Method for stamping and stacking sheet metal parts into sheet stacks

Abstract

A method for punching and stacking sheet metal parts (2) into a sheet metal pack (3) is shown. In order to facilitate the separation of the connected sheet metal parts (2) into the sheet metal pack (3), in a step before the first free punching, at least one second sheet metal part (20) is punched out in a second free punching, a separating element (19) is pressed back into the region of the electrical steel strip (5) in which the second sheet metal part (20) has been punched out, and the separating element (19) is pressed out of the electrical steel strip (5) by means of the first free punching.

Description

Technical Field

[0001] The present invention relates to a method for punching and stacking sheet metal parts into plate stacks, the method comprising the following steps: first freely punching out a first sheet metal part from an electrical steel strip, the electrical steel strip having a curable adhesive layer, in particular a heat-curing melt-bonding lacquer layer, on at least one flat side thereof, then stacking the first sheet metal parts, and connecting the stacked first sheet metal parts, in particular connecting them in a material-locking manner, wherein the method has measures for facilitating the separation of the connected first sheet metal parts into plate stacks, the measures comprising stacking at least one separating element with the first sheet metal parts. Background Art

[0002] It is known in the prior art that a separation element is arranged between the first sheet metal parts stacked in the channel after the last punching stage of the sequential punching die (WO2017 / 060483A1). The separation element makes it easier to separate the sheet metal parts connected by material locking into a stack of sheets, for example, by the surface of the non-non-stick coating, and the surface of the non-stick coating reduces the adhesion to the cured polymer adhesive layer of the adjacent first sheet metal parts. Such a separation element is introduced under the electrical steel strip in the last punching stage for free punching, and is squeezed into the channel by free punching out the first sheet metal part for stacking with other first sheet metal parts. Disadvantageously, when the separation element is introduced under the electrical steel strip, it is required to be relatively accurately positioned so as not to cause the separation element to be punched along with it, which can also cause damage to the sequential punching die. Summary of the invention

[0003] It is therefore an object of the present invention to modify a method of the aforementioned type in such a way that despite the use of separating elements stacked together with the first sheet metal part, a high degree of stability can be ensured.

[0004] The invention achieves the stated object by means of a method according to the invention for stacking punched sheet metal parts to form a sheet metal pack.

[0005] If the measures for facilitating the separation of the connected first sheet metal parts into sheet metal packs include a second step of punching out at least one second sheet metal part in a step before the first punching out, the electrical steel strip can already be included in the measures for facilitating the separation of the connected first sheet metal parts into sheet metal packs. Due to the second punching out, the electrical steel strip has a recessed area which can represent a receptacle in the electrical steel strip.

[0006] If the separating element is further pressed back (“pushed back”) into the region of the electrical steel strip from which the second sheet metal part has been punched out, the separating element can be connected to the electrical steel strip and also fed together with the electrical steel strip to the first blanking.

[0007] This results in the separation element being fed to the stacking method step in the same manner as the first sheet metal parts. It is thus possible to avoid complex measures in the final punching stage for arranging the separation element between the sheet metal parts, for which purpose it is sufficient to press the separation element out of the electrical steel strip by means of the first free punching.

[0008] Furthermore, the positioning of the electrical steel strip during the first free punching also necessarily results in a reproducible orientation of the separating element relative to the punching stage, which reliably avoids damage to the electrical steel strip. Compared to the prior art, the method according to the invention can therefore have a particularly long service life.

[0009] For example, the curable adhesive layer can be based on polyvinyl butyral, polyamides, polyamide, polyester, modified polyamide or epoxy resin. Preferably, a baking varnish, in particular a heat-curing one, is used as the adhesive layer. Curable polymer adhesive layers have proven to be advantageous.

[0010] If the measures include the step of passivating, curing and / or removing the adhesive layer of the second sheet metal part, the second sheet metal part can be used as a separating element. This not only avoids additional separating elements, but also ensures that the separated element pressed back always corresponds to the size of the freed area on the electrical steel strip. The separating element can thus be connected to the electrical steel strip in a reproducible manner, which can further increase the use time of the method.

