Bending die for a bending machine, and method for producing a bending die

Abstract

The invention relates to a bending die (5) for a bending machine (1), for carrying out a bending operation on a sheet-metal workpiece (2), wherein a centre point (M1) of a first radius (R1) of a first inlet contour portion (15a) of a first inlet contour (15_1) of a V-shaped recess (13) and a centre point (Ml) of a first radius (Rl) of a first inlet contour portion (15a) of a second inlet contour (15_2) of the V-shaped recess (13) are spaced apart from each other by a centre-to-centre spacing (L) in a first plane (E1) independently of a first die angle (al) between a first side face (14a) and a separating plane (E2) of the recess (13), the separating plane being normal to the first plane (El), and a second die angle (α2) between a second side face (14b) and the separating plane (E2), where L = W + 2 * R1, and wherein the first inlet contour (15_1) comprises a second inlet contour portion (15b) which is situated between the first inlet contour portion (15a) and the first side face (14a) and has a second radius (R2), and / or wherein the second inlet contour (15_2) comprises a second inlet contour portion (15b) which is situated between the first inlet contour portion (15a) and the second side face (14b) and has a second radius (R2), wherein a radii ratio (X) between a value of the second radius (R2) and the value of the first radius (RI) is 2.5 ≤ X ≤ 5.

Description

[0001] BENDING DIE FOR A BENDING MACHINE AND METHOD FOR MANUFACTURING A BENDING DIE

[0002] The invention relates to a bending die for a bending machine for performing a bending process on a sheet metal workpiece, wherein the bending die comprises a support surface for the sheet metal workpiece, which lies in a first plane, wherein a substantially V-shaped recess is provided on the support surface, which divides the support surface into two partial surfaces, wherein the recess comprises a flat first side surface, which is inclined at a fixed first die angle with respect to a parting plane of the recess, which is normal to the first plane, and an opposite flat second side surface, which is inclined at a fixed second die angle with respect to the parting plane, wherein the first side surface is connected to the first partial surface via a first inlet contour and the second side surface is connected to the second partial surface via a second inlet contour,wherein the first inlet contour and second inlet contour each comprise a first inlet contour section with a first radius, the value of which depends on a predetermined theoretical die width of the bending die.

[0003] The invention further relates to a tool system, a bending machine and a method for producing a bending die for a bending machine for carrying out a bending process on a sheet metal workpiece.

[0004] Bending dies, also called bending dies, are well-known in the art and are used as lower tools in die bending. A bending die has a support surface for a sheet metal workpiece to be bent, in which a V-shaped recess is provided. The unbent or pre-bent sheet metal workpiece can be placed on the support surface. The sheet metal forming can take place through a controlled downward movement of an upper tool, also called a punch.

[0005] A distinction is made between air bending, coin bending and three-point bending. A characteristic of air bending is that the workpiece only touches the bending die on its two edges. To produce bends with sufficient accuracy, precise control of the punch is necessary, for which a CNC control is usually used. A particular advantage of air bending is the ability to produce different sheet angles without changing tools. For this reason, it is used more frequently than coin bending or three-point bending. The bending process can be specifically influenced by the geometry of the V-shaped recess, in particular the geometry of an inlet contour between the support surface and the side surfaces of the V-shaped recess. In particular, the geometry of the inlet contour can influence the surface pressure on the workpiece and consequently the depth of an impression on the workpiece. On the other hand, the rolling or rolling motion can be influenced.Sliding behavior of the workpiece on the bending die and consequently the length of the impression can be influenced.

[0006] EP 0 605 022 B1 discloses a V-shaped bending die with an inlet contour whose radius of curvature increases from the support surface towards the side surface of the V-shaped recess, wherein a radius ratio between the radius of curvature at the end of the inlet curve and the radius of curvature at the beginning of the inlet curve is determined according to a relatively complex formula.

[0007] JP4383931 B2 discloses a bending die having an inlet contour with two different consecutive radii, the first radius being larger than the second radius.

[0008] The object of the present invention was to provide a standardized bending die with a geometry that can be produced as simply and cost-effectively as possible, with which the length and depth of the impression on the workpiece can be reduced.

[0009] This object is achieved by the bending die mentioned at the outset in that a center point of the first radius of the first inlet contour section of the first inlet contour and a center point of the first radius of the first inlet contour section of the second inlet contour are spaced apart from one another in the first plane, regardless of the first die angle and second die angle, at a center distance which is L = W + 2 * RI and that the first inlet contour comprises a second inlet contour section having a second radius lying between the first inlet contour section and the first side surface and / or that the second inlet contour comprises a second inlet contour section having a second radius lying between the first inlet contour section and the second side surface, wherein a radius ratio between a value of the second radius and the value of the first radius is 2.5 < X < 5.Because the center-point distance is independent of the die angle used, the contact points on the bending die are at the same distance from the workpiece, even with different die angles. Bending dies with different die angles, e.g. 30°, 80 and 84°, therefore have the same contact point distance for the same workpiece bending angle. This means that the same bending behavior and bending result are always achieved, regardless of the die angle of the bending die. Bending dies with different die angles are therefore easy to combine. The radius ratio according to the invention can, on the one hand, have a positive influence on the rolling or sliding behavior of the workpiece and, on the other hand, can reduce surface pressure. This leads to a reduction in the length and depth of the imprint on the workpiece, requiring fewer or no reworking steps.

