Method for pressing stamped sheet metal parts into a laminate stack

Abstract

The present invention relates to a method for stacking pressed sheet metal parts (2) to form a plurality of laminate stacks (3), wherein, to facilitate separation of the joined sheet metal parts (2) into a plurality of laminate stacks (3), a first outline punching step and a step of pushing back a release element (19) into a portion of the electromagnetic steel strip (5) from which the second sheet metal part (20) was punched are preceded by a second outline punching step of at least one second sheet metal part (20), and then the release element (19) is pushed back into the electromagnetic steel strip (5) in the first outline punching step.

Description

[Technical field]

[0001] The invention relates to a method for stacking pressed sheet metal parts to form a stack of sheets, the method comprising: firstly stamping a first sheet metal part from an electromagnetic steel strip having a layer of hardenable adhesive, in particular a hot melt adhesive coating, on at least one of its planar sides, followed by stacking the first sheet metal parts and joining the first sheet metal parts by bonding, in particular by material-to-material bonding. The method comprises means for facilitating separation of the joined first sheet metal parts into a stack of sheets, the means comprising stacking at least one release element together with the sheet metal parts. [Background technology]

[0002] It is known in the prior art (WO 2017 / 060483) to provide a release element between a plurality of first sheet metal parts stacked in a longitudinal hole adjacent to the final pressing stage of a progressive die press. This release element, for example with a non-stick coated surface, reduces the adhesion of the curable polymer adhesive layer of adjacent first sheet metal parts and facilitates the separation of the material-bonded plurality of sheet metal parts into a plurality of stacked stacks. Such a release element is inserted under the magnetic strip for punching in the final pressing step and enters the longitudinal hole by punching the first sheet metal parts to form a stack with other punched first sheet metal parts. A disadvantage is that the release element requires a relatively high positioning accuracy when inserted under the magnetic strip so that it is not punched as well, which may result in damage to the press die, among other things. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2017 / 060483 Summary of the Invention [Problem to be solved by the invention]

[0004] The object of the invention is to improve a method of the above-mentioned kind in such a way that high stability is guaranteed even when release elements are used in the lay-up together with a number of first sheet metal parts. [Means for solving the problem]

[0005] The problem of the present invention is solved by the features of claim 1.

[0006] If the means for facilitating the separation of the joined first sheet metal parts into a stack includes a second punching step of punching at least one second sheet metal part preceding the first punching step, the electromagnetic strip may already be included in the step of facilitating the separation of the joined first sheet metal parts into a stack, the electromagnetic strip having a recess due to the second punching step and capable of acting as a support for the electromagnetic strip side.

[0007] If the demolding element is pushed back onto the portion of the magnetic steel strip from which the second sheet metal part has been punched, the demolding element will be coupled with the magnetic steel strip and they can be fed together into the first outline punching process.

[0008] That is, the release element is fed to the lay-up process in the same way as the first sheet metal part. Expensive measures for inserting the release element between the sheet metal parts in the last press stage can therefore be avoided; punching the release element from the magnetic strip using the first profile punching process is sufficient for this. Furthermore, the positioning of the magnetic strip in the first press stage ensures a reproducible alignment of the release element using the press stage, so that damage to the press stage is reliably prevented. In contrast to the prior art, therefore, a particularly long service life can be achieved with the method according to the invention.

[0009] For example, the curable adhesive layer may be based on polyvinyl butyral, polyamide, polyester, modified polyamide or epoxy resin. Preferably, the adhesive layer is a baked varnish, in particular a thermosetting varnish. Coatings of curable polymer adhesives have been found to be advantageous.

[0010] If the measure includes a step of inactivating, hardening and / or removing the adhesive layer of the second sheet metal part, this second sheet metal part can be used as a release element, which not only eliminates the need for an additional release element, but also ensures that the pushed back release element always corresponds to the dimensions of the punched area of ​​the magnetic strip, so that the release element can be reproducibly bonded to the magnetic strip and the service life of the press tool can be further extended.