[0011] If the second sheet metal part is at least partially stretched before being pressed back, the second sheet metal part can be arranged firmly in the electrical steel strip as a separating element. For example, the stretching can be carried out by stretching, pressing or the like.

[0012] If the second sheet metal part is connected to the first sheet metal part to form a sheet metal pack, it is also possible to use the second sheet metal part as part of a sheet metal stack and thus further increase the utilization of the electrical steel strip for forming a sheet metal pack or reduce waste.

[0013] If the second free punching and the pressing back are carried out in different stages during the punching of the stack, the throughput of the method is not changed by the measures for facilitating the separation of the connected first sheet metal parts into sheet metal stacks.

[0014] It is conceivable that the second free punching is carried out before the sequential punching die, which performs the first free punching with the second punching stage. Therefore, in order to connect the separating element to the electrical steel strip, no structural changes to the sequential punching die are required.

[0015] Alternatively, it is conceivable that the second free punching is performed by the third punching stage of a sequential punching die, which performs the first free punching with the second punching stage. This requires structural changes to the sequential punching die known from the prior art, but the reproducibility of the method can be further increased by the advantages of the synchronization of the stages with each other.

[0016] If the pressing back takes place in a stage immediately preceding the first free punching, no separate elements can be pressed out of the preceding, subsequent punching tool stage, which can contribute to increasing the reliability of the method.

[0017] The idling of the previous punching stage on the sequential punching die can be avoided in the following manner, that is, the second free punching is carried out in a step immediately before the pressing back. This reduces the risk of damage to the punching die or the bottom die cooperating with the punching die in particular.

[0018] The reliability of the method can be further increased if at least one guide hole is punched into the electrical steel strip before or during the second free punching and the separating element and the electrical steel strip are positioned relative to one another during the pressing back via the guide hole.

[0019] The electrical steel strip can be prepared particularly advantageously for pressing back if the second sheet metal part is punched out such that its outer dimensions are smaller than the first sheet metal part.

[0020] The second sheet metal part is preferably punched out so as to be at most 2 mm smaller.

[0021] If a press fit is formed between the decoupling element and the electrical steel strip, the decoupling element can be securely accommodated in the electrical steel strip.

[0022] This press fit can be formed particularly reproducibly if the separating element and / or the electrical steel strip has a projection on which the press fit is formed.

[0023] Preferably, the separation of the connected first sheet metal parts into sheet metal cores is facilitated in that the separating element is designed in such a way that adhesion to adjacent first sheet metal parts is reduced.

[0024] It has proven to be advantageous to use at least one separating element pressed back into the region of the electrical steel strip having the curable adhesive layer to facilitate the separation of the first sheet metal parts punched out of the electrical steel strip into sheet metal packs during punching of the stack. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The subject matter of the invention is illustrated in detail in the drawings, for example, based on a number of embodiment variants. Among them:

[0026] Figure 1 shows a partially interrupted side view of an apparatus for carrying out the method according to the first embodiment;

[0027] Figure 2a Shown in accordance with Figure 1 A top view of an electrical steel strip in the apparatus shown;

[0028] Figure 2b Show Figure 2a Detailed view of

[0029] Figure 3 A side view of a device for carrying out a method according to a second exemplary embodiment is shown. DETAILED DESCRIPTION

[0030] according to Figure 1 , a first embodiment of the invention schematically shows an apparatus 1 for carrying out the method according to the invention. The apparatus 1 is used to stack first sheet metal parts 2 punched out to form a sheet metal stack 3. For this purpose, an electrical steel strip 5 is unwound from a coil 4, which has a full-surface, curable polymer adhesive layer 8, 9, i.e. a melt adhesive layer, such as a heat-curing baking varnish, on one or both flat sides 6, 7 of the electrical steel strip. The adhesive layer 8, 9 can be applied, for example, to Figure 1 As can be seen in the enlarged section.