[0010] Further advantages are: the same minimum leg length of the sheet metal workpiece for bending dies (designed according to the invention) with different die angles, the same bending compensation values, low effort for tool selection in the design, no cutting adjustment required, less coordination effort between design and production, with small die angles shorter leg lengths are possible than before, no excessive force compared to previously used bending dies, bending dies (designed according to the invention) with different die angles can be combined with each other, with bending dies (designed according to the invention) with different die angles the bending robot can use the same bending trajectory.

[0011] Preferably, the V-shaped recess is symmetrical with respect to the parting plane. This means that the first inlet contour and the second inlet contour are identical, and that the first die angle is also the same as the second die angle.

[0012] The first die angle and the second die angle can be the same or different. This makes it possible, for example, to provide a bending die that includes the second inlet contour section with the second radius at only one of the two inlet contours (or at both inlet contours) and that has different die angles. During the bending process, the bending die is preferably arranged in the bending machine so that the larger die angle faces the operator. This can reduce the risk of injury because the angular velocity of the leg of the workpiece facing the operator is lower than that of the opposite leg.

[0013] Preferably, the first inlet contour section of the first inlet contour is tangentially connected to the first partial surface and / or the first inlet contour section of the second inlet contour is tangentially connected to the first partial surface. Alternatively or additionally, the first inlet contour section and the second inlet contour section of the first inlet contour can be tangentially connected and / or the first inlet contour section and the second inlet contour section of the second inlet contour can be tangentially connected. Alternatively or additionally, the second inlet contour section of the first inlet contour can be tangentially connected to the first side surface of the recess and / or the second inlet contour section of the second inlet contour can be tangentially connected to the second side surface of the recess.

[0014] The theoretical die width is preferably between 4 and 150 mm. This allows for the most common bending processes to be performed.

[0015] The value of the first radius is preferably 5 to 15% of the theoretical die width, preferably 10%. These values ​​have proven particularly advantageous in tests.

[0016] The radius ratio X between the value of the second radius and the value of the first radius is preferably 3.5 to 4.5, preferably 4. Tests have shown that this can minimize the length of the impression.

[0017] According to an advantageous embodiment, a first transition point of a transition from the first inlet contour section to the second inlet contour section of the first inlet contour and a second transition point of a transition from the first inlet contour section to the second inlet contour section of the second inlet contour are set at a transition angle of 100° to 120°, preferably at 105° to 115°, in particular at 110°. This makes the bending die suitable for the most common bending applications, which are usually in the range of 90°.

[0018] The first die angle and / or the second die angle can be 10° to 55°, preferably 15°, 42°, or 45°. This allows the most common die angles to be covered. Particularly preferably, the first die angle and / or the second die angle can be 13° to 15°, in particular 14°, or 33° to 35°, in particular 34°. To improve pre-bending, it is advantageous if the first or second die angle is 13° to 15°, in particular 14°.

[0019] In order to be able to bend high-strength steels, whose springback can be up to 20°, to 90°, it is advantageous if the first and / or second die angles are flatter, preferably 33° to 35°, in particular 34°.

[0020] Preferably, an intersection point of the first side surface and the second side surface is rounded off by means of a curve. This can increase the fatigue strength.

[0021] It may be advantageous to provide a first chamfer between the first partial surface of the support surface and a first outer surface of the bending die parallel to the parting plane, and / or to provide a second chamfer between the second partial surface of the support surface and a second outer surface of the bending die parallel to the parting plane. This makes even shorter limbs of the workpiece accessible for ease measurement.

[0022] Preferably, a tool system can be provided with several of the bending dies according to the invention, wherein at least two bending dies with the same theoretical die width, the same center distance and different first die angles and / or second die angles are provided.

[0023] The bending die is preferably used as a lower tool in a bending machine designed to perform a bending process on a sheet metal workpiece. The bending machine comprises a lower bending beam with a lower tool holder for receiving a lower tool, an upper bending beam with an upper tool holder for receiving an upper tool, at least one lower tool, and at least one upper tool.

[0024] The object is further achieved with the method mentioned at the outset by carrying out the following steps: providing a metallic, preferably cuboid-shaped, base body with a support surface for the sheet metal workpiece lying in a first plane or creating the support surface on the base body, creating a substantially V-shaped recess dividing the support surface into two partial surfaces with a defined theoretical die width in the support surface, creating a flat first side surface which is inclined at a defined first die angle with respect to a parting plane perpendicular to the first plane in the recess and an opposite flat second side surface which is inclined at a defined second die angle with respect to the parting plane,Creating a first inlet contour between the first side surface and the first partial surface and a second inlet contour between the second side surface and the second partial surface, each having a first inlet contour section with a first radius, the value of which depends on the theoretical die width, wherein a center point of the first radius of the first inlet contour section of the first inlet contour and a center point of the first radius of the first inlet contour section of the second inlet contour are arranged spaced apart from one another in the first plane at a center distance independent of the first die angle and second die angle, which corresponds to a sum of the die width and twice the value of the first radius,and generating a second inlet contour section with a second radius on the first inlet contour between the first inlet contour section and the first side surface and / or a second inlet contour section with a second radius on the second inlet contour between the first inlet contour section and the second side surface, wherein a radius ratio between a value of the second radius and the value of the first radius is set at 2.5 to 5, preferably 4.

[0025] For a better understanding of the invention, it is explained in more detail using the following figures.

[0026] They show in a highly simplified, schematic representation:

[0027] Fig. 1 the basic structure of a bending machine;

[0028] Fig. 2 a bending die with a basic geometry;

[0029] Fig. 3 shows a bending die according to the invention of an exemplary embodiment;

[0030] Fig. 4 is a block diagram of the method according to the invention;

[0031] Fig.5a a bent sheet metal workpiece with an impression on each of the legs;

[0032] Fig.5b is an exemplary diagram with the print length plotted against the second

[0033] Radius of the second inlet contour section; Fig.6a a diagram with the contact pressure on the workpiece plotted against the bending angle and

[0034] Fig.6b a diagram with a force on the workpiece plotted against the bending angle;

[0035] Fig.7 shows a bending die according to the invention of a further exemplary embodiment.

