted to the cutting process and the respective optimization size depending on the geometry and the hold-down force. This does not require any formative or surface-destroying form elements or other complex assemblies, such as force redirection through slides.

When the first force is applied, the elastic deformation in the second direction may include a unidirectional contraction or expansion of the hold-down body in the second direction. The transverse deformation of the hold-down device can therefore be either a transverse contraction or a transverse expansion in a predetermined direction, depending on the design.

The second force may be a thrust force on a surface of the workpiece. The direction of the thrust force on the workpiece surface depends on the design of the hold-down device and can cause either tensile stresses or compressive stresses in the workpiece plane.

The hold-down body can be designed to effect a stress superposition in a shear zone of the workpiece. This stress superposition in the shear zone is used to influence the cutting process in terms of cut surface quality or force requirement/wear.

The second direction of force can be oriented toward a shear zone of the workpiece or away from a shear zone of the workpiece. Tensile or compressive forces can be induced accordingly.

The contact surface can be arranged on the hold-down body. This means that the hold-down device is made compact.

The hold-down body can essentially be designed, at least in sections, in a Z-shaped, inverse Z-shaped, bellows-shaped or helical-turn-shaped manner. This provides particularly elastically deformable shapes and directed deformations, since the transverse contraction usually develops symmetrically.

The hold-down body can be designed to be arranged adjacent to a cutting punch of the cutting tool. This means that the hold-down device can be arranged particularly close to the shear zone in order to be able to specifically influence the cutting process there.

The hold-down device can further comprise at least one application surface. The application surface can be designed to connect to an active element of the hold-down holder for applying the first force. This allows a predetermined force to be specifically applied to the hold-down device in order to deform it elastically. The hold-down device then transmits this predetermined force to the workpiece in two components that are essentially oriented perpendicular to one another.

The application surface can be arranged on the hold-down body. This means that the hold-down device is made compact.

The contact surface can be arranged at a first end of the hold-down body. The application surface can be arranged at a second end of the hold-down body. The second end can be opposite the first end. This enables a particularly good transfer of the force applied to the hold-down device to the workpiece.

The first end and the second end may be connected to each other by means of a connecting portion. The connecting section may be wider at an end adjacent to the second end than at an end adjacent to the first end. This provides a particularly good design for voltage superposition.

The active element can include a hold-down stamp or be designed as a hold-down stamp. This makes it particularly easy to apply the predetermined force to the hold-down device.

The hold-down body can have a height and a width, wherein the height and the width can be essentially identical. This provides a particularly good design for voltage superposition. However, it is explicitly emphasized that, depending on the respective application, a different design for the hold-down body is also possible, in which the height is greater than the width or the width is greater than the height.

The hold-down device can have a straight, curved or part-circular outer contour. The outer contour can therefore be adapted to the cutting line.

The hold-down device can be made at least partially and preferably completely from tool steel, in particular 1.2379 or 1.1730 according to DIN EN 10027 valid in the version on the date of filing of the present patent application. This means that a material with elastic properties is used, which has sufficient strength (static/yield strength and dynamic/fatigue strength).

In a further aspect of the present invention, a cutting tool for shear cutting a workpiece, in particular a sheet of metal, is proposed. The cutting tool comprises a cutting punch, a die, a hold-down holder and at least one hold-down device according to one of the embodiments described above or described below. The hold-down body of the hold-down device is arranged in or on the hold-down holder.

The first force fixes the workpiece in the plane for the cutting process and prevents the workpiece from lifting off. During the return stroke of the cutting punch, the hold-down device prevents the workpiece from being lifted or strips the cut or perforated sheet metal from the cutting punch. In comparison to conventional hold-down devices, the transversely elastic hold-down device also enables targeted influence on the state of stress during the cutting process in the shear zone. The hold-down device is subjected to a first, such as vertical, force via a hold-down holder and thereby fixes the workpiece between the cutting punch and the die before, during and after the cutting process. Due to its geometric design, the uniaxial application of force leads, in addition to the first force, to a second, such as horizontal, transverse deformation of the hold-down device. An additional horizontal thrust force is thus transmitted to the workpiece via the frictional contact surface with the workpiece. Depending on the orientation of the transversely elastic hold-down device, this means that compressive forces can be superimposed in the shear zone, which lead to a later onset of the breaking process and thus to a higher proportion of smooth cuts and reduced edge indentations during shear cutting. On the other hand, in the opposite orientation, a tensile force can be induced in the shear zone and thus lead to a significant reduction in the required cutting force. In order to influence the cutting process, there is only a ring serration in fine cutting, which is impressed into the sheet metal and only causes compressive stresses in the shear zone. A basic idea of the present invention lies in the topology-optimized hold-down geometry, which experiences a vertical transverse deformation in the horizontal direction through a vertical introduction of force. Overall, this novel approach differs in that the stress state can be adapted to the cutting process and the respective optimization size depending on the geometry and the hold-down force. This does not require any formative or surface-destroying form elements or other complex assemblies, such as force redirection through slides.

The friction contact surface of the hold-down body or the contact surface can have an increased surface roughness. This means that shear forces can be better transferred to the sheet surface in a friction-controlled manner. Surfaces with increased roughness or specially structured surfaces increase the static friction, whereas a ground or polished contact surface of the hold-down device would significantly reduce the effect of stress overlay in the shear zone.

The hold-down device can be arranged adjacent to the cutting punch. This means that the hold-down device can be arranged particularly close to the shear zone in order to be able to specifically influence the cutting process there.

The hold-down body can have an internal shape that is adapted to an external shape of the cutting punch. This allows the hold-down device to be adapted to the shape of the cutting punch and positioned particularly close to the cutting punch.

The hold-down holder can have an active element. The hold-down device can have an application surface. The application surface can be connected to the active element of the hold-down holder for applying the first force. This allows a predetermined force to be specifically applied to the hold-down device in order to deform it elastically. The hold-down device then transmits this predetermined force to the workpiece in two components that are essentially oriented perpendicular to one another.

The active element can include a hold-down stamp. This makes it particularly easy to apply the predetermined force to the hold-down device.

The hold-down holder can have at least one spring element. The first force can be transferred to the hold-down body by means of the spring element. This makes it particularly easy to apply the predetermined force to the hold-down device.

The hold-down device can be arranged on a top side of the workpiece. The hold-down device can be designed to cause an overlay of tensile stress. Alternatively, the hold-down device can be designed to cause an overlay of compressive stress. This allows the quality of the cutting process to be specifically influenced.

