METHOD FOR JOINING TWO SHEETS WITH A VARIABLE TOTAL THICKNESS

Description

[0001] The invention relates to a method for joining at least two superimposed sheets with a variable total thickness by means of a clinching device which has at least one punch and a die arranged coaxially thereto, and at least the punch is arranged to be movable in an axial direction relative to the die in a manner controlled by an electronic control system, wherein the two sheets are arranged in a plane between the punch and the die, and the penetration depth required for joining the sheets is adjustable, wherein before the sheets are joined the current total thickness is determined with the aid of the control system and the penetration depth is adjusted as a function of the total thickness.

[0002] Such a method is known, for example, from EP 3 020 498 B1. A similar method is known from DE 20 2019 104 412 U1.

[0003] To join two superimposed sheets by forming, they are placed one on top of the other between the punch and the die. The sum of the sheet thicknesses of the first and second sheets determines the total thickness, which therefore varies depending on the sheets used. The punch is lowered onto the sheets and pressed down, forcing the material into the die or into the cavity formed by the die and an anvil. To enlarge the cavity so that the displaced material can be accommodated, several die segments are usually provided, which can move transversely to the vertical axis of the base body during the forming process. The anvil is pressed into the base body.

[0004] To achieve a joint that is optimally formed in terms of holding force and / or visual appearance, it is necessary to assign a die with a specially adapted die depth to each joining task, which is defined in particular by the sheet thickness, sheet materials, sheet surfaces, and / or joining direction. This determines the penetration depth. However, several different joining tasks often have to be performed on a single component. In operational applications, it is therefore primarily for cost reasons to perform as many joining tasks as possible with the same die, as this reduces the number of required joining devices and thus, above all, the investment costs associated with their acquisition.

[0005] If the die depth is fixed, different joining tasks can only be performed with the same die if it is appropriately averaged out by accepting compromises. A compromise die depth enables the desired reduction in the number of required drive units, but has the disadvantage that usually none of the completed joining tasks exhibits an optimal appearance and / or holding force. If the depth is too large, the necessary holding force is lacking; if it is too small, the appearance of the joint suffers.

[0006] Also known from DE 10 2015 016 957 A1 is a method for joining at least two superimposed sheets with a variable total thickness by means of a clinching device which has at least one punch and a die arranged coaxially thereto, and at least the punch is arranged so as to be movable in an axial direction relative to the die that can be controlled by an electronic control system, wherein the two sheets are arranged in a plane between the punch and the die, and the penetration depth required for joining the sheets is adjustable, wherein before the sheets are joined, the current total thickness is determined with the aid of the control system and the penetration depth is set as a function of the total thickness, wherein in each case the penetration depth is assigned to a total thickness or a total thickness range and the punch is moved axially from a first zero position into a position in which it rests on the upper side of the first sheet.The joining device known for implementing this process solves the aforementioned problem by means of an anvil that is movably mounted in the base body and designed to be fixable in different positions so that the die depth is formed at different depths. However, this document does not explain how variable adjustment of the die depth and the fixation of the anvil can be achieved.

[0007] From US 2001 / 0002506 A1 a device and a method for mechanically joining metal sheets are known, which can be used to automate production and sensors and actuators are provided with which various process parameters, including different sheet thicknesses, can be stored.

[0008] A clinching device with an adjustable penetration depth can be used to join sheets of varying thickness. This means that sheets of different thicknesses can be joined using the same device if the penetration depth is adapted to the respective total thickness of the sheets lying on top of each other. The penetration depth must be set by the machine operator. If the penetration depth is not set correctly, the same problem arises that also occurs with devices where the die has a predetermined volume. If the penetration depth is set too large in relation to the total thickness of the two sheets, the necessary holding force is lacking; if the joining depth is set too small, the appearance of the joint suffers. In the worst case, damage to the device cannot even be ruled out.