[0031] This thermally curable or heat-curable melt adhesive lacquer or melt adhesive layer is also known by the name "baking varnish". For example, the melt adhesive lacquer can have an epoxy resin base. Preferably, the melt adhesive lacquer is a bisphenol-based epoxy resin system with a curing agent, for example, a dicyandiamide-based system. In particular, the above-mentioned melt adhesive lacquer can be a bisphenol A-epichlorohydrin resin system with dicyandiamide as a curing agent. This two-stage cured epoxy resin system is present on the electrical steel strip in the B state. Therefore, the partially crosslinked melt adhesive lacquer still has the ability to react. Through heat transport, the melt adhesive lacquer in the B state is further reacted and can therefore be converted into a fully crosslinked C state, which is also called baking molding. Typically, the partially crosslinked melt adhesive lacquer layer has a thickness of several microns.

[0032] By means of the first sequential punching die 10.1, a plurality of first sheet metal parts 2 are punched out or separated from the painted electrical steel strip 5. Such punching can be (as usually mentioned) cutting, cutting, breaking, trimming, breaking by pressing out, etc.

[0033] from Figure 1It can also be seen that the punching die 10, for example here the first sequential punching die 10.1, performs cutting in a plurality of strokes 11 by cooperating its upper tool 12 with its lower tool 13. For this purpose, the punching die 10 has a plurality of punching stages 14, 15, 16.

[0034] The electrical steel strip 5 is pre-processed for free punching by means of the cutting edge 14.1 of the pre-processing punching stage 14 on the upper tool 11, and then the first sheet metal part 2 is free punched out of the electrical steel strip 5 or the first sheet metal part is separated therefrom by means of the second cutting edge 15.1 of the second and last punching stage 15 on the upper tool 11. For this purpose, the cutting edges 14.1, 15.1, 16.1 cooperate with the corresponding bottom dies 14.2, 15.2, 16.2 of the punching stages 14, 15, 16 on the lower tool 13.

[0035] In addition, this sequential cutting can be Figure 1 It can also be seen in FIG. 1 that parts 17 are separated from the electrical steel strip 5 during the pre-processing stamping in order to prepare the electrical steel strip 5 for free punching out the first sheet metal part 2 .

[0036] The first sheet metal parts 2 which are free-punched by means of the punching stage 15 are pressed into the stacking device 18 by the pressure of the upper tool 11 or the cutting blade 14.1 and stacked there. For this purpose, the stacking device 18 comprises a channel 18.1 and a bracket 18.2 in the lower tool 13. The bracket 18.2 in the lower tool 13 brakes the first sheet metal parts 2, thereby physically and / or chemically connecting these sheet metal parts 2 under the pressure of the upper tool 11 and by means of the adhesive layers 8, 9 located between the sheet metal parts 2. It is generally mentioned that the stacking device 18 can be actively heated so that the first sheet metal parts 2 are connected in a material-locking manner in the channel 18.1. In addition, the first sheet metal stack 3 can be subjected to a further curing step, not shown, in order to establish a material-locking connection between the first sheet metal parts 2. In addition, there is the possibility of rotating the stacking device 18, so that, for example, a sheet metal stack 3 of segmented segments is formed from a stack of first sheet metal parts 2 arranged side by side and stacked one above the other, which is also not shown.

[0037] In order to make it easier to separate the sheet metal packs 3 leaving the stacking device 18 from one another, at least one separating element 19 is stacked together with the first sheet metal parts 2. For this purpose, the separating element 19 is designed in such a way that the adhesion to the adhesive layer 8, 9 of at least one first sheet metal part 2 adjacent thereto is reduced. This leads to a reduction in the adhesion strength between the first sheet metal parts 2 of adjacent sheet metal packs 3, which makes it easier to separate the connected first sheet metal parts 2 into sheet metal packs 3.