Alternatively, the hold-down device can be arranged on an underside of the workpiece. The hold-down device can be designed to cause an overlay of tensile stress. Alternatively, the hold-down device can be designed to cause an overlay of compressive stress. This allows the quality of the cutting process to be specifically influenced.

The cutting tool can include at least two hold-down devices. In other words, the cutting tool can have several hold-down devices. These can, for example, be designed as hold-down segments to form an entire hold-down device. The second force may be a thrust force on a surface of the workpiece. The direction of the thrust force on the workpiece surface depends on the design of the hold-down device and can cause either tensile stresses or compressive stresses in the workpiece plane.

The hold-down devices can be set up to be arranged on identical sides of the workpiece. In other words, the hold-down devices can be arranged on a single side of the workpiece, such as on a top or a bottom of the workpiece. By arranging an element with a horizontal tension or compression direction, another element can be integrated into the cutting die on the underside of the sheet in order to increase the lateral force effect.

The hold-down devices can be arranged to be arranged on opposite sides of the workpiece. By arranging an element with a horizontal tension or compression direction, another element can be integrated into the cutting die on the underside of the sheet in order to increase the lateral force effect.

The second force of the hold-down devices on the opposite sides of the workpiece can be in the same direction or in opposite directions. By arranging an element with a horizontal tension or compression direction, another element can be integrated into the cutting die on the underside of the sheet in order to increase the lateral force effect.

The hold-down devices can be designed to effect a tensile stress superimposition, a compressive stress superimposition or a shear stress superimposition. By arranging an element with a horizontal tension or compression direction, another element can be integrated into the cutting die on the underside of the sheet in order to increase the lateral force effect.

In a further aspect of the present invention, a method for operating a cutting tool according to one of the embodiments described above or below is proposed. The method includes arranging a workpiece, in particular a sheet metal, on the die, arranging the hold-down device on or in the hold-down holder, applying a first force to the workpiece in a first force direction by means of the contact surface of the hold-down device, wherein the hold-down device body is elastically deformable in such a way that Applying the first force by means of the contact surface, a second force is applied to the workpiece in a second direction of force, the second direction of force being substantially perpendicular to the first direction of force, moving the cutting punch for shear cutting of the workpiece.

The cutting punch can be moved by motor or with motor support.

The method may further include releasing the first force after completing the shear cutting.

The method may further include ejecting a blank produced by shear cutting the workpiece.

The term "cutting tool" as used herein is a broad term which should be given its ordinary and common meaning as understood by those skilled in the art. The term is not limited to a special or adapted meaning. The term may, without limitation, refer in particular to a device that allows the partial or complete separation of a workpiece, body or system allowed in two or more parts. A special feature of such a device is that it processes the material mechanically without forming chips. Such a cutting tool includes a die on which the workpiece to be cut is placed and a cutting punch that carries out the cutting process.

The term "shear cutting" as used herein is a broad term which should be given its ordinary and common meaning as understood by those skilled in the art. The term is not limited to a special or adapted meaning. The term can, without limitation, refer in particular to the cutting of a material by two cutting edges moving past each other. Shear cutting processes are described in more detail in DIN 8588 in the version valid on the day the present patent application was filed. The material is sheared off by shear forces. This cutting process is one of the most frequently used manufacturing processes in sheet metal processing. Tools for this cutting process are scissors (household scissors, guillotine scissors, tin snips, cable scissors) as well as, among others. Punch press, rescue scissors or nibbler.

The term "shear zone" as used herein is a broad term which should be given its ordinary and common meaning as understood by those skilled in the art.

The term is not limited to a special or adapted meaning. The term may, without limitation, refer in particular to the area of a cutting tool in which cutting of a workpiece takes place and where the cutting punch divides the workpiece into the cut part and the slug.

The term “hold-down” as used herein is a broad term that should be given its ordinary and common meaning as understood by those skilled in the art. The term is not limited to a special or adapted meaning. The term can, without limitation, refer in particular to a component that is designed to fix the workpiece, such as a sheet of metal, in the plane during the cutting process and to prevent the workpiece from lifting off. During the return stroke of the cutting punch, the hold-down device prevents the workpiece from being lifted or strips the cut or perforated workpiece from the cutting punch.

The term "hold-down" as used herein is a broad term that should be given its ordinary and common meaning as understood by those skilled in the art. The term is not limited to a special or adapted meaning. The term can, without limitation, refer in particular to a component on or in which a hold-down device can be arranged and which is designed by means of its component or components to apply a predetermined force to the hold-down device so that it can fix the workpiece, such as for example a sheet of metal, can transmit the force required during the cutting process in the plane and to prevent the workpiece from lifting off.

The term "hold-down punch" as used herein is a broad term that should be given its ordinary and common meaning as understood by those skilled in the art. The term is not limited to a special or adapted meaning. The term can, without limitation, refer in particular to a component of the hold-down holder, which is designed to apply a predetermined force to the hold-down device so that it can fix the workpiece, such as a sheet of metal, in the plane during the cutting process and to prevent can transmit the force required to lift the workpiece.

The term "thrust force" as used herein is a broad term which should be given its ordinary and common meaning as understood by those skilled in the art. The term is not limited to a special or adapted meaning. The term may, without limitation, refer in particular to a force that is quantitatively described by Newton's second and third laws. When a system expels or accelerates mass in one direction, the accelerated mass exerts a force of equal magnitude but opposite direction on the system.

The term "stress" as used herein is a broad term which should be given its ordinary and common meaning as understood by those skilled in the art. The term is not limited to a special or adapted meaning. The term can, without limitation, refer in particular to a mechanical stress. The mechanical stresses σ and τ are a measure of the internal stress on a body as a result of its external load. Since there is no risk of confusion with electrical voltage within mechanics, it is referred to as voltage for short. The normal mechanical stress σ on an imaginary sectional surface A through a body is the component F _n of an external force F acting perpendicularly to it: $$\sigma =\underset{\Delta A\to 0}{\text{lim}}\frac{\Delta F_n}{\Delta A}$$

The diagonal elements σ _xx , σ _yy , σ _zz in the stress matrix represent the normal stresses, i.e. the stresses that act perpendicular to the coordinate surface. In other words: the normal and effective directions match. Depending on the sign, normal stresses are called tensile stress (positive sign) or compressive stress (negative sign). Compressive stress is sometimes also referred to as surface pressure. In contrast to compressive stress, pressure is exclusively isotropic. This means that pressure is not a vector, but the negative hydrostatic part of the stress tensor. It acts in all directions at the same time and is therefore the negative mean of the normal stresses in the three spatial directions (p = - (σ _xx + σ _yy + σ _zz ) / 3). It is positive for hydrostatic pressure and negative for hydrostatic tension. The off-diagonal elements τ _ij are called shear or shear stresses. They act tangentially to the surface, i.e. they represent a shear load.