[0009] A similar problem arises simply because fluctuations in sheet thickness cannot be ruled out. Even if the same type of sheet is processed over a longer period of time, the total thickness of the overlapping sheets is subject to tolerance fluctuations. If the thickness tolerances of the two sheets add up, it might be more sensible to increase the penetration depth to achieve a secure joint. However, detecting such tolerance fluctuations requires an extremely experienced and attentive machine operator.

[0010] Based on this, the invention is based on the object of improving the method described at the outset in such a way that a good joining connection can be produced on sheets with a variable total thickness and that process reliability is guaranteed regardless of the experience of the machine operator.

[0011] This problem is solved by a method according to claim 1, claim 2 or claim 9.

[0012] Due to this design, the volume of the die always matches the volume of the displaced material, so that a secure connection is achieved and damage to the device is excluded because the volume of the die will never be smaller than the volume to be displaced.

[0013] The penetration depth can be adjusted continuously or in steps.

[0014] The determination of the total thickness and the setting of the penetration depth is achieved with the following steps: 1. Storing a plurality of different total thicknesses or total thickness ranges in the control system, 2. Assigning a penetration depth to a total thickness or to a total thickness range and then 3. calibrating the clinching device, 4. Positioning the clinching device with respect to the sheets to be joined such that the die rests on the underside of the second sheet, 5. Axial movement of the punch into a position in which the punch rests on the top side of the first sheet, 6. Determining the distance traveled by the punch, 7. Determining the total thickness from the distance traveled by the punch and the calibrated zero position of the die, 8. Comparing the determined total thickness with the stored total thicknesses or total thickness ranges, 9. Selecting the value for the penetration depth assigned to the determined total thickness, 10. Setting the penetration depth depending on the comparison made, and 11.Joining the two sheets with the set penetration depth. Of course, the necessary remaining base thickness must be taken into account. or 1. Saving a plurality of different total thicknesses or total thickness ranges in the control system, 2. Assigning a penetration depth to a total thickness or total thickness range, 3. Axial movement of the punch from a first zero position to a position in which the punch rests on the top side of the first sheet, 4. Determining the traveled distance of the punch, 5. Axial movement of the die from a second zero position to a position in which the die rests on the underside of the second sheet, 6. Determining the traveled distance of the die, 7. Determining the total thickness from the distance between the first zero position and the second zero position and the traveled distances of the punch and die, 8. Comparing the determined total thickness with the stored total thicknesses or total thickness ranges, 9.Select the penetration depth value associated with the determined total thickness, 10. Adjust the penetration depth based on the comparison made, and 11. Join the two sheets with the adjusted penetration depth.

[0015] To calibrate the clinching device, the punch is preferably moved from a zero position in the axial direction until it rests against the die and the path traveled by the punch then defines the zero position of the die, which is stored in the control system.

[0016] To adjust the penetration depth, an anvil is preferably provided, which is arranged concentrically in the die and can be displaced axially relative to the die. The anvil is driven by an adjusting device that is either wedge-shaped or stepped. If the adjusting device is wedge-shaped, the penetration depth can be adjusted continuously; if the adjusting device is stepped, the penetration depth is adjusted in corresponding steps.

[0017] The invention will be described in more detail below with the aid of a drawing. It shows: Figure 1 - a partial view of a clinching device in its initial position in longitudinal section; Figure 2 - an enlarged partial view from Figure 1 ; Figure 3 - a detail from Figure 2 ; Figure 4 - the representation according to Figure 1 in measuring position; Figure 5 - an enlarged partial view of Figure 4 ; Figure 6 - a detail from Figure 5; Figure 7 - the representation according to Figure 1 after clinching; Figure 8 - an enlarged partial view from Figure 7 ; Figure 9 - a detail from Figure 8 ; Figure 10 - a first embodiment of a die in longitudinal section; Figure 11 - an enlarged view of Figure 10 ; Figure 12 - the section along the line XII-XII to Figure 10 ; Figure 13 - a die with a punch arranged above it in cross-section; Figure 14a - the representation according to Figure 13 before a joining process with a first joining task; Figure 14b - the representation after Figure 14a after the joining process; Figure 14c - an enlarged detail after Figure 14a .