[0011] Pushback before If the second sheet metal part is at least partially removed at the separation of the electromagnetic steel strip, The lengthening can be achieved, for example, by pulling, pressing, etc. This can be done.

[0012] When a second sheet metal part is joined with a first sheet metal part to form a laminate stack, the second sheet metal part can also be used as part of the laminate stack, further improving the utilization efficiency when forming a laminate stack from the magnetic steel strip, thereby reducing waste.

[0013] Even if measures are taken to facilitate the separation of the joined first sheet metal parts into a stack, the process throughput can remain unchanged if the second blanking and push-back operations are carried out in different stages in the press die.

[0014] It is also conceivable that the second profile punching step is performed in a progressive press die in which the first profile punching step is performed in the second press stage, i.e. there is no need to change the design of the progressive press die in order to bond the release element to the magnetic steel strip.

[0015] Alternatively, the second profile punching step could be performed in a third press stage downstream from the press stage in which the first profile punching step is performed in the second press stage. This would require design modifications to the progressive press dies known in the prior art, but the synchronization of the stages could further improve the repeatability of the process.

[0016] If the push-back is applied in the stage immediately prior to the first contour punching process, the demolding element will not be punched out in the preceding stage of the progressive press die, improving the reliability of the process.

[0017] By carrying out the second profile punching step in the stage immediately following the push back, it is possible to avoid idle running of the preceding stages of the progressive press die, which in particular reduces the risk of damage to the press die or the cooperating dies.

[0018] If at least one guide hole is punched before or during the second contour punching process, the release element and the magnetic steel strip can be positioned relative to each other on this guide hole during the push-back process, which further improves the reliability of the process.

[0019] The magnetic strip can be prepared in a particularly advantageous manner for pushing back if the second sheet metal part is stamped out so that its outer contour is smaller than that of the first sheet metal part.

[0020] Preferably, the second sheet metal part is stamped to have a maximum outer diameter smaller than that of the first part by 2 mm.

[0021] When an interference fit is formed between the release element and the magnetic strip, the release element can be held firmly to the magnetic strip. If protrusions are present on the release element and / or on the magnetic steel strip, with which an interference fit is formed, this interference fit can be formed particularly reproducibly.

[0022] Preferably, the release element is configured to reduce adhesion between adjacent first sheet metal parts to facilitate separation of the joined plurality of first sheet metal parts into a plurality of laminated stacks.

[0023] Advantageously, it has been found that the use of at least one release element pressed back against the portion of the magnetic steel strip having the hardenable adhesive layer facilitates separation of the multiple first sheet metal parts joined during press lamination into multiple laminated sticks.

[0024] In the drawings, for example, the object of the present invention is illustrated in detail based on several embodiments. [Brief description of the drawings]

[0025] [Figure 1] FIG. 1 is a side view, with a part cut away, of an apparatus for carrying out a method according to a first embodiment. [Figure 2a] FIG. 2a is a top view of the electromagnetic steel strip in the apparatus shown in FIG. [Figure 2b] FIG. 2b is a detailed view of FIG. 2a. [Diagram 3] FIG. 3 shows a side view of an apparatus for carrying out the method according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] In the first exemplary embodiment shown in Fig. 1, an apparatus 1 for carrying out the method according to the invention is diagrammatically shown. This apparatus 1 is used for laminating stamped sheet metal parts 2 into a laminate stack 3. For this purpose, an electromagnetic steel strip 5 is unwound from a coil 4 and one or both of its functional faces 6, 7 are provided with perfectly flat curable polymer adhesive layers 8, 9, i.e. hot-melt adhesive layers, for example thermosetting sintered varnish. These adhesive layers 8, 9 are shown, for example, in the enlarged part of Fig. 1.