The term "substantially perpendicular" as used herein is a broad term that should be given its ordinary and common meaning as understood by those skilled in the art. The term is not limited to a special or adapted meaning. The term can, without limitation, refer in particular to an orientation that deviates from an exactly perpendicular orientation by no more than 15°, preferably no more than 10° and even more preferably no more than 5°.

Furthermore, within the scope of the present invention, a computer program is proposed which, when executed on a computer or computer network, carries out the method according to the invention in one of its embodiments.

Furthermore, within the scope of the present invention, a computer program with program code means is proposed in order to carry out the method according to the invention in one of its embodiments when the program is executed on a computer or computer network. In particular, the program code means can be stored on a computer-readable data carrier and/or a computer-readable storage medium.

The terms “computer-readable data carrier” and “computer-readable storage medium” as used herein can refer in particular to non-transitory data storage, for example a hardware data storage medium on which computer-executable instructions are stored. The computer-readable data carrier or the computer-readable storage medium can in particular be or include a storage medium such as a random access memory (RAM) and/or a read-only memory (ROM).

In addition, within the scope of the present invention, a data carrier is proposed on which a data structure is stored, which, after loading into a main memory and/or main memory of a computer or computer network, can carry out the method according to the invention in one of its embodiments.

Furthermore, within the scope of the present invention, a non-transient computer-readable medium is proposed, comprising instructions which, when executed by one or more processors, cause the one or more processors to carry out the method according to the invention in one of its embodiments.

In the context of the present invention, a computer program product with program code means stored on a machine-readable carrier is also proposed in order to carry out the method according to the invention in one of its embodiments when the program is executed on a computer or computer network.

A computer program product is understood to mean the program as a tradable product. In principle, it can be in any form, for example on paper or a computer-readable data carrier, and can in particular be distributed via a data transmission network.

Finally, within the scope of the present invention, a modulated data signal is proposed which contains instructions that can be executed by a computer system or computer network for carrying out a method according to one of the described embodiments.

With regard to the computer-implemented aspects of the invention, one, several or even all method steps of the method according to one or more of the embodiments proposed here can be carried out using a computer or computer network. Thus, in general, any of the method steps, including providing and/or manipulating data, may be performed using a computer or computer network. In general, these steps may include any of the method steps except those steps that require manual work, such as preparing taking samples and/or certain aspects of making actual measurements.