[0018] The sheets B 1 , B 2 to be joined are placed one on top of the other between the upper tool carrier 10.1 and the lower tool carrier 10.2 of a clinching tool 10 of the known type. In the upper tool carrier 10.1, a punch 11 is mounted so as to be displaceable in the axial direction A. The lower tool carrier 10.2 contains the die 12 with the anvil 12.1 arranged concentrically thereto. Reference numeral 20 indicates an electronic control system which controls the clinching device 10 and its individual components. The anvil 12.1 is driven by the actuating element 13 which is arranged so as to be displaceable in its longitudinal direction L and which can have a stepped cross-section, as indicated by 13.1, or a wedge-shaped cross-section.

[0019] The initial position of the clinching device 10 is in the Figures 1 to 3shown. The punch 11 and the die 12 are in their respective zero positions A S0 , A M0 . After the sheets B 1 , B 2 have been brought into a plane between the upper tool carrier 10.1 and the lower tool carrier 10.2, the punch 11 and the die 12 are moved in the axial direction A until the punch 11 rests on the top side B 10 of the sheet B 1 and the die 12 rests on the bottom side B 20 of the second sheet B 2 and the punch 11 and die 12 are then in their measuring positions A S1 , A M1. The total thickness D 1 of the first sheet B 1 and the second sheet B 2 corresponds in this position to the distance between the punch 11 and the die 12.

[0020] The penetration depth DT i must generally be smaller than the total thickness D i of the sheets B 1 , B 2 . It results from the path of the punch 11 into the die 12 and the volume formed by the cavity 12.3 within the die 12, which is variable due to the anvil 12.1 being movable in the axial direction A.

[0021] Different total thicknesses or total thickness ranges D i for different sheets B 1 , B 2 to be joined can be stored in the controller 20. Thickness ranges D i can include the sheet thickness ± a specified tolerance or different sheet thicknesses without tolerance.

[0022] The total thickness D 1 can be calculated from the fixed distance in the zero position of punch 11 and die 12 and the path traveled by punch 11 from its zero position A S0 and its measuring position A S1 or the path traveled by die 12 from its zero position A M0 to its measuring position A M1.

[0023] Once the total thickness D 1 of the sheets B 1 , B 2 has been determined as above, this value is compared with the values ​​D i stored in the controller 20 and the penetration depth DT i , which is assigned to the corresponding value in the controller 20, is set by displacing the anvil 12.1 in the axial direction A from the underside B 20 of the second sheet 2 into the interior of the die 12. Once this penetration depth DT i has been set, the punch 11 is displaced in the direction of the die 12 and the two sheets B 1 , B 2 are joined together and thus connected.

[0024] The total thickness D i is determined before each joining process of the newly inserted sheets B 1 , B 2 and is used for process monitoring. As long as the total thickness D i is within a tolerable range, the penetration depth DT i is not adjusted. If the penetration depth DT is continuously adjustable, the control system 20 can be configured to adjust the penetration depth DT i individually for each joining process by moving the anvil 12.1 in the axial direction A.

[0025] An alternative way to determine the total thickness D i of the two sheets B 1 , B 2 is as follows: Before the two sheets B 1 , B 2 are inserted, the punch 11 is moved in the axial direction A onto the die 12 until it has direct contact with the anvil 12.1. The path traveled by the punch 11 then defines the zero position A MO ( Figure 1) of the die 12, which is stored in the control system 20. The sheets B 1 , B 2 are placed in a plane between the die 12 and the punch 11.