[0036] By way of introduction, it should be noted that in the variously described embodiments, identical parts are provided with identical reference symbols or component designations. The disclosures contained throughout the description can be applied analogously to identical parts with identical reference symbols or component designations. Furthermore, the positional information chosen in the description, such as top, bottom, side, etc., refers to the directly described and illustrated figure, and these positional information must be applied analogously to the new position in the event of a change in position.

[0037] Fig.l shows a highly simplified basic structure of a bending machine 1 for carrying out a bending process on a sheet metal workpiece 2. The bending machine 1 comprises a lower bending beam 3 with a lower tool holder 4 for receiving a lower tool 5. The lower bending beam 3 can, for example, be arranged on a base frame (not shown), which in turn can be arranged on a preferably flat floor, preferably firmly anchored in the floor.

[0038] Furthermore, the bending machine 1 comprises a movable upper bending beam 6 with an upper tool holder 7 for receiving an upper tool 8. An exemplary upper tool 8 is arranged in the upper tool holder 7, and an exemplary lower tool 5 is arranged in the lower tool holder 4. Depending on the bending process, a desired upper tool 8 and a desired lower tool 5 can be used. The bending die 5 according to the invention, described in more detail below, can be used as the lower tool.

[0039] To carry out the bending process, the upper tool 8 with the upper bending beam 6 can be moved in a generally vertical direction of movement Z towards the sheet metal workpiece 2, as indicated in Fig. 1 by the corresponding arrow, until the sheet metal workpiece 2 is clamped between the upper tool 8 and the lower tool 5 or the bending die. A suitable bending robot 10 (shown schematically in Fig. 1) can then grip a free section of the sheet metal workpiece 2, and the sheet metal workpiece 2 can be bent along a predetermined bending trajectory T, as indicated by the dashed line. For gripping the sheet metal workpiece 2, the bending robot 10 can comprise one or more interchangeable grippers (not shown), for example a known vacuum gripper.

[0040] Furthermore, the bending machine 1 can comprise one or more so-called backstops 9. The backstops 9 enable the sheet metal workpiece 2 to be positioned with repeatable precision on the lower tool 5. The bending machine 1 can also comprise a laser measuring device (not shown) to measure an actual value of a bending angle of the sheet metal workpiece 2 during the bending process. A target value for the bending angle can be specified via a control unit (not shown). The bending robot 10 can perform the bending process according to a corresponding bending trajectory T until the desired target bending angle is reached.

[0041] Fig. 2 shows a bending die 5' with a basic geometry. This basic geometry forms the basis for the geometry of the bending die 5 according to the invention, which is explained in more detail below with reference to Figs. 3 and 7. On the left in Fig. 2, the bending die 5' is shown in a side view. On the right in Fig. 2, a detail of area A is shown.

[0042] The bending die 5' comprises a substantially cuboid-shaped base body 11 with a height H, a width B, and a (not shown) length (normal to the plane of the drawing). The base body 11 comprises a substantially flat support surface 12 lying in a first plane E1. A substantially V-shaped recess 13 is provided in the support surface 12 in a known manner. The recess 13 is symmetrical with respect to a parting plane E2 normal to the first plane E1. In the longitudinal direction (normal to the plane of the drawing), the recess is connected to the opposite end faces of the base body 11. The recess 13 divides the support surface 12 into a first partial surface 12a and a second partial surface 12b.

[0043] The recess 13 comprises a flat first side surface 14a, which is inclined at a fixed first die angle α1 to the parting plane E2, and comprises a flat second side surface 14b opposite the first side surface 14a, which is inclined at a fixed second die angle α2 to the parting plane E2. The first side surface 14a is connected to the first partial surface 12a of the support surface 12 via a first inlet contour 15_1, and the second side surface 14b is connected to the second partial surface 12b of the support surface 12 via a second inlet contour 15_2. The partial surfaces 12a, 12b can each be connected tangentially to the corresponding inlet contour 15_1, 15_2. The first inlet contour 15_1 and the second inlet contour 15_2 each comprise a circular arc-shaped first section with a radius R in cross section.The inlet contours 15_1, 15_2 thus each comprise a cylindrical outer surface which extends in the longitudinal direction of the bending die 5'.

[0044] The radius R depends on a specified theoretical die width W and is, for example, 10% of the theoretical die width W. Within the context of the present invention, the theoretical die width W is understood to be the normal distance between two planes E3, E4, each of which is perpendicular to the first plane E1 and arranged tangentially to the inlet contours 15_1, 15_2. This is illustrated in Fig. 1 on the right in detail A, which shows a detailed view of the first inlet contour 15_1.

[0045] The centers M (or center axes) of the two inlet contours 15_1, 15_2 are spaced apart in the first plane El by a center distance L. The center distance L is L=W+2*R.

[0046] Figure 3 shows a bending die 5 according to an exemplary embodiment of the invention. On the left side of Figure 3, the bending die 5 is again shown in a side view. On the right side of Figure 3, a detail C is shown, which shows the first inlet contour 15_1 in an enlarged view.