• Ausführungsform 1: Niederhalter für ein Schneidwerkzeug zum Scherschneiden eines Werkstücks, insbesondere eines Blechs, umfassend mindestens eine Anlagefläche zum Anliegen an einem Werkstück, wobei die Anlagefläche zum Aufbringen einer ersten Kraft auf das Werkstück in einer ersten Kraftrichtung 122 ausgebildet ist, einen Niederhalterkörper, wobei der Niederhalterkörper zum Anordnen in oder an einer Niederhalteraufnahme des Schneidwerkzeugs ausgebildet ist, wobei der Niederhalterkörper derart elastisch verformbar ist, dass bei Aufbringen der ersten Kraft mittels der Anlagefläche eine zweite Kraft in das Werkstück in einer zweiten Kraftrichtung aufbringbar ist, wobei die zweite Kraftrichtung im Wesentlichen senkrecht zu der ersten Kraftrichtung ist.
• Ausführungsform 2: Niederhalter nach der vorhergehenden Ausführungsform, wobei der Niederhalterkörper bei Aufbringen der ersten Kraft in einer ersten Richtung parallel zu der ersten Kraftrichtung und in einer zweiten Richtung parallel zu der zweiten Kraftrichtung elastisch verformbar ist.
• Ausführungsform 3: Niederhalter nach der vorhergehenden Ausführungsform, wobei bei Aufbringen der ersten Kraft die elastische Verformung in der zweiten Richtung eine einseitig gerichtete Kontraktion oder Expansion des Niederhalterkörpers in der zweiten Richtung umfasst.
• Ausführungsform 4: Niederhalter nach einer der vorhergehenden Ausführungsformen, wobei die zweite Kraft eine Schubkraft auf eine Oberfläche des Werkstücks ist.
• Ausführungsform 5: Niederhalter nach einer der vorhergehenden Ausführungsformen, wobei der Niederhalterkörper ausgebildet ist zum Bewirken einer Spannungsüberlagerung in einer Scherzone des Werkstücks.
• Ausführungsform 6: Niederhalter nach einer der vorhergehenden Ausführungsformen, wobei die zweite Kraftrichtung zu einer Scherzone des Werkstücks hin oder von einer Scherzone des Werkstücks weg orientiert ist.
• Ausführungsform 7: Niederhalter nach einer der vorhergehenden Ausführungsformen, wobei die Anlagefläche an dem Niederhalterkörper angeordnet ist.
• Ausführungsform 8: Niederhalter nach einer der vorhergehenden Ausführungsformen, wobei der Niederhalterkörper im Wesentlichen zumindest abschnittsweise Z-förmig, invers Z-förmig, faltenbalgförmig oder schraubenwindungsförmig ausgebildet ist.
• Ausführungsform 9: Niederhalter nach einer der vorhergehenden Ausführungsformen, wobei der Niederhalterkörper zum Anordnen angrenzend an einen Schneidstempel des Schneidwerkzeugs ausgebildet ist.
• Ausführungsform 10: Niederhalter nach einer der vorhergehenden Ausführungsformen, weiterhin umfassend mindestens eine Aufbringungsfläche, wobei die Aufbringungsfläche zum Verbinden mit einem Wirkelement der Niederhalteraufnahme zum Aufbringen der ersten Kraft ausgebildet ist.
• Ausführungsform 11: Niederhalter nach der vorhergehenden Ausführungsform, wobei die Aufbringungsfläche an dem Niederhalterkörper angeordnet ist.
• Ausführungsform 12: Niederhalter nach der vorhergehenden Ausführungsform, wobei die Anlagefläche an einem ersten Ende des Niederhalterkörpers angeordnet ist, wobei die Aufbringungsfläche an einem zweiten Ende des Niederhalterkörpers angeordnet ist, wobei das zweite Ende dem ersten Ende gegenüberliegt.
• Ausführungsform 13: Niederhalter nach der vorhergehenden Ausführungsform, wobei das erste Ende und das zweite Ende mittels mindestens eines Verbindungsabschnitts miteinander verbunden sind, wobei der Verbindungsabschnitt an einem an das zweite Ende angrenzenden Ende breiter als an einem an das erste Ende angrenzenden Ende ist.
• Ausführungsform 14: Niederhalter nach einem der drei vorhergehenden Ansprüche, wobei das Wirkelement einen Niederhalterstempel umfasst.
• Ausführungsform 15: Niederhalter nach einer der vorhergehenden Ausführungsformen, wobei der Niederhalterkörper eine Höhe und eine Breite aufweist, wobei die Höhe und die Breite im Wesentlichen identisch sind.
• Ausführungsform 16: Niederhalter nach einer der vorhergehenden Ausführungsformen, wobei der Niederhalter eine gerade, gekrümmte oder teilkreisförmige Außenkontur aufweist.
• Ausführungsform 17: Niederhalter nach einer der vorhergehenden Ausführungsformen, wobei der Niederhalter zumindest teilweise und bevorzugt vollständig aus Werkzeugstahl hergestellt ist, insbesondere 1.2379 oder 1.1730.
• Ausführungsform 18: Schneidwerkzeug zum Scherschneiden eines Werkstücks, insbesondere eines Blechs, umfassend einen Schneidstempel, eine Matrize, eine Niederhalteraufnahme und mindestens einen Niederhalter nach einer der vorhergehenden Ausführungsformen, wobei der Niederhalterkörper des Niederhalters in oder an der Niederhalteraufnahme angeordnet ist.
• Ausführungsform 19: Schneidwerkzeug nach der vorhergehenden Ausführungsform, wobei der Niederhalter an den Schneidstempel angrenzend angeordnet ist.
• Ausführungsform 20: Schneidwerkzeug nach einer der ein Schneidwerkzeug betreffenden Ausführungsformen, wobei der Niederhalterkörper eine Innenform aufweist, die einer Außenform des Schneidstempels angepasst ist.
• Ausführungsform 21: Schneidwerkzeug nach einer der ein Schneidwerkzeug betreffenden Ausführungsformen, wobei die Niederhalteraufnahem ein Wirkelement aufweist, wobei der Niederhalter eine Aufbringungsfläche aufweist, wobei die Aufbringungsfläche mit dem Wirkelement der Niederhalteraufnahme zum Aufbringen der ersten Kraft verbunden ist.
• Ausführungsform 22: Schneidwerkzeug nach der vorhergehenden Ausführungsform, wobei das Wirkelement einen Niederhalterstempel umfasst.
• Ausführungsform 23: Schneidwerkzeug nach einer der ein Schneidwerkzeug betreffenden Ausführungsformen, wobei die Niederhalteraufnahme mindestens ein Federelement aufweist, wobei mittels des Federelements die erste Kraft auf den Niederhalterkörper übertragbar ist.
• Ausführungsform 24: Schneidwerkzeug nach einer der ein Schneidwerkzeug betreffenden Ausführungsformen, wobei der Niederhalter auf einer Oberseite oder einer Unterseite des Werkstücks anordenbar ist, wobei der Niederhalter zum Bewirken einer Zugspannungsüberlagerung oder einer Druckspannungsüberlagerung ausgebildet ist.
• Ausführungsform 25: Schneidwerkzeug nach einer der ein Schneidwerkzeug betreffenden Ausführungsformen, umfassend mindestens zwei Niederhalter, wobei die zweite Kraft eine Schubkraft auf eine Oberfläche des Werkstücks ist.
• Ausführungsform 26: Schneidwerkzeug nach der vorhergehenden Ausführungsform, wobei die Niederhalter eingerichtet sind, auf gegenüberliegenden Seiten des Werkstücks angeordnet zu werden.
• Ausführungsform 27: Schneidwerkzeug nach der vorhergehenden Ausführungsform, wobei die zweite Kraft der Niederhalter auf den gegenüberliegenden Seiten des Werkstücks gleichsinnig oder gegensinnig ist.
• Ausführungsform 28: Schneidwerkzeug nach der vorhergehenden Ausführungsform, wobei die Niederhalter zum Bewirken einer Zugspannungsüberlagerung, einer Druckspannungsüberlagerung oder einer Scherspannungsüberlagerung ausgebildet sind.

In summary, the following embodiments are proposed, without limiting further possible configurations:

• Embodiment 1: Hold-down device for a cutting tool for shear-cutting a workpiece, in particular a sheet of metal, comprising at least one contact surface for resting on a workpiece, the contact surface being designed to apply a first force to the workpiece in a first force direction 122, a hold-down body, wherein the Hold-down body is designed for placement in or on a hold-down holder of the cutting tool, wherein the hold-down body is elastically deformable in such a way that when the first force is applied by means of the contact surface, a second force can be applied to the workpiece in a second direction of force, the second direction of force being essentially vertical to the first direction of force.
• Embodiment 2: Hold-down device according to the previous embodiment, wherein the hold-down device body is elastically deformable in a first direction parallel to the first direction of force and in a second direction parallel to the second direction of force when the first force is applied.
• Embodiment 3: Hold-down device according to the previous embodiment, wherein when the first force is applied, the elastic deformation in the second direction comprises a unidirectional contraction or expansion of the hold-down body in the second direction.
• Embodiment 4: Hold-down device according to one of the preceding embodiments, wherein the second force is a thrust force on a surface of the workpiece.
• Embodiment 5: Hold-down device according to one of the preceding embodiments, wherein the hold-down device body is designed to effect a stress superimposition in a shear zone of the workpiece.
• Embodiment 6: Hold-down device according to one of the preceding embodiments, wherein the second direction of force is oriented towards a shear zone of the workpiece or away from a shear zone of the workpiece.
• Embodiment 7: Hold-down device according to one of the preceding embodiments, wherein the contact surface is arranged on the hold-down device body.
• Embodiment 8: Hold-down device according to one of the preceding embodiments, wherein the hold-down device body is essentially Z-shaped, inverse Z-shaped, bellows-shaped or helical-turn-shaped, at least in sections.
• Embodiment 9: Hold-down device according to one of the preceding embodiments, wherein the hold-down device body is designed to be arranged adjacent to a cutting punch of the cutting tool.
• Embodiment 10: Hold-down device according to one of the preceding embodiments, further comprising at least one application surface, wherein the application surface is designed to be connected to an active element of the hold-down holder for applying the first force.
• Embodiment 11: Hold-down device according to the previous embodiment, wherein the application surface is arranged on the hold-down device body.
• Embodiment 12: Hold-down device according to the previous embodiment, wherein the contact surface is arranged at a first end of the hold-down body, wherein the application surface is arranged at a second end of the hold-down body, the second end being opposite the first end.
• Embodiment 13: Hold-down device according to the previous embodiment, wherein the first end and the second end are connected to one another by means of at least one connecting section, the connecting section being wider at an end adjacent to the second end than at an end adjacent to the first end.
• Embodiment 14: Hold-down device according to one of the three preceding claims, wherein the active element comprises a hold-down stamp.
• Embodiment 15: Hold-down device according to one of the preceding embodiments, wherein the hold-down device body has a height and a width, the height and the width being essentially identical.
• Embodiment 16: Hold-down device according to one of the preceding embodiments, wherein the hold-down device has a straight, curved or part-circular outer contour.
• Embodiment 17: Hold-down device according to one of the preceding embodiments, wherein the hold-down device is at least partially and preferably completely made of tool steel, in particular 1.2379 or 1.1730.
• Embodiment 18: Cutting tool for shear cutting a workpiece, in particular a sheet metal, comprising a cutting punch, a die, a hold-down holder and at least one hold-down holder according to one of the preceding embodiments, wherein the hold-down body of the hold-down holder is arranged in or on the hold-down holder.
• Embodiment 19: Cutting tool according to the previous embodiment, wherein the hold-down device is arranged adjacent to the cutting punch.
• Embodiment 20: Cutting tool according to one of the embodiments relating to a cutting tool, wherein the hold-down body has an inner shape that is adapted to an outer shape of the cutting punch.
• Embodiment 21: Cutting tool according to one of the embodiments relating to a cutting tool, wherein the hold-down holder has an active element, the hold-down holder having an application surface, the application surface being connected to the active element of the hold-down holder for applying the first force.
• Embodiment 22: Cutting tool according to the previous embodiment, wherein the active element comprises a hold-down punch.
• Embodiment 23: Cutting tool according to one of the embodiments relating to a cutting tool, wherein the hold-down holder has at least one spring element, the first force being transferable to the hold-down body by means of the spring element.
• Embodiment 24: Cutting tool according to one of the embodiments relating to a cutting tool, wherein the hold-down device can be arranged on an upper side or an underside of the workpiece, wherein the hold-down device is designed to effect a tensile stress overlay or a compressive stress overlay.
• Embodiment 25: Cutting tool according to one of the embodiments relating to a cutting tool, comprising at least two hold-down devices, wherein the second force is a thrust force on a surface of the workpiece.
• Embodiment 26: Cutting tool according to the previous embodiment, wherein the hold-down devices are arranged to be arranged on opposite sides of the workpiece.
• Embodiment 27: Cutting tool according to the previous embodiment, wherein the second force of the hold-down devices on the opposite sides of the workpiece is in the same direction or in opposite directions.
• Embodiment 28: Cutting tool according to the previous embodiment, wherein the hold-down devices are designed to effect a tensile stress superimposition, a compressive stress superimposition or a shear stress superimposition.

Short description of the characters

• 1 eine Schnittansicht eines Schneidwerkzeugs gemäß einer Ausführungsform der vorliegenden Erfindung;
• 2A bis 2E eine schematische Darstellung eines Ablaufs eines Verfahrens zum Betreiben des Schneidwerkzeugs;
• 3 eine Darstellung zur Erläuterung der Schnittflächencharakterisierung;
• 4A bis 4C eine Gegenüberstellung der Schnittflächenqualität verschiedener Schneidverfahren;
• 5 eine Darstellung zur Erläuterung des Einflusses auf den Schneidprozess durch Spannungsüberlagerung;
• 6 eine Gegenüberstellung des Kraftbedarfs verschiedener Schneidverfahren;
• 7 eine Schnittansicht eines Schneidwerkzeugs gemäß einer weiteren Ausführungsform der vorliegenden Erfindung;
• 8 eine Schnittansicht eines Schneidwerkzeugs gemäß einer weiteren Ausführungsform der vorliegenden Erfindung;
• 9 eine Schnittansicht eines Schneidwerkzeugs gemäß einer weiteren Ausführungsform der vorliegenden Erfindung;
• 10 eine Schnittansicht eines Schneidwerkzeugs gemäß einer weiteren Ausführungsform der vorliegenden Erfindung;
• 11 eine Schnittansicht eines Schneidwerkzeugs gemäß einer weiteren Ausführungsform der vorliegenden Erfindung;
• 12 eine Draufsicht eines Schneidwerkzeugs gemäß einer weiteren Ausführungsform der vorliegenden Erfindung; und
• 13 eine Draufsicht eines Schneidwerkzeugs gemäß einer weiteren Ausführungsform der vorliegenden Erfindung.

Further details and features emerge from the following description of exemplary embodiments, in particular in connection with the subclaims. The respective features can be implemented alone or in combination with each other. The invention is not limited to the exemplary embodiments. The exemplary embodiments are shown schematically in the figures. The same reference numbers in the individual figures designate elements that are the same or have the same function or correspond to one another in terms of their functions. Show in detail:

• 1 a sectional view of a cutting tool according to an embodiment of the present invention;
• 2A until 2E a schematic representation of a sequence of a method for operating the cutting tool;
• 3 a representation to explain the cut surface characterization;
• 4A until 4C a comparison of the cut surface quality of different cutting processes;
• 5 a representation to explain the influence on the cutting process through stress superimposition;
• 6 a comparison of the power requirements of different cutting processes;
• 7 a sectional view of a cutting tool according to another embodiment of the present invention;
• 8th a sectional view of a cutting tool according to another embodiment of the present invention;
• 9 a sectional view of a cutting tool according to another embodiment of the present invention;
• 10 a sectional view of a cutting tool according to another embodiment of the present invention;
• 11 a sectional view of a cutting tool according to another embodiment of the present invention;
• 12 a top view of a cutting tool according to another embodiment of the present invention; and
• 13 a top view of a cutting tool according to another embodiment of the present invention.

Description of the exemplary embodiments

1 shows a sectional view of a cutting tool 100 according to an embodiment of the present invention. The cutting tool is designed for shear cutting of a workpiece 102. The workpiece 102 is, for example, a sheet metal 104. The cutting tool 100 comprises a cutting punch 106. The cutting punch 106 can be designed, for example, for punching. The cutting tool 100 also has a die 108. The workpiece 102 is placed on the die 108 for shear cutting. The cutting tool 100 also has a hold-down holder 110. The hold-down holder 110 has an active element 112. The active element 112 includes a hold-down stamp 114 or is designed as a hold-down stamp 114. The hold-down holder 110 has at least one spring element 116. The spring element 116 acts on the active element 112 or the hold-down stamp 114 and is arranged between the hold-down holder 110 and the active element 112 or the hold-down stamp 114.