[0026] The clinching device 10 is then positioned with respect to the sheets B 1 , B 2 to be joined such that the die 12 rests against the underside B 20 of the second sheet B 2 . The punch 11 is displaced in the axial direction A until it rests against the top side B 10 of the first sheet B 1 . The path traveled by the punch 11 is then determined, and the total thickness D i of the two sheets B 1 , B 2 is determined from the path traveled by the punch 11 and the calibrated zero position A MO of the die 12. In this case too, a plurality of penetration depths DT i were previously stored in the controller 20. The determined total thickness D 1 is then compared with the stored total thicknesses or total thickness ranges D i , and the value for the penetration depth DT 1 assigned to the determined total thickness D 1 is selected, and the clinching process is then started. First example:

[0027] In the Figures 10 and 14In the more schematically illustrated first embodiment, the die 12 consists mainly of the base body 12.2 and the anvil 12.1, which is displaceably mounted therein and can be fixed in at least two positions and which together form a cavity 12.3 into which the workpiece is inserted. The base body 12.2 of the die 12 is fastened in the lower tool carrier 10.2. Transverse to the joining direction (= axial direction A), an adjusting element 13 is provided, which is formed by a stepped adjusting slide 13.1, which is slidably guided in the longitudinal direction L in a recess 10.3 provided in the lower tool carrier 10.2. In the simplest case, the recess 10.3 is designed as a through-bore. In a two-part tool carrier 10.2, it is formed by two opposing grooves. The control slide 13.1 is driven by an electric motor, hydraulically, or pneumatically. The control slide 13.1 is provided with a slot 13.1.1 in the center, which the anvil 12 engages.1 with its lower end 12.1.1 and is mounted in a bore provided in the lower tool holder 10.2, running in the joining direction. For better guidance in the slot 13.1.1, the lower end 12.1.1 of the anvil 12.1 is diametrically flattened, as shown in . Figure 11can be seen. The adjusting slide 13.1 is formed with a step 13.1.1, which is realized by a chamfer 13.1.2 and thus has a first area, thinner in the joining direction, with which a first, greater penetration depth DT of the die 12 is set, and a second area, thicker in the joining direction, with which a second, smaller penetration depth is set. The cavity 12.3 is thus enlarged or reduced. By moving the adjusting slide 13.1 in the longitudinal direction L, the annular bead 12.1.2 of the anvil 12.1 rests either on the first area 13.3, which results in a greater penetration depth DT, or on the second area 13.4, which results in a smaller penetration depth DT, and is supported in the tool carrier 10.2 via the adjusting slide 13.1. To be able to set more than two penetration depths DT, additional steps can be provided in the adjusting slide 13.1. The angle of the chamfer 13.1.2 is selected so that the bead 12.1.2 can easily slide up or down over the step 13.1.1. It is not absolutely necessary to slot the adjusting slide 13.1. The lower end of the anvil 12.1 could also be formed by the annular bead 12.1.2, which then forms a flange that rests on the adjusting slide 13.1 if the guidance of the anvil 12.1 in the upper part of the tool carrier 10.2 is sufficient and additional support in the lower area does not appear necessary. In this case, the adjusting slide 13.1 can be designed without a slot.

[0028] The die 12 can consist of several die segments 12a, 12b, as described for the second embodiment. The additional components there can also be used in the die according to this first embodiment. Only the adjusting means 13 is replaced. Second embodiment:

[0029] The die 12 consists of the base body 12.2, the anvil 12.1, which is movably mounted therein and can be fixed in various positions, the opposing die segments 12a, 12b, which are mounted in a casing sleeve 14 with a substantially rectangular cross-section and open at the top, which is attached to the base body 12.2, and the tool carrier 10.2, in which the base body 12.2 is fastened by means of screws 16. The die segments 12a, 12b are mounted in the base body 12.2 so that they can be moved transversely to the joining direction against the force of leaf springs 15.

[0030] The die segments 12a, 12b, together with the upper end of the anvil 12.1, form a cavity 12.3 into which the workpiece is inserted. To change the depth of the cavity 12.3, the position of the anvil 12.1 in the base body 12.2 can be continuously adjusted and fixed in place. For this purpose, a force-operated wedge 13.2 is provided, which is also arranged to be movable transversely to the vertical axis H (= joining direction). In addition to the adjusting movement, the wedge 13.2 also exerts a bearing force on the anvil 12.1, which determines the holding force required during joining.

[0031] The wedge 13.2 is preferably designed to be self-locking in order to absorb the necessary holding forces. It can be driven by any means, preferably hydraulically or pneumatically. Drive via a stepper motor or lever mechanism is also conceivable.