[0027] Such thermosetting or thermosetting hot melt adhesives or hot melt adhesive layers are known as baking varnishes. For example, the hot melt adhesive varnish may be based on epoxy resin. Preferably, the hot melt adhesive varnish is, for example, a bisphenol-based epoxy resin system using a dicyandiamide-based hardener. In particular, the mentioned hot melt adhesive varnish may be a bisphenol A epichlorohydrin resin system using dicyandiamide as hardener. This two-stage curing epoxy resin system is in the B state on the magnetic steel strip. Thus, the partially cross-crosslinked hot melt varnish is still reactive. By heating, the reaction of the hot melt varnish in the B state can proceed and thus transition to the fully cross-crosslinked C state, also referred to as bond. Typically, the thickness of this partially cross-crosslinked hot melt coating is a few microns.

[0028] A plurality of first sheet metal parts 2 are stamped or separated from the baking lacquer coated magnetic steel strip 5 using a progressive press die 10.1. Such stamping is generally a cut-out, cut-out, separation, cut-off, pressing separation, etc.

[0029] 1, a press die 10, for example a progressive punch die 10.1, performs cutting by multiple strokes 11 of an upper die 12 cooperating with a lower die 13. For this purpose, the punch die 10 comprises multiple press stages 14, 15, 16.

[0030] A first punch 14.1 of a pre-pressing stage 14 of the upper tool 11 is used to prepare the electromagnetic steel strip 5 for the outline punching process, after which a second punch 15.1 of a second and final press stage 15 of the upper tool 11 is used to outline punch or separate the first metal part 2 from the electromagnetic steel strip 5. To this end, the punches 14.1, 15.1, 16.1 work together with the dies 14.2, 15.2, 16.2 of the press stages 14, 15, 16 of the lower tool 13, respectively.

[0031] Such a progressive press die is shown in Figure 1. It can be seen inter alia that a part 17 is punched out in a preparatory pressing step in order to prepare the magnetic steel strip 5 for the outline punching of the first sheet metal part 2.

[0032] The first sheet metal parts 2 punched to the shape by the press stage 15 are fed into the lamination device 18 by the pressure of the upper die 11 or punch 14.1 and laminated into a stack shape. For this purpose, the lamination device 18 comprises a vertical hole 18.1 and a counter plate 18.2 in the lower die 13. The counter plate 18.2 of the lower die 13 brakes the first sheet metal parts 2, so that the first sheet metal parts 2 are physically and / or chemically bonded by means of the adhesive layers 8, 9 present between the sheet metal parts 2 under the pressure of the upper die 11. It is generally mentioned that the lamination device 18 may be actively heated to laminate the first sheet metal parts 2 in the vertical hole 18.1. In addition, the first laminate stack 3 may be subjected to a hardening process (not shown) to form a material bond between the first sheet metal parts 2. Further, for example, although not shown, it is also possible to remove a divided stack of the laminated stack 3 from the laminated device 18 and rotate the laminated device 18 to form layers in which multiple first sheet metal parts 2 are arranged adjacently and laminated on top of each other.

[0033] To facilitate separation of the plurality of laminate stacks 3 leaving the lamination device 18, at least one release element 19 is laminated together with the plurality of first sheet metal parts 2. To this end, the release element 19 is designed to reduce the adhesion of at least one adjacent first sheet metal part 2 to the adhesive layer 8, 9. This reduces the bond strength between the plurality of first sheet metal parts 2 of the adjacent plurality of laminate stacks 3, facilitating separation of the bonded plurality of first sheet metal parts 2 into the plurality of laminate stacks 3.

[0034] According to the invention, the demolding element 19 is inserted into the laying device 18 by means of the electrical steel strip 5. For this purpose, a second profile punching process is first carried out in the press stage 16 by cooperation of the punch 16.1 and the die 16.2, whereby the second sheet metal part 20 is separated from the electrical steel strip 5. In this process, a recess 21 is formed in the electrical steel strip 5.