The cutting tool 100 further comprises at least one hold-down device 118. The hold-down device 118 has a contact surface 120 for resting against the workpiece 102. The contact surface 120 is designed to apply a first force F 1 to the workpiece 102 in a first force direction 122

The hold-down device 118 also has a hold-down device 124. The hold-down body 124 is designed to be arranged in or on the hold-down holder 110 of the cutting tool 100. 1 shows the hold-down body 124 in a state arranged in or on the hold-down holder 110 of the cutting tool 100. The contact surface 120 is arranged on the hold-down body 124.

The hold-down device 118 further comprises an application surface 126. The application surface 126 is designed to be connected to the active element 112 of the hold-down device 110 for applying the first force F1. The application surface 126 is arranged on the hold-down body 124. In particular, the contact surface 120 is arranged at a first end 128 of the hold-down body 122 and the application surface 126 is arranged at a second end 130 of the hold-down body 122. The second end 130 is opposite the first end 128. The first end 128 and the second end 130 are connected to one another by means of a connecting section 132. The connecting section 132 may be wider at an end adjacent to the second end 130 than at an end adjacent to the first end 128. In the embodiment shown, the hold-down body 124 is essentially designed to be Z-shaped, at least in sections and in particular essentially completely. Accordingly, the contact surface 120 and the application surface 126 are oriented parallel to one another. The hold-down body 124 is designed to be disposed adjacent to the cutting punch 106 of the cutting tool 100. The hold-down body 124 has a height 134 and a width 136. The height 134 and the width 136 are essentially identical. However, it is made clear that these can differ from each other.

The hold-down device 118 is at least partially and preferably completely made of tool steel. For example, the hold-down device 118 is made of steel 1.2379 or 1.1730 according to DIN EN 10027 valid in the version on the day the present patent application was filed.

The hold-down body 124 is elastically deformable in such a way that when the first force F1 is applied by means of the contact surface 120, a second force F2 can be applied to the workpiece 102 in a second force direction 138. The second direction of force 138 is essentially perpendicular to the first direction of force 122. The first force can be transferred to the hold-down body 124 by means of the spring element 116 of the hold-down holder 110.

When the first force F1 is applied, the hold-down body 124 is elastically deformable in a first direction 140 parallel to the first direction of force 122 and in a second direction 12 parallel to the second direction of force 138. When the first force F1 is applied, the elastic deformation in the second direction 142 includes, depending on the design of the hold-down body 124, a unidirectional contraction or expansion of the hold-down body 124 in the second direction 142. The second force F2 is a thrust force on a surface 144 of the workpiece 102 The direction of the thrust force depends on the design of the hold-down device 118 and can be either tensile stresses or compressive stresses in the plane of the workpiece 102 cause. Thus, the hold-down body 124 is designed to effect a stress superposition in a shear zone of the workpiece 102. The second direction of force 138 is oriented towards a shear zone 146 of the workpiece 102 in the embodiment shown. It is understood that in order to realize closed cuts, more than one hold-down device 118 must be provided, which surround the cutting punch 106 in the circumferential direction in order to ensure transverse elasticity. An internal shape of the hold-down body 124 is in each case adapted to an external shape of the cutting punch 106. For this reason, the hold-down stamp 114 must have a special holder and connection to the respective hold-down devices 118.

The hold-down device 118 can be modified as follows. The hold-down body 124 can basically be designed in an inverse Z-shaped, bellows-shaped or helical-turn-shaped manner, at least in sections. The hold-down body 124 can have more than one contact surface 120 and/or application surface 126. For example, the hold-down body 124 can have two parallel contact surfaces 120 and application surfaces 126. The parallel contact surfaces 120 and application surfaces 126 can be connected to one another via one or more connecting sections of any transversely elastic geometry, for example in a Z shape or similar to a bellows. The second direction of force 138 can be oriented away from a shear zone 146 of the workpiece 102.

A method of operating the cutting tool 100 is described in more detail below.

The 2A until 2E show a schematic representation of a sequence of a method for operating the cutting tool 100. More precisely, this is a method for shear cutting the workpiece 102. As in 2A shown, the workpiece 102 is first arranged on the die 108. By means of the hold-down holder 110 and the hold-down stamp 114, a predetermined force is applied to the hold-down device 118 arranged on or in the hold-down holder 110. The hold-down body 124 applies the first force Flin of the first force direction 122 to the workpiece 102 via the contact surface 120. The first force direction 122 is perpendicular to the surface 144 of the workpiece 102. The first force F1 serves to fix the workpiece 102 for the subsequent cutting process in the plane of the workpiece 102 and to prevent the workpiece 102 from lifting off. The hold-down body 124 is elastically deformed . The cutting punch 106 is moved or placed onto the workpiece 102 with a predetermined force F, as indicated by a first direction of movement 148.

As in 2 B shown, an elastic and plastic deformation of the workpiece 102 subsequently occurs during a further movement of the cutting punch 106 in the first direction of movement 148. Without the application of the first force F1 by the hold-down device 118, the workpiece 102 would be lifted off, as in 2 B is indicated. However, this lifting is prevented by the application of the first force F 1 to the workpiece 102. Due to the elastic deformation of the hold-down body 124, the second force F2 is applied to the workpiece 102 in the second force direction 138. The second direction of force 138 is essentially perpendicular to the first direction of force 122. The second force F2 acts as a shear force on the surface 144 of the workpiece 102, the direction depending on the design of the hold-down device 118 and either tensile stresses or compressive stresses in the plane of the Workpiece 102 can cause.

As in 2C shown, subsequent movement of the cutting punch 106 in the first direction of movement 148 results in shearing and cracking of the workpiece 102.

As in 2D shown, the workpiece 102 breaks through when the cutting punch 106 moves further in the first direction of movement 148.

As in 2E shown, the cutting punch 106 is finally moved in a second direction of movement 150, which is opposite to the first direction of movement 148, so that a cut part 152 produced by cutting is stripped off. During the return stroke of the cutting punch 106, the hold-down device 118 prevents the workpiece from being lifted or strips the cut or perforated cut part 152 from the cutting punch 106. A resulting slug 154 can be discarded as waste or otherwise utilized. Finally, after stripping, the predetermined force applied to the hold-down device 118 and thus the first force F1 is also released.