[0032] In the Figure 14In the position shown, the anvil 12.1 has been moved far upwards, so that a small cavity 12.3 is formed for joining thin sheets B 1 , B 2 . For joining, the sheets B 1 , B 2 are placed against the die 12 and the punch 11 is moved towards the die 12. The material of the sheets B 1 , B 2 is deformed into the cavity 12.3, with the die segments 12a, 12b being displaced transversely to the vertical axis (H) against the force of the leaf springs 15, whereby the cavity 12.3 enlarges in the radial direction. Of course, the die 12 can also have just a single die element or several immovable die segments.

[0033] At the Figure 13In the joining task shown, thicker sheets B 1 , B 2 are to be joined together. For this purpose, the wedge 13.2 is moved to the right (in the drawing), which shifts the anvil 12.1 downward and forms a larger cavity 12.3. The joining is carried out as previously described. Instead of joining the overlapped sheets B 1 , B 2 by clinching, they can also be joined using semi-tubular self-piercing rivets. A rivet (not shown here) is then pressed into the cavity 12.3.

[0034] The explanations given for this embodiment can also apply analogously to the first embodiment if the wedge 13.2 is replaced by the adjusting slide 13.1 (and vice versa). List of reference symbols

[0035] 10Clinching device 10.1Tool holder 10.2Tool holder 10.3Recess 11Punch 12Die 12.1Anvil 12.1.2Bead 12.2Base body 12.3Cavity 12a, bDie segment 13Adjusting means 13.1Adjusting slide 13.1.1Step 13.1.2Bevel 13.1.3Slot 13.2Wedge 13.3First area 13.4Second area 14Sleeve 15Leaf spring 16Screw 20Electronic control AAxial direction A S0 First zero position A S1 Measuring position A M0 Second zero position A M1 Measuring position B 1, B 2 Sheets B 10 Top side B 20 Bottom side D i Total thickness / Total thickness range D 1 Current total thickness DT i Penetration depth DT 1 current penetration depth H vertical axis LLongitudinal direction

Claims

1. A method for joining at least two metal sheets (B1, B2) resting on one another with a variable total thickness (Di) by means of a clinching device (10) comprising at least one punch (11) and a die (12) arranged coaxially to said punch, and at least the punch (11) is arranged so as to be controllable by means of an electronic control unit (20) and movable in an axial direction (A) relative to the die (12), wherein the two metal sheets (B1, B2) are arranged in a plane between the punch (11) and the die (12), and the penetration depth (DT) necessary for joining the metal sheets (B1, B2) is adjustable, wherein before joining the metal sheets (B1, B2), the current total thickness (D1) is determined with the aid of the control unit (20) and the penetration depth (DT1) is set depending on the total thickness (Di), characterized by the following steps: 1.1 Storing a number of different total thicknesses or total thickness ranges (Di) in the control unit (20), 1.2 Assigning a penetration depth (DTi) to a total thickness or to a total thickness range (Di), 1.3 Calibrating the clinching device (10) 1.4 Positioning of the clinching device (10) with respect to the sheets to be joined (B1, B2) to be joined in such a way that the die (12) rests against the underside (B20) of the second sheet (B2), 1.5 Axially moving the punch into a position (AS1) in which the punch (11) rests against the upper side (B10) of the first metal sheet (B1), 1.6 Detecting the path covered by the punch (11), 1.7 Detecting the total thickness (D1) from the path covered by the punch (11) and the calibrated zero position of the die (12), 1.8 Comparing the detected total thickness (D1) with the stored total thicknesses or total thickness ranges (Di), 1.9 Selecting the value assigned to the detected total thickness (D1) for the penetration depth (DT), 1.10 Adjusting the penetration depth (DT) depending on the comparison made, and 1.11 Joining the two metal sheets (B1, B2) with the set penetration depth (DT).