[0047] The bending die 5, in turn, has a base body 11 with a support surface 12 in which a substantially V-shaped recess 13 is provided. "Substantially V-shaped" in the context of the present invention means that the recess 13 diverges in the direction of the support surface 12, but does not necessarily have to be symmetrical. The recess 13 comprises a first side surface 14a, which is inclined at a fixed first die angle α1 to the parting plane E2, and a second side surface 14b opposite the first side surface 14a, which is inclined (in the opposite direction) at a fixed second die angle α2 to the parting plane E2. The first side surface 14a is connected to the first partial surface 12a of the support surface 12 via a first inlet contour 15_1 and the second side surface 14b is connected to the second partial surface 12b of the support surface 12 via a second inlet contour 15_2.The basic structure corresponds to the bending die 5' of the basic form according to Fig.2, which is why repetitions are omitted and only the differences are discussed.

[0048] In the illustrated embodiment, the recess 13 is symmetrical with respect to the parting plane E2, i.e., the inlet contours 15_1, 15_2 are identical and the die angles a1, a2 are the same size. As can be seen in detail C, the inlet contours 15_1, 15_2 each comprise a first inlet contour section 15a with a first radius RI, the value of which depends on the theoretical die width W of the bending die 5. The theoretical die width W is defined as explained with reference to Fig. 2 and serves as a reference value in the bending die 5 according to Fig. 3. The theoretical die width W can, for example, be 4 to 150 mm.

[0049] Within the scope of the present invention, however, the recess 13 does not necessarily have to be symmetrical, but could, for example, have differently sized die angles al a2 and / or differently designed inlet contours 15_1 15_2. An example of an asymmetric recess is described in more detail below with reference to Fig. 7.

[0050] The value of the first radius RI can be, for example, 5-15% of the theoretical die width W, preferably 10%. The first inlet contour sections 15a are preferably each connected tangentially to the corresponding partial surface 12a, 12b of the support surface 12. The centers M1 of the first radii RI of the first inlet contour sections 15a of the inlet contours 15_1, 15_2 are spaced apart from one another in the first plane E1 by a center distance L, which is L = W+2*R1.

[0051] For an example theoretical die width W=20mm, the value of the first radius RI is 2mm and the center-to-center distance L is 24mm. The center-to-center distance L therefore only depends on the specified theoretical die width W and the value of the radius RI, but is independent of the first die angle α1 and the second die angle α2. This means that two bending dies 5 with the same theoretical die width W, the same value of the first radius RI and different first die angles α1 and / or different second die angles α2 have the same center-to-center distance L. The contact points for the sheet metal workpiece 2 thus remain the same for a specified theoretical die width W, regardless of the die angles α1, α2. Compared to the basic shape according to Fig.2, the first inlet contour 15_1 comprises a second inlet contour section 15b with a second radius R2, located between the first inlet contour section 15a and the first side surface 14a. Analogously, the second inlet contour 15_2 comprises a second inlet contour section 15b with a second radius R2, located between the first inlet contour section 15a and the second side surface 14b. Within the scope of the present invention, however, it would generally be sufficient if only one of the two inlet contours 15_1, 15_2 comprised a second inlet contour section 15b. The other inlet contour 15_1, 15_2 could, for example, be designed as in the basic form according to Fig. 2.

[0052] According to the invention, a radius ratio X between the value of the second radius R2 of the second inlet contour section 15b and the value of the first radius RI of the first inlet contour section 15a is 2.5 to 5. For the above-mentioned exemplary theoretical die width W=20mm with Rl=2mm, the second radius R2 thus results in a value of 5mm to 10mm. The center-to-center distance L between the centers Ml of the first radii RI is again 24mm.

[0053] According to an advantageous embodiment, the radius ratio X is between 3.5 and 4.5. Particularly preferably, the radius ratio X is 4. In the example mentioned (W=20, Rl=2mm), this corresponds to a value of the second radius R2 of R2=8mm.

[0054] Preferably, the first inlet contour sections 15a are each tangentially connected to the second inlet contour sections 15b. Alternatively or additionally, the second inlet contour section 15b of the first inlet contour 15_1 can be tangentially connected to the first side surface 14a of the V-shaped recess 13 and / or the second inlet contour section 15b of the second inlet contour 15_2 can be tangentially connected to the second side surface 14b of the V-shaped recess 13.

[0055] A first transition point U 1 (or a transition line seen normal to the plane of the drawing) of the (preferably tangential) transition from the first inlet contour section 15a to the second inlet contour section 15b of the first inlet contour 15_1 and a second transition point U2 of a transition from the first inlet contour section 15a to the second inlet contour section 15b of the second inlet contour 15_2 can be defined, for example, at a transition angle > of 100° < ß < 120°, preferably at 105° < ß < 115°, in particular at ß = 110°. The transition angle > is shown in Fig. 3 and corresponds to the angle between a first straight line Ga and a second straight line Gb (or planes normal to the plane of the drawing), whose intersection point lies in the second plane E2 and which are arranged at the transition points Ul, U2, each tangential to the corresponding inlet contour 15_1, 15_2. The respective point of contact essentially corresponds to the transition point Ul, U2 (orthe transition line) from the first inlet contour section 15a to the second inlet contour section 15b. Thus, at the transition point Ul, U2, there is a geometric Gl continuity between the first inlet contour section 15a (with first radius RI), the second inlet contour section 15b (with second radius R2) and the respective straight line Ga, Gb.

[0056] Depending on the selected transition angle >, the transition points Ul, U2 shift between the inlet contour sections 15a, 15b. The larger the transition angle □, the closer the transition points Ul, U2 are to the support surface 12 or the first plane El. The smaller the transition angle □, the further the transition points Ul, U2 are from the support surface 12 or the first plane El (each normal to the first plane El).