[0035] This recess 21 is used for receiving the release element 19 on the magnetic strip 5, which is achieved by the press tool 10 comprising a stage 22 with a push-back means for the magnetic strip 5. This means is designed as a movable pressing device 22.1 of the lower tool and a fixed counter plate 22.2 of the upper tool. By means of this stage 22, the release element 19 is pushed back from there into the area 21 of the magnetic strip 5 from which the second sheet metal part 20 was punched out, i.e. the release element 19 moves together with the magnetic strip 5 in the press tool 10. Other means for pushing back are also known, for example from the German European Patent Translation 11207002887T2, which also discloses a push-back process.

[0036] In the final press stage 15, the demolding elements 19 are punched out of the magnetic steel strip 5. The demolding elements 19 are therefore located between the first sheet metal parts 2 in the lamination device 18 and facilitate separation of the lamination stack 3 on exiting the lamination device 18.

[0037] 1, the polymer adhesive layer 8 on one side of the second sheet metal part 20 is deactivated by a heat source 23. That is, the second sheet metal part 20 can also be used as a release element 19 and is pressed back onto the electrical steel strip 5. Other methods of deactivating the polymer adhesive layer 8 are conceivable, such as, for example, curing and / or removal.

[0038] Since only one side of the second sheet metal part 20, i.e. the adhesive layer 8, is passivated, the second sheet metal part 20 not only acts as a release element 19, but also, on the basis of its non-passivated adhesive layer 9, can be bonded to the lamination stack 3 and is thus commonly utilized. This ensures a high utilization rate of the magnetic steel strip 5.

[0039] As shown in FIG. 2a, the second profile punching and the push-back are performed in different stages 16 and 22, respectively, during the press lamination, i.e., the push-back is performed in stage 22 immediately after the first profile punching, and the second profile punch is performed in stage 22 immediately after the push-back. Furthermore, all stages 14, 15, 16 and 22 are part of the press die 10.

[0040] Furthermore, during the second profile punching, two guide holes 24 are punched in the magnetic strip by means of the third stage 16. With the aid of these guide holes 24, the release element 19 and the magnetic strip 5 are positioned relative to one another. For this purpose, the press 22.1 is provided with two pins 25, each protruding into one of the guide holes 24 in the magnetic strip 5. This ensures an accurate positioning of the release element 19 in the recess 21 in the magnetic strip 5, which significantly improves the reproducibility of the process.

[0041] According to Fig. 2b it can be seen that the blanking of the second sheet metal part 20 is carried out with outer dimensions smaller than the first sheet metal part 2 by the normal distance s. The recess 21 is therefore smaller than the outer contour of the second press stage 15. Preferably, the normal distance s corresponds to 2 millimeters (mm).

[0042] Furthermore, it can be seen from Fig. 2b that the release element 19 has protruding portions V. At these rectangular protruding portions V an interference fit P is formed in the magnetic steel strip 5, by which the release element 19 is firmly held on the magnetic steel strip 5. To this end, for example, a second sheet metal part 20, which is used as the release element 19, is passed over the protruding portions V. However, interference fits P are also conceivable in other parts of the release element 19, although they are not shown.

[0043] In Fig. 3 an alternative device 101 for carrying out the method of the invention is shown diagrammatically. This second device 101 differs from the first device 1 shown in Fig. 1 in that there is an additional die 26 preceding the second progressive die 10.2 for the press lamination. This die 26, separate from the second progressive die 10.2, performs the same steps as the progressive die 10 shown in Fig. 1, namely the second profile punching and pushing back. The second profile punching and pushing back are therefore performed in the progressive die 10.2 which performs the first profile punching in the second press 16, in addition to the preparatory pressing. In Fig. 1, the stage 14 of the progressive die 10.2 is used.