2. A method for joining at least two metal sheets (B1, B2) resting on one another with a variable total thickness (Di) by means of a clinching device (10) comprising at least one punch (11) and a die (12) arranged coaxially to said punch, and at least the punch (11) is arranged so as to be controllable by means of an electronic control unit (20) and movable in an axial direction (A) relative to the die (12), wherein the two metal sheets (B1, B2) are arranged in a plane between the punch (11) and the die (12), and the penetration depth (DT) necessary for joining the metal sheets (B1, B2) is adjustable, wherein before joining the metal sheets (B1, B2), the current total thickness (D1) is determined with the aid of the control unit (20) and the penetration depth (DT1) is set depending on the total thickness (Di), characterized by the following steps: 2.1 Storing a number of different total thicknesses or total thickness ranges (Di) in the control unit (20), 2.2 Assigning a penetration depth (DTi) to a total thickness or to a total thickness range (Di), 2.3 Axially moving the punch (11) out of a first zero position into a position (AS0) into a position (AS1) in which the punch (11) rests against the upper side (B10) of the first metal sheet (B1), 2.4 Detecting the path covered by the punch (11), 2.5 Axially moving the die (12) out of a second zero position (AM0) into a position (AM1) in which the die (12) rests against the lower side (B20) of the second metal sheet (B2), 2.6 Detecting the path covered by the die (12), 2.7 Detecting the total thickness (D1) from a distance between the first zero position (AS0) and the second zero position (AM0) and the paths covered by the punch (11) and die (12), 2.8 Comparing the detected total thickness (D1) with the stored total thicknesses or total thickness ranges (Di), 2.9 Selecting the value assigned to the detected total thickness (D1) for the penetration depth (DT), 2.10 Adjusting the penetration depth (DT) depending on the comparison made, and 2.11 Joining the two metal sheets (B1, B2) with the set penetration depth (DT).

3. The method according to claim 1, characterized in that to calibrate the clinching device (10), the punch (11) is moved from a zero position (AS0) in the axial direction until it comes into contact with the die (12) and the path covered by the punch (11) then defines the zero position (AMO) of the die (12), which is stored in the control unit (20).

4. The method according to claim 1 or 2, characterized in that the penetration depth (DT) is infinitely variable.

5. The method according to claim 1 or 2, characterized in that the penetration depth (DT) can be adjusted in at least two steps.

6. The method according to one of the preceding claims, characterized in that to adjust the penetration depth (DT), an anvil (12.1) is arranged concentrically in the die (12) and can be displaced in the axial direction (A) relative to the die (12).

7. The method according to claim 4 and 6, characterized in that an adjustment device (13) is provided to displace the anvil (12.1), said device being formed by a wedge.

8. The method according to claims 5 and 6, characterized in that an adjustment device (13) is provided to displace the anvil (12.1), said device being 30 formed by an adjustment slide (13.1) that in its longitudinal direction (L) comprises at least one effective step (12.1.1) in the axial direction (A).

9. Method for joining at least two metal sheets (B1, B2) resting on one other with a variable total thickness (Di) by means of a clinching device (10) comprising at least one punch (11) and a die (12) arranged coaxially to said punch, and at least the punch (11) is arranged so as to be controllable by means of an electronic control unit (20) and movable in an axial direction (A) relative to the die (12), wherein the two metal sheets (B1, B2) are arranged in a plane between the punch (11) and the die (12), and the penetration depth (DT) necessary for joining the metal sheets (B1, B2) is adjustable, wherein before joining the metal sheets (B1, B2), the current total thickness (D1) is determined with the aid of the control unit (20) and the penetration depth (DT1) is set depending on the total thickness (D1) with the following steps: 9.1 Storing a plurality of different total thicknesses or total thickness ranges (Di) in the control unit (20), 9.2 Assigning a respective penetration depth (DTi) to a total thickness or to a total thickness range (Di), 9.3 calibrating the clinching device (10), wherein 9.4 the penetration depth (DT) is continuously adjustable, 9.5 an anvil (12.1) arranged concentrically in the die (12) is arranged to be displaceable in the axial direction (A) relative to the die (12) in order to set the penetration depth (DT), 9.6 an adjusting means (13) formed by a wedge is provided for displacing the anvil (12.1.