[0057] Since the first inlet contour sections 15a are preferably connected tangentially to the respective partial surface 12a, 12b of the support surface 12, the position of the center points M1 of the first inlet contour sections 15a is defined both in the direction parallel to the first plane E1 (by the specified center distance L) and in the direction normal to the first plane E1 (due to the tangentiality). Consequently, the position of the center points M2 of the second radii R2 of the second inlet contour sections 15b shifts depending on the transition angle □.

[0058] For comparison, the basic geometry of the bending die 5' according to Fig. 2 with the same die angles a1, a2 is shown in dashed lines on the left in Fig. 3. It can be seen that the V-shaped recess 13 of the bending die 5 according to the invention is narrower than the recess 13 of the bending die 5 due to the larger second radius R2 of the second inlet contour sections 15b. 1 with the basic geometry.

[0059] In general, the first die angle al can be, for example, al = 10° to al = 55°.

[0060] Standard dimensions are, for example, al = 15°, al = 42°, or al = 45°. According to an advantageous embodiment, the first die angle is al = 13° to al = 15°, in particular al = 14°, or al = 33° to al = 35°, in particular al = 34°. The same applies analogously to the second die angle a2.

[0061] The intersection point of the first side surface 14a and the second side surface 14b in the region of the parting plane E2 can be rounded by means of a rounding 16. This reduces the notch effect and increases the fatigue strength of the bending die 5.

[0062] A first chamfer 17a can be provided between the first partial surface 12a of the support surface 12 and a first outer surface 18a of the base body 11, which is parallel to the dividing plane E2. Similarly, a second chamfer 17b can be provided between the second partial surface 12b of the support surface 12 and a second outer surface 18b of the base body 11, which is parallel to the dividing plane E2. This improves accessibility for laser measurement.

[0063] Advantageously, a tool system can be provided that comprises a plurality of bending dies 5 according to the invention. Two or more bending dies 5 can be provided, each having the same theoretical die width W, the same center-to-center distance L, but different first die angles a2 and / or different second die angles a2. Due to identical contact points for the sheet metal workpiece 2 (see Fig. 1), bending dies 5 with different die angles a1, a2 can be easily combined. "Combining" means that the bending dies 5 can be arranged side by side on the lower tool holder 4 and used in the same bending process.

[0064] Figure 4 shows a block diagram illustrating the inventive method for producing a bending die 5, for example, according to Figure 3. Each block corresponds to a method step. Blocks with dashed lines represent optional steps.

[0065] In step S 1, a metallic, preferably cuboid-shaped, base body 11 is first provided, which has the substantially flat support surface 12 for the sheet metal workpiece 2.

[0066] Alternatively, the support surface 12 can also be produced in an optional second step S2, e.g., by means of a suitable, preferably machining, manufacturing process. In a third step S3, the substantially V-shaped recess 13 is produced in the base body 11. The recess 13 can optionally be produced such that it is symmetrical with respect to a parting plane E2 perpendicular to the first plane E1 (analogous to that shown in Fig. 3). In the recess 13, the flat first side surface 14a with the specified first die angle a1 and the flat second side surface 14b with the specified second die angle a2 are produced. The first die angle a1 and the second die angle a2 can, for example, be the same size (as shown in Fig. 3) or different (as shown in Fig. 7 and described in more detail below).

[0067] Of course, step S1 does not necessarily require a cuboid-shaped base body 11; rather, a semi-finished product could also be used, for example, in which a rough contour of the recess 13 is already provided. The geometry according to the invention can then be created in step S3 by fine machining the rough contour. The creation of the recess 13 can again be carried out using a suitable machining process.

[0068] In a further step S4, the first inlet contour 15_1 is created between the first side surface 14a and the first partial surface 12a of the support surface 12, and the second inlet contour 15_2 is created between the second side surface 14b and the second partial surface 12b of the support surface 12. In step S4a, the respective first inlet contour section 15a is created with the first radius RI, the value of which depends on the desired theoretical die width W. The value of the first radius RI can be, for example, 10% of the theoretical die width W. The center point Ml of the first radius RI of the first inlet contour section 15a of the first inlet contour 15_1 and the center point Ml of the first radius RI of the first inlet contour section 15a of the second inlet contour 15_2 are arranged, measured in the first plane E1, at a center distance L from each other, which is L = W+2*R1.

[0069] In step S4b, a second inlet contour section 15b with a second radius R2 is created between the first inlet contour section 15a of the first inlet contour 15_1 and the first side surface 14a and / or between the first inlet contour section 15a of the second inlet contour 15_2 and the second side surface 14ab. A value of the second radius R2 is determined according to the radius ratio X as a function of the value of the first radius RI. The radius ratio X is 2.5 to 5, preferably X=4. This means that, within the scope of the invention, a second inlet contour section 15b does not necessarily have to be created on both sides of the recess 13, but possibly also only on one side.

[0070] In an exemplary embodiment, the theoretical die width W can be 20, the value of the first radius RI can be 10% of the die width W, i.e., R1=2 mm, and the value of the second radius R2 can be 4*R1, i.e., R2=8 mm. The center-to-center distance L results in L=20+2*2 = 24 mm and is thus unchanged from the basic geometry shown in Fig. 2. Steps S4a and S4b can, of course, also be performed in reverse order.

[0071] In optional step S5, a first chamfer 17a can be created between the first partial surface 12a of the support surface 12 and a first outer surface 18a of the base body 11, parallel to the parting plane E2. Alternatively or additionally, a second chamfer 17b can also be created between the second partial surface 12b of the support surface 12 and a second outer surface 18b of the base body 11, parallel to the parting plane E2.