[0038] According to the invention, the separating element 19 is introduced into the stacking device 18 by means of the electrical steel strip 5. For this purpose, firstly a second free punching is performed by means of the punching stage 16 by means of the cooperation of the cutting edge 16.1 and the bottom die 16.2, whereby the second sheet metal part 20 is separated from the electrical steel strip 5. As a result, a recessed area 21 is formed in the electrical steel strip 5.

[0039] This free-standing area 21 is used to accommodate the separating element 19 in the electrical steel strip 5, more precisely in that the stamping die 10 has a stage 22 for pressing the device back to the electrical steel strip 5. These devices are designed as a movable extruder 22.1 in the lower tool and a fixed bracket 22.2 in the upper tool. With this stage 22, the separating element 19 is pressed back into the area 21 of the electrical steel strip 5 from which the second sheet metal part 20 has been punched out. Therefore, the separating element 19 will then be transported together with the electrical steel strip 5 in the stamping die 10. For example, other devices for pressing back are known from DE 11207002887 T2, which also discloses the method steps of pressing back.

[0040] In the last punching stage 15 , the separating elements 19 are then pressed out of the electrical steel strip 5 . The separating elements 19 are thus located between the first sheet metal parts 2 in the stacking device 18 , which facilitates the separation of the sheet metal core 3 when leaving the stacking device 18 .

[0041] according to Figure 1 It can also be seen that the polymer adhesive layer 8 on one side of the second sheet metal part 20 has been passivated by the heat source 23. As a result, the second sheet metal part 20 can also be used as a separating element 19 and pressed back into the electrical steel strip 5. Other measures for passivating the polymer adhesive layer 8 are conceivable, such as curing and / or removal.

[0042] Since only one side of the second sheet metal part 20, namely the adhesive layer 8, is passivated, the second sheet metal part 20 can not only function as a separating element 19, but (due to its unpassivated second adhesive layer 9) can also be joined to the laminated core 3 or thus also used together with the laminated core. This ensures a high utilization rate of the electrical steel strip 5.

[0043] As from Figure 2a It can be seen that the second free punching and the pressing back are carried out in different stages 16 or 22 during the punching of the stack, more precisely, the pressing back is carried out in the stage 22 immediately before the first free punching, and the second free punching is carried out in the stage 22 immediately before the pressing back. In addition, all stages 14, 15, 16, 22 are part of the stamping die 10.

[0044] Furthermore, during the second free punching, two guide holes 24 are punched into the electrical steel strip using the third punching stage 16. The separating element 19 and the electrical steel strip 5 are positioned relative to one another by means of these guide holes 24. For this purpose, two pins 25 on the extruder 22.1 extend into a respective guide hole 24 in the electrical steel strip 5. This ensures that the separating element 19 is arranged precisely in the recessed region 21 of the electrical steel strip 5, which significantly increases the reproducibility of the method.

[0045] according to Figure 2b It can be seen that the outer dimensions of the second sheet metal part 20 produced by the second free punching are smaller than the first sheet metal part 2 by a standard distance s. Therefore, the left-out area 21 is smaller than the outer contour of the second punching stage 15. Preferably, the standard distance s is equivalent to two millimeters (mm). In addition, Figure 2b It can be seen in the drawing that the decoupling element 19 has projections V. At these rectangular projections V, a press fit P is formed with the electrical steel strip 5, which firmly holds the decoupling element 19 in the electrical steel strip 5. For this purpose, the second sheet metal part 20 serving as the decoupling element 19 is, for example, elongated in the region of the projections V. Press fits P are also conceivable in other regions of the decoupling element 19, which are not shown.