In summary, the hold-down holder 110 is acted upon by a vertical force via the hold-down holder 110 by means of the spring element 116 and thereby fixes the workpiece 102 between the cutting punch 106 and the die 108 before, during and after the cutting process. Due to its geometric design, the uniaxial force application leads in addition to the vertical force to a horizontal transverse contraction of the hold-down device 118. Via the friction contact surface to the workpiece 102, an additional horizontal thrust force is thus transmitted to the workpiece 102. Depending on the orientation of the transversely elastic hold-down device 118, compressive forces can be superimposed in the shear zone 146, which lead to a later onset of the breaking process and thus to a higher proportion of smooth cuts during shear cutting.

3 shows a representation to explain the cut surface characterization so that it becomes clear what is meant by a smooth cut portion. An example of a cut workpiece 102 is shown. After cutting, the workpiece 102 has a total height s ₀ at a cutting edge 156. The cutting edge 156 can be characterized by an edge intake height h _E , a smooth cutting height h _S , a fracture surface height h _B , a cutting burr height h _G , an edge intake width b _E , a cutting burr width b _G and a fracture surface angle β. An increased proportion of smooth cuts due to the hold-down device 118 according to the invention is characterized, for example, by a higher smooth cut height hs than in conventional cutting processes.

The 4A until 4C show a comparison of the cut surface quality of different cutting processes. It is shown in the 4A until 4C each a cutting edge 156 of an exemplary workpiece 102 over a thickness that is plotted as workpiece thickness 158 in mm. Furthermore, in the 4A until 4C each showing a burr 160, a break 162, a smooth cut portion 164 and an edge 166. The 4A shows the cutting surface quality for normal cutting. The 4B shows the cut surface quality for fine blanking. The 4C shows the cut surface quality for shear cutting with the hold-down device 118 according to the invention. As can be seen, the smooth cut portion 166 is significantly higher in fine cutting than in normal cutting. However, fineblanking is very complex and cost-intensive. An increased proportion of smooth cuts can also be achieved very well with the hold-down device 118 according to the invention, as in 4C can be recognized.

5 shows a representation to explain the influence on the cutting process through stress superimposition. The stress σ is shown as the X-axis and the shear stress τ as the Y-axis. In the middle, a curve 168 shows the effect of conventional shear cutting. The shear yield limit 170 and the shear failure limit 172 are also shown. Depending on the design, the hold-down device 118 according to the invention can be used to achieve a compressive stress superposition through the elastic deformation and the application of the second force F2, which is represented by a curve 174. This results in a prolonged flow process for an increased proportion of smooth cuts. Alternatively, the elastic deformation and the application of the second force F2 can achieve a tensile stress superimposition, which is represented by a curve 176. This results in premature breakage resulting in reduced cutting force. This illustrates how the cutting process can be specifically influenced by the hold-down device 118 according to the invention.

6 shows a comparison of the power requirements of different cutting processes. The thickness of the workpiece 102 is plotted in mm on the X axis 178. The cutting force in N is plotted on the Y axis 180. Curve 182 represents the course of the cutting force as a function of the thickness of the workpiece 102 for normal cutting. Curve 184 represents the course of the cutting force as a function of the thickness of the workpiece 102 for fine cutting. Curve 186 represents the course of the cutting force depending on the thickness of the workpiece 102 for shear cutting with the hold-down device according to the invention with a compressive stress superimposition. As can be seen, the cutting force is suddenly reduced during normal cutting from a thickness of approximately 0.5 mm. In contrast, the cutting force during fine cutting and when cutting with the hold-down device 118 according to the invention has an approximately similar course with a gradual reduction in the cutting force towards a thickness of 1 mm.

7 a sectional view of a cutting tool 100 according to another embodiment of the present invention. Below are only the differences to the embodiment 1 explained and identical or comparable components and features are provided with the same reference numbers. Optionally, the cutting tool 100 can have a counter punch 188 opposite the cutting punch 106. A hold-down device 118 is arranged on only one side of the workpiece 102, which is, for example, the top side. The hold-down device 118 is designed in a Z shape, so that when the first force F1 is applied in the first direction of force 122, it applies the second force F2 in the second direction of force 138 perpendicular to the first direction of force 122 to the workpiece 102 due to its elastic deformation. The second direction of force 138 is oriented towards the shear zone 146. The second force F2 leads to a compressive stress superimposition in the shear zone 146 due to the Z-shaped design.

8th shows a sectional view of a cutting tool 100 according to another embodiment of the present invention. Next Here only the differences to the embodiment of the 7 explained and identical or comparable components and features are provided with the same reference numbers. The hold-down device 118 is designed in an inverse Z-shape, so that when the first force F1 is applied in the first direction of force 122, it applies the second force F2 in the second direction of force 138 perpendicular to the first direction of force 122 to the workpiece 102 due to its elastic deformation. The second direction of force 138 is oriented away from the shear zone 146. The second force F2 leads to a tensile stress superimposition in the shear zone 146 due to the inverse Z-shaped design.

9 shows a sectional view of a cutting tool 100 according to another embodiment of the present invention. Below are only the differences to the embodiment 7 explained and identical or comparable components and features are provided with the same reference numbers. Two hold-down devices 118 are provided, which are arranged on opposite sides of the workpiece 102. In other words, the two hold-down devices are arranged mirror-symmetrically to one another with respect to the workpiece 102. Accordingly, there is a hold-down device 118 on the top of the workpiece 102 and another hold-down device 118 on the underside of the workpiece 102. Accordingly, the die 108 is designed to be smaller, for example as a die sleeve 190. Each of the hold-down devices 118 is designed to be Z-shaped, so that When the first force F1 is applied in the first force direction 122, it applies the second force F2 in the second force direction 138 perpendicular to the first force direction 122 to the workpiece 102 through its elastic deformation. The second direction of force 138 is oriented towards the shear zone 146. The second force F2 leads to a compressive stress superimposition in the shear zone 146 due to the Z-shaped design.

10 a sectional view of a cutting tool 100 according to another embodiment of the present invention. Below are only the differences to the embodiment 9 explained and identical or comparable components and features are provided with the same reference numbers. The hold-down devices 118 are inverted Z-shaped, so that when the first force F1 is applied in the first force direction 122, they apply the second force F2 in the second force direction 138 perpendicular to the first force direction 122 to the workpiece 102 through their elastic deformation. The second direction of force 138 is oriented away from the shear zone 146. The second force F2 leads to a tensile stress superimposition in the shear zone 146 due to the inverse Z-shaped design.

It is explicitly emphasized that an opposite arrangement of the hold-down devices 118 is also possible, so that, for example, one hold-down device 118 causes an overlay of tensile stress and the other hold-down device 118 causes an overlay of compressive stress. This results in an overall shear stress superimposition.