[0072] In the optional step S6, an intersection point of the first side surface 14a and the second side surface 14b in the region of the parting plane E2 can be rounded by means of a rounding 16.

[0073] At this point, it should be noted that the described steps S1-S6 do not necessarily have to be performed in the order shown in Fig. 4. The method can be adapted accordingly so that a bending die 5 with the features described above with reference to Fig. 3 can be produced.

[0074] Fig. 5a shows an exemplary sheet metal workpiece 2, which was bent at a fixed bending angle γ using the bending die 5 of the invention. The sheet metal workpiece 2 has two legs 2a, 2b, which are positioned at an opening angle β to each other. According to the common definition, the bending angle γ starts at 0° and extends to 180°, while the opening angle β behaves in exactly the opposite way.

[0075] On each of the two legs 2a, 2b, an imprint A is indicated, which results during the bending process from the force acting on the sheet metal workpiece 2 in the area of ​​the inlet contours 15_1, 15_2. The imprints A each have an imprint length Y in the longitudinal direction of the legs 2a, 2b, as shown in Fig. 5a. The imprints A also each have a specific imprint depth (not shown).

[0076] Fig. 5b shows a diagram in which the impression length Y of the impression A on the bent sheet metal workpiece 2 is plotted against the value of the second radius R2 of the second inlet contour section 15b of the inlet contours 15_1, 15_2. The bending die 5 has a symmetrical V-shaped recess 13, a theoretical die width W=20mm, and a value of the first radius of RI=2mm, i.e., 0.1*W.

[0077] The diagram shows that the minimum imprint length Y lies in the range between R2 = 6 mm and R2 = 10 mm, in particular in the range R2 = 8 mm. This corresponds to a radius ratio X of X = 3 to X = 5, in particular X = 4. It can be seen from this that the radius ratio X defined according to the invention can advantageously reduce, and in particular minimize, the imprint length Y on the bent sheet metal workpiece 2. The reduction in the imprint length Y results from the fact that the legs 2a, 2b roll over the inventive run-in contour 15 to a greater extent and slide less. In the example shown, the imprint length Y is approximately 1.4 mm for X = 4 or R2 = 8 mm.

[0078] Fig. 6a shows a diagram in which a contact pressure p on the sheet metal workpiece 2 is plotted against the bending angle y. The solid line with a marker corresponds to the bending die 5 according to the invention shown in Fig. 3. The solid line without a marker corresponds to the bending die 5' of the basic geometry shown in Fig. 2, which is shown for comparison.

[0079] It can be seen that the curve of the bending die 5 according to the invention shows a significant drop in the contact pressure p. The drop lies in the range of the bending angle y in which the transition points U1, U2 (or transition lines) of the (preferably tangential) transitions between the first inlet contour sections 15a (e.g. with R1=2mm) and the second inlet contour sections 15b (e.g. with R2=8mm) lie. Due to the second radius R2 being larger than the first radius R1, a significantly lower contact pressure p and consequently a lower surface pressure on the sheet metal workpiece 2 results at the second inlet contour section 15b. The imprint depth of the impressions A can thus be reduced due to the reduced surface pressure and due to a smaller relative movement between the sheet metal workpiece 2 and the bending die 5. Fig.6b shows a diagram in which an actuating force F (e.g. measured at the upper bending beam 6 or upper tool 8 - see Fig.l) is again plotted against the bending angle y. The bending force F was measured during a bending process using the bending die 5 according to the invention. The solid line with a marker again corresponds to the bending die 5 according to the invention shown in Fig. 3. The solid line without a marker corresponds to the bending die 5' of the basic geometry shown in Fig. 2, which is shown for comparison.

[0080] It can be seen that in the bending die 5 according to the invention, the actuating force F is at a higher level over a longer bending angle y than in the bending die 5' of the basic geometry. While in the bending die 5' the actuating force F decreases significantly in the further course in the dashed area, the actuating force F in the bending die 5 remains essentially constant over a longer bending angle y. The dashed area in which the curves diverge is located at the point of the transition points Ul, U2 (or the transition lines) between the first inlet contour sections 15a (e.g. with Rl=2mm) and the second inlet contour sections 15b (e.g. with R2=8mm).

[0081] As can be seen from the curves, the maximum value of the actuating force F for bending die 5 is essentially the same as for bending die 5', but not higher. This means that when using bending die 5, no higher demands are placed on the upper tool or bending machine than for bending die 5' with the basic geometry.

[0082] Fig. 7 shows another exemplary embodiment of the bending die 5 according to the invention. To avoid repetition, only the differences from the embodiment shown in Fig. 3 will be discussed in more detail below. Regarding the remaining features, reference is made to the above explanations, which apply analogously.

[0083] The bending die 5 in turn has a substantially V-shaped recess 13. The first side surface 14a is inclined at the first die angle α1 to the parting plane E2, and the second side surface is inclined in the opposite direction at the second die angle α2 to the parting plane E2. In contrast to the embodiment according to Fig. 3, however, the recess 13 is designed asymmetrically here, in that the first die angle α1 is greater than the second die angle α2. The first inlet contour 15_1 and / or the second inlet contour 15_2 can be designed as explained with reference to Fig. 3, in particular detail C, i.e. either the first inlet contour 15_1 can comprise a second inlet contour section 15b and / or the second inlet contour 15_2 can comprise a second inlet contour section 15b.The center distance L is again only dependent on the theoretical die width W and the value of the radius RI, but not on the die angles a1, a2 and results in L=W+2*R1.