[0044] Thus, a known progressive press tool 10.2 can be replicated with a die 26 to carry out the process of the present invention. [Explanation of symbols]

[0045] 1 device 101 Equipment 2. Sheet metal parts 3. Laminated Stack 4 Coils 5. Electromagnetic Steel Strip 6, 7 Functionality 8, 9 Adhesive layer 10 Press mold 10.1 Progressive press dies 10.2 Progressive press dies 11 Strokes 12 Upper mold 13 Lower mold 14, 15, 16 Press Stage Stages 14, 15, 16 14 Pre-treatment press stage 14.1, 15.1, 16.1 Punch 14.2, 15.2, 16.2 Dies 17 parts 18 Stacking device 18.1 Shafts 18.2 Counterplate 19 Release elements 20 Sheet metal parts 21 Recess 22 Stages 22.1 Movable Press Equipment 22.1 Pressing Equipment 22.2 Fixed opposing plate 23 Heat source 24 Guide hole 25-pin P Interference fit V protrusion

Claims

1. A method for stacking stamped sheet metal parts (2) to form a plurality of stacked stacks (3), comprising the steps of: a first outline punching step of pressing a first sheet metal part (2) from an electromagnetic steel strip (5) having a curable adhesive layer (8, 9) on at least one of its flat sides (6, 7); Then, the plurality of first sheet metal parts are stacked and joined together by joining the plurality of first sheet metal parts (2). The method comprises a means for facilitating separation of the joined first sheet metal parts (2) into a stack (3), the means comprising stacking at least one release element (19) together with the plurality of first sheet metal parts (2). The means is Prior to the first outline punching step, at least one second sheet metal part (20) is outline punched. A second outer shape punching process. a pushing-back step of pushing the release element (19) back onto the portion of the electromagnetic steel strip (5) from which the second sheet metal part (20) has been punched; a third outline punching step of punching the release element (19) from the electromagnetic steel strip (5) in the first outline punching step; A method comprising:

2. 2. The method according to claim 1, further comprising the step of passivating, hardening and / or removing the adhesive layer (8, 9) of the second sheet metal part (20) and using it as a release element (19).

3. 3. The method of claim 2, wherein the second sheet metal part (20) is elongated in a plurality of areas prior to the pushing back step.

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

5. 5. The method according to claim 1, wherein the second profile punching step and the pushing back step in the press lamination process are performed in different press stages (16, 22).

6. 6. The method according to claim 1, wherein a second profile punching step is performed before the first profile punching step, which is performed by a progressive press die (10.2) using a second press stage (15).

7. 6. The method according to claim 1, wherein the second profile punching step is performed by a third press stage (16) of a progressive press die (10.1) which performs the first profile punching step using a second press stage (15).

8. 8. The method according to claim 7, characterized in that the pushing back step is performed in a stage (22) immediately prior to the first pressing step.

9. 9. The method according to claim 8, characterized in that the second profile punching step is performed in a stage (16) immediately prior to the pushing back step.

10. 10. The method according to claim 1, further comprising punching at least one guide hole (24) in the magnetic strip (5) before or during the second profile punching step, and the release element (19) and the magnetic strip (5) are positioned relative to each other with the aid of the guide hole (24).

11. 11. The method according to claim 1, wherein the outer diameter of the second sheet metal part (20) is smaller than that of the first sheet metal part (2).

12. 12. The method according to claim 11, characterized in that the second sheet metal part (20) is stamped out to be max. 2 mm undersized.

13. 13. The method according to any one of claims 1 to 12, characterized in that an interference fit (P) is formed between the demolding element (19) and the electromagnetic steel strip (5).

14. 14. The method according to claim 13, characterized in that the demolding element (19) and / or the electromagnetic steel strip (5) have a protruding portion (V) through which the interference fit (P) is formed.

15. 15. The method according to any one of claims 1 to 14, characterized in that the release element (19) is designed to weaken the adhesive forces of the joined first sheet metal parts (2) in order to facilitate separation of the joined first sheet metal parts (2) into a plurality of laminate stacks (3).

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