11 shows a sectional view of a cutting tool 100 according to another embodiment of the present invention. Below are only the differences to the embodiment 1 explained and identical or comparable components and features are provided with the same reference numbers. The cutting tool has a punch holder 192 for the cutting punch 106. The die 108 is arranged in a die holder 194. There are at least two hold-down devices 118 arranged on the same side of the workpiece 102. The hold-down devices 118 adjoin the cutting punch 106. An inner contour 196 or inner shape of the hold-down body 124 is adapted to an outer shape of the cutting punch 106. The hold-down devices 118 can adjoin the cutting punch 106 at least on two opposite sides. However, several hold-down devices 118 are preferably arranged, which surround the cutting punch 106 on all sides in a circumferential direction.

12 shows a top view of a cutting tool 100 according to another embodiment of the present invention. Below are only the differences to the embodiment 11 explained and identical or comparable components and features are provided with the same reference numbers. At the in 12 In the embodiment shown, the cutting punch 106 has a rectangular cross section. Furthermore, a total of four hold-down devices 118 are provided, which surround the cutting punch 106 on all sides in a circumferential direction. A type of segmented arrangement of the hold-down devices 118 can therefore be implemented. An outer surface or outer contour 198 of the hold-down body 124 is straight or flat.

13 a top view of a cutting tool 100 according to another embodiment of the present invention. Below are only the differences to the embodiment 11 explained and identical or comparable components and features are provided with the same reference numbers. At the in 12 In the embodiment shown, the cutting punch 106 has a circular cross section. Furthermore, a total of eight hold-down devices 118 are provided, which surround the cutting punch 106 on all sides in a circumferential direction. A type of segmented arrangement of the hold-down devices 118 can therefore be implemented. An outer surface or outer contour 198 of the Niederhal The body 124 is each part-circular. For example, the outer contour 198 has an extension of 45°.

Reference symbol list

100

cutting tool

102

workpiece

104

sheet

106

cutting die

108

die

110

Hold-down holder

112

Active element

114

Hold-down stamp

116

Spring element

118

Hold-down device

120

investment area

122

first direction of force

124

Hold-down body

126

Application surface

128

first ending

130

second ending

132

connection section

134

Height

136

Width

138

second direction of force

140

first direction

142

second direction

144

surface

146

shear zone

148

first direction of movement

150

second direction of movement

152

Cut part

154

Slugs

156

cutting edge

158

Workpiece thickness

160

ridge

162

fracture

164

Smooth cut portion

166

Edge

168

Effects of conventional shear cutting

170

Shear yield point

172

Shear failure limit

174

Compressive stress superposition

176

Tensile stress superposition

178

X axis

180

Y axis

182

Cutting force curve for normal cutting

184

Cutting force progression for fine blanking

186

Course of cutting force for shear cutting with hold-down device according to the invention

188

Counterstamp

190

Die sleeve

192

Stamp recording

194

Matrix recording

196

Inner contour

198

Outer contour

F

predetermined force

F1

first force

F2

second force

s0

Total height

hE

Edge feed height

hS

Smooth cutting height

hB

Fracture surface height

hG

cutting burr height

bE

Edge feed width

bG

Cutting burr width

β

Fracture surface angle

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 2208552 B1 [0004]

Claims (16)

Hold-down device (118) for a cutting tool (100) for shear cutting a workpiece (102), in particular a sheet of metal (104). at least one contact surface (120) for contacting a workpiece (102), the contact surface (120) being designed to apply a first force (F1) to the workpiece (102) in a first force direction (122), a hold-down body (124), wherein the hold-down body (124) is designed to be arranged in or on a hold-down holder (110) of the cutting tool (100), wherein the hold-down body (124) is elastically deformable in such a way that when the first force (F1) is applied By means of the contact surface (120), a second force (F2) can be applied to the workpiece (102) in a second force direction (138), the second force direction (138) being essentially perpendicular to the first force direction (122). Hold-down device (118) according to the preceding claim, wherein the hold-down device body (124) is elastically deformable in a first direction parallel to the first direction of force (122) and in a second direction parallel to the second direction of force (138) when the first force (F1) is applied is. Hold-down device (118) according to one of the preceding claims, wherein the second force (F2) is a thrust force on a surface (144) of the workpiece (102). Hold-down device (118) according to one of the preceding claims, wherein the hold-down device body (124) is designed to effect a stress superimposition in a shear zone (138) of the workpiece (102). Hold-down device (118) according to one of the preceding claims, wherein the second force direction (138) is oriented towards a shear zone (138) of the workpiece (102) or away from a shear zone (138) of the workpiece (102). Hold-down device (118) according to one of the preceding claims, wherein the contact surface (120) is arranged on the hold-down device (124). Hold-down device (118) according to one of the preceding claims, wherein the hold-down device body (124) is essentially Z-shaped, inverse Z-shaped, bellows-shaped or helical-turn-shaped, at least in sections. Hold-down device (118) according to one of the preceding claims, further comprising an application surface (126), wherein the application surface (126) is designed to be connected to an active element (112) of the hold-down holder (110) for applying the first force (F1). Cutting tool (100) for shear cutting a workpiece (102), in particular a sheet metal, comprising a cutting punch (106), a die (108), a hold-down holder (110) and at least one hold-down device (118) according to one of the preceding claims, wherein the hold-down body (124) of the hold-down device is arranged in or on the hold-down holder (110). Cutting tool (100) according to the preceding claim, wherein the hold-down device (118) is arranged adjacent to the cutting punch (106). Cutting tool (100) according to one of the claims relating to a cutting tool (100), wherein the hold-down body (124) has an inner shape which is adapted to an outer shape of the cutting punch (106). Cutting tool (100) according to one of the claims relating to a cutting tool (100), wherein the hold-down device (118) can be arranged on an upper side or an underside of the workpiece (102), wherein the hold-down device (118) is designed to effect a tensile stress superimposition or a compressive stress superimposition . Cutting tool (100) according to one of the claims relating to a cutting tool (100), comprising at least two hold-down devices (118), wherein the second force (F2) is a thrust force. Cutting tool (100) according to the preceding claim, wherein the hold-down devices (118) are arranged to be arranged on opposite sides of the workpiece (102). Cutting tool (100) according to the preceding claim, wherein the second force (F2) of the hold-down devices (118) on the opposite sides of the workpiece (102) is in the same direction or in opposite directions. Cutting tool (100) according to the preceding claim, wherein the hold-down devices (118) are designed to effect a tensile stress superimposition, a compressive stress superimposition or a shear stress superimposition.

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