[0084] It can be seen that due to the larger first die angle a1 (compared to the second die angle a2), a first contact point Ka of a first leg 2a of a sheet metal workpiece 2 being bent on the bending die 5 is further away from the parting plane E2 than a second contact point Kb of the second leg 2b (for the sake of simplicity, the sheet metal workpiece 2 is only indicated by a dash-dotted line in Fig. 7). The larger distance results in a first angular velocity coa of the first leg 2a being lower than a second angular velocity cob of the second leg 2b during the bending process.

[0085] If the bending machine 1 is operated manually, it is advantageous if the bending die 5 is arranged in the lower tool holder 4 of the lower bending beam 3 so that the larger die angle a1 faces the operator. The relatively lower first angular velocity coa of the first leg 2a can increase operator safety.

[0086] The embodiments show possible embodiments, whereby it should be noted at this point that the invention is not limited to the specifically illustrated embodiments thereof, but rather various combinations of the individual embodiments with each other are also possible and this possibility of variation lies within the skill of the person skilled in the art in this technical field due to the teaching of technical action by means of the objective invention.

[0087] The scope of protection is determined by the claims. However, the description and the drawings must be used to interpret the claims. Individual features or combinations of features from the various embodiments shown and described can represent independent inventive solutions in themselves. The problem underlying the independent inventive solutions can be derived from the description. All information on value ranges in this description is to be understood as including any and all sub-ranges thereof. For example, the reference 1 to 10 is to be understood as including all sub-ranges starting from the lower limit of 1 and the upper limit of 10. This means that all sub-ranges begin with a lower limit of 1 or greater and end with an upper limit of 10 or less, for example 1 to 1.7, or 3.2 to 8.1, or 5.5 to 10.

[0088] For the sake of clarity, it should finally be pointed out that, in order to better understand the structure, some elements have been shown out of scale and / or enlarged and / or reduced in size.

[0089] Reference symbol list

[0090] 1 bending machine RI first radius

[0091] 2 Sheet metal workpiece R2 Second radius

[0092] 2a First leg M Center Radius R

[0093] 2b Second leg Ml Center of first radius RI

[0094] 3 Lower bending beam M2 center of second radius R2

[0095] 4 Lower tool holder W Theoretical die width

[0096] 5, 5' bending die, lower tool L center distance

[0097] 6 Upper bending beam al First die angle

[0098] 7 Upper tool holder a2 Second die angle

[0099] 8 Upper tool ß bending angle,

[0100] 9 Back stop y opening s angle

[0101] 10 Bending robot □ Transition angle

[0102] 1 1 Basic body Ga First line

[0103] 12 Support surface Gb Second straight line

[0104] 12a First partial area U 1 First transition point

[0105] 12b Second partial area U2 Second transition point

[0106] 13 V-shaped recess El First level

[0107] 14a First side surface E2 division plane

[0108] 14b Second side surface B width

[0109] 15_1 First inlet contour H height

[0110] 15_2 Second inlet contour Y impression length

[0111] 15a First inlet contour section Ka First contact point

[0112] 15b Second inlet contour section Kb Second contact point

[0113] 16 Rounding

[0114] 17a First phase

[0115] 17b Second phase

[0116] 18a First outer surface

[0117] 18b Second outer surface

[0118] Z Direction of movement

[0119] T bending trajectory

[0120] R radius

Claims

P a t e n t a n s p r ü c h e 1. Bending die (5) for a bending machine (1) for performing a bending operation on a sheet metal workpiece (2), wherein the bending die (5) comprises a support surface (12) for the sheet metal workpiece (2), which lies in a first plane (El), wherein a substantially V-shaped recess (13) is provided on the support surface (12), which divides the support surface (12) into two partial surfaces (12a, 12b), wherein the recess (13) comprises a flat first side surface (14a) which is inclined at a predetermined first die angle (α1) with respect to a parting plane (E2) of the recess (13) which is normal to the first plane (El), and an opposite flat second side surface (14b) which is inclined at a predetermined second die angle (α2) with respect to the parting plane (E2),wherein the first side surface (14a) is connected to the first partial surface (12a) via a first inlet contour (15_1) and the second side surface (14b) is connected to the second partial surface (12b) via a second inlet contour (15_2), wherein the first inlet contour (15_1) and the second inlet contour (15_2) each comprise a first inlet contour section (15a) with a first radius (RI), the value of which is dependent on a fixed theoretical die width (W) of the bending die (5), characterized in that a center point (Ml) of the first radius (RI) of the first inlet contour section (15a) of the first inlet contour (15_1) and a center point (Ml) of the first radius (RI) of the first inlet contour section (15a) of the second inlet contour (15_2) in the first plane (El) independently of first die angle (al) and second die angle (a2) are spaced apart from each other at a center distance (L),which is L = W + 2 * RI and that the first inlet contour (15_1) comprises a second inlet contour section (15b) lying between the first inlet contour section (15a) and the first side surface (14a) with a second radius (R2) and / or that the second inlet contour (15_2) comprises a second inlet contour section (15b) lying between the first inlet contour section (15a) and the second side surface (14b) with a second radius (R2), wherein a radius ratio (X) between a value of the second radius (R2) and the value of the first radius (RI) is 2.5 < X < 5., 2. Bending die (5) according to claim 1, characterized in that the recess (13) is symmetrical with respect to the parting plane (E2).

3. Bending die (5) according to claim 1 or 2, characterized in that the first inlet contour section (15a) of the first inlet contour (15_1) is connected tangentially to the first partial surface (12a) and / or that the first inlet contour section (15a) of the second inlet contour (15_2) is connected tangentially to the second partial surface (12b).

4. Bending die (5) according to one of claims 1 to 3, characterized in that the first die angle (al) and the second die angle (a2) are equal or that the first die angle (al) and the second die angle (a2) differ.