[0046] according to Figure 3 , schematically shows an alternative device 101 for performing the method according to the present invention. The second device 101 and the Figure 1 The first device 1 differs in that it has an additional tool 26 which is arranged upstream of the second sequential punching die 10.2 for punching the stack. With this tool 26 which is arranged separately from the second sequential punching die 10.2, the punching is performed according to Figure 1 The second free punching and pressing back are therefore performed before the second sequential punching die 10.2, which performs the first free punching with the second punching stage 16, and furthermore, according to Figure 1 The pre-punching is performed by means of the stage 14 of the second sequential punching die 10 . 2 .

[0047] The known second progressive punching die 10 . 2 can thus be retrofitted with the tool 26 in order to carry out the method according to the invention.

Claims

1. A method for stacking freely punched sheet metal parts (2) into a sheet metal stack (3), the method comprising the following steps: A first sheet metal part (2) is first punched out of an electrical steel strip (5) which has a curable adhesive layer (8, 9) on at least one flat side (6, 7), The first sheet materials (2) are then stacked, and Connecting the stacked first sheet metal parts (2), The method comprises measures for facilitating the separation of the connected first sheet metal parts (2) into sheet metal packs (3), which measures include stacking at least one separating element (19) with the first sheet metal parts (2). Characterized in that the measures include the following steps: In a step before the first free punching, at least one second sheet metal part (20) is punched out in a second free punching process, The separating element (19) is pressed back into the region of the electrical steel strip (5) from which the second sheet metal part (20) has been punched out, and The separating element (19) is pressed out of the electrical steel strip (5) by means of the first free punching.

2. The method according to claim 1, characterized in that The measures also include the following steps: The adhesive layers (8, 9) of the second sheet metal part (20) are deactivated, cured or removed and the second sheet metal part (20) is used as a separating element (19).

3. The method according to claim 2, characterized in that The second sheet metal element (20) is at least partially stretched before being pressed back.

4. The method according to claim 2 or 3, characterized in that: The second sheet metal part (20) is connected to the first sheet metal part (2) to form a sheet metal stack (3).

5. The method according to any one of claims 1 to 3, characterized in that The second free punching and pressing back are carried out in different stages during the stacking of the free punched sheet metal parts (2) to form a sheet metal core (3).

6. The method according to any one of claims 1 to 3, characterized in that The second free punching is carried out before a second sequential punching die (10.2), which performs the first free punching with a second punching stage (15).

7. The method according to any one of claims 1 to 3, characterized in that The second free punching is performed by a third punching stage (16) of a first sequential punching die (10.1) which performs the first free punching with a second punching stage (15).

8. The method according to claim 7, characterized in that The pressing back is performed immediately in a stage before the first free punching.

9. The method according to claim 8, characterized in that The second free punching is carried out in a third punching stage (16) immediately before the pressing back.

10. The method according to any one of claims 1 to 3, characterized in that Before or during the second free punching, at least one guide hole (24) is punched into the electrical steel strip (5), and during pressing back, the separating element (19) and the electrical steel strip (5) are positioned relative to one another by means of the guide hole (24).

11. The method according to any one of claims 1 to 3, characterized in that The second sheet metal part (20) is punched out such that its outer dimensions are smaller than those of the first sheet metal part (2).

12. The method according to claim 11, characterized in that The second sheet metal part (20) is punched out so as to be at most 2 mm smaller.

13. The method according to any one of claims 1 to 3, characterized in that A press fit (P) is formed between the separating element (19) and the electrical steel strip (5).

14. The method according to claim 13, characterized in that The separating element (19) and / or the electrical steel strip (5) has a projection (V) at which the press fit (P) is formed.

15. The method according to any one of claims 1 to 3, characterized in that The separating element (19) is designed to reduce adhesion to the first sheet metal parts (2) adjacent thereto, thereby facilitating the separation of the connected first sheet metal parts (2) into sheet metal packs (3).

16. The method according to claim 1, characterized in that The curable adhesive layer (8, 9) is a heat-cured melt-adhesive lacquer layer.

17. The method according to claim 1, characterized in that In the step of connecting the stacked first sheet metal parts (2), the stacked first sheet metal parts (2) are connected in a material-locking manner.

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