5. Bending die (5) according to one of claims 1 to 4, characterized in that the first inlet contour section (15a) and the second inlet contour section (15b) of the first inlet contour (15_1) are connected tangentially and / or that the first inlet contour section (15a) and the second inlet contour section (15b) of the second inlet contour (15_2) are connected tangentially.

6. Bending die (5) according to one of claims 1 to 5, characterized in that the second inlet contour section (15b) of the first inlet contour (15_1) is connected tangentially to the first side surface (14a) of the recess (13) and / or that the second inlet contour section (15b) of the second inlet contour (15_2) is connected tangentially to the second side surface (14b) of the recess (13).

7. Bending die (5) according to one of claims 1 to 6, characterized in that the theoretical die width (W) is 4 < W < 150 mm.

8. Bending die (5) according to one of claims 1 to 7, characterized in that the value of the first radius (RI) is 5-15% of the theoretical die width (W), preferably 10%.

9. Bending die (5) according to one of claims 1 to 8, characterized in that the radius ratio (X) between the value of the second radius (R2) and the value of the first radius (RI) is 3.5 < X < 4.5, preferably X = 4.

10. Bending die (5) according to one of claims 1 to 9, characterized in that a first transition point (Ul) of a transition from the first inlet contour section (15a) to the second inlet contour section (15b) of the first inlet contour (15_1) and a second transition point (U2) of a transition from the first inlet contour section (15a) to the second inlet contour section (15b) of the second inlet contour (15_2) are defined at a transition angle (Q) of 100° < Q < 120°, preferably at 105° < Q < 115°, in particular at □ = 110°.

11. Bending die (5) according to one of claims 1 to 10, characterized in that the first die angle (al) is 10° < al < 55°, preferably al = 15°, al = 42° or al = 45° and / or that the second die angle (a2) is 10° < a2 < 55°, preferably a2 = 15°, a2 = 42° or a2 = 45°.

12. Bending die (5) according to claim 11, characterized in that the first die angle (al) is 13° < al < 15°, preferably al = 14°, or (al) 33° < al < 35°, preferably al = 34° and / or that the second die angle (a2) is 13° < a2 < 15°, preferably a2 = 14°, or 33° < a2 < 35°, preferably a2 = 34°.

13. Bending die (5) according to one of claims 1 to 12, characterized in that an intersection point of the first side surface (14a) and the second side surface (14b) is rounded by means of a rounding (16).

14. Bending die (5) according to one of claims 1 to 13, characterized in that a first chamfer (17a) is provided between the first partial surface (12a) of the support surface (12) and a first outer surface (18a) of the base body (11) lying parallel to the parting plane (E2) and / or that a second chamfer (17b) is provided between the second partial surface (12b) of the support surface (12) and a second outer surface (18b) of the base body (11) lying parallel to the parting plane (E2).

15. Tool system comprising a plurality of bending dies (5), each designed according to one of claims 1 to 14, wherein at least two bending dies (5) with the same theoretical die width (W), the same center distance (L) and different first die angles (al) and / or second die angles (a2) are provided.

16. Bending machine (1) for carrying out a bending process on a sheet metal workpiece (2), comprising a lower bending beam (3) with a lower tool holder (4) for receiving a lower tool, an upper bending beam (6) with an upper tool holder (7) for receiving an upper tool (8), at least one lower tool and at least one upper tool (8), characterized in that the at least one lower tool is a bending die (5) according to one of claims 1 to 14.

17. Bending machine (1) according to claim 16, characterized in that the bending machine (1) comprises a tool system according to claim 15.

18. Method for producing a bending die (5) for a bending machine (1) for carrying out a bending operation on a sheet metal workpiece (2), wherein the following steps are carried out: - providing a metallic, preferably cuboid-shaped, base body (11) with a support surface (12) for the sheet metal workpiece (2) lying in a first plane (El) or producing the support surface (12) on the base body (11), - producing a substantially V-shaped recess (13) dividing the support surface (12) into two partial surfaces (12a, 12b) with a fixed theoretical die width (W) in the support surface (12), - producing a flat first side surface (14a) which is inclined at a fixed first die angle (α1) with respect to a parting plane (E2) perpendicular to the first plane (α1) in the recess (13) and an opposite flat second side surface (14b) which is inclined at a fixed second die angle (α2) with respect to the parting plane (E2), - generating a first inlet contour (15_1) between the first side surface (14a) and the first partial surface (12a) and a second inlet contour (15_2) between the second side surface (14b) and the second partial surface (12b), wherein the inlet contours (15_1, 15_2) each have a first inlet contour section (15a) with a first radius (RI), the value of which depends on the theoretical die width (W), wherein a center point (Ml) of the first radius (RI) of the first inlet contour section (15a) of the first inlet contour (15_1) and a center point (Ml) of the first radius (RI) of the first inlet contour section (15a) of the second inlet contour (15_2) are arranged spaced apart from one another in the first plane (El) at a center point distance (L) independent of the first die angle (al) and second die angle (a2), which is L = W + 2 * RI, and - Creating a second inlet contour section (15b) with a second radius (R2) on the first inlet contour (15_1) between the first inlet contour section (15a) and the first side surface (14a) and / or a second inlet contour section (15b) with a second radius (R2) on the second inlet contour (15_2) between the first inlet contour section (15a) and the second side surface (14b), wherein a radius ratio (X) between a value of the second radius (R2) and the value of the first radius (RI) is set to 2.5 < X < 5, preferably X = 4.

19. Method according to claim 18, characterized in that a bending die (5) is produced according to one of claims 2 to 14.

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